Lake Ecosystems and Abiotic Factors

Catchment Area

Lakes (also referred to as lentic systems along with ponds) exhibit physical and chemical characteristics unique to the soils, vegetation, and land use activities present on immediately surrounding lands; thus, no two lakes are exactly the same (Moss et al. 1996, Brönmark and Hansson 2005). All lakes occur within catchment areas. A catchment area can also be referred to as a watershed or drainage basin, which is simply the zone of land surrounding a lake that drains precipitation into the lake basin (Brönmark and Hansson 2005). The area, geology, edaphic (soil) properties, land use, and vegetation of catchment areas affect the acidity, water color, nutrient input, and chemical composition of lakes (Wetzel 2001, Brönmark and Hansson 2005). Large catchment areas have a more pronounced impact on the chemical properties of lakes because they drain more precipitation, and thus the potential for more nutrients, into the lake basin. Consequently, land use activities that release excessive nutrient inputs into large catchment areas (e.g., intensive agriculture) are likely to cause eutrophication (Casterlin et al. 1984, Brönmark and Hansson 2005).

Water Color

The observed color of natural lake waters is caused by the selective absorption of wavelengths as light penetrates through the water column (Wetzel 2001). Organic matter (i.e., dead and decomposing plant and animal parts) is the principal determinant of water color in lakes (Juday and Birge 1933, Rasmussen et al. 1989, Brönmark and Hansson 2005). Due to differences in wavelength absorption, waters with little dissolved organic matter, such as hardwater lakes or glacial streams, appear blue/green, and, in contrast, lakes containing much dissolved organic matter in the form of humic substances (e.g., Carolina bay lakes and bogs) appear yellow/red or “tea-stained” in color. Humic substances are large molecules formed as a result of decomposing organic matter; they are difficult for the microbial community to degrade and are long-lived within the lake system (Brönmark and Hansson 2005).

Trophic status

Trophic status refers to the rate at which organic matter is supplied by or transported into a lake. Humic substances are the most common component in allochthonous organic matter; consequently, wetlands that receive the bulk of their organic matter from allochthonous sources (e.g., Carolina bay lakes, bogs, pocosins) are heavily “tea-stained” and are commonly referred to in the southeastern United States as “black water” lakes, streams, rivers, ponds. Lakes receiving the majority of their organic matter from allochthonous sources have been given the term dystrophic. Dystrophic lakes have low productivity and are often acidic due to large quantities of allochthonous humic input.

Phosphorous is limiting in freshwater systems and is therefore a useful determinant for production. Phosphorous concentrations are easier to quantify than carbon content and production, and, as a result, trophic status is often classified based on phosphorous content (Brönmark and Hansson 2005). Oligotrophic lakes experience low productivity associated with autochthonous carbon production and low levels of phosphorous and nitrogen. Eutrophic lakes experience high productivity associated with autochthonous production and high levels of phosphorous and nitrogen.

pH

The unit commonly used to measure acidity is pH. It is technically defined as the reciprocal of the activity of free hydrogen ions (H⁺; Covington et al. 1985). Because pH is measured on a logarithmic scale, a change of one unit in pH corresponds to a ten-fold increase in hydrogen ions (Brönmark and Hansson 2005). pH is measured on a scale of 1–14; most lakes possess a pH between 6 and 9, but extreme cases of acidity (1–5) and alkalinity (10–14) also exist depending upon various abiotic and biotic conditions within a lake’s catchment area (see above; Brönmark and Hansson 2005). Geological and hydrological conditions within catchment areas primarily control the pH of lakes; however, acid rain can also affect the pH of lakes. In North America, coal-fired power plants and other industries emit sulfur dioxide (SO₂) into the atmosphere. As weather systems make their way across North America from west to east, they pick up this sulfur dioxide (SO₂) and deposit it across the landscape in the form of precipitation (i.e., acid rain). The cumulative effects of acid rain deposition on both terrestrial and aquatic systems is known to be most severe in the eastern United States; this is due to the region's geographic location in relation to broad-scale weather paterns and industries emitting sulfur dioxides (Schindler 1988).

Photosynthesis and respiration are also known to affect the pH of waters by influencing the amount of carbon dioxide (CO₂) in the water column. When CO₂ is taken up and stored by aquatic macrophytes, phytoplankton, and algae during photosynthesis, free hydrogen ions (H⁺) are neutralized or taken up by carbonates, bicarbonates, and hydroxides, causing a reduction in H⁺ and thus a higher pH. Respiration adds CO₂ into the system, thus releasing free H⁺ into the water column and lowering the pH (Brönmark and Hansson 2005). Because photosynthesis and respiration can cause fluctuating differences in pH within a 24-hour cycle, alkalinity is typically considered to be a better measurement of a lake's acidification status (Brönmark and Hansson 2005).

Alkalinity

Alkalinity refers to a lake's ability to neutralize strong inorganic acids (i.e., it is a measure of how sensitive a lake is to acidification). It is now used synonymously with acid neutralizing capacity (ANC; Wetzel 2001). Today, alkalinity is generally expressed in milliequivalents per liter (meq/L), but has commonly been recorded in the past in milligrams per liter (mg/L; Brönmark and Hansson 2005). Lakes with an alkalinity above 0.5 meq/L have good buffering capacities, whereas lakes with alkalinities below 0.01 meq/L have little or no buffering capacities (Wetzel 2001Brönmark and Hansson 2005). Lakes with low alkalinities are susceptible to drops in pH with only small additions of acid (H⁺), whereas lakes with high alkalinities can withstand the addition of acid (H⁺) into their systems without proportional drops in pH (Brönmark and Hansson 2005).

Wetzel (2001) noted that the property of alkalinity in most fresh waters is imparted by the presence of carbonates (i.e., carbonate, bicarbonate, calcium carbonate). Carbonates and hydroxides remove hydrogen ions (H⁺) from lakes, thus neutralizing their acidity (i.e., raising the pH to a more basic status). Lake Waccamaw, the largest Carolina bay lake, has a high alkalinity (7.0−12 mg/L or 0.14−0.24 meq/L; Weiss and Kuenzler 1976) due to the presence of both subsurface and surficial limestone deposits within and around the lake. As a result, it possesses a neutral to basic pH (6.8−8.5 s.u.) and has the ability to handle larger additions of acid.

Carolina Bays, Bay Lakes, and Pocosins

Carolina Bays

The core concentration of Carolina bays occurs in southeastern North Carolina and northeastern South Carolina (Ross 2003; Fig. 1). Although these depressions share the same elliptical shape, they vary dramatically in length along their long axis from 50 m to 8 km (with some as large as 3,600 ha; Prouty 1935, Thom 1970, Savage 1982, Sharitz and Gibbons 1982). Nifong (1982) suggested that there are fewer than 13,000 bays (unaltered and altered) left in the Coastal Plain of the Carolinas, as opposed to the 400,000 proposed by Prouty (1935). It was not until the early 20^th century that researchers fully recognized the magnitude and extent of Carolina bay distribution by the use of airplanes and soon-to-be aerial imagery.

Figure 1.  

Core distribution of Carolina bays. Carolina bays are known to occur from the Delmarva Peninsula south to southern Georgia. Although many historical texts frequently cite the distribution range of Carolina bays as occurring from New Jersey south to Florida, the more narrow range from the Delmarva Peninsula to southern Georgia is more accurate. Conversations with state agencies and personnel from all states included in the broader range of Carolina bays confirm their “apparent absence” in southern New Jersey and northern Florida. The core distribution of Carolina bays is located in northeast South Carolina and southeast North Carolina (darker gray). The bays in this region would be considered “classic” Carolina bays (i.e., matching all of the well-known and consistent geomorphological criteria in the literature), whose geomorphology is described well by Prouty (1952) and Ross (2003). Toward the peripheries of the known Carolina bay distribution range, the term Carolina bay tends to be used loosely and is not used in its strictest sense (i.e., depression wetlands; Chick Gaddy, pers. comm.). Figure taken from Ross (2003).

Savage (1982) declared that: “When seen from the air, Carolina bays are an astounding, unforgettable revelation. But though hundreds of thousands lie clearly visible, scattered across the Atlantic Coastal Plain from Maryland to northern Florida, they are often all but unrecognizable to the uninitiated eyes of groundlings”. The first aerial images produced of the Atlantic Coastal Plain exposed Carolina bays to both citizens and scientists on a broad scale; moreover, they initiated a flurry of scientific research on Carolina bay distribution, numbers, origin, vegetation, and soils.

The term bay is used to describe these landscape features not because they commonly contain hydric soils or are inundated with water, but because of the presence of three species of bay tree typically found within and around their elliptical boundaries (i.e., Magnolia virginiana L. [sweetbay; Magnoliaceae], Persea palustris (Raf.) Sarg. [swamp bay; Lauraceae], and Gordonia lasianthus (L.) J. Ellis [loblollybay; Theaceae]. Traditionally, the term “bay” tree has been used when speaking of the laurel trees within the Lauraceae family. While Persea palustris may be properly referred to as a “bay” tree, Gordonia lasianthus and Magnolia virginiana may not (sensu stricto), hence their common names being one word (i.e., loblollybay and sweetbay). Gordonia lasianthus and Magnolia virginiana bear a noticeable morphological resemblence to the laurels of the Lauraceae; thus, they are generally referred to as “bay” trees (sensu lato). North of Virginia, these mysterious landscape features are referred to as Delmarva potholes, bays, or basins (Tiner and Burke 1995, Lide 1997, Sharitz 2003, Tiner 2003). The inability to agree upon a clear-cut definition and universal name for these unique geological features has caused some discrepancy among estimates of bay numbers (Lide 1997).

Collectively, Carolina bays and pocosins represent the largest total acreage of palustrine wetlands in the Carolinas (Wilson 1962, Richardson 1983, Richardson and Gibbons 1993, Nifong 1998). Pocosins occur on the Atlantic Coastal Plain from southern Virginia to northern Florida (essentially the same range as Carolina bays). Unlike Carolina bays, pocosins have been poorly mapped throughout the whole of their range. Wilson (1962) and Richardson (1981) comprehensively mapped the pocosins of North Carolina. It is estimated that ca. 70% of the nation's pocosin habitat occurs in North Carolina and that over 50% of the state's palustrine wetlands are comprised of pocosins (Richardson and Gibbons 2003). Richardson (1981) suggested that ca. 8,300 km² (3,200 mi²) of unaltered pocosins were drained for other land uses between 1962 and 1979; and ca. 3,700 km² (1,450 mi²) of unaltered pocosins remained in North Carolina in 1980. Based on the presence of wetland soils (i.e., “soils formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part” [Vepraskas and Richardson 2001]), North Carolina is estimated to have contained nearly 7.5 million acres (3.03 million hectares) of wetlands prior to European settlement of the state; 95% of these wetlands were located in the Coastal Plain (North Carolina Division of Environmental Management 1994).

Geographic location, soil depth, soil type, surrounding land use, varying hydrology, and fire regimes interact to create vastly different vegetative and wetland assemblages within Carolina bays. Nifong (1998) summarized this diversity, noting that bays included “in some form, virtually every non-marine wetland system found on the southeastern Coastal Plain, including brackish marsh, freshwater pond, freshwater marsh, freshwater prairie, pocosin, bay forest, bog, swamp forest, depression meadow, cypress savanna, and longleaf pine savanna communities, among others”. Other communities found within Carolina bays include Pinus taeda L. (loblolly pine) plantations, cropland, and open lakes (Carolina bay lakes).

Carolina bays can be divided into two classes based on soil substrate: clay-based bays and peat-based bays. The vast majority of Carolina bay literature has referenced peat-based bays, frequently using terms such as “pocosin” or “evergreen shrub bog” to describe the vegetation growing over deep organic soils. However, there are about 27 bays (as of 1982) located in the Carolinas that contain clay subsoil not overlain with sand or peat (Kelley and Batson 1955, Nifong 1982). These clay-based bays are restricted to Cumberland, Scotland, Hoke, and Robeson Counties in North Carolina. The vegetative physiognomy of clay-based bays differs from peat-based bays in that the structure is more open in the former (i.e., they have a sparse overstory of Taxodium and an herbaceous understory composed mostly of herbaceous taxa). However, clay-based bays do share some of the classical Carolina bay morphology features (e.g., elliptical boundaries, varying size, sand rims) with peat-based Carolina bays.

Clay-based bays are species-rich communities, often supporting rare taxa within their boundaries (Nifong 1982). Clay-based bays in high quality condition typically have an open canopy with a species-rich herbaceous understory. Fire and water level fluctuations are two disturbance regimes that account for the diversity found in these bays (Sutter and Kral 1994, Nifong 1998). Peat based bays are more prevalent throughout the Coastal Plain of the Carolinas. Peat-based bays are not as restricted to the inner Coastal Plain and are not as floristically rich as high quality clay-based bays.

Bladen County, North Carolina, is well-known for its many Carolina bays. Nifong (1998) found 617 Carolina bays within Bladen County; of these, 325 were classified as fully vegetated and 292 were classified as cleared (i.e., > 50% of their natural vegetation removed). Bladen County hosts the densest cluster of unaltered bays in the state (the county is fourth densest for bays in any condition). The majority of the bays in Bladen County are found in the Cape Fear River Valley, between the Cape Fear River and the South and Black Rivers. All of these bays are considered peat-based bays. Among extent Carolina bay lakes, all but one occur in Bladen County.

Carolina bays should not be confused with pocosins; they are two distinct physiographic features that just so happen to coexist with one another on the Atlantic Coastal Plain. These two landscape features differ from one another and using the terms synonymously is a common mistake among both laymen and professionals (Ross 2003). The term pocosin originated as an eastern Algonquian term meaning “swamp-on-a-hill” (Richardson 1983). It is defined by Ross (2003) as “a Coastal Plain wetland area of variable shape and size in an area of poor surface drainage whose vegetation is mostly broad-leafed evergreen shrubs and Pinus serotina Michx. growing on organic peaty soils” and by Brinson (1991) as “ecosystems dominated by woody, predominantly evergreen species and that normally occur on histosols (organic peat or muck soils ≥ 40 cm deep) or on soils with a histic epipedon (uppermost soil horizon used to classify a soil)”. Pocosins typically are located on broad, flat, interstream areas or near estuaries where rising sea levels affect their hydrology and hinder their drainage. Although there may be “pocosin-like vegetation” within a Carolina bay, the features are structurally of different origins. Unlike Carolina bays, the origin of pocosins is generally more understood (Whitehead 1972, Whitehead 1981, Brinson 1991, Richardson and Gibbons 1993).

Brinson (1991) attributed pocosin formation and subsequent persistence to two factors: climate and topography. Climate, he attested, “determines the exchange of matter and thermal energy between pocosins and the atmosphere”. The bulk of this exhange is in the form of precipitation, much of which is lost to evapotranspiration following its input. Brinson (1991) added “while the muted topographic relief of the Atlantic Coastal Plain is probably the main contributor to pocosin formation, the feedback between climate and topography is likely essential”. In summary, pocosins have formed in landscape positions with low topgraphic relief where the regional climate and lack of surficial hydrologic connections with adjacent wetland systems interact to form ombrotrophic conditions. Here, organic matter in the form of dead terrestrial vegetation is deposited onto wetland soils and accumlates at a slow, consistent rate through geologic time, resulting in the formation of pocosins.

Historically, the Atlantic and Gulf Coastal Plains supported a heterogeneous landscape of longleaf pine savannas, xeric sandhills, upland mixed-pine hardwoods, pocosins, Carolina bays, bottomland hardwood forests, natural lakes, and black and brown-water river systems (Garren 1943, Christensen 1999). However, it is now a highly fragmented and fire-suppressed region dominated by agriculture, residential developments, and large cities with few large intact parcels of natural ecosystems remaining. Demotechnic growth (Wetzel 2001, Dudgeon et al. 2006), global warming (Smith and Tirpak 1989), increasing agricultural production (Tilman et al. 2002), fire supression (Nowacki and Abrams 2008, Palmquist et al. 2014), urbanization (Terando et al. 2014), shoreline development (Radomski and Goeman 2001, Ford and Flaspohler 2010, Frost and Hicks 2012), and introduction of invasive species (Pimentel et al. 2005) continue to threaten and encroach upon the few “natural”, intact, terrestrial and freshwater ecosystems remaining in the Southeast, including Carolina bays and bay lakes.

Carolina bays are valuable components of our national and state natural heritage (Nifong 1998). Their variable hydrology and size, presence of rare and endemic taxa, and isolated landscape position, make them valuable habitats for southeastern flora and fauna and provide important ecosystem services (Suppl. material 4). Unfortunately, Carolina bays and other palustrine wetland systems have suffered from extensive habitat loss and degradation during the past three centuries (Bennett and Nelson 1991, Mitsch and Gosselink 1993, North Carolina Division of Environmental Management 1996, Kirkman et al. 1996, Nifong 1998). Using 1988 aerial imagery, Nifong (1998) found 8,057 Carolina bays in the state of North Carolina. Of these 8,057 total bays, 6,331 (79%) had more than half of their natural vegetation removed.

Sharitz and Gibbons (1982) and Nifong (1998) suggested several ways to better preserve and manage Carolina bays in the future. For an excellent review on the copious amount of Carolina bay literature available, see Ross (2000), Ross (2003); and for detail specifically about bays in the Carolinas, see Nifong (1998).

Carolina Bay Lakes

Several Carolina bays in southeastern North Carolina contain large (i.e., > 50 hectares) natural lakes within their elliptic boundaries (Frey 1949), thereby giving them the name Carolina bay lakes. Each lake is located in the southernmost portion of the elliptical feature known as a Carolina bay (Fig. 2). The northern portions of the bays (i.e., the portions not inundated by lake waters) contain organic, peaty soils and a unique vegetative assemblage comprised of bay trees (Gordonia lasianthus, Magnolia virginiana, Persea palustris), ericaceous shrubs (e.g., Chamaedaphne calyculata (L.) Moench, Eubotrys racemosa (L.) Nutt., Kalmia L., Lyonia Nutt., Rhododendron L., Vaccinium L., Zenobia pulverulenta (W. Bartram ex Willd.) Pollard), and several other species well-associated with nutrient-poor soils (e.g., Chamaecyparis thyoides (L.) Britton, Sterns & Poggenb., Nyssa biflora Walter, Pinus serotina, and Smilax laurifolia L.).

Figure 2.  

Position of Carolina bay lakes within Carolina bays. Carolina bay lakes are located in the southeasternmost portions of Carolina bays. The northern portions of the bays (i.e., the portion not inundated by lake waters) support shrub-bog plants over organic soils. Here, Salters (top left) and Jones (middle right) Lakes exemplify the typical bay lake position within Carolina bays. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Nine Carolina bay lakes (i.e., Bakers Lake, Bay Tree Lake, Horseshoe Lake, Jones Lake, Lake Waccamaw, Little Singletary Lake, Salters Lake, Singletary Lake and White Lake) are known to exist within the known distribution of Carolina bays. All nine lakes occur in Bladen and Columbus counties, North Carolina (Frey 1949, LeBlond 1995, LeBlond and Grant 2005; Fig. 3). Carolina bay lakes, with the exception of Lake Waccamaw and White Lake, are nutrient poor because they receive the bulk of their hydrologic inputs in the form of precipitation. These lakes are also characteristically dystrophic due to the dominance of organic soils within their catchment area. Organic soils do not allow for the rapid decomposition of plant and animal matter, resulting in the high amount of humic substances found in the water column.

Figure 3.  

Geographic location of all nine Carolina bay lakes (green text boxes). Bladen County (light yellow) supports eight of the nine Carolina bay lakes known to exist; all eight lakes occur within the Cape Fear River Valley between the Cape Fear River and South River. Bay Tree Lake is the largest Carolina bay lake in Bladen County; the smallest is Bakers Lake. Lake Waccamaw is the largest Carolina bay and bay lake in North Carolina and is the only bay lake known to exist in Columbus County (tan). Baseline vector data obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map Produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Although some Carolina bays may contain shallow marshes or ponds (Bennett and Nelson 1991, Nifong 1998), these are not considered lakes. There is no universally accepted technical definition that distinguishes a lake from a pond (Heinonen et al. 2008); however, it seems reasonable to accept as distinguishing that lakes have a clearly defined littoral and profundal zone, a larger overall size (>8 hectares), a shoreline exposed to wave dynamics, greater water depth, a mixing of the water column by wind induced turbulence, and the ability to retain the bulk of their water volume even in years of drought (Cowardin et al. 1979, Moss et al. 1996, Williams et al. 2004, Biggs et al. 2005, Brönmark and Hansson 2005).

Carolina bays are considered to be geographically isolated wetlands with their primary water source coming directly from precipitation (Sharitz 2003, Tiner 2003). Although the vast majority of Carolina bays lack surface water connections to outside aquatic systems, Carolina bay lakes are an exception. Carolina bay lakes all contain drainage outlets--usually along their southern shorelines, but in the northwest for White Lake (Frey 1949)--that release excess water into the Cape Fear and Waccamaw River drainages during periods of high precipitation. However, during years of scarce rainfall, these lakes are more or less isolated from surrounding lotic systems and are confined to their basins (N. Howell, pers. obs.).

Lacustrine Zonation (derived from Wetzel 2001)

Lakes, including Carolina bay lakes, can be divided into distinct transitional zones, moving from the shoreline to the center of the lake (Fig. 4).

Figure 4.  

Lacustrine zonation. EPI = epilittoral zone, EU = eulittoral zone. Aerial imagery obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map Produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014). Illustration (top right) by Nathan Howell.

(1) Epilittoral zone: The zone that lies entirely above the lake surface and is not influenced by the spray of surf. This zone can be thought of as the terrestrial or upland zone; the highest water levels never reach it and it is not affected by lakeshore dynamics or hydrology.

(2) Supralittoral zone: The zone that lies entirely above the lake surface and is influenced by the spray of the surf.

(3) Eulittoral zone: The zone encompassing the entire region of the shoreline from the highest and lowest seasonal water levels. This zone experiences natural disturbances such as water level fluctuations and wave dynamics.

(4) Infralittoral zone: This zone is subdivided into three zones in relation to the occurrence and distribution of the major classes of aquatic macrophytes: upper infralittoral zone where emergent rooted macrophytes persist; middle infralittoral zone where floating-leaved rooted macrophytes occur; and lower infralittoral zone where submersed-rooted, adnate, or free-floating macrophytes occur. The eulittoral and infralittoral zones collectively constitute the littoral zone.

(5) Littoriprofundal zone: The zone occupied by photosynthetic algae and bacteria, often associated with the metalimnion (i.e., the stratum between the epilimnion and hypolimnion representing a marked thermal change; also synonymous with thermocline) of stratified lakes.

(6) Profundal zone: The zone that consists of the remainder of the vegetation free sediments.

The Littoral Zone

The littoral zone of lakes (i.e., the eulittoral and infralittoral zones) is an important transition zone between adjacent uplands and the deeper pelagic area of the lake. This zone contains vascular macrophytes (i.e., aquatic vascular plants large enough to see with the naked eye) that have evolved from their terrestrial ancestors to cope with the physical and physiological demands of persisting in an aquatic environment (Sculthorpe 1967, Wetzel 2001, Brönmark and Hansson 2005, Keddy 2010). The vascular macrophytes and coarse woody debris that exist in this zone provide critical habitat for zooplankton, photosynthetic and heterotrophic microflora, macroinvertebrates, herpetofauna, avifauna, fish, and mammals (Brusnyk and Gilbert 1983, Pieczynska 1990, North Carolina Division of Environmental Management 1996, Wetzel 2001, Keddy 2010, Ewert et al. 2011). The littoral zone is characterized by having high productivity, including some of the highest rates of organic matter synthesis in the biosphere (Wetzel 2001).

Aquatic Macrophytes (derived from Wetzel 2001)

Aquatic macrophytes may be divided into four classes. Moving from the shoreline out to deeper water, these classes are as follows [taxa vouchered or reported from Carolina bay lakes are indicated by ^c]:

(1) Emergent macrophytes: Species rooted in saturated and inundated soils with a water depth up to 1.5 meters; root systems remain in anoxic soil conditions while leaves and reproductive organs stay above the water surface. These plants are often rhizomatous, stoloniferous, or cormous with the potential to reproduce asexually. Heterophyllous (i.e., when a plant exhibits vegetative polymorphism, having morphologically different submersed and aerial organs) species may also be emergent. Examples of genera that may be grouped in this category include Carex L.^c, Cephalanthus L.^c, Cladium P. Browne^c, Juncus L.^c, Panicum L.^c, Pontederia L.^c, Rhynchospora Vahl^c, Scirpus L.^c, and Typha L.

(2) Floating-leaved macrophytes: Species rooted in the substratum with floating leaves attached to long flexible petioles or on short petioles attached to an ascending stem.

Submersed leaves precede the floating leaves in heterophyllous species. Reproductive organs remain atop or above the water surface. Examples of genera grouped into this category include Brasenia Schreb.^c, Nelumbo Adans.^c, Nuphar Sm.^c, Nymphaea L.^c, Nymphoides Ség.^c, and Potamogeton L^c.

(3) Submersed macrophytes: Species that remain completely submersed in the water column, but are rooted to the substratum. Leaf morphology is highly variable in this group, from finely dissected to very broad, and reproductive organs may be emersed, floating, or submersed. Examples of genera included in this group are Ceratophyllum L., Isoetes L., and Myriophyllum L^c.

(4) Freely floating macrophytes: Species that remain unattached to the substratum and are completely dependent upon the nutrients in the water column for survival. Reproductive organs may be floating or aerial. Examples of genera include Azolla Lam., Eichhornia Kunth, Hydrocharis L., Limnobium Rich., Trapa L., and Utricularia L^c.

Factors affecting Aquatic Macrophyte Richness in Lakes

Lacoul and Freedman (2006) provided a thorough review on how various environmental influences affect aquatic plants in freshwater systems. A few of these environmental factors are reviewed below.

Latitude

It is well known that generally the number of species occuring at the equator greatly exceeds that of the temperate and northern latitudes (Edmonds 1997). Although this general rule applies across most groups of taxa, it does not seem to apply to aquatic plants. Crow (1993) found that aquatic plants are more diverse in temperate rather than tropical latitudes. When comparing temperate wetland floras to those of tropical climes, this pattern is reinforced (Stuckey 1975, Henry and Scott 1984, Peet and Allard 1993, Ruch et al. 2009). Because Carolina bay lakes differ little in latitude, this factor does not significantly affect species richness in these systems.

pH and Alkalinity

Peat-based Carolina bays are known to have acidic (< 7 pH), nutrient poor, organic soils (Daniels et al. 1984, Leab 1990, Newman and Schalles 1990). In many respects, these isolated wetlands of the Southeast are quite similar to the peatlands of the northern United States and Canada. Floristic diversity in peatlands has been shown to increase with increased levels of calcium and alkalinity in the groundwater (Glaser et al. 1990, Vitt and Chee 1990). Similarly, aquatic macrophyte richness of lakes tends to be lower in unproductive lakes with low pH (e.g., Carolina bay lakes) and higher in more productive lakes with higher alkalinities (Roelofs 1983, Roberts et al. 1985, Rørslett 1991, Dodson et al. 2000, Vestergaard and Sand-Jensen 2000, Søndergaard et al. 2005).

Water Color

Waters with increased levels of humic substances are typically, dystrophic, acidic, and tea-stained. Tea-stained waters are not as transparent as lakes with low humic substances, thus humic lakes have a shallow euphotic zone and a narrow littoral zone, reducing the abundance and depth at which aquatic macrophytes may grow (Spence 1982). Vestergaard and Sand-Jensen (2000) also saw decreased richness in aquatic macrophytes when water transparency was low. An excellent example of how increased humic substances affect water transparency and macrophyte richness and composition can be seen when comparing White Lake to the other Carolina bay lakes. White Lake is an oligotrophic lake with transparent water due to the presence of natural springs on the lake floor. Secchi depths commonly reach to the bottom of the lake (3m/10 ft) and submerged aquatic macrophytes are able to colonize the deepest portions of the lake with ease (i.e., the euphotic zone is deep compared to the other bay lakes).

Hydrography

Frey (1949) documented the morphometry and hydrography of the Carolina bay lakes and determined that the southern portions of the lakes possessed a gentle, tapering hydrography while the northern portions possessed a steep hydrography. Floristic inventories by the first author confirm that aquatic macrophyte richness is higher along southern shorelines; so much so, that the surveying of northern shorelines was abandoned early in the life of the project. A broad sandy terrace occurring along the southern shore of Lake Waccamaw (Fig. 5) creates a wide littoral zone compared to other Carolina bay lakes. This stretch of shoreline, with its gentle hydrography, is known to support over 140 species of wetland plants, while the Bladen lakes, with their comparatively steeper hydrography, are known to support < 55 wetland plant taxa (see floristic summary).

Figure 5.  

Broad, shallow, sandy terrace along Lake Waccamaw’s southern shoreline. The gentle relief of this terrace creates a wide littoral zone. Wide littoral zones are more floristically diverse and contain more available area for the establishment of aquatic macrophytes. Alternatively, narrow littoral zones do not have much area for the establishment of aquatic macrophytes and are species-poor. Aerial imagery obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Lake Size

As a general rule, species richness usually increases with increasing area (Arrhenius 1921, Williams 1964, Connor and McCoy 1979, Rosenzweig and M.L. 1995, Søndergaard et al. 2005). Findlay and Houlahan (1997) found that species richness increased with area sampled for birds, mammals, hepertofauna, and plants in southeastern Ontario wetlands. Results from this work also support these findings with Bakers Lake (i.e., the smallest bay lake) supporting the least diverse littoral zone flora and Lake Waccamaw (i.e., the largest bay lake) supporting the most species-rich littoral zone flora. Other large natural lakes of North Carolina Coastal Plain (e.g., Lake Phelps, Lake Mattamuskeet, Lake Waccamaw) are known to support diverse shoreline floras, more so than the smaller lakes of the region (Lynch and Peacock 1982, Schafale 2012; N. Howell, pers. obs.).

Water Level Variation, Disturbance, and Soil Fertility

Keddy and Fraser (2000) summarized factors that govern littoral zone diversity irrespective of geographic location or size. Three environmental factors (i.e., water levels, soil fertility, and disturbance) govern the composition and floral diversity of littoral zones. Shorelines exposed to intermediate levels of natural disturbances will support a richer flora than those experiencing little to no disturbances and those experiencing extremely harsh disturbances. Natural disturbances may include wave action, ice scour, water level fluctuations, fire, or grazing. If water level fluctuations were absent from a lake or similar waterbody (e.g., in a permanently impounded pond), a two-staged littoral zone would result, with aquatic macrophytes in the aquatic zone and shrubs and trees in the terrestrial zone. Under long-term water level fluctuations, a multi-staged littoral zone would result, leading to increased heterogeneity and a richer flora. Keddy and Fraser (2000) attested that “simply changing water levels from one year to the next doubles the number of vegetation types”. Rørslett (1991) observed that northern European lakes experiencing water level fluctuations of 1–2 meters per year showed greater macrophyte richness than sites experiencing little or intense disturbances. Carolina bay lakes historically would have experienced long-term water level fluctuations, but the installation of water control structures (i.e., dams) in some of the lakes outlet channels has resulted in more stabilized systems (N. Howell, pers. obs.).

Shorelines exposed to frequent disturbances typically have silt and clay stripped from them; and consequently, contain few nutrients. Sheltered shorelines receive clay and silt deposits and therefore contain a higher nutrient content. Foreshores will have a distinct vegetative community characterized as having low biomass and rare species, while backshores (bays or backwater areas sheltered from disturbance) will support a higher biomass community composed of a few clonal dominants (Keddy 2010). Macrophyte richness is always higher in areas of intermediate disturbance. Eutrophification of littoral zones causes increased soil fertility, which increases biomass and negatively impacts macrophyte richness and rare plant taxa.

Bakers Lake

Bakers Lake (30.35 hectares; 75 acres) is a small, privately owned, Carolina bay lake, located in northwestern Bladen County between Little Singletary Lake and the Cape Fear River north of Thoroughfare Bay, ca. 1.5−2 miles east of the intersection of SR 1318 (Old River Road) and SR 1320 (Middle Road; LeBlond and Grant 2005; Fig. 6). This site is located along the northwest boundary of the Bladen Lakes Macrosite, a large tract of undeveloped and relatively unfragmented land between the Cape Fear, South, and Black River systems (LeBlond and Grant 2005; Figs 7, 8). The macrosite extends from southern Cumberland County, through Bladen County, and into southwestern Pender County. This large area is given the name “macrosite” because it contains numerous “standard sites” (i.e., smaller tracts of land with high ecological integrity) that are strongly geographically associated with one another. The majority of the macrosite is located in Bladen County and contains the largest concentration of unaltered, intact, Carolina bays.

Figure 6.  

Bakers Lake and surrounding lands. Bakers Lake is located in northern Bladen County and is surrounded by a mix of agriculture and forestland. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Figure 7.  

Bladen Lakes Macrosite (vector). The Bladen Lakes Macrosite (hatched pattern) is a large area encompassing parts of southern Cumberland County, eastern Bladen County, and northwest Pender County. Historically, macrosites were established by the North Carolina Natural Heritage Program (NCNHP) in efforts to identify large, intact, natural areas that withheld numerous other smaller natural areas within their boundaries. The NCNHP no longer uses macrosites as viable natural area boundaries, but it is useful to show the extent of the Bladen Lakes Macrosite boundary. When moving from north to south, the lands are as follows: Bushy Lake State Natural Area (teal green), Suggs Mill Pond Gameland (light mint green), Bladen Lakes State Forest (forest green), Jones Lake State Park (pink), Bay Tree Lake State Park (orange), and Singletary Lake State Park (yellow). Lake Waccamaw State Park (neon green) can be seen farther south along with Friar and Brown Marsh Swamps in Columbus County. Baseline vector data obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Figure 8.  

Bladen Lakes Macrosite (ortho). The North Carolina Natural Heritage Program no longer uses macrosites as viable natural area boundaries, but here it is useful to show the extent of the Bladen Lakes Macrosite boundary. Note the large areas of fragmented land surrounding the macrosite and the relatively unfragmented land within the boundaries of the macrosite. This large tract of land contains one of the largest remaining portions of intact unaltered Carolina bay complexes known to exist. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Dr. Clemuel Johnson and wife Nancy Johnson, of Elizabethtown, have owned Bakers Lake and surrounding lands (451.40 hectares; 1,155.45 acres) since 1980. Prior to the Johnson’s ownership, Agnes Holden Williams owned the lake and surrounding lands. Ms. Williams’ father acquired the land from an unknown seller during the early 20^th century. This seller was able to successfully purchase the lake before 1929, when North Carolina legislation mandated that all lakes greater than 50 acres in size be made property of the state.

Bakers Lake forms the headwaters of Phillips Creek, which drains southward into the Cape Fear River. Bakers Lake Natural Area (i.e., Bakers Lake bay and immediate surrounding lands) is known to support five natural community types (i.e., Pond Pine Woodland – Typic Subtype (S3,G3), Peatland Atlantic White Cedar Forest (S1,G2), Low Pocosin – Gallberry/Fetterbush Subtype (S2,G2), Sand Barren – Typic Subtype (S2,G2), and Natural Lake Shoreline – Cypress Subtype (S2,G3; LeBlond and Grant 2005). Bakers Lake has been known to support heron rookeries and small populations of the state rare Anhinga (Anhinga anhinga [W2; S3B, G5]; LeGrand et al. 2014) during the spring and summer months (S. Clark, pers. comm.; N. Howell, pers. obs.). In addition, the site provides important stopover habitat for large flocks of migrating waterfowl (e.g., Aix sponsa [Wood Duck], Anas americana [American Widgeon], Anas clypeata [Northern Shoveler], Anas crecca [Green-winged Teal], Anas discors [Blue-winged Teal], Anas platyrhynchos [Mallard], Anas strepera [Gadwall], Aythya collaris [Ring-necked Duck], Aythya valisineria [Canvasback], Branta canadensis [Canada Goose], Bucephela albeola [Bufflehead], Lyphodytes cucullatus [Hooded Merganser], Oxyura jamaicensis [Ruddy Duck; G. German and S. Clark, pers. comm; N. Howell pers. obs.).

Anthropogenic disturbances (i.e., silvicultural practices, dam installation in the outflow channel, agricultural fields, confined animal feeding operations (CAFOs), fire supression, and rural residential development) have either been documented on site or on adjacent properties (LeBlond and Grant 2005; S. Clark, pers. comm.). These disturbances have lowered the integrity of several of the aforementioned natural community types within and adjacent to Bakers Lake Natural Area (N. Howell, pers. obs.), but restoration potential is still relatively high. The installation of a flashboard riser system in the outflow channel has altered the natural hydrology of the lake and caused natural water level fluctuations to essentially cease. Following the installation of the dam, the lake consistently stays at a high level, thus narrowing the littoral zone and forcing aquatic macrophytes to occur at or just below the maximum annual high water mark (N. Howell, pers. obs.).

The water quality of Baker’s Lake has not been formally tested by state agencies, but appears high in humic substances (N. Howell, pers. obs.) and the chemistry is likely similar to that of the other Bladen lakes. The lake is here considered dystrophic and relatively unproductive.

Bay Tree Lake

Bay Tree Lake (formerly Black Lake; 588.81 hectares; 1,455 acres) is a large, state-owned Carolina bay lake, located in east-central Bladen County along NC Hwy 41 east of White Lake and west of NC Hwy 210. Bay Tree Lake is part of Bay Tree Lake State Park, a 1,006.85 hectare (2,488 acre) park that includes Bay Tree Lake bay and large parcels of land lying to the north and west of Bay Tree Lake (Fig. 9).

Figure 9.  

Bay Tree Lake State Park (highlighted in green) and surrounding lands. Lands surrounding Bay Tree Lake State Park to the south are privately owned and have been partially converted to agriculture. Black Creek Bay and several others in the vicinity have been cleared of their original vegetation and converted to agriculture (primarily blueberry farms in this area). Historically, Horsepen Bay was a peat-filled Carolina bay. During the development of the residential community seen along the northeast shoreline (Bay Tree Resorts), it was turned into a body of open water. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

The North Carolina General Assembly passed legislation in 1911 confirming the status of Bay Tree Lake as a state-owned public trust resource (North Carolina Division of Parks and Recreation, Planning and Development Section 2006b). Historically, Bay Tree Lake was not included within the original natural area site boundary determined by the North Carolina Natural Heritage Program (NCNHP) due to high levels of shoreline disturbance. Today, the lake is considered part of the natural area due to the presence of three rare dragonflies (Gomphus australis [Clearlake Clubtail], Gomphus cavillaris brimleyi [Brimley’s “Sandhill” Clubtail], and Progomphus bellei [Belle’s Sanddragon]) that utilize the lake throughout their life cycle.

In January 1965, a private land development group had the option to purchase 5,665.59 hectares (14,000 acres) of land surrounding Bay Tree Lake with the intent of creating an inland resort community (North Carolina Division of Parks and Recreation, Planning and Development Section 1996a). Later that year, a proposal was constructed and sent to the North Carolina Department of Conservation and Development concerning the drainage of Bay Tree Lake. The purpose for draining the lake was to improve the quality of the water and lake bottom for recreational purposes (e.g., swimming and boating). Permission to lower lake levels 4 feet was granted in 1965 and in January of 1966, the development group made a request to completely drain the lake where peat deposits and debris could be taken from the lake bottom (North Carolina Division of Parks and Recreation, Planning and Development Section 1996a).

The purpose of the drainage project was to release tannic, tea-colored, waters from the lake and divert all incoming tannic waters from a northerly adjacent swamp to below the outflow channel. Drainage of the lake was completed in the winter of 1966. The lake remained dry for 5 years while developers removed debris and peat deposits and imported large quantities of white sand, which would later be distributed around the entirety of the lakeshore. In 1970, the lakes outflow channel was plugged and the lake began to refill (North Carolina Division of Parks and Recreation, Planning and Development Section 1996a). After two years, the lake had nearly reached its original water levels. Shortly after residential lots went for sale, a breach of the lake rim occurred and tea-stained waters were allowed to re-enter the lake. The breach was plugged within 24 hours, but the lake had already returned to its original dystrophic condition (North Carolina Division of Parks and Recreation, Planning and Development Section 1996a). The lake has not been significantly altered since and remains in a dystrophic condition to this day.

Bay Tree Lake State Park contains five natural community types (Mesic Pine Savanna – Coastal Plain Subtype [S2,G2G3]; Sand Barren – Typic Subtype [S2,G2]; Small Depression Drawdown Meadow – Typic Subtype [S2S3,G2?]; Small Depression Pocosin – Blueberry Subtype [S2,G3?]; and Xeric Sandhill Scrub – Typic Subtype [S3S4,G3?]. A Natural Lake Shoreline community was not assigned to Bay Tree Lake by the NCNHP due to the shoreline’s disturbance history. The present authors agree with this determination and have chosen not to assign a natural lake shoreline community to this site. However, it is worth noting that the shoreline flora of Bay Tree Lake differs only slightly from the other Bladen Lakes.

Bay Tree Lake forms the headwaters of Lake Creek, a small blackwater creek that drains southeast to the South River (the boundary between Bladen and Sampson counties). Much of the land surounding Bay Tree Lake State Park has been cleared for agriculture (particularly blueberry farms) and has limited the landscape connectivity between it and other intact natural areas. Several bay complexes occur in the immediate vicinity of Bay Tree Lake including Beagle Bay, Black Creek Bay, Causeway Bay, Cooley Bay, Horsepen Bay (now an artificially created lake/pond), Floodgate Bay, Kelso Bay, and Spring Bay. A residential resort community is located along the north and east shorelines of the lake. The boundaries of this community have continued to extend around the east and southeast shorelines. Residential development, agricultural expansion, severe offroad vehicle use, and fire supression are the primary threats to biological diversity within and around Bay Tree Lake State Park (N. Howell pers. obs.). Available water quality parameters for Bay Tree Lake are provided in Table 1.

Horseshoe Lake

Horseshoe Lake (also known as Suggs Mill Pond; 109 hectares; ca. 270 acres) is an irregularly shaped Carolina bay lake located in northern Bladen County south of Bushy Lake State Natural Area, east of Little Singletary Lake, north of SR 1325 (Gum Springs Rd), and west of SR 1002 (Old Fayetteville Rd). Horseshoe Lake is one of two Carolina bay lakes within Suggs Mill Pond Game Land (4469.34 hectares; 11,044 acres; Fig. 10), the other being Little Singletary Lake. Suggs Mill Pond Game Land is owned by the State of North Carolina and the North Carolina Wildlife Resources Commission (NCWRC) and is located in northern Bladen County and southern Cumberland County. This game land is located in the northwestern portion of the Bladen Lakes Macrosite and contains one of the largest remaining examples of unaltered Carolina bay complexes.

Figure 10.  

Suggs Mill Pond Game Land (outlined in green) and surrounding lands. Lands north of the red dividing line occur in Cumberland County while lands south of the red line occur in Bladen County. Suggs Mill Pond Game Land contains two large bay lakes within its boundary. Little Singletary Lake is located along the western boundary of the property and Horseshoe Lake (aka Suggs Mill Pond) is located in the center of the property. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

The state first gained rights to the property in 1994 when a 62-acre (25 ha) parcel was donated to the NCWRC from Canal Woods Industries. Thereafter, much of the remaining property was purchased from Canal Woods. The fact that Horseshoe Lake and Little Singletary lake were not owned by the state of North Carolina until the mid-1990s suggests that these lakes were involved in a similar ownership situation as Bakers Lake (i.e., these lakes must have been privately owned prior to 1929 when legislation mandated that all lakes greater than 50 acres (20.2 ha) in size be released to the state of North Carolina). Suggs Mill Pond Game Land is one of four North Carolina game lands enrolled in the Cooperative Upland habitat Restoration and Enhancement program (CURE), where management for early successional habitat is the top priority (Allen et al. 2015). Traditionally, hunters and fishermen were primary users of Suggs Mill Pond Game Land, but an increasing number of non-traditional users (i.e., birders, canoers, hikers, photographers, and researchers) visit the site regularly.

The largest bay on site contains a horsehoe-shaped artificial impoundment (Horseshoe Lake). Horseshoe Lake forms the headwaters of Ellis Creek, which drains southwest to the Cape Fear River. Although an old milldam currently maintains Horseshoe Lake, it is thought that a smaller body of open water may have been present prior to the dam’s installation in the late 19^th or early 20^th centuries. Horseshoe Lake was formed subsequent to the dam installation, as water levels began to rise into the peat-filled Carolina bay. Today, it is best described as a semi-permanent impoundment; however, the presence of floating bogs within the lake makes it unique from other semi-permanent impoundments in North Carolina. Parts of the lake support patches of the rare floating bog community (the largest extent known from the state), which is dominated by sedges, orchids, carnivorous plants, and ericaceous shrubs. Other portions comprise the Coastal Plain Semipermanent Impoundment community, which is characterized by open water, dominated by floating-leaved macrophytes, and a sparse overstory of Taxodium ascendens Brongn.

The floating bog community type is quite unique. Manifestations of this community type occur just above the water surface and range in size from ca. 10 × 10 m to a few hectares in size (N. Howell, pers. obs.). Some bogs may contain well-developed herbaceous vegetation in addition to small (e.g., < 3 m tall) trees of Chamaecyparis thyoides, Nyssa biflora, and Taxodium ascendens, while others contain a strictly herbaceous component. Exposed portions of peat can be seen around the peripheries of some bogs; here, Drosera intermedia Hayne, Eleocharis baldwinii (Torr.) Chapm. /E. vivipara Link, Pogonia ophioglossoides (L.) Ker Gawl, Utricularia striata Leconte ex Torr., Utricularia purpurea Walter, and other small-statured herbaceous plants can be seen colonizing the apparently young peat formations. Isolated floating bogs (i.e., bogs surrounded by open water and separated from adjacent bogs and upland habitats) of varying size show a consistent zonation pattern. Small statured herbaceous taxa colonize the outer periphery and are slowly replaced by larger herbaceous taxa (Andropogon glaucopsis, Dulichium arundinaceum (L.) Britton, Hypericum virginicum L., Rhexia nashii Small, Rhynchospora alba (L.) Vahl, Rhynchospora inundata (Oakes) Fernald, Xyris fimbriata Elliott, and Xyris smalliana Nash) and woody species (Acer rubrum L., Chamaecyparis thyiodes, Decodon verticillatus (L.) Elliott, Nyssa biflora, and Taxodium ascendens) when moving toward the center. Thus, a dome-shaped appearance is typically seen.

Few examples of floating bogs or mats of vegetation are known to science. The floating peat mats of New Hampshire are most similar to those of Horseshoe Lake. These peat mats possess the same general structure and abiotic conditions as those of Horseshoe Lake and are known to contain several overlapping taxa, inculding Drosera intermedia, Dulichium arundinaceum, Eleocharis R. Br. spp., Hypericum virginicum, Nymphaea odorata W.T. Aiton, Rhynchospora alba, and Utricularia spp. (New Hampshire Division of Forests and Lands 2015).

A separate but similar case of floating vegetation mats, forming as a result of dam installation, has been observed at Goose Creek Reservoir in South Carolina (Hunt 1943). In 1933, a dam was installed on Goose Creek, ca. 12 miles north of Charleston, subsequently flooding historic rice plantations that had reverted to brackish marsh vegetation. Hunt (1943) described the zonation (looking across to the center of the mat from the outer periphery) of a typical floating mat as follows: (1) pioneer zone (i.e., the outer margins of the mats): Alternanthera philoxeroides (Mart.) Griseb., Bidens laevis (L.) Britton, Sterns & Poggenb., Boehmeria cylindrica (L.) Sw., Habenaria repens, Hydrocotyle ranunculoides L.f., Persicaria glabra (Willd.) M. Gómez, and Sacciolepis striata (L.) Nash, (2) the cat-tail/shrub zone: Kosteletzkya pentacarpos (L.) Ledeb., Typha latifolia L., and Salix nigra Marshall, and (3) the main body: Acer rubrum, Apios americana Medik., Decodon verticillatus, Mikania scandens (L.) Willd., Panicum virgatum L. var. virgatum, Persea palustris, Rubus L. spp., and Taxodium distichum (L.) Rich.

The floating “sudd” vegetation of the upper Nile River is also somewhat similar, forming large floating mats of marsh vegetation both along the margins and within the river. Denny (1984) gave a general description of the sudd vegetation as seen only from a boat. Several taxa commonly observed along the margins of the Sudd included: Ceratophyllum demersum L., Cyperus papyrus L., Eichhornia crassipes (Mart.) Solms, Phragmites karka (Retz.) Trin. ex Steud., Typha domingensis Pers., Vossia cuspidata (Roxb.) Griff. A complete checklist of the vascular plants collected from this vegetative study can be found in the attached appendix of Denny (1984).

Eleven natural community types exist within Suggs Mill Pond Game Land, but the low and high pocosin communities are dominant, comprising 48% (2,119.74 hectares; 5,238 acres) of the site (Allen et al. 2015). Lakes and impoundments make up 8.6% (381.21 hectares; 942 acres) of the total acreage of the game land. Fair to high quality landscape connections exist between Suggs Mill Pond Game Land and adjacent natural areas within the Bladen Lakes Macrosite (i.e., Bushy Lake State Natural Area, Charlie Long Mill Pond/Big Colly Bay Natural Area, Jessups Pond, Mill Pond Bay Natural Area, and White Pond Bay Natural Area; LeBlond and Grant 2005). These connections to other large natural areas provide relatively uninterrupted habitat for the movement of plants and animals. Records of Horseshoe Lake’s water quality are lacking, but the lakes water appears high in humic substances and the chemistry is more than likely similar to the other Bladen Lakes. The lake is dystrophic and probably exhibits a pH of < 5.

Jones Lake

Jones Lake (91.05 hectares; 225 acres) is one of two dystrophic Carolina bay lakes located within Jones Lake State Park (893.54 hectares; 2,208 acres; Fig. 11), the other being Salters Lake. This lake is located in central Bladen County four miles north of Elizabethtown west of NC Hwy 242 and east of NC Hwy 53. Jones Lake State Parkforms the headwaters of an unnamed tributary of Turnbull Creek, which drains into the Cape Fear River. The state park sits on a sandy terrace (of Upper Pleistocene age) of the Cape Fear River (Soller 1988). Jones Lake was originally referred to as Woodward’s Lake, after Samuel Woodward, justice of the peace for the area in 1734 (North Carolina Division of Parks and Recreation, Planning and Development Section 2006b). It is believed that the lake later received its current name from Isaac Jones, an adjacent landowner to Samuel Wooodward, on whose land Elizabethtown was later established in 1773. Jones Lake State Park was established in 1939 and became the first state park specifically devoted to African Americans (North Carolina Department of Conservation and Development 1940).

Figure 11.  

Jones Lake State Park (outlined in green) and surrounding lands. Jones Lake State Park is located between state highways 53 and 242, north of the Cape Fear River. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

LeBlond and Grant (2005) described both Jones and Salters Lakes as “among the very best examples of Carolina bay lakes in nearly pristine condition”. Jones Lake State Park is connected by fair to high quality landscape connections to Bethel Flatwoods, Cotton Bay Sand Ridge, Tatum Mill Pond/Cypress Bay, and Turnbull Creek Swamp natural areas.

Eleven natural community types have been described from Jones Lake State Park (i.e., Bay Forest, Coastal Plain Small Stream Swamp, High Pocosin, Low Pocosin, Natural Lake Shoreline, Peatland Atlantic White Cedar Forest, Pine/Scrub Oak Sandhill Mixed Oak Variant, Pond Pine Woodland, Wet Pine Flatwoods Wet Spodosol Variant, Xeric Sandhill Scrub Coastal Plain Variant, Xeric Sandhill Scrub Sandbarren Variant; LeBlond and Grant 2005, Schafale 2012), several of which are of extremely high quality and globally rare, such as the Low Pocosin, Peatland Atlantic White Cedar Forest, and Xeric Sandhill Scrub (LeBlond and Grant 2005, Schafale 2012). Available water quality parameters for Jones Lake are provided in Table 2.

Lake Waccamaw

Lake Waccamaw is located south of the township of Lake Waccamaw, between Friar Swamp to the northeast, and the Waccamaw River to the south. It is the only Carolina bay lake located in Columbus County and is the largest Carolina bay and bay lake (3,617.48 hectares; 8,939 acres) in North Carolina (LeBlond 1995). Lake Waccamaw is the third largest lake in North Carolina behind Lake Mattamuskeet and Lake Phelps. The lake is part of Lake Waccamaw State Park (4,327.70 hectares; 10,694 acres; Fig. 12), which also includes lands directly abutting the lake’s southern shoreline. Stager and Cahoon (1987) estimated Lake Waccamaw to be ca. 15,000 years old or less.

Figure 12.  

Lake Waccamaw State Park (outlined in green) and surrounding lands. Lake Waccamaw State Park is a large state park encompassing Lake Waccamaw and adjacent swampland and uplands. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Prior to European civilization in the Southeast, the Waccamaw-Sioux Native American peoples, one of five Native American tribes known to inhabit the Cape Fear Region, inhabited the lands surrounding the lake (North Carolina Division of Parks and Recreation, Planning and Development Section 2006a). Native American artifacts, including dugout canoes, dating back to 1015−315 B.P. have been found within and around Lake Waccamaw. In the early 18^th century, an unknown young man traveled through Columbus County on his way from north Georgia and, upon seeing Lake Waccamaw, described it as “the most pleasantest place that ever I saw in my life. It is at least eighteen miles round, surrounded with exceeding good land, as oak of all sorts, hickory and fine cypress swamps” (Gentleman 1737).

This bay lake differs from the Bladen lakes in its larger size, neutral pH, mesotrophic status, and presence of alluvial hydrologic inputs (Big Creek). Tea-stained waters from Friar Swamp are delivered into northeast Lake Waccamaw via Big Creek, the largest of several creeks draining into the lake from Friar Swamp. Lake Waccamaw forms the headwaters of the Waccamaw River, a species-rich river system known to support several rare plant (e.g., Fimbristylis perpusilla R.M. Harper ex Small & Britton, Ilex amelanchier M.A. Curtis ex Chapm., Lipocarpha micrantha (Vahl) G.C. Tucker, Oldenlandia boscii (DC.) Chapm., Rhynchospora decurrens Chapm., and Sabatia kennedyana Fernald) and animal taxa (Alligator mississipiensis [American Alligator], Elliptio folliculata [Pod Lance], Etheostoma perlongum [Waccamaw Darter], Lampsilis ochracea [Tidewater Mucket], Menidia extensa [Waccamaw Silverside], Noturus spp. 2 [Broadtail Madtom], and Procambarus leptodactylus [Pee Dee Lotic Crayfish; LeBlond 1995]).

Much of the land surrounding Lake Waccamaw has been converted to agriculture (north of the lake) and loblolly pine plantations (south of the lake). A small portion of Lake Waccamaw’s bay is still present on the northern end.

The Coastal Plain Marl Outcrop occurs along a roughly 394 m (1,000 ft.) stretch of northern shoreline and is characterized by having vertical and overhanging low cliffs in the supralittoral zone of the lake. Portions of these cliffs are submerged in the upper eulittoral zone, but local residents privately own terrestrial portions. This marl community is known for supporting the only naturally occuring population of Venus hair fern (Adiantum capillus-veneris L.) in the state.

Shoreline residential development extends along the northern shores of the lake from the lake outlet (southwest corner of lake) to just south of Big Creek. These shorelines support the globally rare Natural Lake Shoreline Marsh (Lake Waccamaw Pondlily Subtype) community. Undeveloped shorelines (i.e., Natural Lake Shoreline Swamp – Lake Waccamaw Subtype) occur from just south of Big Creek to the lake’s outlet. Historically, Lake Waccamaw experienced wide-ranging water level fluctuations determined by precipitation. In 1925, a poorly constructed dam was built at the lakes outlet in an effort to stabilize lake levels for increased recreational use. Before construction began, lake levels were so low that vehicles could be driven to the construction site on the dried lake bed (North Carolina Division of Parks and Recreation, Planning and Development Section 2006a).

The physical and hydrographic nature of Lake Waccamaw’s shoreline also differs from the other bay lakes. Lake Waccamaw’s shoreline is sandy around its entire periphery (Frey 1949), whereas the Bladen lakes may be either sandy or peaty along their shorelines.

A broad, sandy, terrace (lacking in Bladen lakes) is also present along the southeast shoreline of Lake Waccamaw (Fig. 5). This shallow underwater terrace extends perpendicularly out into the lake as far as 305 m (1,000 ft.; Frey 1949). The gentle relief of the terrace gradually extends shoreward resulting in a shallow, broad, littoral zone. This littoral zone is the most floristically rich of all Carolina bay lakes and is rivaled only by Lake Phelps in Washington County, North Carolina (N. Howell, pers. obs.). Varying water depths in the littoral zone of Lake Waccamaw result in the temporary and sometimes permanent presence of offshore sandbars and islands. This hydrographical heterogeneity in the littoral zone increases the floristic richness. A more detailed review of the lakes shoreline flora is provided in the floristic summary section and in Suppl. material 6.

The buffering effect of subsurface and surficial limestone on the naturally acidic waters of Lake Waccamaw result in an unusually diverse fauna. Lake Waccamaw contains the largest number of endemic animal species (i.e., endemic to this lake and nowhere else in the world; 10 taxa) of any site in North Carolina (Hubbs and Raney 1946, LeBlond 1995). An additional species, Fundulus waccamawensis (Waccamaw Killfish), is found only in waters within and adjacent to Lake Waccamaw and Lake Phelps (Washington County, North Carolina). Six other faunal taxa known to be rare but not endemic also occur within or adjacent to the lake. Available water quality parameters for Lake Waccamaw are provided in Table 3.

Little Singletary Lake

Little Singletary Lake (626 acres; 253.33 hectares) is located in the western half of Suggs Mill Pond Game Land (Fig. 10). Unlike Horseshoe Lake, Little Singletary Lake is natural in origin and exhibits a more “typical” bay lake physiognomy. Little Singletary Lake forms the headwaters of Lake Run, a tributary of Ellis Creek, which drains into the Cape Fear River. Relatively intact landscape connections exist to the northeast (Horseshoe Lake), southeast (Marshy Bay Natural Area), and southwest (Cedar Swamp Seep Natural Area) from Little Singletary Lake.

Lands abutting the southern shoreline are privately owned and were once subject to residential development. Remnants of bulkheads and recreational piers can still be seen today along the southeast shoreline. The North Carolina Wildlife Resources Commission gained property rights to all remaining lands surrounding Little Singletary Lake before residential development could ensue. On June 20, 2011, a lightning caused wildfire (Simmons Road Fire) started just west of Little Singletary Lake and by August 18^th, had burned over 2,023 hectares (5,000 acres) of Carolina bay and pocosin habitat, much of which surrounded Little Singletary Lake. During growing seasons of extreme drought, water levels have been known to recede low enough to reveal a clean sandy lake bottom 90−275 m (100−300 yds) out into the lake (G. Lewis, pers. comm.). Native American projectile points have been found on this lake bottom during drought years (G. Lewis, pers. comm.).

The water quality of Little Singletary Lake has not been documented by state agencies. The water appears high in humic substances and is likely similar to the other Bladen lakes (i.e., dystrophic, acidic, shallow, nutrient poor).

Salters Lake

Salters Lake (127.47 hectares; 315 acres) is the larger of the two Carolina bay lakes located in Jones Lake State Park (Fig. 11). Salters Lake was named after Sallie Salter, a revolutionary war hero who spied on the Tories while encamped at Elizabethtown. Her spying played a role in the defeat over the Tories on August 28, 1771, at the battle of Elizabethtown, where 70 Whigs defeated 400 Tories (JNorth Carolina Division of Parks and Recreation, Planning and Development Section 2006b).

Salters Lake is similar to Jones Lake in many respects, but quite possibly could be the most “pristine” of all Carolina bay lakes. Salters Lake has no shoreline development, appreciable recreational activities (e.g., outboard motor use), immediate surrounding agricultural (crop or animal production) land use, water level control structures, or historical manipulation of any kind. Natural communities and landscape features for Salters Lake are the same as those for Jones Lake (above). Available water quality parameters for Salters Lake are provided in Table 4.

Singletary Lake

Singletary Lake (233.09 hectares; 576 acres) is located within Singletary Lake State Park (494.12 hectares; 1,221 acres; Fig. 13). This lake was named after Richard Singletary, who received the grant of land in 1729 (North Carolina Division of Parks and Recreation, Planning and Development Section 1996b). Singletary Lake State Park is located just southeast of White Lake in central-southeast Bladen County between the Cape Fear River and Colly Swamp. Singletary Lake forms the headwaters of Lake Drain Creek, which drains into Big Colly Creek, which drains to the Black River, which drains into the Cape Fear River.

Figure 13.  

Singletary Lake State Park (outlined in green) and surrounding lands. Singletary Lake State Park is primarily comprised of lands immediately surrounding Singletary Lake. In addition to the lands surrounding Singletary Lake, White Lake is also managed by Singletary Lake State Park. Singletary Lake State Park is located north of the Cape Fear River and State Hwy 53 and southeast of White Lake. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

Singletary Lake is similar to the other Bladen lakes in that it is dystrophic, acidic, and nutrient poor. It contains high quality examples of the Natural Lake Shoreline Swamp (Cypress Subtype) and Natural Lake Shoreline Marsh (Typic Subtype) communities. LeBlond and Grant (2005) described this lake’s shoreline community as “one of the most aesthetically pleasing natural communities in the North Carolina Coastal Plain”. A direct landscape connection exists between Singletary Lake and Colly Swamp and the Black River to the northeast. Fair quality landscape connections exist between the state park and the Cape Fear River to the southwest. Available water quality parameters for Singletary Lake are provided in Table 5.

White Lake

Although not included in the sampling aspect of this study, White Lake is unique and deserves a brief summary. White Lake (432.20 hectares; 1,068 acres) is a large Carolina bay lake located in east-central Bladen County about 6 miles east of Elizabethtown, just east of the intersection of NC Hwy 53 and U.S. Hwy 701 (Fig. 14). White Lake is owned by the state of North Carolina, and is managed by Singletary Lake State park. Unlike all of the remaining bay lakes, White lake’s water is clear and not tea-stained. This feature has made it an incredibly attractive location for development and vacationers. This lake is primarily used for recreation (e.g., water sports, swimming, fishing) and essentially all of its shoreline is residentially and commercially developed.

Figure 14.  

White Lake and surrounding lands. Like the majority of Carolina bay lakes, White Lake is a state-owned lake. All but a very small portion of White Lake’s shoreline has been altered. Aerial imagery, transportation, and hydrography layers obtained from NRCS Geospatial Data Gateway: https://gdg.sc.egov.usda.gov. Map produced by Nathan Howell using ArcGis Desktop: Version 10.2.2. (Environmental Systems Research Institute (ESRI) 2014).

White Lake’s remarkable water clarity is attributed to the presence of artesian springs on the lake bottom (Wells and Boyce 1953). The clarity of the lake’s water yields a deep euphotic zone (i.e., sunlight can penetrate through the entirety of the water column) with submerged aquatic macrophytes (e.g., Myriophyllum humile (Raf.) Morong; N. Howell pers. obs.) present at the lakes deepest depths. White Lake receives its hydrologic inputs principally in two forms, precipitation and groundwater (through springs). Although this lake is primarily fed by springs, its overall water levels are determined by the regional water table (i.e., during drought years, White Lake’s water levels will drop just like all other bay lakes). Another unique feature of White Lake is the location of its outlet channel. White Lake’s outlet channel is located in the northwestern section of the lake as opposed to the southeastern section where it occurs in all other bay lakes. Frey (1954) reported that William Bartram, a renowned naturalist who documented the flora, fauna, and Native American culture of the southeastern United States in the 18^th century, operated a sawmill on White Lake during the 20 years following 1770. A map in Bartram and Harper (1942) shows that White Lake was formerly called Lake Bartram. Available water quality parameters for White Lake are provided in Table 6.

Bladen Lake Group (Bladen County, NC)

Climate data from the nearest weather station to the Bladen County bay lakes, ca. 1.6 kilometers away in Elizabethtown, North Carolina (Bladen County: 34.68° N, -78.58°W; 30.5 m elev.), show that during the thirty-year period between 1971-2000, the average annual temperature was 16.44 °C (61.6 °F) and mean annual precipitation 1,254.76 mm (49.4 in). Average daily maximum and minimum temperatures were 22.83 °C (73.1 °F) and 10.11 °C (50.2 °F; State Climate Office of North Carolina 2014; Fig. 15).

a

b

Figure 15.

Walter climate diagrams for weather stations closest to the Bladen Lakes (Bladen County, NC; a) and Lake Waccamaw (Columbus County, NC; b), based on data from the State Climate Office of North Carolina (2014). At the top left of each figure, the town closest to the weather station is listed as well as the elevation of the weather station in meters and the number of years climate data were recorded (30). At the top right of each figure, the mean annual temperature and precipitation over thirty years for each site is listed. Climate data for these figures were recorded from 1971 to 2000. Solid black areas in the diagrams represent “excess rainfall”. When the precipitation curve rises above 100 mm, there is an excess amount of precipitation present that plants do not need in order to survive. Areas marked with vertical lines between the temperature curve and the 100 mm precipitation mark on the secondary y-axis represent a “wet period”. These diagrams show that plants in these two locations are not water-stressed (i.e., the precipitation curve does not drop below the temperature curve for the 30-year climatic period).

The lowest temperature recorded for Bladen County was -14.4 °C (6 °F) on January 17, 1977 (Leab 1990). The highest recorded temperature for Bladen County was 37.7 °C (100 °F) on July 20, 1977 (Leab 1990). Monthly average temperatures were highest in July and August and lowest in December and January. Monthly precipitation amounts were also highest in July and August, while the lowest monthly precipitation amounts were in April and November (State Climate Office of North Carolina 2014; Fig. 15). The annual growing season, defined as the number of days in five out of ten years during which the daily minimum air temperature exceeds -2.2 °C (28 °F), is 243 days in Bladen County (weather data recorded from 1957-1979; Leab 1990).

Lake Waccamaw (Columbus County, NC)

Climate data from the nearest weather station to Lake Waccamaw, ca. 16 km away in Whiteville, North Carolina (Columbus County: 34.27287° N, -78.71499° W; 29.8 meters above sea level), show that for the 30-year period between 1971 and 2000, the average annual temperature was 17.16 °C (62.9 °F) and mean annual precipitation 1,275.08 mm (50.2 in). The average daily maximum and minimum temperatures over the same thirty-year period were 24.3 °C (75.8 °F) and 10 °C (50 °F; State Climate Office of North Carolina 2014; Fig. 15).

The lowest temperature recorded for Columbus County was -15 °C (5 °F) on February 12, 1973 (Spruill 1990). The highest recorded temperature for Columbus County was 40.5 °C (105 °F) on June 27, 1954 (Spruill 1990). Monthly average temperatures were highest in July and August and lowest in January and February. Monthly precipitation amounts were also highest in July and August, while the lowest monthly precipitation amounts were in April and November (State Climate Office of North Carolina 2014; Fig. 15). The annual growing season, defined as the number of days in five out of ten years during which the daily minimum air temperature exceeds -2.2 °C (28 °F), is 240 days in Columbus County (weather data recorded from 1951-1981; Spruill 1990).

Four plant community types and two subtypes can be distinguished within the littoral zone of Carolina bay lakes (Schafale 2012; Table 7). Of these four community types and subtypes, three are globally critically imperiled (Natural Lake Shoreline Swamp – Lake Waccamaw Subtype; Natural Lake Shoreline Marsh – Typic Subtype; Natural Lake Shoreline Marsh − Lake Waccamaw Pondlily Subtype), while the others do not have a conservation ranking (Table 7).

Natural Lake Shoreline Swamp (Cypress Subtype; S2G3) [Taxodium distichum – T. ascendens / Panicum hemitomon Schult. Woodland (CES203.044)].

This natural community type covers Carolina bay lake shorelines with narrow littoral zones characterized by an absent to sparse herbaceous component and a nearly closed canopy of Chamaecyparis Spach, Nyssa L., or Taxodium Rich. in the upper eulittoral zone. If a cross-section of this littoral zone were to be drawn, the epilittoral vegetation would abruptly coincide with the littoral zone (i.e., a zone of emergent herbaceous vegetation is lacking where it typically would occur between the epilittoral and infralittoral zones). This “two-staged” zonation pattern typical of this community type is directly attributable to the steeper hydrography and narrow littoral zone. The Natural Lake Shoreline Swamp (Lake Waccamaw Subtype) and the Natural Lake Shoreline Marsh community types can be distinguished from the depauperate Natural Lake Shoreline Swamp (Cypress Subtype) community type by having a broader littoral zone, a well-developed zone of herbaceous emergent macrophytes, a sparse to open canopy of Nyssa, Taxodium, or other obligate wetland hardwoods, and the absence of Nuphar sagittifolia (Walter) Pursh. Examples of this community type are found at Bakers Lake, and the western, northern, and eastern shorelines of Jones, Salters, Little Singletary, and Singletary Lakes.

Natural Lake Shoreline Swamp (Lake Waccamaw Subtype; S1G1) [Taxodium distichum – T. ascendens / Panicum hemitomon – Sclerolepis uniflora (Walter) Britton, Sterns & Poggenb. Woodland (CEGL004465)].

This natural community type covers the southern shoreline of Lake Waccamaw located between Big Creek and the lake’s outlet on the southwest shore. This stretch of natural shoreline is characterized by gentle hydrography, which results in a broad littoral zone, and a species-rich flora dominated by emergent herbaceous macrophytes, many of which are rare. Emergent macrophytes typical of this community type include Cladium mariscoides (Muhl.) Torr., Eriocaulon aqutaicum (Hill) Druce, Panicum hemitomon, Sclerolepis uniflora, and Xyris smalliana, among others. This community type can be distinguished from the species-poor Natural Lake Shoreline Swamp (Cypress Subtype) community type by its broader littoral zone and species-rich herbaceous component (95 taxa). It can be distinguished from the Natural Lake Shoreline Marsh community types by the absence or only irregular presence of Nuphar sagittifolia and the unique assemblage of diverse herbaceous taxa (e.g., Bacopa caroliniana (Walter) B.L. Rob., Boltonia asteroides (L.) L’Hér. var. glastifolia, Cladium mariscoides, Ludwigia brevipes (B.H. Long ex Britton, A. Braun & Small) Eames, L. sphaerocarpa Elliott, and Sclerolepis uniflora).

Natural Lake Shoreline Marsh (Typic Subtype; S1G1) [Panicum hemitomon – Juncus spp. Coastal Plain Lakeshore Herbaceous Vegetation (CEGL004307)].

This natural community type covers the southern shorelines of the Bladen Lakes. The southern shorelines have a broader littoral zone than the remaining portions of the lakes. Consequently, they support a more diverse emergent herbaceous component. Herbs found in this community type include Eleocharis baldwinii, E. equisetoides (Elliott) Torr., E. vivipara, Juncus pelocarpus E. Mey., Panicum hemitomon, Panicum verrucosum Muhl., Rhexia nashii, Rhynchospora distans, Saccharum giganteum (Walter) Pers., Sacciolepis striata, Scirpus cyperinus (l.) Kunth, and Xyris smalliana. This community type is also characterized as having a sparse to open canopy of Nyssa and Taxodium. This community type can be distinguished from the Natural Lake Shoreline Marsh (Lake Waccamaw Pondlily Subtype) by the absence of Nuphar sagittifolia and from the Natural Lake Shoreline Swamp (Lake Waccamaw Subtype) by the occurence of < 30 herbaceous taxa, none of which include the unique and rare herbs found at Lake Waccamaw. Examples of this community type include the southern shorelines of Jones, Little Singletary, Salters, and Singletary Lakes.

Natural Lake Shoreline Marsh (Lake Waccamaw Pond-lily Subtype; S1G1) [Nuphar sagittifola – Eriocaulon aquaticum Lakeshore Herbaceous Vegetation (CEGL004297)].

This natural community type covers the western, northern, and eastern shorelines of Lake Waccamaw (i.e., where residential and commercial development is present). It is the only Natural Lake Shoreline community type dominated by Nuphar sagittifolia (a distinguishing feature) and Eriocaulon aquaticum. Nuphar sagittifolia is essentially absent from the Natural Lake Shoreline Swamp (Lake Waccamaw Subtype) community type save for small stands around the mouth of Big Creek and around the dam at the lakes outlet.

floating Bog [Rhynchospora alba Saturated Herbaceous Vegetation (CEGL004463)]

This natural community type covers the rare examples of vegetation occuring on floating peat mats in deep water of natural or artificial ponds and lakes. Horseshoe Lake is the only Carolina bay lake known to support floating bogs. The floating bogs of Horseshoe Lake are the largest in the state. These floating bogs are saturated and nutrient-poor, supporting taxa that characteristically inhabit such stressful conditions (e.g., Calopogon tuberosus (L.) Britton, Sterns & Poggenb., Drosera intermedia, Dulichium arundinaceum, Hypericum virginicum, Pogonia ophioglossoides, Rhynchospora alba, R. inundata, and Xyris fimbriata). This community type’s “floating” nature and the presence of the aforementioned plant taxa sets it apart from all others.

Coastal Plain Semipermanent Impoundment (Cypress-Gum Subtype; G4G5) [Taxodium distichum / Lemna minor L. Forest (CEGL002420)]

All portions of Horseshoe Lake not considered floating Bog fall into the Coastal Plain Semipermanent Impoundment community type. This community type is characterized by a sparse to absent canopy of Taxodium ascendens with sporadically occurring beds of floating-leaved and submersed aquatics (e.g., Brasenia schreberi J.F. Gmel, Cabomba caroliniana A. Gray, Nymphaea odorata ssp. odorata, and Utricularia spp.). This community type can be distinguished from all others by the sparse presence of Taxodium throughout the lake with floating-leaved and submersed aquatics occurring underneath.

Across All Sites

The littoral zone vascular flora of Carolina bay lakes, based on vouchered collections, reports, and personal observations, consists of 205 taxa (170 species, 4 subspecies, 30 varieties, 1 hybrid) in 136 genera and 80 vascular plant families (Table 8; Suppl. material 6). Of these 205 taxa, 186 (90.7%) are vouchered and 19 (9.3%) are known only from reports (Peet et al. 2013a, Peet et al. 2013b, North Carolina Natural Heritage Program 2014; NCSU Crop Science Department [Rob Richardson and Justin Nawrocki, pers. comm., April 9, 2015]). Of the 186 vouchered taxa, 157 (84.4%) were collected by the first author; the remaining 29 (15.6%) vouchered taxa were collected from Carolina bay lake shorelines by others and were found by completing systematic searches of major herbaria (DUKE, NCSC, and NCU). Nineteen taxa (9.3%) are listed as significantly rare and twelve taxa (5.8%) are on the NCNHP Watch List (Table 9). Four taxa (1.9%) are Federal Species of Concern (Ludwigia brevipes; Nuphar sagittifolia; Rhexia aristosa Britton; Sagittaria weatherbiana). Pair-wise comparisons of species similarity for all bays are provided in Table 10.

Among all taxa treated in this guide, the major vascular plant groups consisted of the following total taxa: Eudicotyledons (101 taxa; 86 species, 1 subspecies, 13 varieties, 1 hybrid), monocotyledons (86 taxa; 71 species, 1 subspecies, 14 varieties), pteridophytes (7 taxa; 6 species and 1 subspecies), gymnosperms (5 species), basal angiosperms (4 taxa; 3 species and 1 subspecies), and magnoliids (2 taxa; 1 species and 1 variety; Table 8; Fig. 16). The richest families in the eudicotyledons are Asteraceae (13 taxa; 11 species, 1 variety, 1 hybrid), Ericaceae (8 taxa; 6 species, 2 varieties), Lentibulariaceae (6 taxa), Melastomataceae (5 taxa; 4 species, 1 variety), Hypericaceae (4 taxa; 3 species, 1 variety), and Rosaceae (4 taxa; Fig. 17). The richest genera in the eudicotyledons are Utricularia (6 taxa), Rhexia L. (5 taxa), and Hypericum L. (4 taxa). The richest families in the monocotyledons are Cyperaceae (25 taxa; 20 species, 5 varieties), Poaceae (21 taxa; 17 species, 4 varieties), Juncaceae (8 taxa), Orchidaceae (5 taxa; 4 species, 1 variety), Alismataceae (4 taxa), Smilacaceae (4 taxa), and Xyridaceae (4 taxa: Fig. 17). The richest genera in the monocotyledons are Rhynchospora (9 taxa; 8 species, 1 variety), Juncus (8 taxa), Dichanthelium (Hitchc. & Chase) Gould (6 taxa; 5 species, 1 variety), Carex (4 taxa; 3 species, 1 variety), Eleocharis (4 taxa; 3 species, 1 variety), Sagittaria L. (4 taxa), Smilax L. (4 taxa), and Xyris L. (4 taxa).

Figure 16.  

Distribution of plant habit across all Carolina bay lakes. Lakes dominated by herbs have broader littoral zones, which encourage the establishment of herbaceous emergent macrophytes. Lakes dominated by trees and shrubs have narrow littoral zones, which discourage the establishment of herbaceous emergent macrophytes.

Figure 17.  

The thirteen most species-rich vascular plant families across all Carolina bay lakes. Cyperaceae (orange), Ericaceae (yellow), Juncaceae (dull green), Poaceae (purple), Smilacaceae (neon green), and Xyridaceae (black) consistently occur across all sites.

Among all taxa treated in this guide, the most species-rich habit is herbs (140 taxa; 119 species, 2 subspecies, 18 varieties, 1 hybrid), followed by trees and shrubs (51 taxa; 42 species, 1 subspecies, 8 varieties), and vines (14 taxa, 12 species, 2 varieties; Fig. 16). Among the herbs, Cyperaceae (25 taxa), Poaceae (20 taxa), Asteraceae (11 taxa), Juncaceae (8 taxa), Lentibulariaceae (6 taxa), Melastomataceae (5 taxa), and Orchidaceae (5 taxa) are the most species-rich families. Among trees and shrubs, the Ericaceae (8 taxa) and Rosaceae (4 taxa) were the most species-rich families. Among vines, the Smilacaceae (4 taxa) and Vitaceae (2 taxa) were the most species rich families.

Among the natural community types included in this work, the Natural Lake Shoreline Swamp (Lake Waccamaw Subtype) is the most species-rich (145 taxa) and the Natural Lake Shoreline Marsh (Lake Waccamaw Pondlily Subtype) is the least species-rich (< 10 taxa; Table 7). Five exotic taxa are known to occur in the bay lakes, four (Alternanthera philoxeroides [Amaranthaceae], Colocasia esculenta (L.) Schott [Araceae], Hydrilla verticillata (L.F.) Royle [Hydrocharitaceae], Triadica sebifera (L.) Small [Euphorbiaceae]) from Lake Waccamaw and one (Hypochaeris radicata L. [Asteraceae]) from Bay Tree Lake.

Individual Lakes

Among the lakes, the largest number of littoral zone taxa (i.e., species, subspecies, and varieties) occurred in Lake Waccamaw (145 taxa), followed by Bay Tree Lake (56 taxa) and Horseshoe Lake (52 taxa; Table 11). The least number of littoral zone taxa occurred in Bakers Lake (18 taxa).

Bakers Lake

The littoral zone vascular flora of Bakers Lake is depauperate with respect to the other bay lakes (Table 11). A total of 18 taxa (14 species, 4 varieties) in 17 genera and 14 vascular plant families were found in this lake’s littoral zone (Suppl. material 6). All but one taxon (Tillandsia usneoides) from Bakers Lake were collected by the first author (i.e., there were no reports or historical vouchers). The richest eudicotyledonous family was Ericaceae (5 taxa; Fig. 17).

The most species-rich habit class was trees and shrubs (14 taxa; 10 species, 4 varieties), followed by herbs (3 taxa), and vines (1 taxa; Fig. 16). Among the trees and shrubs, the Ericaceae (5 taxa) is the most species-rich family. No exotic taxa or taxa of conservation concern occured at this site. One species (Rhus copallinum L.) was unique to this Carolina bay lake (i.e., it was not found/reported from any other bay lake in this study; Suppl. material 5).

Bay Tree Lake

The littoral zone vascular flora of Bay Tree Lake is comprised of 56 taxa (48 species, 2 subspecies, and 6 varieties), in 47 genera and 34 vascular plant families (Table 11; Suppl. material 6). All but 2 taxa from Bay Tree Lake were vouchered; Decodon verticillatus and Pontederia cordata L. var. cordata were personal observations. No species of conservation concern were collected or reported from Bay Tree Lake’s littoral zone. One exotic taxon (Hypochaeris radicata) was collected from this site (Suppl. material 6). Twelve taxa are unique to this bay lake (i.e., they were not found/reported from any other bay lake in this study; Suppl. material 6: [Amelanchier canadensis (L.) Medik., Carex longii Mack., Cyperus odoratus L. var. odoratus, Diodia virginiana L., Fuirena pumila (Torr.) Spreng., Hypochaeris radicata, Juncus acuminatus Michx., Krigia virginica (L.) Willd., Nuttallanthus canadensis (L.) D.A. Sutton, Panicum virgatum, Rumex hastatulus Baldwin, Smilax glauca Walter, and Stipulicida setacea Michx. var. setacea]).

The richest eudicotyledon families are Asteraceae (3 taxa), followed by Ericaceae (2 taxa) and Aquifoliaceae (2 taxa;) . The richest monocotyledonous families are Poaceae (7 taxa; 6 species, 1 subspecies), Cyperaceae (5 taxa; 4 species, 1 variety), and Juncaceae (5 taxa). The richest monocotyledon genera are Juncus (5 taxa; 3 species, 1 subspecies, 1 variety) and Panicum (3 taxa).

The most species-rich habit class was herbs (35 taxa; 29 species, 2 subspecies, 4 varieties), followed by trees and shrubs (16 taxa; 15 species, 1 variety), and vines (4 species, 1 variety; Fig. 16). Among the herbs, Poaceae (7 taxa; 6 species, 1 subspecies), Cyperaceae (5 taxa; 4 species, 1 variety), Juncaceae (5 taxa), and Asteraceae (3 taxa) are the most species-rich families. Among the trees and shrubs, Cupressaceae (3 taxa), Aquifoliaceae (2 taxa), and Ericaceae (2 taxa) are the most species-rich families.

Horseshoe Lake

The littoral zone vascular flora of Horseshoe Lake is comprised of 52 taxa (45 species, 2 subspecies, and 5 varieties), in 41 genera and 29 vascular plant families (Table 11; Suppl. material 6). All but three taxa from Horseshoe Lake were vouchered; Eleocharis baldwinii/vivipara, Rhexia aristosa, and Tillandsia usneoides were the only taxa not vouchered from the site. No exotic taxa were collected from this site. Sixteen taxa are unique to this bay lake (i.e., they were not found/reported from any other bay lake in this study; Suppl. material 6). Five taxa of conservation concern were collected or reported from this site (Rhexia aristosa, Rhynchospora alba, Rhynchospora inundata, Sagittaria isoetiformis J.G. Sm., and Xyris smalliana; Table 9).

The richest eudicotyledon families are Ericaceae (4 taxa), Lentibulariaceae (3 taxa) and Melastomataceae (3 taxa). The richest eudicotyledonous genera are Rhexia (3 taxa), Utricularia (3 taxa), followed by Hypericum (2 taxa). The richest monocotyledonous families are Cyperaceae (5 taxa), Juncaceae (4 taxa), Poaceae (3 taxa), followed by Orchidaceae (2 taxa), Smilacaceae (2 taxa) and Xyridaceae (2 taxa). The richest monocotyledonous genera are Juncus (4 taxa), followed by Rhynchospora (2 taxa), Smilax (2 taxa), and Xyris (2 taxa).

The most species-rich habit class was herbs (38 taxa; 31 species, 2 subspecies, 4 varieties), followed by trees and shrubs (11 taxa; 10 species, 1 variety), and vines (3 taxa; Fig. 16). Among the herbs, Cyperaceae (6 taxa), Juncaceae (4 taxa), followed by Lentibulariaceae (3 taxa), Melastomataceae (3 taxa), Poaceae (3 taxa), Orchidaceae (2 taxa), and Xyridaceae (2 taxa) are the most species-rich families. Among the trees and shrubs, the most species-rich family is Ericaceae (4 taxa).

Jones Lake

The littoral zone vascular flora of Jones Lake is comprised of 33 taxa (29 species, 1 subspecies, and 3 varieties), in 31 genera and 23 vascular plant families (Table 11; Suppl. material 6). All taxa, save for Cyrilla racemiflora, were vouchered by the first author or others. No exotic taxa were collected from this site. Two taxa are unique to this bay lake (i.e., they were not found/reported from any other bay lake in this study; Suppl. material 6: [Cyperus polystachyos Rottb., Rhynchospora inexpansa (Michx.) Vahl]). Xyris smalliana was the only species of conservation concern collected from this site (Table 9).

The richest eudicotyledonous family is Ericaceae (5 taxa). The richest eudicotyledonous genus is Lyonia (2 taxa; 1 species, 1 variety). The richest monocotyledonous families are Cyperaceae (3 taxa) and Poaceae (3 taxa). Monocotyledons are comprised of ten different genera.

The most species-rich habit class was trees and shrubs (20 taxa; 16 species, 1 subspecies, 3 varieties), followed by herbs (11 taxa), and vines (2 taxa; Fig. 16). Among the herbs, Cyperaceae (3 taxa) and Poaceae (3 taxa) are the most species-rich families. Among the trees and shrubs, Ericaceae (5 taxa) and Cupressaceae (3 taxa) are the most species-rich families.

Lake Waccamaw

The littoral zone vascular flora of Lake Waccamaw is comprised of 145 taxa (122 species, 3 subspecies, 19 varieties, 1 hybrid), in 111 genera and 72 vascular plant families (Table 11; Suppl. material 6). Of the 145 total catalogued taxa, 127 are vouchered and 18 are known only from reports (Suppl. material 6). Twenty-six species of conservation concern were collected or reported from Lake Waccamaw’s littoral zone. Four exotic taxa (Alternanthera philoxeroides [Amaranthaceae], Colocasia esculenta [Araceae], Hydrilla verticillata [Hydrocharitaceae], Triadica sebifera [Euphorbiaceae]) are known from this site. Ninety-five taxa are unique to Lake Waccamaw (i.e., they were not found/reported from any other bay lake in this study; Suppl. material 6).

The richest eudicotyledonous families are Asteraceae (10 taxa; 8 species, 1 variety, 1 hybrid), followed by Lentibulariaceae (4 taxa), Ericaceae (3 taxa), Rosaceae (3 taxa), and Salicaceae (3 taxa). The richest eudicotyledonous genera are Utricularia (4 taxa), Eupatorium L. (2 taxa), Hypericum (2 taxa), Ludwigia L. (2 taxa), Nyssa (2 taxa), and Salix L. (2 taxa). The richest monocotyledonous families are Poaceae (17 taxa; 13 species, 1 subspecies, 3 varieties), Cyperaceae (14 taxa; 11 species, 3 varieties), Alismataceae (4 taxa), Juncaceae (3 taxa), Orchidaceae (3 taxa), and Smilacaceae (3 taxa). The richest monocotyledonous genera are Dichanthelium (Hitchc. & Chase) Gould (6 taxa; 5 species and 1 variety), Rhynchospora (6 taxa; 5 species and 1 variety), Sagittaria L. (4 taxa), Juncus (3 taxa; 3 species, 1 subspecies, 1 variety) and Smilax L. (3 taxa).

The most species-rich habit class was herbs (96 taxa; 80 species, 3 subspecies, 13 varieties, 1 hybrid), followed by trees and shrubs (36 taxa; 32 species, 4 varieties), and vines (13 taxa; 11 species, 2 varieties; Fig. 16). Among the herbs, the Poaceae (16 taxa; 13 species, 1 subspecies, 2 varieties), Cyperaceae (14 taxa; 11 species, 3 varieties), Asteraceae (8 taxa; 6 species, 1 variety, 1 hybrid), Alismataceae (4 taxa), Lentibulariaceae (4 taxa), Juncaceae (3 taxa), and Orchidaceae (3 taxa) are the most species-rich families. Among the trees and shrubs, the Ericaceae (3 taxa), Rosaceae (3 taxa), Salicaceae (3 taxa), Betulaceae (2 taxa), Cupressaceae (2 taxa), Nyssaceae (2 taxa), and Sapindaceae (2 taxa) are the most species-rich families.

Little Singletary Lake

The littoral zone flora of Littoral Singletary Lake is comprised of 39 taxa (35 species, 1 subspecies, 3 varieties), in 32 genera and 21 vascular plant families (Table 11; Suppl. material 6). All of the 39 total catalogued taxa were vouchered (i.e., no taxa were known strictly from reports or observations; Suppl. material 6). Two species of conservation concern (i.e., Eleocharis equisetoides and Eleocharis vivipara) were collected from Little Singletary Lake’s littoral zone (Table 9). No exotic taxa are known from this site. Three taxa are unique to Little Singletary Lake (i.e., they were not found/reported from any other bay lake in this study; Suppl. material 6: [Agrostis hyemalis (Walter) Britton, Sterns & Poggenb., Rhexia virginica L., and Xyris jupicai Rich.])

The richest eudicotyledonous genus is Rhexia (2 taxa). The richest monocotyledonous families are Cyperaceae (6 taxa; 5 species and 1 variety), Juncaceae (4 taxa; 2 species, 1 subspecies, 1 variety), and Poaceae (3 taxa). The richest monocotyledonous genera are Juncus (4 taxa), Eleocharis (3 taxa), and Panicum (2 taxa).

The most species-rich habit class was herbs (23 taxa; 20 species, 1 subspecies, 2 varieties), followed by trees and shrubs (15 taxa; 14 species and 1 variety), and vines (1 taxon; Fig. 16). Among the herbs, the Cyperaceae (6 taxa), Juncaceae (4 taxa), and Poaceae (3 taxa) are the most species-rich families. Among the trees and shrubs, the Ericaceae (5 taxa) is the most species-rich family.

Salters Lake

The littoral zone flora of Salters Lake is comprised of 22 taxa (16 species, 2 subspecies, 4 varieties), in 18 genera and 16 vascular plant families (Table 11; Suppl. material 6). Twenty of the twenty-three total catalogued taxa were vouchered; Decodon verticillatus, Nyssa biflora, and Xyris iridifolia, were reports or personal observations (Suppl. material 6). Two species of conservation concern (i.e., Xyris iridifolia and Xyris smalliana) were collected/reported from Salters Lake’s littoral zone (Suppl. material 6; Table 9). No exotic taxa are known from this site. One taxon is unique to Salters Lake (i.e., not found/reported from any other bay lake in this study; Suppl. material 5: [Xyris iridifolia])

The richest eudicotyledon family is Ericaceae (5 taxa). The richest eudicotyledonous genera are Lyonia (2 taxa) and Vaccinium (2 taxa). The richest monocotyledonous family is Xyridaceae (2 taxa). The richest monocotyledon genus is Xyris (2 taxa).

The most species-rich habit class was trees and shrubs (15 taxa; 11 species, 1 subspecies, 3 varieties), herbs (5 taxa; 4 species and 1 subspecies), and vines (2 taxa; Fig. 16). Among the trees and shrubs, the Ericaceae (5 taxa) and Cupressaceae (2 taxa) are the most species-rich families. Among the herbs, the Xyridaceae (2 taxa) is the most species-rich family.

Singletary Lake

The littoral zone vascular flora of Singletary Lake is comprised of 36 taxa (32 species, 1 subspecies, 3 varieties), in 30 genera and 22 vascular plant families (Table 11; Suppl. material 6). All thirty-six total catalogued taxa were vouchered (i.e., none were reports or personal observations; Suppl. material 6). One taxon from Singletary Lake’s littoral zone is of conservation concern (i.e., Xyris smalliana; Suppl. material 6; Table 9). No exotic taxa are known from this site. One taxon is unique to Salters Lake (i.e., not found/reported from any other bay lake in this study; Suppl. material 6: [Rhododendron viscosum (L.) Torr. var. serrulatum (Small) H.E. Ahles]).

The richest eudicotyledonous families are Ericaceae (7 taxa) and Rosaceae (2 taxa). The richest eudicotyledonous genus is Vaccinium (2 taxa). The richest monocotyledonous families are Juncaceae (3 taxa), Poaceae (2 taxa), and Xyridaceae (2 taxa). The richest monocotyledonous genera are Juncus (3 taxa) and Xyris (2 taxa).

The most species-rich habit class was trees and shrubs (22 taxa; 19 species and 3 varieties), herbs (11 taxa; 10 species and 1 subspecies), and vines (3 taxa; Fig. 16). Among the trees and shrubs, the Ericaceae (7 taxa), Cupressaceae (3 taxa), Pinaceae (2 taxa), and Rosaceae (2 taxa) are the most species-rich families. Among the herbs, the Juncaceae (3 taxa), Poaceae (2 taxa), and Xyridaceae (2 taxa) are the most species-rich families.

White Lake

White Lake was not included in this study due to the severity of the lake’s shoreline development. A provisional checklist of plants known to occur within the littoral zone of White Lake (from historical vouchers, personal observation, and literature review) is provided in Suppl. material 7. The intent of the provisional checklist is to provide a baseline for future research in this lake.