Guide to the littoral zone vascular flora of Carolina bay lakes (U.S.A.)

Abstract Background Carolina bays are elliptic, directionally aligned basins of disputed origin that occur on the Atlantic Coastal Plain from the Delmarva Peninsula to southern Georgia. In southeastern North Carolina, several large, natural, lacustrine systems (i.e., Carolina bay lakes) exist within the geomorphological features known as Carolina bays. Within the current distribution of Carolina bays, Bladen and Columbus counties (North Carolina) contain the only known examples of Carolina bay lakes. The Carolina bay lakes can be split into two major divisions, the “Bladen Lakes Group” which is characterized as being relatively unproductive (dystrophic – oligotrophic), and Lake Waccamaw, which stands alone in Columbus County and is known for its high productivity and species richness. Although there have been several studies conducted on these unique lentic systems, none have documented the flora comprehensively. New information Over the 2013−2014 growing seasons, the littoral zone flora of Carolina bay lakes was surveyed and vouchered. Literature reviews and herbarium crawls complemented this fieldwork to produce an inventory of the vascular plant species. This survey detected 205 taxa (species/subspecies and varieties) in 136 genera and 80 vascular plant families. Thirty-one species (15.2%) are of conservation concern. Lake Waccamaw exhibited the highest species richness with 145 catalogued taxa and 26 species of conservation concern. Across all sites, the Cyperaceae (25 spp.), Poaceae (21 spp.), Asteraceae (13 spp.), Ericaceae (8 spp.), Juncaceae (8 spp.), and Lentibulariaceae (6 spp.) were the six most species-rich vascular plant families encountered. A guide to the littoral zone flora of Carolina bay lakes is presented herein, including dichotomous keys, species accounts (including abundance, habitat, phenology, and exsiccatae), as well as images of living species and vouchered specimens.

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 (SO ) into the atmosphere. As weather systems make their way across North America from west to east, they pick up this sulfur dioxide (SO ) 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 (CO ) in the water column. When CO 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 CO into the system, thus releasing + 2 2 2 2 + + 2 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 andHansson 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
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 century that researchers fully recognized the magnitude and extent of Carolina bay distribution by the use of airplanes and soon-tobe aerial imagery.
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 + + + + th Guide to the littoral zone vascular flora of Carolina bay lakes (U.S.A.) 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- 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).
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 firesuppressed 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.
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.
Although some Carolina bays may contain shallow marshes or ponds (Bennett andNelson 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).
(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. 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 (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 freefloating 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 andGilbert 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 ]: (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. , Cephalanthus L. , Cladium P. Browne , Juncus L. , Panicum L. , Pontederia L. , Rhynchospora Vahl , Scirpus L. , 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. , Nelumbo Adans. , Nuphar Sm. , Nymphaea L. , Nymphoides Ség. , and Potamogeton L .
(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 .
(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 . 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 c c c c 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 andChee 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 teastained. 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).

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 andPeacock 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 longterm 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 ( 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).  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. 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. 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 capillusveneris 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 andRaney 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. 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.

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.
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 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 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 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.  20, 197720, (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 1957Leab 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 thirtyyear 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). 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 yaxis 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).

Plant Communities
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).

Richness Plant Community Types State Rank Global Rank
Lowest Highest Natural Lake Shoreline Marsh (Lake Waccamaw Pondlily Subtype) S1 G1 Coastal Plain Semipermanent Impoundment S4 G4G5 floating Bog S1 G1?

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 "twostaged" zonation pattern typical of this community type is directly attributable to the steeper hydrography and narrow littoral zone. The Natural Lake Shoreline Swamp (Lake 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. 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 (  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.  Table 8.

Species and Subspecies/Varieties
Summary of vascular plant taxa collected or reported from Carolina bay lake littoral zones Table 9.
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

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).  Figure 17.

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).

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).

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).

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 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).

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.

Materials and methods
This work is restricted to the littoral zone vascular flora of unaltered Carolina bay lake shorelines. The littoral zone was defined as the zone of vegetation occurring between the maximum annual high water mark and the point at which submerged aquatic plants cease to persist (Fig. 4). Unaltered shorelines were defined as those lacking residential or commercial development (therefore, the entirety of White Lake and the developed shorelines of Lake Waccamaw and Bay Tree Lake were not included in this inventory).
During the 2013 and 2014 growing seasons, 36 total visits were made to the eight study sites meeting the criteria articulated above (i.e., Bakers Lake, Bay Tree Lake, Horseshoe Lake, Jones Lake, Lake Waccamaw, Little Singletary Lake, Salters Lake, Singletary Lake), resulting in 121 field hours and the identification of 204 taxa (species, subspecies, and varieties). A 10-foot aluminum boat with a transom-mounted trolling motor was used to transport equipment along Carolina bay lake shorelines. Where water was too shallow for the use of the trolling motor, we walked and pulled the boat by rope. GPS locations (NAD 83) were taken at numerous intervals and associated with all specimens collected within 30 m of each point. Digital photographs of plant habit and overall morphology were taken prior to collection using a Panasonic Lumix FZ−150. Plant specimens were pressed while in the field. Tissue samples were taken in the field and dessicated with blue indicating silica gel (purchased from Delta Enterprises Inc.) in ziploc bags. Voucher specimens and tissue samples were deposited respectively at the North Carolina State University Vascular Plant Herbarium (NCSC) and its DNA bank. The entirety of Carolina bay lake shorelines was surveyed, but it was quickly observed that all shorelines, save for the southernmost, were relatively depauperate. All taxa occurring along western, northern, and eastern shorelines could be found within the littoral zone of the southern shoreline, but the inverse did not hold true. The significantly gentler hydrography (see Frey 1949 for lake longitudinal profiles), and consequently wider littoral zone of southern shorelines, produces a more species-rich macrophyte community. Consequently, survey time was much longer on the southern, more diverse shorelines of Carolina bay lakes.
The flora is organized by the following major vascular plant groups: (1) pteridophytes, (2) gymnosperms, (3) monocots, and (4) basal angiosperms, magnoliids, and eudicotyledons. Dichotomomous keys are provided to each major group, as well as to families, genera, and species within each group. Notes are provided above some keys to aid in the identification process. Within each group, taxa are arranged alphabetically, by family, then genus, then species.
The following information is provided for each taxon account: taxon concept mapping, basionym, conservation status, habit, habitat, flowering and fruiting phenology, abundance, and presence/absence data for each site (Suppl. material 3). Unless stated otherwise, accepted taxon concepts follow Weakley (2012) and are tied to those in the following major works: RAB = Radford et al. (1968); GW = Godfrey and Wooten (1979), Godfrey and statement "= RAB, FNA" means that the taxon concept, as well as the species name used here, is the same as that used in RAB and FNA (see Dryopteris ludoviciana (Kunze) Small). The use of a "less than" symbol (e.g., "< Onoclea sensibilis L. -RAB, FNA"), indicates that the taxon concept used here is narrower than that used by RAB and FNA (alternatively, a "greater than" symbol would mean that the concept of a particular taxon is broader than in the cited works). An equals symbol followed by a different species name than the one bolded, indicates that the taxon concept used here is the same as in the work cited, except that the taxon was treated under a different name in the work cited (see Sagittaria filiformis J.G. Sm. vs. Sagittaria stagnorum Small).
Abundance estimates following the recommendations of Palmer et al. (1995) are provided for each lake in which a taxon was collected or observed by the current author (Table 12; Suppl. material 3). Taxa designated as "exotic" are not native to North America and are indicated by an asterisk preceding the scientific name. The conservation status and rank of species of conservation concern precede the habitat description in each taxon entry (e.g., E, FSC; S1, G2. "Habitat description"). Conservation status and rank of species are designated according to NatureServe (2012)

Density Description
Abundant Dominant or co-dominant in one or more communities.

Frequent
Easily seen or found in one or more common communities but not dominant in any common community

Occasional
Widely scattered but not difficult to find Infrequent Difficult to find with few individuals or colonies but found in several locations Rare Very difficult to find and limited to one or very few locations or uncommon communities When available, digital photographs and line drawings were obtained from: Britton and Brown (1913)  Descriptions for estimating the abundance of taxa (adapted from Palmer et al. 1995) In addition, relevant historical vouchers are cited based on systematic searches of the three major herbaria−DUKE, NCSC, and NCU. Unfortunately, it is not uncommon to find historical specimens containing vague habitat or locality descriptions. For a taxon to be included in the present study, a clear label statement referencing Carolina bay lake shoreline habitat was required (e.g., "collected from peat-drained lake bed of Suggs Mill Pond"). Herbarium vouchers meeting this criterion were annotated (following taxon concepts accepted here) and their label information was subsequently entered into spreadsheets for organization. Label information for new collections resulting from this study was captured in a DarwinCore compliant spreadsheet for upload to the online portal of the Southeastern Regional Network of Expertise and Collections (www.sernecportal.org) , which feeds into iDigBio and the Global Biodiversity Data Facility (GBIF).  The first author has not encountered this taxon in the field, but a single voucher specimen (see above) confirms its historic presence within the lake. Fig. 30 Sagittaria graminea Michx.

Nomenclature:
Taxon   . "Generally infertile in our area" (Weakley 2012). This species is exotic and has become naturalized in roadside ditches, canals, and portions of the lakes shoreline. It spreads by way of rhizome dispersal, which is almost cartainly caused by residential homeowners digging up rhizomes from their flower beds and either tossing them into the lake or into the canals that surround the lake. Notes: The first author has not encountered taxa within this genus in the field; however, the Carolina Vegetation Survey reported "Wolffia spp." from the southwest side Lake Waccamaw. Although a species-level identification has not been made, a key to the two species most likely to inhabit this location is provided in the Identification Keys section below.

Nomenclature:
Basionym: Renealmia usneoides L.            Notes: Arborescent herbs. Eulittoral zone; at or just below the mean annual high water mark (NLSS−LW). Apr−Jul. The first author has not encountered this taxon in the field, but a single voucher specimen (see above) places it within the immediate vicinity. Fig.  80 Coleataenia longifolia var. longifolia

Nomenclature:
Basionym: Poa refracta Muhl. ex Elliott    Notes: Shrubs. Eulittoral zone; can be found on saturated soil at or just below the mean annual high water mark or growing from the bases of Taxodium in the littoral zone (NLSS−LW). Aug−Oct. Fig. 112f a b c d e f   Notes: Annual or biennial herbs. Eulittoral zone; saturated sandy soils (NLSS−LW). May−Nov. (Fig. 159). The first author did not encounter this taxon in the field, but a single voucher confirms its historic presence (see above).   Notes: Annual or perennial herbs. Eulittoral zone; sandy soils at or just below the maximum annual high water mark. Jun-Dec. Fig. 195 a b c d Notes: Perennial herbs. Eulittoral zone; at or just below maximum annual high water mark (NLSS-LW). Apr-May. Fig. 196 a b c d , not all the way to the rachis or midrib, as in the leaflets of Anchistea virginica). Pinnate-pinnatifid refers to a leaf blade that is oncepinnate and whose segments (pinnae) are themselves pinnatifid. Sori are the spore-producing structures found on many species of ferns; these may be either exposed or covered by the margin of the leaves (a false indusium) or a separate structure altogether (a true indusium). Leaf-like structures that bear sporangia are called sporophylls; these may be similar to the sterile leaves or be highly modified (e.g., the compact, cone-like structures, or strobili of the Lycopodiaceae)". Cupressaceae Key adapted from Watson and Eckenwalder (1993) and Weakley (2012).
1 Leaves scale-like, 1−3 mm long, opposite or whorled, evergreen; mature seed cones woody, 4−9 mm broad, scales imbricate; seeds 1-2 (−3) per scale Key adapted from Watson (1993), Weakley (2012), and Thornhill et al. (2014). Note: "In the following key, leaf and branchlet characters of T. ascendens refer to mature trees; foliage of juvenile trees often mimics that of T. distichum. Leaf and branchlet characters of T. distichum refer to both mature and juvenile trees; however, in the crowns of mature T. distichum, leaf and branchlet characters sometimes mimic those of T. ascendens. For these reasons, accurate identification of the two species often requires observation of other, non-foliage features, including the stature of the "knees", the thickness and texture of the bark, and the habitat in which the trees grow" (Thornhill et al. 2014).

Taxodium distichum
1 Open seed cones about as broad as long, "top-shaped", 3-6 cm long, serotinous; trunks typically producing epicormic branches, especially in response to fire  Flowering head involucrate, white to gray, hemispheric, "buttonlike", < 1 cm tall; flowers 2−3-merous, unisexual, 1.5−4 mm long, pale to grayish, not subtended by a scale-like bract, sepals and petals partially coated with club-shaped hairs; anthers black, 2-locular Eriocaulaceae -Flowering head not involucrate, brown, globose to cylindrical, "cone-like", 0.5−3.5 cm tall; flowers 3-merous, bi-sexual, individual petals 3−6 mm long, yellow, subtended by a conspicuous scale-like bract, sepals and petals not coated with white club-shaped hairs; anthers yellow, 2−4-locular Xyridaceae 8 Flowers and fruits subtended by imbricate or distichous bracts or scales and for the most part hidden by them, usually only the stamens and styles protruding at anthesis; fruit 1-seeded -Flowers and fruits not subtended by imbricate or distichous scales, or if so, then the flowers exceeding or equalling the bracts or scales and not hidden; fruit > 1-seeded 10 9

Pinus serotina
Leaves usually 3-ranked, sheaths typically closed; culms typically triangular in cross-section and solid; fruit an achene Cyperaceae Leaves opposite or whorled (if opposite but appearing whorled, then leaf bases dilated and sheathlike); flowers either lacking perianth parts as in Najas or inconspicuous as in Hydrilla Key adapted from Weakley (2012). Note: The first author did not encountered taxa within this genus in the field; however, the Carolina Vegetation Survey reported "Wolffia spp." from the southwest side of Lake Waccamaw. Although a species-level identification has not been made, a key to the two species most likely to inhabit this location is provided below.  Carex L.
Key adapted from Smith et al. (2002) and Weakley (2012). Note: Achene measurements in this key do not include the tubercle. Eleocharis baldwinii and E. vivipara can be difficult to distinguish in the field when they are both in their vegetative forms. One should pay particular attention to the sheaths encircling the culms; the differences are highlighted in the key below.
1 Culm as broad or broader than width of terminal spike, nodose-septate

Rhynchospora Vahl
Key adapted from Kral (2002a) and Weakley (2012). Note: A voucher (Wilbur 49814, DUKE) for Rhynchospora fascicularis (Michx.) Vahl was collected from the shoreline of Lake Waccamaw; however, this specimen appears referable to R. distans (Michx.) Vahl. Nonetheless, though not otherwise reported from the littoral zone of Carolina bay lakes, R. fascicularis has the potential to occur in these sites and is therefore included in the key below. Achene measurements in this key do not include the tubercle (i.e., the tubercle and achene should be measured as two separate entities). Eriocaulaceae Key adapted from Kral (2000a) and Weakley (2012). Note: Although the first author has only encountered E. aquaticum in the field, E. compressum was reported from the NCSU Crop Science Department (Rob Richardson and Justin Nawrocki, pers. comm., April 9, 2015) and is therefore included in the key below. guadalupensis Fig. 63 Juncaceae Key adapted from Godfrey and Wooten (1979), Brooks and Clemants (2000), and Weakley (2012). Plant producing simple culms with terminal "spring" paniculate inflorescences before mid-summer, the culms branching and producing lateral "autumnal" inflorescences from mid to lower culm nodes in the summer and autumn, these often his by the fascicles of smaller "autumnal" leaves; upper florets not disarticulating at maturity Xyridaceae Key adapted from Godfrey and Wooten (1979), Kral (2000b), and Weakley (2012). Summit of the scape distinctly flattened and broad relative to the spike; scape ridges 2−3, the two more prominent ridges comprising the flattened edge of the scape, therefore the upper scape ellipsoidal or fusiform in cross-section Xyris iridifolia -Summit of the scape not flattened and broad relative to the spike; scape ridges > 3 (at least on the mid to lower portions of the scape), scape much narrower than the spike, terete or slightly flattened in cross-section Fig.  101  radicans Fig. 106 Apiaceae Key adapted from Radford et al. (1968), Godfrey and Wooten (1981), and Weakley (2012).

Hypericum canadense
mutilum Fig. 150 Lentibulariaceae Key adapted from Godfrey and Wooten (1981), Taylor (1989), and Weakley (2012). Note: Traditionally, in the southeastern United States, U. biflora and U. gibba have been recognized as distinct species (Radford et al. 1968). However, Radford et al. (1968) described the two as "doubtfully distinct" and neither Godfrey and Wooten (1981), nor Taylor (1989), recognized a distinction. Here, we follow Weakley (2012) in provisionally recognizing the two species as distinct, pending a world-wide revision. During the present work, only U. gibba was encountered in the field, but U. biflora (bracketed in key below) is keyed here due to its morphological similarity, overlapping range, and similar habitat requirements.  Nymphaeaceae Key adapted from Godfrey and Wooten (1981) and Weakley (2012).
odorata Fig. 176 1 Petioles of mature leaves 3−6 cm long; mature leaf blades exceeding 10 cm long, margins with a few irregular teeth; drupes ≥ 20 mm long Nyssa aquatica Fig.  177 -Petioles of mature leaves < 3 cm long; mature leaves ≤ 10 cm long, margins lacking irregular teeth; drupes 10−15 mm long Nyssa biflora Fig.  178 Onagraceae Key adapted from Weakley (2012). -Plant a small shrub, 0.2-2.5 m tall, rhizomatous; pedicels nearly uniform in length, usually < 1 cm long; petals 5.9-7.7 mm long Fig. 190 4 Leaves odd-pinnately compound, leaflet margins usually crenulate to serrulate; fruit a hip, developing from an urceolate hypanthium, enclosing the ovaries and achenes except for the apical orifice Fig.  192 -Leaves palmately compound, leaflet margins usually serrate to doubly serrate; fruit an aggregate of drupelets, developing from a flatish to hemispheric hypanthium, ovaries and druplets exposed, not borne inside a hypanthium Fig. 193 Rubiaceae Key adapted from Godfrey and Wooten (1981) and Weakley (2012   Crop Science Department provided a list of several plant species found from Lake Waccamaw that added greatly to this work.

Rubus pensilvanicus
I am deeply indebted to the North Carolina Native Plant Society and the Society of Herbarium Curators. These two organizations were kind enough to provide funding for this research. Without their financial assistance, my wallet would surely be a little lighter. Ed Corey has helped me immeasurably through the years and I am deeply indebted to him. Dr. Jon Stucky has been a true pal and never once hesitated to reply to my numeroussometimes assuredly annoying − emails concerning plant identifications. My girlfriend Morgan Kirby has stuck by my side through this project and on several occassions has been swindled into mounting plant specimens; for that, she deserves an award for her patience and understanding.
Colter Chitwood has been a loyal friend, editor, and dog sitter. I don't know what I would have done without him. I wish him the very best in his future travels and research. Maybe we can meet on the Madison one of these days. I would also like to thank past and present floristics students at North Carolina State University. Robert Thornhill captivated me with his exuberant passion for North Carolina's diverse Coastal Plain flora and encouraged me to pursue a flora of my own. To the kind gentleman who gave me a ride to Bay Tree Resorts after my boat was taken by devilish winds of Bay Tree Lake on the morning of July 9, 2014, THANK YOU! Drs. Layne Huiet and Bob Wilbur of DUKE and CarolAnn McCormick of NCU helped tremendously with herbarium crawls. Those herbaria can get quite lonely, and having a conversation with someone is worth its weight in gold.
littoral zones by the present author, abundance estimates sensu Palmer et al. (1995) are provided. Abundance estimates in this checklist reflect the abundance in which the taxa occur within each lake. Status and rank designations are also provided for rare taxa monitored by the NC Natural Heritage Program (Robinson and Finnegan 2014). The term "restricted" is used here only to indicate the presence of a taxon within a particular lake among all those surveyed and not in a global sense (e.g., a taxon here considered restricted to Lake Waccamaw has not been found in the other lakes surveyed, but may exist in other localities in the state or country). A = Abundant; F= Frequent; I=Infrequent; O = Occasional; R = Rare; = þ restricted to lake indicated; () = not vouchered (i.e., reported by state agencies or observed by the present author, but not collected as a voucher specimen; see text for details); H = taxon has been collected and vouchered in the past but not by the present author. BALA = Bakers Lake; BATR = Bay Tree Lake; HOLA = Horseshoe Lake; JOLA = Jones Lake; LAWA = Lake Waccamaw; LISI = Little Singletary; SALA = Salters Lake; SILA = Singletary Lake.
Filename: Appendix F.doc -Download file (385.50 kb) Suppl. material 7: Provisional checklist of the littoral zone vascular flora from White Lake based on historical vouchers, personal observations, and literature reviews.

Authors: Nathan Howell
Data type: occurrences Brief description: This checklist does not represent a complete inventory of this locality, but rather serves as a baseline for future research. Taxa are arranged by major groups (i.e., gymnosperms, magnoliids, monocotyledons, and eudicotyledons), then alphabetically by family, genus, and species. Basal angiosperms and pteridophytes were not represented by vouchers, observations, or reports and are therefore not included in the following checklist. Brackets around a taxon indicate that it is unvouchered (i.e., it has been reported by outside agencies or has been observed by the present author, but has not been collected). Status and rank designations are also provided for rare taxa monitored by the NC Natural Heritage Program (Robinson and Finnegan 2014).