Marine invertebrate and seaweed biodiversity of continental coastal Ecuador

Abstract This study summarises the diversity of living macroinvertebrates and seaweeds from the intertidal and subtidal rocky shores along Ecuadorian continental coast. Benthic macroinvertebrate communities and seaweeds were quantified over quadrants (50 × 50 cm) randomly placed on transects of 50 m length. A checklist of 612 species was generated: 479 species of macroinvertebrates and 133 species of seaweeds. Groups recorded were Mollusca (184 species), Cnidaria (70), Arthropoda (68), Annelida (60), Echinodermata (42), Chordata (18), Bryozoa (13), Porifera (22), Sipuncula (2), Brachiopoda and Platyhelminthes (only identified as morphotypes). The seaweeds were represented by Rhodophyta (78), Chlorophyta (37), Ochrophyta (13), Cyanobacteria (5) and 19 biotic complexes. Furthermore, 22 new taxa and six alien species were recorded from the intertidal zone. This study provides the first large scale report of benthic communities in different marine coastal ecosystems in mainland Ecuador, covering 1,478 km2 of protected areas and 382 km2 of non-protected areas. The highest benthic diversity was registered in the protected areas and rocky shores from the intertidal zone. The biological data, herein reported, are useful for a long-term monitoring programme to evaluate the status of conservation and to detect rapid changes in the benthic biodiversity from coastal areas.


Introduction
Biodiversity studies are commonly used to identify changes in the community structure of terrestrial, marine and other aquatic systems and to understand the effects of natural or anthropogenic disturbances on these communities (Cruz-Motta et al. 2010, Vinagre et al. 2016. Managers and scientists are aware of the importance of biological inventories as relevant technical information: to assist sustainable management of biological resources (Drew et al. 2012), to establish baselines for future comparison (Pauly 1995), to expand Marine Protected Areas (MPAs) (Lubchenco et al. 2003), to state biodiversity conservation priorities, to evaluate the environmental quality and health of ecosystems (Edgar et al. 2011), as well as to describe the patterns of biodiversity considering latitudinal gradients (Aued et al. 2018). Changes in biological communities reveal important signals to evaluate the conservation status and the management efficiency of MPAs.
There have been several works carried out on the marine biodiversity in different coastal geographic zones of the south Pacific through expeditions undertaken by European and North American researchers since the 1700s (Olsson 1961). However, most of these surveys have been concentrated in shallow-water and deeper-water down to 200 m depth in Panama, Colombia and Ecuador (Miloslavich et al. 2011). Ecuador is considered an area of high richness of species due to its location in the great Panamic-Pacific zoogeographic province, more precisely from the region extending from Costa Rica southwards to northern Peru (Olsson 1961).
Ecuador has approximately 2,900 km of continental coastline; there is a wide range of geological characteristics, such as bluff, barriers and strand plains, estuaries and lagoons (Boothroyd et al. 1994). Around 1,380 species of invertebrates have been identified in Ecuador, where the Molluscs are the largest group with 110 species. The highest species richness is observed in the southern central coast in the Gulf of Guayaquil ). There are very few studies of benthic diversity in the rocky shores on the Ecuadorian continental coast. The localities surveyed comprise the north of Ecuador in Galera San Francisco Marine Reserve, Esmeraldas (Reck and Luna 2000), the central coast in Machalílla National Park (Rivera 2012, Ministerio del Ambiente 2015 and the southern central coast in the El Pelado Marine Reserve , Cárdenas-Calle et al. 2019, Cárdenas-Calle et al. 2018. The main groups registered in literature in the intertidal and subtidal are Mollusca, Cnidaria, (Rivera et al. 2008); Arthropoda (Mair et al. 2002, Ministerio del Ambiente 2011, Rivera 2012 and Echinodermata (Mair et al. 2002, Rivera et al. 2008. Other studies on the coastal zone included a variety of sites along the five coastal provinces of Ecuador recording a total of 140 species of macroinvertebrates including the north (Sua and Punta Galera), central (Puerto Lopez, Los Frailes, Isla de la Plata) and south central shores (Playas, Salinas, Ballenita), including 92 species of molluscs, 31 crustaceans and 17 echinoderms (Mair et al. 2002). Another study was done along 43 sites reporting 527 species in the intertidal zone and 97 species in the subtidal zone (Rivera 2012). All these studies used diverse protocol sampling methods on different spatial and temporal scales. Nevertheless, the spatial distribution of macroinvertebrates associated with rocky shores are similar to other countries near Ecuador in the tropical eastern Pacific, such as Gorgona Island in Colombia, where it was shown that the Mollusca and Crustacea were the most abundant and species rich and where the localities with more irregular topography registered a higher diversity.
The previous studies focused mainly on taxonomic lists, diversity and description of species (Cruz 2004, Cruz 2009, Cruz 2013, Mair et al. 2002, Massay et al. 1993, Mora 1989, Mora 1990, Müller-Gelinek and Salazar 1996, Villamar and Cruz 2007, Villamar 2009. Studies on benthic communities from intertidal rocky shores and sandy beaches of Ecuadorian mainland and from zones affected by anthropogenic activity are scarce in literature. Therefore, the objective of this study was to carry out a macrobenthic biodiversity inventory for the intertidal and subtidal zones along the mainland coast of Ecuador.

Study area descriptions
In order to preserve the marine biodiversity living in the protected areas, the Ecuadorian Government through the Global Environment Funds (GEF) and Inter-American Development Bank (IADB), contributed to update the knowledge of biodiversity in six marine areas (Bioelite 2016). In this work, we report the presence and diversity of marine invertebrates and algae in 10 localities (83 sites) of intertidal and subtidal zones (Tables 1,  2). The study area is extended from Playa Escondida, Esmeralda Province (Lat. 0.818901586 -Long 80.00629363) from the north to Santa Clara Island, El Oro Province (Lat. -3.171890174-Long. 80.4331793) at the south of the Ecuadorian coast, covering 1,478 km of protected areas and 382 km of other areas on the mainland coast (Table 1)

North Coast of Ecuador
Esmeraldas Province. Galera San Francisco Marine Reserve (RMGSF): this reserve is located in the south of the "Panamic Eco-region" in the southwest of Esmeraldas Province. It was declared a marine reserve in 2008 and has 37 km of coastline. In the marine area, coral reefs and rocky substrates in the subtidal area are observed. On the coast, low cliffs and sandy beaches are predominant. There is an estuarine area where mangroves are present (Ministerio del Ambiente 2014).

Central Coast
Manabí Province. Machalilla National Park (PNM): this is situated between Jipijapa, Puerto Lopez and Montecristi. It was declared a National Park in 1979. The Humboldt cold current directly affects this area. The National Park is composed of two areas: 1) the terrestrial and 2) the marine area. The latter belongs to the "Guayaquil Eco-region" (Sullivan and Bustamante 1999) and has two types of ecosystems, the marine and the coastal.
Pacoche Wild Life and Marine Reserve (RVSMCP) is located between Manta and Montecristi. Its surface is mainly terrestrial. However, 26468.21 ha are marine coastal environments (Ministerio del Ambiente 2015). The coast is characterised by cliffs, rocky shores, sandy beaches and coral reefs.
Ayampe -La Entrada: This area is not a protected area and is located between Santa Elena and Manabí Provinces. The importance of this area lies in its connectivity with the National Park Machalilla.
Canoa: Located to the north of Caraquez Bay. It is divided into four terrestrial areas of forests.
Jama: It has a surface of approximately 579 km . In the coast cliffs, coral reefs and sandy beaches are predominant. The studied intertidal localities are summarised in Table 1

Material and methods
Methodology applied in intertidal studies for sessile and mobile organisms.
The presence of sessile organisms (macroinvertebrates and seaweeds) in rocky shores was registered following the protocol developed and validated by the group of experts from the "South American Research Group on Coastal Ecosystems (SARCE)" for the sampling of rocky coastlines (SARCE 2012). At each station, three levels of the intertidal levels were studied (high, medium and low), determined according to the dominant biological groups by level. In each level, a transect of 50 m length was applied parallel to the coastline. Over the transect, quadrants (50 × 50 cm) were placed randomly, sampling 30 quadrants per site (10 quadrants for each intertidal level). In each level, the presence of sessile organisms was estimated.
The mobile organisms whose sizes were larger than 1 cm in each quadrant, were identified in the field. The organisms which were not identified, were fixed in 10% formaldehyde and taken as a voucher. Before this, they were relaxed with menthol crystals for two or three hours according to the field guide for specimen collection of the Universidad de Guayaquil (Mair et al. 2000). To register the history of each site, photographs of each quadrant were taken (Rogers et al. 1994).
For sandy beach localities, the methodology used by Aerts et al. (2004) was followed. The fieldwork was undertaken at low tide. Over a transect of 50 m length parallel to the beach line, five quadrants of 50 × 50 cm were placed every 10 m. In each quadrant, the sediment of 10 cm depth was collected and sieved through a 1 mm mesh. Finally, the samples were fixed in seawater with 8% formaldehyde.
Methodology applied in subtidal studies for sessile organisms and mobile organisms. Composition of sessile organisms were studied by using a quadrant of 50 × 50 cm and each quadrant was subdivided in 81 intersections. The quadrant was placed every 5 m, along the transect of 50 m length (Edgar et al. 2011). A diver was used to note the taxon or substrate that coincided with each point of intersection. In the cases where the points of intersection did not fall on any organism, only the type of substrate was recorded. The mobile invertebrates (crustaceans, molluscs, echinoderms) were recorded by a second diver on each side of the transect (1 m). The diver registered the presence of species every 5 m.
General spatial coverage. The spatial coverage ranged from Lat. 0.818900°; Long -80.006300° at the northernmost site to Lat. -3.189200°; Long -80.452833° at the southernmost site. It encompasses coastal environments of 1860 km (see Fig. 1).

Figure 1.
Study area and location of the sampling sites in the Ecuadorian coast.
Occurrence of taxa from mobile macroinvertebrates registered in the subtidal zone in the Ecuadorian coast in ten areas sampled.  Table 6.
Occurrence of taxa from sessile invertebrates and seaweeds registered in the subtidal zone in the Ecuadorian coast in ten areas of studies. Taxonomic coverage. This study recorded 612 species (479 of macroinvertebrates and 133 species of seaweeds). In the intertidal zones, a greater number of species was found (423 species) in relation of subtidal zones (189 species). The most represented groups were Mollusca, Annelida and Rhodophyta (Fig. 2). The Phyla Platyhelminthes and Sipuncula were not identified to species level, but only as morphotype. The highest diversity of mobile macroinvertebrates (323 species) were registered in the intertidal zone, in comparison with the subtidal zone where 157 species of macroinvertebrates (see Tables 3, 5).

Discussion
The results, herein reported, provide the most recent and extensive baseline study of benthic macroinvertebrates and macroalgae composition in the intertidal and subtidal zones along the Ecuadorian continental coastline from marine protected and non-protected areas. The number of taxa observed in this study was higher in relation to the results reported by Mair et al. (2002) and lower than those registered by Rivera (2012). However, the latter study included in the analysis additional substrates like cracks, stones, beaches and exposed surfaces, while the methodology, herein applied, only included rocky shores and beaches.
The results, herein reported, are the baseline for long term monitoring studies using agile and non-destructive protocols as those used in SARCE and MBON Pole to Pole Projects (SARCE 2012, MBON, P2P 2019). The Molluscs, Cnidarian and Rhodophyta are the main common groups recorded in Ecuadorian coast. More precisely, in the intertidal zone, the gastropods and algae were the more dominant organisms. The invertebrate composition showed a vertical zonation where the low intertidal zone was dominated by Echinolittorina paytensis, E. modesta, E. aspera and E. porcata. These results coincide with studies previously performed in Ballenita and Puntilla de Santa Elena and other sites in Ecuadorian coasts, where the family Littorinidae was the most common on the rocky shores (Giraldo et al. 2014, Miloslavich et al. 2016). The species Brachidontes playasensis, B. adamsianus, B. puntarenensis, B. semilaevis, Chthamalus sp., C. panamensis, C. southwardorum and Jehlius cirratus are part of a biotic complex in the high intertidal zone. This complex indicates that, besides the physical variation given by desiccation, insolation and thermal stress in the intertidal zone, the incidence of the tide itself contributes with food resources necessary for the survival of grazing gastropods and filtering organism (Littler et al. 1983). Physiological adaptation, such as stomach water storage in gastropods, makes their survival possible in areas with longer drying periods (Herrera-Paz et al. 2013). Nevertheless, sediment and bare rock availability strongly affect the presence of gastropods on the platform (Minchinton and Fels 2013).
This work improves the available information for continental Ecuadorian coasts related to benthic communities living in protected and non-protected areas. It also provides a standardised quantitative report of macroinvertebrates and seaweeds living in the intertidal and subtidal zones. Additionally, this study provides information for ecological and conservation research of marine-coastal environments that has been incipient until the present time, with limited systematised information on biodiversity. However, the scientific study of the marine biodiversity along the Ecuadorian coast remains to be completed as the present survey was developed for areas of special interest to Ecuador's Ministry of Environment. The available information is especially about commercial species focused on different taxa, such as fishes, crustaceans and molluscs (Coello and Herrera 2010), but is very scarce for the rest of the species. Within this context, the contribution of new research on benthic communities is important to support the country's fishery exports, ensure the sustainability of the food security of Ecuadorians, obtain extraction of active substances for biomedical uses and control the quality of the marine and estuarine ecosystems through bio-indicators of pollution. For this reason, the implementation of a biomonitoring programme is important to compare with other benthic communities and to monitor changes in biodiversity over time by using international standardised methodology.

Conclusions
The biological data, herein reported, are useful for a long-term monitoring programme to evaluate the status of conservation in protected areas, the influence of anthropogenic factors and the environmental natural changes on the community structure of macroinvertebrates and sessile organisms.