Abstract
Temperate rocky reefs in Atlantic Patagonia are productive areas that support a high diversity of invertebrates, algae, and fishes. Complex surface structures on rocky reefs offer a range of microhabitats, which in turn, lead to a broad variety of co-existing species. Despite their ecological importance and the ecosystem services they provide, Patagonian rocky reef habitats have received limited attention. Until now studies have not discerned nor consequently described the assemblages found on each of the different surface orientations, namely horizontal, vertical, overhang and cavefloor. During this study we developed a protocol for sampling different surface orientations on subtidal rocky reefs using georeferenced high-resolution photoquadrats. We described and compared the epibenthic assemblage of surface orientations on 7 rocky reefs within 1–25 m depth in a northern Patagonia gulf. A total of 70 taxa were identified (12 macroalgae, 44 invertebrates, 10 tunicates, and 4 fishes), which doubles the number of species previously reported for the area. Each surface orientation presented a different assemblage structure while species richness was higher on vertical surfaces. The overhang surfaces had the most distinct assemblage conformed by cnidarians, tunicates, sponges and the absence of algae. The average overall species richness increased with depth due to the increase of sponge and tunicate species. Our results highlight the need of including several surface orientations in rocky reef biodiversity monitoring. This study offers a protocol for large-scale programs aimed at monitoring changes in biodiversity, which is broadly accessible and will provide accurate information. With robust yet simple, non-destructive and relatively low-cost practices this protocol can adequately assess changes in marine habitats, which provide important ecosystem services.
Highlights
Rocky subtidal reefs are recognized as highly biodiverse and productive areas, in temperate waters of the world where other types of communities, such as coral reefs are scarce or absent
A total of 70 taxa were identified from 560 georreferenced photoquadrats covering more than 1,500 m of rocky reef ledge (Supplementary Table 1)
This paper highlights the importance of sampling different surface orientations in subtidal monitoring programs as distinct epibenthic assemblages were associated to each orientation of the rocky reefs
Summary
Rocky subtidal reefs are recognized as highly biodiverse and productive areas, in temperate waters of the world where other types of communities, such as coral reefs are scarce or absent. These areas generally support communities dominated by macroalgae that are habitat forming species that provide shelter, food and substrate for a broad range of organisms in turn. Monitoring of EOVs are intended to provide the scientific, governance and policy baselines against which anthropogenic driven effects may be measured and reported This knowledge is needed for conservation and management of ecosystem functions and services of subtidal rocky reefs that are often overlooked. Long term monitoring programs, such as MBON (Marine Biodiversity Observation Network) Pole to Pole which monitor biodiversity on rocky shores from the American continent, could be a way of coordinating activities that may fill local knowledge gaps whilst simultaneously providing broader scale information on the effects of global change
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