Biodiversity and food web indicators of community recovery in intertidal shellfish reefs

Contains fulltext : 168969.pdf (publisher's version ) (Closed access)8 p

Biodiversity and food web indicators of community recovery in intertidal shellfish reefs

In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundation species (e.g. seagrasses, mangroves and reef-building corals, shellfish) with the implicit goal to protect or restore associated communities and their interactions. However, the number and accuracy of community level metrics to measure the success of these strategies are limited. Using intertidal shellfish reefs as a model, we tested to what extent foundation species alter community and food web structure, and explored whether basic metrics of food web structure are useful indicators of ecosystem complexity compared to other often-used indices. We found that shellfish reefs strongly modified community and foodweb structure by modifying habitat conditions (e.g. hydrodynamics, sediment grain size). Stable isotope-based food web reconstruction captured important differences between communities from bare mudflat and shellfish reefs that did not emerge from classic abundance or diversity measures. On shellfish reefs, link density and the number of top predators were consistently higher, while both connectance and the richness of intermediate species was lower. Species richness (+42%), species density (+79%) and total biomass of benthos, fish and birds (+41%) was also higher on shellfish reefs, but this did not affect the Shannon diversity or Evenness. Hence, our results showed that basic foodweb metrics such as link density and number of top consumers and intermediate species combined with traditional measures of species richness can provide a robust tool to measure conservation and restoration success. We therefore suggest that these metrics are included as Essential Biodiversity Variables (EBV), and implemented as ecosystem health indicators in legislative frameworks such as the Marine Strategy Framework Directive (MSFD)

Biodiversity and food web indicators of community recovery in intertidal shellfish reefs

In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundation species (e.g. seagrasses, mangroves and reef-building corals, shellfish) with the implicit goal to protect or restore associated communities and their interactions. However, the number and accuracy of community level metrics to measure the success of these strategies are limited. Using intertidal shellfish reefs as a model, we tested to what extent foundation species alter community and food web structure, and explored whether basic metrics of food web structure are useful indicators of ecosystem complexity compared to other often-used indices. We found that shellfish reefs strongly modified community and food web structure by modifying habitat conditions (e.g. hydrodynamics, sediment grain size). Stable isotope-based food web reconstruction captured important differences between communities from bare mudflat and shellfish reefs that did not emerge from classic abundance or diversity measures. On shellfish reefs, link density and the number of top predators were consistently higher, while both connectance and the richness of intermediate species was lower. Species richness (+ 42%), species density (+ 79%) and total biomass of benthos, fish and birds (+ 41%) was also higher on shellfish reefs, but this did not affect the Shannon diversity or Evenness. Hence, our results showed that basic food web metrics such as link density and number of top consumers and intermediate species combined with traditional measures of species richness can provide a robust tool to measure conservation and restoration success. We therefore suggest that these metrics are included as Essential Biodiversity Variables (EBV), and implemented as ecosystem health indicators in legislative frameworks such as the Marine Strategy Framework Directive (MSFD)

Benthic primary producers are key to sustain the Wadden Sea food web: stable carbon isotope analysis at landscape scale

Coastal food webs can be supported by local benthic or pelagic primary produc-ers and by the import of organic matter. Distinguishing between these energy sources is essen-tial for our understanding of ecosystem functioning. However, the relative contribution ofthese components to the food web at the landscape scale is often unclear, as many studies lackgood taxonomic and spatial resolution across large areas. Here, using stable carbon isotopes,we report on the primary carbon sources for consumers and their spatial variability across oneof the world’s largest intertidal ecosystems (Dutch Wadden Sea; 1460 km2intertidal surfacearea), at an exceptionally high taxonomic (178 species) and spatial resolution (9,165 samplesfrom 839 locations). The absence of overlap in d13C values between consumers and terrestrialorganic matter suggests that benthic and pelagic producers dominate carbon input into thisfood web. In combination with the consistent enrichment of benthic primary producers(d13C 16.3&) relative to pelagic primary producers (d13C 18.8) across the landscape, thisallowed the use of a two-food-source isotope-mixing model. This spatially resolved modellingrevealed that benthic primary producers (microphytobenthos) are the most important energysource for the majority of consumers at higher trophic levels (worms, molluscs, crustaceans,fish, and birds), and thus to the whole food web. In addition, we found large spatial hetero-geneity in the d13C values of benthic primary producers (d13C 19.2 to 11.5&) and primaryconsumers (d13C 25.5 to 9.9&), emphasizing the need for spatially explicit sampling of ben-thic and pelagic primary producers in coastal ecosystems. Our findings have important impli-cations for our understanding of the functioning of ecological networks and for themanagement of coastal ecosystems

Benthic primary producers are key to sustain the Wadden Sea food web: stable carbon isotope analysis at landscape scale

Coastal food webs can be supported by local benthic or pelagic primary producers and by the import of organic matter. Distinguishing between these energy sources is essential for our understanding of ecosystem functioning. However, the relative contribution of these components to the food web at the landscape scale is often unclear, as many studies lack good taxonomic and spatial resolution across large areas. Here, using stable carbon isotopes, we report on the primary carbon sources for consumers and their spatial variability across one of the world's largest intertidal ecosystems (Dutch Wadden Sea; 1460 km2 intertidal surface area), at an exceptionally high taxonomic (178 species) and spatial resolution (9,165 samples from 839 locations). The absence of overlap in δ13C values between consumers and terrestrial organic matter suggests that benthic and pelagic producers dominate carbon input into this food web. In combination with the consistent enrichment of benthic primary producers (δ13C −16.3‰) relative to pelagic primary producers (δ13C −18.8) across the landscape, this allowed the use of a two-food-source isotope-mixing model. This spatially resolved modelling revealed that benthic primary producers (microphytobenthos) are the most important energy source for the majority of consumers at higher trophic levels (worms, molluscs, crustaceans, fish, and birds), and thus to the whole food web. In addition, we found large spatial heterogeneity in the δ13C values of benthic primary producers (δ13C −19.2 to −11.5‰) and primary consumers (δ13C −25.5 to −9.9‰), emphasizing the need for spatially explicit sampling of benthic and pelagic primary producers in coastal ecosystems. Our findings have important implications for our understanding of the functioning of ecological networks and for the management of coastal ecosystems