Understanding coral reef functioning is a priority in the context of climate change and widespread increase of anthropogenic impacts. Productivity is an approach that integrates species specific traits to the measure of biomass, allowing a better comprehension of the drivers of the reef ecosystem dynamics and processes. Previous studies conducted in the hotspots of biodiversity, showed that productivity is mainly driven by pelagic subsidies. We aimed to understand the main environmental variables and trophic guilds that lead the productivity in the marginal Southwestern Atlantic by modeling data collected with underwater visual censuses. The value of productivity found in Brazilian reefs is 3,329 kg/ha/day, comparable to the ones found on the pelagic-driven ecosystems in the Indo-Pacific. However, our generalized additive model revealed a productivity controlled by benthic components: turf, coral and bare rock coverage. Ten species are responsible for 75% of the productivity, and most of them are invertivores or omnivores. Those species are generalist feeders which opportunistically feed on the planktonic empty niche without competition with many planktivores. Through the import of nutrients from the water column and soft bottom outside of the reef, these generalist species represent an important source of external nutrients. The South-Atlantic marginal is a benthic driven system employing a different strategy and trophic pathway for productivity compared to biodiversity hotspots.
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