![]() The diversity of species within coral reef food webs and their associations with bottom‐up drivers likely buffers against trophic cascading across GBR functional guilds when reef shark assemblages are depleted, as has been demonstrated in other complex ecosystems. In turn, physical processes such as wave exposure and current velocity were both correlated well with multiple functional groups, reflecting how changes to energetic conditions and food availability, or modification of habitat affect fish distribution. They are the best loved example of indirect effects in undergraduate ecology. We found reef sharks to be positively associated with habitat complexity. Trophic cascades are the time-honored focal point of food-web dynamics. Instead, many functional groups, including sharks, responded positively to environmental drivers. While a fourfold difference in reef shark density was observed across our survey sites, this had no impact on either the density or biomass of teleost mesopredators or prey, providing evidence for a lack of trophic cascading across nGBR systems. Using a structural equation modelling (SEM) approach, we explored the interactions between the shark abundance and teleost mesopredator and prey functional group density and biomass, whilst explicitly accounting for the potentially confounding influence of environmental variation across sites. Using extensive survey data from coral reefs across the relatively unfished northern Great Barrier Reef (nGBR), we quantified the role of reef sharks in structuring coral reef fish assemblages. On coral reefs, which support highly diverse food‐webs, the degree to which top‐down trophic cascades can occur remains equivocal. Global overfishing of higher‐level predators has caused cascading effects to lower trophic levels in many marine ecosystems. Photo taken by Ken Marks on the Global Reef Expedition. Published in Ecology Abstract A whitetip reef shark (Triaenodon obesus) swims near a square frame used to survey corals. In the marine environment, trophic cascades are found mostly in coastal and benthic system ( 10, 11) but are believed to be uncommon in the open ocean ( 12, 13 ). Revisiting the paradigm of shark‐driven trophic cascades in coral reef ecosystems. Trophic cascades have been described as indirect top-down effects on two or more trophic levels ( 7, 8) that have the potential to drive regime shifts in aquatic systems ( 3, 9 ). Revisiting the paradigm of shark‐driven trophic cascades in coral reef ecosystemsĭesbiens, Amelia A., Roff, George, et al. Revisiting the paradigm of shark‐driven trophic cascades in coral reef ecosystems.
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