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Biogeography and anthropogenic pressures influence coral reef food webs Mémoire

par Paul, Emma
Président du jury Roisin, Yves
Promoteur Danis, Bruno ;Parravicini, Valeriano
Publication Non publié, 2021-07-08

Mémoire

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Résumé :

In the context of the Anthropocene, coral reefs face many threats: ocean acidification, coralbleaching, increased frequency and strength of hurricanes, overfishing and pollution. To protectthose hyper-diverse ecosystems, many studies have been conducted to understand their functioning.However, most of them overlooked a crucial feature: interactions between organisms. Food webs arenonetheless a key to ecosystems stability, resilience and resistance to disturbances since they governtheir structure and the fluxes that transit across them and enable scientists to forecast howecosystems will evolve under new environmental conditions.To fill knowledge gaps on trophic networks in coral ecosystem, we provide the first globaldatabase of weighted bipartite reef fish food webs, based on the most comprehensive empiricaldataset on species interactions, machine learning and a newly developed bioenergetic model.We found that reef fish food webs’ structure is not homogeneous across oceans and thatcomplex systems are more vulnerable, more modular and less connected than simple ones whilegeneralist, nested and non-modular networks tend to be more connected. Moreover, we carried outProcrustes analysis at both global and regional scale and developed a Bayesian framework to assessthe influence of biogeography and human activities on food webs’ structure. We found that reef fishfood webs area not equally impacted by biogeography and human pressures across tropical oceans.More precisely, mean SST, reef area, wave exposure, connectivity between reefs and gravity of fishmarkets were evidenced to be key variables to reef fish food web’s architecture.This master thesis raises questions about how reef fish food webs will evolve under newenvironmental conditions, due to global changes and human pressures, and how conservationstrategies should be adapted their architecture.