Abstract

Fisheries are threatening marine biodiversity, but global warming might worsen their adverse effects due to an expected reduction in the global biomass of the most basal species of food-webs, plankton. We use an allometric trophic network model to analyze the independent and combined effects of small-scale artisanal fisheries and climate change on the dynamic of an empirical intertidal rocky-shore food web of the Central Coast of Chile. We simulate the foodweb dynamic under different exploitation rates (fisheries impact) and depleting the plankton subsidy biomass (climate change impacts). We simulate each perturbation separately (independent effect) and also, we coupled them in one single simulation (combined effects). At the end of the simulations, we quantify the species biomass change between before and after perturbation. Both perturbations were propagated through the entire food-web. After fishing, all harvested species decrease their biomass while mostly all non-harvested species grew. Harvested macroalgae were vulnerable to very low exploitation rates. After depleting plankton subsidy, the biomass of filter-feeders, carnivores, and top predators strongly decreased while the biomass of omnivores, herbivores, and macroalgae increased weakly. Fisheries and climate change together, intensified the independent effects more than their simple additive effects, especially in harvested species.