Alteration of coastal productivity and artisanal fisheries interact to affect a marine food web

M Isidora Ávila-Thieme,Derek Corcoran,Evie A Wieters,Pablo A Marquet,Sergio A Navarrete,Fernanda S Valdovinos,Alejandro Pérez-Matus

doi:10.1038/s41598-021-81392-4

Abstract

Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food web to these two global change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and changes in plankton productivity on food web dynamics. The food web was robust to the loss of all harvested species but sensitive to the decline in plankton productivity. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species by reducing the predation pressure of harvested consumers on non-harvested resources, and reducing the interspecific competition between harvested and non-harvested basal species. In contrast, the decline in plankton productivity increased the sensitivity of harvested species to fishing by reducing the total productivity of the food web. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.

Highlights

Top-down and bottom-up forces determine ecosystem function and dynamics
We found that the removal of all 22 harvested species negatively affected the structural properties of the food web, reducing the overall number of trophic interactions by 48%
Approach included the sessile filter-feeders, and four harvested species important for the fisheries: the Chilean muricid whelk Concholepas concholepas, the giant barnacle Austromegabalanus pssitacus, the sea squirt Pyura chilensis and the whelk Acanthina monodon. These results suggest that while the intertidal food web is robust to harvest-driven extinctions, it can be sensitive to a drastic decrease in plankton productivity

Summary

Introduction

Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a topdown force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. Network ecology has advanced our understanding of ecosystems by providing a powerful framework to analyze biological communities[36,37] Previous studies used this framework to assess food web robustness against species extinctions, defined as the fraction of initial species that remain present in the ecosystem after a primary extinction[38,39,40,41,42,43,44,45]. Other studies used a dynamic approach, which considers the structure and intensity of interactions in a food web, and the changes in species biomasses through time and the indirect effects that these changes have on other species[39,40,41,48,49,50] We use both approaches to understand the relative importance of harvested species in our food web. We analyze the (4) independent and (5) combined effects of fisheries and changes in plankton productivity on the food web dynamics through altering the plankton subsidy

Methods

Results

Conclusion