Written by Nereus Program Research Associate Ryan Swanson,
Nereus Program research fellow Hubert du Pontavice (Agrocampus Ouest) is lead author with co-authors Didier Gascuel (Agrocampus Ouest), Gabriel Reygondeau (UBC/Yale University), Aurore Maureaud and William Cheung (UBC) on a recently published article in the journal Global Change Biology. The authors analyzed seawater temperature effects on the spatial patterns of marine food webs, influencing how marine communities are expected to change over the course of the 21st century. For the time period 1950-2010, they looked at global coastal regions where a majority of fisheries production occurs, using seawater temperature and catch data to gain better insight into the structure of nearby marine communities. They compared both observed and modelled trends using three Earth model systems under two greenhouse gas emission (GHG) scenarios (RCP2.6 and RCP8.5) and found that ocean temperatures significantly influence biomass transfers through global coastal marine ecosystems and food webs. Additionally, the authors find that human-caused changes to species assemblages may have already impacted how coastal marine food webs function, and will continue to do so throughout the 21st century. You can read the full abstract below:
Abstract: Sea water temperature affects all biological and ecological processes that ultimately impact ecosystem functioning. In this study, we examine the influence of temperature on global biomass transfers from marine secondary production to fish stocks. By combining fisheries catches in all coastal ocean areas and life history traits of exploited marine species, we provide global estimates of two trophic transfer parameters which determine biomass flows in coastal marine food web: the trophic transfer efficiency and the biomass residence time in the food web. We find that biomass transfers in tropical ecosystems are less efficient and faster than in areas with cooler waters. In contrast, biomass transfers through the food web became faster and more efficient between 1950 and 2010. Using simulated changes in sea water temperature from three Earth system models, we project that the mean trophic transfer efficiency in coastal waters would decrease from 7.7% to 7.2% between 2010 and 2,100 under the ‘no effective mitigation’ Representative Concentration Pathway (RCP 8.5), while biomass residence time between trophic level 2 and 4 is projected to decrease from 2.7 to 2.3 year on average. Beyond the global trends, we show that the trophic transfer efficiencies and biomass residence times may vary substantially among ecosystem types and that the polar ecosystems may be the most impacted ecosystems. The detected and projected changes in mean trophic transfer efficiency and biomass residence time will undermine food web functioning. Our study provides quantitative understanding of temperature effects on trophodynamic of marine ecosystems under climate change.
du Pontavice, H., Gascuel, D., Reygondeau, G., Maureaud, A., and Cheung, W.W.L. (2019). Climate change undermines the global functioning of marine food webs. Global Change Biology, doi:10.1111/gcb.14944 link.