Abstract
Climate change increases exposure and bioaccumulation of pollutants in marine organisms, posing substantial ecophysiological and ecotoxicological risks. Here, we applied a trophodynamic ecosystem model to examine the bioaccumulation of organic mercury (MeHg) and polychlorinated biphenyls (PCBs) in a Northeastern Pacific marine food web under climate change. We found largely heterogeneous sensitivity in climate-pollution impacts between chemicals and trophic groups. Concentration of MeHg and PCBs in top predators, including resident killer whales, is projected to be amplified by 8 and 3%, respectively, by 2100 under a high carbon emission scenario (Representative Concentration Pathway 8.5) relative to a no-climate change control scenario. However, the level of amplification increases with higher carbon emission scenario for MeHg, but decreases for PCBs. Such idiosyncratic responses are shaped by the differences in bioaccumulation pathways between MeHg and PCBs, and the modifications of food web dynamics between different levels of climate change. Climate-induced pollutant amplification in mid-trophic level predators (Chinook salmon) are projected to be higher (~10%) than killer whales. Overall, the predicted trophic magnification factor is ten-fold higher in MeHg than in PCBs under high CO2 emissions. This contribution highlights the importance of understanding the interactions with anthropogenic organic pollutants in assessing climate risks on marine ecosystems.
Highlights
Ocean warming, deoxygenation and ocean acidification amplify these impacts by increasing the exposure and bioaccumulation rates for contaminants in marine food webs[1,6,7,16]
The model accounts for the flow of biomasses and contaminants across 20 species groups in the ecosystem through their trophic interactions (Fig. S2 and Table S1), and includes the mean temperature tolerance (MTT) in marine invertebrates and fish (Table S2) and contaminant input data (Tables S3 and S4), but it does not account for some pollutant biogeochemical processes such as polychlorinated biphenyls (PCBs) cycling and increased rates of mercury methylation in a warming environment
In contrast to MeHg, PCB concentrations were projected to be amplified by climate change, the level of amplification was lower under the higher emission representative concentration pathways (RCPs) 8.5 scenario (Fig. 3A–F)
Summary
Deoxygenation and ocean acidification amplify these impacts by increasing the exposure and bioaccumulation rates for contaminants in marine food webs[1,6,7,16]. Model bias (MB) and MB standard deviation (i.e. MBSD, an indicator of variability and uncertainty of trophodynamic model predictions) were calculated by using projections of historical concentrations of PCBs and MeHg (i.e. from 1930–2010) simulated in southern resident killer whales, Orcinus orca (SRKW hereafter), and Chinook salmon (Oncorhynchus tshawytscha) with Ecotracer, and empirical PCB data reported for these species (see Methods; Supplementary Information). This is done by comparing the simulated contaminant data to the empirical contaminant data observed in these species to test the performance of the modelling approach and reveal any underlying variations linked to contaminant concentrations and lipid content reported in the literature
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