Impacts of warming and ocean acidification on the southern Benguela food web and fisheries

South African marine environments are forecast to experience an increase in sea surface temperature of ~ 3°C and a decrease of ~ 0.3 pH units by the end of the century. Sensitivity to acidification is intensified when taxa... [ view full abstract ]

South African marine environments are forecast to experience an increase in sea surface temperature of ~ 3°C and a decrease of ~ 0.3 pH units by the end of the century. Sensitivity to acidification is intensified when taxa are simultaneously exposed to increased seawater temperature. The warming and acidification forecast for South Africa can be expected to have detrimental effects on a number of species and potentially on the ecosystem as a whole. The effects of acidification and warming were evaluated for the southern Benguela system using climate projections of temperature and pH derived from the NEMO-MEDUSA 2.0 model under the RCP 2.6 and 8.5 emission scenarios. In the simulations, because of limited information, acidification is assumed to affect only the mortality of plankton, squid and macrobenthos. Of the drivers examined in this study, warming had the greatest effect on species biomass and the effect was mainly negative. The magnitude of the effects of warming were stronger under the RCP 8.5 than under the 2.6 emission scenario. Our results suggest that the southern Benguela system is likely to experience substantial changes in the abundance of some species important to the region’s fisheries as a result of climate change. Future planning for fisheries needs to account for these changes including management measures that strive to maintain the resilience of key species and the system as a whole. Our results reinforce the importance of including consideration of the indirect and combined impacts of climate change and fishing in management and planning.