Global change impact on plankton from Patagonian coastal waters: Role of interacting drivers

Abstract

The coastal South West Atlantic Ocean (SWAO), including Patagonia, is one of the most productive aquatic areas of the World, supporting important commercial fishery and being the breeding site of several flagship species. The area is affected by global change, as evidenced through historical patterns of diverse drivers (e.g., temperature), and by important urban influence (i.e., sewages, industrial and agricultural wastes) in spite of its low population density. In this chapter we will focus on the impacts of global change on plankton, but mostly on phytoplankton as they constitute the base of this highly productive trophic web. The impacts of different global change drivers on these organisms are diverse, and range from an inhibition of primary productivity (with solar UVR being the main driver of this effect) to an enhancement, caused mainly by increased inputs of nutrients (that can even result in eutrophication at local scales). However, the different drivers of global change generally interact in an antagonistic or synergistic manner thus reducing or enhancing the individual effects. On long-term scales of exposure to drivers of global change, the species composition and size distribution of the communities can be significantly altered towards more fitted groups. However, they not necessarily support higher trophic levels and eventually, they could be toxic for humans and / or can alter the exchange atmosphere-sea and potential sequestration of CO2 through the biological pump. The interaction of phytoplankton with heterotrophs (e.g., bacterioplankton, zooplankton, meroplankton) would affect the overall response to global change of plankton mainly by cascading effects but surprisingly, very few studies were performed with these organisms. Most of these studies were designed to evaluate the individual responses of UVR and in few others, global change was evaluated in the context of human disturbances (i.e., pollution) affecting the distribution of zooplankton communities. Overall, the lack of integral data difficult our understanding of plankton responses and thus, more multifarious experimentation and including multi-trophic levels are needed to improve our models and predictions on the impact of global change on the coastal ecosystems of the SWAO, such as those of Patagonia.