Project: Changes in vertical stratification and their impact on phytoplankton communities

NWO Award Abstract:

Global warming will change physical, chemical and biological processes in the oceans. Ocean-climate models predict that warming of the surface layer may strengthen vertical stratification, starting earlier in spring and lasting longer in autumn. This results in suppressed upward mixing of nutrients from the deep ocean. Changes in stratification will have major effects on the growth and species composition of the phytoplankton. This will subsequently impact grazing, viral lysis and sedimentation rates, with cascading effects on ecosystem functioning and biogeochemical fluxes. Little is known, however, on the exact implications of global warming for these fundamental processes. We propose to investigate how changes in vertical stratification affect phytoplankton communities (growth, losses and composition) along a North-South gradient in the Atlantic Ocean. Our study will be based on oceanographic cruises from Iceland to the Canary Islands and detailed laboratory experiments with representative phytoplankton species, both integrated in advanced models of hydrodynamics and plankton dynamics and productivity. We have chosen for the Northeast Atlantic Ocean, because it is a key area in global ocean circulation and a large sink for atmospheric CO2, and a major determinant of the climate in Western Europe. Furthermore, the Atlantic Ocean offers a gradient from weak seasonal stratification in the North to strong permanent stratification in the (sub)tropics. This gradient offers ideal opportunities for the comparative study of different stratification regimes. Our integrated approach of physical, chemical, and biological processes, by a new multidisciplinary research team, will enable a better understanding of the implications of global warming for plankton growth in the Northeast Atlantic Ocean.