Effects of phytoplankton dominance on marine coastal ecosystem processes

Marine phytoplankton is of great importance for climate regulation, contributing nearly 50% to global oxygen production and fixing atmospheric carbon dioxide (CO2). Yet, ongoing climate warming alters plankton metabolism, and leads to geographical redistribution of species. Climate driven changes in the phytoplankton dominance structure (the degree of dominance and the identity of the dominant species) directly affect ecosystem processes, such as carbon sequestration and resulting emissions of CO2, methane (CH4) and nitrous oxide (N2O). While numerous studies have investigated the impact of climate change on marine plankton, it is astonishing how little we know about the effects of phytoplankton dominance shifts on carbon burial and greenhouse gas (GHG) emissions. In this project, we aim to elucidate the effects of dominance changes in marine phytoplankton communities on two coastal ecosystem processes: carbon sequestration and resulting emissions of CO2, CH4 and N2O to the atmosphere. In particular, we will test (1) how the degree of dominance affects carbon export to the seafloor and the emission of GHGs, (2) how the dominance shift from diatoms to dinoflagellates affect those ecosystem processes during spring phytoplankton bloom, and (3) how the increasing cyanobacteria dominance affects carbon cycling and GHG emissions in summer. To answer these questions we will use state of the art mesocosm facilities at the Tvärminne Zoological Station and continuous measurements of CO2, CH4 and N2O fluxes from the sea to the atmosphere using instruments deployed offshore. The proposed research will bridge across trait-based plankton ecology, biogeochemistry, and atmospheric research, opening new research horizons for ecologists, atmospheric scientists and climate modelers willing to understand what will be the footprint of global biodiversity crisis on climate in the future.