Phytoplankton diversity is essential for the productivity and functioning of the marine environment. Coastal ecosystems are particularly prone to changes in phytoplankton diversity due to intense anthropogenic activities, and understanding the drivers of this is of primary importance for predicting and managing human-induced impacts. Here, we present a holistic view of the causal network associated with phytoplankton diversity. We aim to elucidate the strongest causal determinant in coastal environments by investigating nutrients; temperature; and plankton abundances. We applied Convergent Cross Mapping (CCM) to the Helgoland Roads time series, one of the most extensive datasets in the world. CCM allows to build a causal network by examining non-linear causal links and pairwise feedbacks, within an empirical dynamic modeling (EDM) framework. Our results show uneven phytoplankton communities dominated by fewer species at Helgoland Roads the last 20 years. We found that SST and N/P ratios are the strongest causal determinants of phytoplankton diversity and that phytoplankton diversity has the potential to impact on nutrient cycling and particularly silicate concentrations and ratios. 

Primary Presenter: Areti Balkoni, Alfred-Wegener Institute for Polar and Marine Research (areti.balkoni@awi.de)

Authors:

Areti Balkoni, Alfred-Wegener-Institute for Polar and Marine Research  (areti.balkoni@awi.de)

Maïté Guignard, Alfred-Wegener-Institute for Polar and Marine Research  (maite.guignard@awi.de)

Johannes Rick, Alfred-Wegener-Institute for Polar and Marine Research   (johannes.rick@awi.de)

Maarten Boersma, Alfred-Wegener-Institute for Polar and Marine Research   (Maarten.Boersma@awi.de)

Inga Kirstein, Alfred-Wegener-Institute for Polar and Marine Research  (inga.kirstein@awi.de)

Karen Wiltshire, Alfred-Wegener-Institute for Polar and Marine Research  (Karen.Wiltshire@awi.de)