Speaking: Dr. Jens M. Nielsen, Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington
Dr. Jens M. Nielsen will discuss comparing empirical models which can be used with satellite ocean color data to estimate phytoplankton size-fractionated chlorophyll in the Bering and Chukchi seas. Models were compared using total chlorophyll as the predictor for three size-fractions (<5, 5-20 and > 20 m). First, existing size fraction models were accessed, with their global original parameters, and then compared them to models which were regionally-tuned using 266 in-situ surface chlorophyll samples for each size, collected in 2017 and 2019. In addition, other input variables (e.g. sea surface temperature (SST), spatial location) were tested to improve predictions of chlorophyll size fractions.
Finally, the utility of general additive and Random Forest models was assessed. Comparison among models show the regionally tuned models perform best regardless of size fraction, with total chlorophyll being the most important predictor. SST appears to improve the models primarily for the smallest size fraction. Future implementation of these models with long-term satellite ocean color data can help us understand the effects of long-term environmental change in the Bering and Chukchi ecosystems, and aid the prediction of future trophic scenarios, which is necessary for ecosystem management.
Bio
Dr. Jens M. Nielsen is an aquatic ecologist. Focusing primarily on plankton ecology, his research aims to understand community and trophic dynamics in ecosystems. He is further interested in how chemical, physical and biological factors influence the functioning of ecosystems, and how ecological research can inform ecosystem management. His current research focuses on analyzing long-term ichthyoplankton data in an effort to develop biological indicators of ecosystem changes along the US west coast from California to Alaska. Dr. Jens M. Nielsen's past research has centered on food web ecology and diet tracing techniques through a variety of empirical, modeling and syntheses studies. Before joining NOAA, he worked as a post-doctoral fellow at University of Washington and at Queen Mary University of London, United Kingdom. He holds a PhD in Marine Ecology from Stockholm University, Sweden.