Phytoplankton are at the basis of the Baffin Bay trophic network. Phytoplankton are a highly diverse set of organisms, with one group, diatoms, particularly important in the food web and in carbon export. Here we investigate what controls the relative abundance of diatoms in the Baffin Bay region. Using sensitivity analysis within a trait-based plankton model, we show how winter nitrate concentration and winter silicic acid concentration are controlling the relative importance of each biogeochemical group in the phytoplankton assemblage. We use a one-dimensional version of the MIT general circulation model coupled to its biogeochemical/ecosystem component. This model is particularly efficient at representing a diversity of phytoplankton functional traits and size classes, and its results are compared to observations at an ice camp for investigating the phytoplankton assemblage. Our study suggests that the absence of nutrient limitation before the bloom prevents a differentiation of the assemblage at this stage. However, numerical experiments varying winter nitrate and winter silicic acid modified the relative contribution of diatoms after the bloom. Hence, a possible departure from the average condition of nutrients following the impacts of climate change in the Arctic would change the relative contribution of diatoms to the phytoplankton assemblage after the bloom; this may have cascading effects on the function of Arctic marine ecosystems.

Primary Presenter: Maxime Benoît-Gagné, Université Laval (maxime.benoit.gagne@gmail.com)

Authors:

Maxime Benoît-Gagné, Université Laval  (maxime.benoit.gagne@gmail.com)

Stephanie Dutkiewicz, Massachusetts Institute of Technology  (stephdut@mit.edu)

Dany Dumont, Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski  (Dany_Dumont@uqar.ca)

Frédéric Maps, Université Laval  (frederic.maps@bio.ulaval.ca)