The effects of CO2 dependencies and dual driver interactions on end-of-century phytoplankton communities - A modelling study

• Main Authors: Seifert, Miriam, Nissen, Cara, Rost, Bjoern, Vogt, Meike, Völker, Christoph, Hauck, Judith
• Format: Conference Object
• Language: unknown
• Published: 2022
• Subjects: Ocean acidification; Southern Ocean
• Online Access: https://epic.awi.de/id/eprint/56121/; https://hdl.handle.net/10013/epic.4c6d5884-177c-4dd8-9a8f-a05b744edf0e

Biogeochemical models are used to project future plankton community composition and biogeochemical fluxes. Phytoplankton growth therein is usually parametrized by sensitivities to the bottom-up factors temperature, light, and nutrient availability. However, many laboratory studies identify the carbonate system as an additional and essential growth-determining factor, especially in light of ongoing ocean acidification. Besides, growth-responses towards one factor are often altered by the level of another factor, and these so-called interactive effects are barely considered in models. In the presented work, model functions for carbonate system dependencies of growth and calcification were developed based on published results of laboratory data and implemented into a biogeochemical model. Using the results of an earlier meta-analysis on dual driver interactions, this new model setup was then substituted by interactive growth effects between the carbonate system, temperature, and light. End-of-century phytoplankton biomass and community composition in a high-emission scenario was projected by using one model version with and one model version without driver interactions. The results reveal that interactive growth effects considerably alter the future community composition compared to the model version without interactions. These alterations are largest in the Southern Ocean. Globally, the model with interactions projects a future phytoplankton community consisting out of more small phytoplankton and fewer diatoms and coccolithophores. Hence, considering interactive growth effects between bottom-up factors can essentially modify the projections of future phytoplankton community composition and related biogeochemical fluxes, and should be considered more closely in biogeochemical models.