A model-based projection of historical state of a coastal ecosystem : relevance of phytoplankton stoichiometry

Kerimoglu, Onur and Große, Fabian and Kreus, Markus and Lenhart, Hermann J. and van Beusekom, Justus E.E. (2018) A model-based projection of historical state of a coastal ecosystem : relevance of phytoplankton stoichiometry. Science of the Total Environment, 639. pp. 1311-1323. ISSN 0048-9697

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    Abstract

    We employed a coupled physical-biogeochemical modelling framework for the reconstruction of the historic (H), pre-industrial state of a coastal system, the German Bight (southeastern North Sea), and we investigated its differences with the recent, control (C) state of the system. According to our findings: i) average winter concentrations of dissolved inorganic nitrogen and phosphorus (DIN and DIP) concentrations at the surface are ∼70–90% and ∼50–70% lower in the H state than in the C state within the nearshore waters, and differences gradually diminish towards off-shore waters; ii) differences in average growing season chlorophyll a (Chl) concentrations at the surface between the two states are mostly less than 50%; iii) in the off-shore areas, Chl concentrations in the deeper layers are affected less than in the surface layers; iv) reductions in phytoplankton carbon (C) biomass under the H state are weaker than those in Chl, due to the generally lower Chl:C ratios; v) in some areas the differences in growth rates between the two states are negligible, due to the compensation by lower light limitation under the H state, which in turn explains the lower Chl:C ratios; vi) zooplankton biomass, and hence the grazing pressure on phytoplankton is lower under the H state. This trophic decoupling is caused by the low nutritional quality (i.e., low N:C and P:C) of phytoplankton. These results call for increased attention to the relevance of the acclimation capacity and stoichiometric flexibility of phytoplankton for the prediction of their response to environmental change.

    ORCID iDs

    Kerimoglu, Onur, Große, Fabian ORCID logoORCID: https://orcid.org/0000-0003-2801-5493, Kreus, Markus, Lenhart, Hermann J. and van Beusekom, Justus E.E.;