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Research article - Peer-reviewed, 2021

Modeling cyanobacteria life cycle dynamics and historical nitrogen fixation in the Baltic Proper

Hieronymus, Jenny; Eilola, Kari; Olofsson, Malin; Hense, Inga; Meier, H. E. Markus; Almroth-Rosell, Elin

Abstract

Dense blooms of filamentous diazotrophic cyanobacteria are formed every summer in the Baltic Sea. These autotrophic organisms may bypass nitrogen limitation by performing nitrogen fixation, which also governs surrounding organisms by increasing bioavailable nitrogen. The magnitude of the nitrogen fixation is important to estimate from a management perspective since this might counteract eutrophication reduction measures. Here, a cyanobacteria life cycle model has been implemented for the first time in a high-resolution 3D coupled physical and biogeochemical model of the Baltic Sea, spanning the years 1850-2008. The explicit consideration of life cycle dynamics and transitions significantly improves the representation of the cyanobacterial phenological patterns compared to earlier 3D modeling efforts. Now, the rapid increase and decrease in cyanobacteria in the Baltic Sea are well captured, and the seasonal timing is in concert with observations. The current improvement also had a large effect on the nitrogen fixation load and is now in agreement with estimates based on in situ measurements. By performing four phosphorus sensitivity runs, we demonstrate the importance of both organic and inorganic phosphorus availability for historical cyanobacterial biomass estimates. The model combination can be used to continuously predict internal nitrogen loads via nitrogen fixation in Baltic Sea ecosystem management, which is of extra importance in a future ocean with changed conditions for the filamentous cyanobacteria.

Published in

Biogeosciences
2021, volume: 18, number: 23, pages: 6213-6227
Publisher: COPERNICUS GESELLSCHAFT MBH

Authors' information

Hieronymus, Jenny
Swedish Meteorological and Hydrological Institute
Eilola, Kari
Swedish Meteorological and Hydrological Institute
Swedish Meteorological and Hydrological Institute (SMHI)
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Hense, Inga
University of Hamburg
Meier, H. E. Markus
Leibniz Institute for Baltic Sea Research Warnemuende Leibniz Institut fur Ostseeforschung Warnemunde
Almroth-Rosell, Elin
Swedish Meteorological and Hydrological Institute

Sustainable Development Goals

SDG14 Life below water

UKÄ Subject classification

Ecology

Publication Identifiers

DOI: https://doi.org/10.5194/bg-18-6213-2021

URI (permanent link to this page)

https://res.slu.se/id/publ/114657