Preprints
https://doi.org/10.5194/esd-2021-33
https://doi.org/10.5194/esd-2021-33

  09 Jun 2021

09 Jun 2021

Review status: this preprint is currently under review for the journal ESD.

Baltic Earth Assessment Report on the biogeochemistry of the Baltic Sea

Karol Kuliński1, Gregor Rehder2, Eero Asmala3, Alena Bartosova4, Jacob Carstensen5, Bo Gustafsson6, Per O. J. Hall7, Christoph Humborg6, Tom Jilbert8, Klaus Jürgens9, Markus Meier10,4, Bärbel Müller-Karulis6, Michael Naumann10, Jørgen E. Olesen11, Oleg Savchuk6, Andreas Schramm12, Caroline P. Slomp13, Mikhail Sofiev14, Anna Sobek15, Beata Szymczycha1, and Emma Undeman6 Karol Kuliński et al.
  • 1Department of Marine Chemistry and Biochemistry, Institute of Oceanology of the Polish Academy of Sciences, ul. Powstańców Warszawy 55, 81-712 Sopot, Poland
  • 2Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, 18119, Germany
  • 3Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, 10900 Hanko, Finland
  • 4Research and Development Department, Swedish Meteorological and Hydrological Institute, Norrköping, 601 76, Sweden
  • 5Department of Bioscience, Aarhus University, Frederiksborgvej399, DK-4000 Roskilde, Denmark
  • 6Baltic Sea Centre, Baltic Nest Institute, Stockholm University, SE-106 91 Stockholm, Sweden
  • 7Department of Marine Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden
  • 8Ecosystems and Environment Research Program, Faculty of Biological and Environmental Sciences, PO Box 65, 00014 University of Helsinki, Finland
  • 9Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, 18119, Germany
  • 10Department of Physical Oceanography and Instrumentation, Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, 18119, Germany
  • 11Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark
  • 12Center for Electromicrobiology, Section for Microbiology, Department of Biology, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
  • 13Department of Earth Sciences, Utrecht University, Princetonlaan 8A, 3584 CB, Utrecht, the Netherlands
  • 14Finnish Meteorological Institute, Erik Palmenin Aukio, 1 00560, Helsinki, Finland
  • 15Department of Environmental Science, Stockholm University, 10691 Stockholm, Sweden

Abstract. Location, specific topography and hydrographic setting together with climate change and strong anthropogenic pressure are the main factors shaping the biogeochemical functioning and thus also the ecological status of the Baltic Sea. The recent decades have brought significant changes in the Baltic Sea. First, the rising nutrient loads from land in the second half of the 20th century led to eutrophication and spreading of hypoxic and anoxic areas, for which permanent stratification of the water column and limited ventilation of deep water layers made favourable conditions. Since the 1980s the nutrient loads to the Baltic Sea have been continuously decreasing. This, however, has so far not resulted in significant improvements in oxygen availability in the deep regions, which has revealed a slow response time of the system to the reduction of the land-derived nutrient loads. Responsible for that is the low burial efficiency of phosphorus at anoxic conditions and its remobilization from sediments when conditions change from oxic to anoxic. This results in a stoichiometric excess of phosphorus available for organic matter production, which promotes the growth of N2-fixing cyanobacteria and in turn supports eutrophication.

This assessment reviews the available and published knowledge on the biogeochemical functioning of the Baltic Sea. In its content, the paper covers the aspects related to changes in carbon, nitrogen and phosphorus (C, N and P) external loads, their transformations in the coastal zone, changes in organic matter production (eutrophication) and remineralization (oxygen availability), and the role of sediments in burial and turnover of C, N and P. In addition to that, this paper focuses also on changes in the marine CO2 system, structure and functioning of the microbial community and the role of contaminants for biogeochemical processes. This comprehensive assessment allowed also for identifying knowledge gaps and future research needs in the field of marine biogeochemistry in the Baltic Sea.

Karol Kuliński et al.

Status: open (until 02 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2021-33', Donald Boesch, 14 Jul 2021 reply
  • RC2: 'Comment on esd-2021-33', Anonymous Referee #2, 01 Sep 2021 reply

Karol Kuliński et al.

Karol Kuliński et al.

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In its content, the paper covers the aspects related to changes in carbon, nitrogen and phosphorus (C, N, P) external loads, their transformations in the coastal zone, changes in organic matter production (eutrophication) and remineralization (oxygen availability), and the role of sediments in burial and turnover of C, N and P. Furthermore, this paper focuses also on changes in the marine CO2 system, structure of the microbial community and the role of contaminants for biogeochemical processes.
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