Aranda's monitoring cruise: Baltic Sea oxygen level normal, but nutrient conditions have deteriorated

The research vessel Aranda has returned from its annual winter monitoring cruise. The cruise investigated the current physical and chemical state of Finnish sea areas and the levels of harmful substances in the sea. Phosphorus levels were found to have increased in Finnish sea areas.

Morning sun in the waters of Haapasaari in Finland's southeast sea areas. Photo: Harri Kankaanpää, SYKE

The oxygen situation was good in December-January in the Archipelago Sea and the Bothnian Sea, but oxygen problems continue in the Northern Baltic Proper and in the near-bottom water of the western Gulf of Finland. Phosphorus levels were high in all of Finland's sea areas. The observed concentrations in the Bothnian Bay were the highest ever recorded, and exceptionally high in the Bothnian Sea. Concentrations were also high in the Gulf of Finland, in some places almost reaching the highest levels ever recorded this time of year.

SYKE and the Finnish Meteorological Institute jointly monitor the state of the open sea

Water and sediment samples were taken on the cruise of the research vessel Aranda 17–29 January 2022, recording temperatures, salinity, oxygen levels, nutrients, and harmful substances such as pharmaceuticals. The sea areas that were monitored included the Gulf of Finland, the Archipelago Sea, the Northern Baltic Proper, the Bothnian Sea and the Bothnian Bay. The ice cover extent and ice properties were also surveyed in the Bothnian Bay. SYKE and the Finnish Meteorological Institute jointly monitor the state of the open sea. The monitoring is part of the monitoring programme of the Baltic Marine Environment Protection Commission (HELCOM) and the Finnish marine strategy. SYKE is responsible for chemical and biological monitoring and the monitoring of underwater noise, Finnish Meteorological Institute is responsible for physical monitoring.

Further information

The state of the Gulf of Finland, harmful chemicals, underwater noise: Leading Researcher, cruise leader Harri Kankaanpää, Finnish Environment institute SYKE, tel. +358 295 251 258, firstname.lastname@syke.fi State of the Gulf of Bothnia, the Archipelago Sea, and the Baltic Proper: Senior Researcher, cruise leader Pekka Kotilainen, Finnish Environment institute SYKE, tel. +358 295 251 317, firstname.lastname@syke.fi Internal nutrient flows of the Baltic Sea: Senior Scientist Jouni Lehtoranta, Finnish Environment institute SYKE, tel. +358 295 251 363, firstname.lastname@syke.fi Microplastic sedimentation: Research Professor Maiju Lehtiniemi, Finnish Environment institute SYKE, tel. +358 295 251 356, firstname.lastname@syke.fi Physical conditions in the Baltic Sea, climate change: Head of Unit Laura Tuomi, Finnish Meteorological Institute, tel. +358 295 396 404, firstname.lastname@fmi.fi

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