Rapport nr 95: Tillståndet i åländska skärgårdsvatten – förslag till kvalitetsparametrar för den åländska vattenlagen
ÖSTMAN, M; BLOMQVIST, E.M (1997)
ÖSTMAN, M
BLOMQVIST, E.M
Åbo Akademi, Husö biologiska station
1997
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This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:952-12-0055-3
https://urn.fi/URN:ISBN:952-12-0055-3
Tiivistelmä
In 1997 a new law af water protection came into force on the Åland Islands. The law includes the establishment of norms for water quality. Any activity that is harmful for the water environment and could jeopardize the fullfilment of the norms af water quality is forbidden by the law. In this report a comparison was made between possible parameters of water quality for which the norms could be established. This was done by surveying water quality information from archipelago waters of the Åland Island from the 1980s and 1990s. The main source of information was the research reports of Husö Biological Station and unpublished water sampling data from the Provincial Governement of Åland, Fisheries Division. The emphasis in this report was entirely put an eutrophication, which is the main threat against the water environment in the region. The most important local sources of nutrients are the discharges from agriculture and fish farming, non-treated waste water from sparsly populated areas and waste water from sewage treatment plants.
In 1985-1992 the research efforts of Husö biological station were concentrated on the brackish water environment in four regions in the vicinity of the Åland mainland. In the inlet system close to the large fjärd Lumparn on central Åland several symptoms of severe eutrophication were observed, i.e. high nitrogen and phosporus concentrations, oxygen deficiency in the bottom water and low diversity, abundance and biomass of the benthic macrofauna. In the archipelago of NW Åland, which was considered an undisturbed area in the 1970s, signs of increasing eutrophication were noted (decreasing number of species and increasing total abundance and biomass due to organic enrichment of the sediment). Further investigations of these areas in 1992-1994 confirmed the trends observed in the previous studies. The phosphorus concentration on 11 monitoring stations in the inner, intermediate and outer archipelago showed an overall significant increase from the late 1980s to the early 1990s, and the Secchi depth values decreased significantly during the same period, indicating an ongoing process of eutrophication du ring the recent 10 years.
Data on the seasonal variation of the most frequently used parameters of water quality (mainly from the Husö viken area) were analyzed with regard to their ability to describe the state of the water environment as a whole. Also, the use of parameters describing communities of water organisms, such as benthic macrofauna, littoral fauna, vegetation and fish, was discussed. As a result it was concluded that no single parameter alone is sufficient to describe the whole system satisfactory. Thus, instead of a singel parameter of water quality, a combination of water quality and benthic macrofauna parameters is proposed to be used in the assessment of the state of the water environment in the future.
In 1985-1992 the research efforts of Husö biological station were concentrated on the brackish water environment in four regions in the vicinity of the Åland mainland. In the inlet system close to the large fjärd Lumparn on central Åland several symptoms of severe eutrophication were observed, i.e. high nitrogen and phosporus concentrations, oxygen deficiency in the bottom water and low diversity, abundance and biomass of the benthic macrofauna. In the archipelago of NW Åland, which was considered an undisturbed area in the 1970s, signs of increasing eutrophication were noted (decreasing number of species and increasing total abundance and biomass due to organic enrichment of the sediment). Further investigations of these areas in 1992-1994 confirmed the trends observed in the previous studies. The phosphorus concentration on 11 monitoring stations in the inner, intermediate and outer archipelago showed an overall significant increase from the late 1980s to the early 1990s, and the Secchi depth values decreased significantly during the same period, indicating an ongoing process of eutrophication du ring the recent 10 years.
Data on the seasonal variation of the most frequently used parameters of water quality (mainly from the Husö viken area) were analyzed with regard to their ability to describe the state of the water environment as a whole. Also, the use of parameters describing communities of water organisms, such as benthic macrofauna, littoral fauna, vegetation and fish, was discussed. As a result it was concluded that no single parameter alone is sufficient to describe the whole system satisfactory. Thus, instead of a singel parameter of water quality, a combination of water quality and benthic macrofauna parameters is proposed to be used in the assessment of the state of the water environment in the future.