Övervakning av mjukbottenfaunanlängs Sveriges västkust Rapport från verksamheten år 2004

• Summary in English The soft-sediment macrofauna of the west coast of Sweden is monitored by comission of the Swedish Environmental Protection Agency in collaboration with “Bohuskustens vattenvårdsförbund” and the counties of Västra Götaland and Halland. The purpose is to detect long time changes in the marine environment, principally those caused by eutrophication and oxygen deficiency. 33 localities along the west coast of Sweden are sampled once a year in May. Four samples are taken with a 0.1m2 Smith-McIntyre grab at 11 localities, two samples at 19 localities and five samples at the two localities along the coast of Halland. The red-ox conditions of the sediment are measured at each locality. All fauna retrieved on a 1mm sieve are taxonomically identified and counted. This report is based on all the samples from 2003, and samples from 2004 which are analyzed. A total of 24.832 individuals belonging to 231 different taxa were identified in the 2003 sampling program which iaround 4000 individuals and 24 taxa less than in 2002. This was mainly caused by the reduction in specieand abundance among the deeper localities in Skagerrak. A more thorough description of these results was given in the report previous year. At one locality (Rivö, Sk 34) situated in a small depression close to the harbour of Göteborg the fauna has been reduced to low abundances and consisted only of species tolerant to environmental stress. This is most probably caused by a period of oxygen deficiency sometime during the year. At the locality outside Laholmsbukten (Ka 6) the fauna is impoverished due to periods of oxygen deficiency in 2000 and 2002. Analysis of similarity in the community structure between all localities, show that the localities ordinates with respect to how exposed the localities are situated in the same pattern as the samples from 2002. Localities along the coast and in the outer archipelago are dominated by species typical for an environment with a strong bento-pelagic coupling. Sub-surface deposit feeders, which are more typical in hydrodynamic calmer environments, are more dominant in localities at greater depth in the open sea. In the inner archipelago and fjords surface deposit feeders are dominant among the fauna. There was no significant statistical difference between the years 2002 and 2003 within any of the degrees of exposure. Neither the red-ox measurements nor the oxygen measurements, performed within the monitoring program of the Swedish Meteorological and Hydrological Institute, indicate that there had been any periods with severe oxygen deficiency at any of the localities during the period May 2003 to May 2004. The samples 2004 which are analyzed so far, shows that changes in fauna structure in the deeper parts of Kattegatt and Skagerrak as well as in Brofjorden and the nearby coast has been relatively small and related to normal population variations and natural variations in the hydrographical environment and that the fauna at the locality outside Laholmsbukten is still affected due to earlier periods of oxygen deficiency.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Monitoring

Benthic fauna

West coast of Sweden

community structure

hydrodynamic environment

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