Rapport nr 162: Småskaliga muddringars effekter på förekomsten och sammansättningen av vattenvegetationen
Rancken, Ellen (2022)
Rancken, Ellen
Editori
Cederberg, Tony
Åbo Akademi, Husö biologiska station
2022
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-12-4151-2
https://urn.fi/URN:ISBN:978-952-12-4151-2
Tiivistelmä
In the summer of 2021, the impact of small-scale dredging on the presence and composition of macrophytes was studied at ten sites in different parts of the Åland islands (Bergö, Strömma, Svartsmara, Bamböle and Hulta). This study focused on small scale dredging sites, such as boat houses or private jetties.
The sites were determined by using Google Earth, Karttapaikka and by verification on site. These sites were dredged at different times and at some sites the dredging might have taken place many decades ago. The vegetation was mapped while snorkelling or diving using a transect line both in and outside of the dredged area.
In most locations it was clear where the dredged area was due to the bottom substrate, the vegetation, the turbidity and so on. In many of these sites the effect of the dredging seemed to be very local, which is expected when considering small-scale dredging sites. Although several small-scale dredging sites might have a cumulative effect. The sedimentation and release of harmful substances (environmental toxins or heavy metals) previously embedded in the sediment can also influence on a bigger scale. In general, more species and a higher cover of vegetation was observed outside of the dredged area, as expected.
The sites were determined by using Google Earth, Karttapaikka and by verification on site. These sites were dredged at different times and at some sites the dredging might have taken place many decades ago. The vegetation was mapped while snorkelling or diving using a transect line both in and outside of the dredged area.
In most locations it was clear where the dredged area was due to the bottom substrate, the vegetation, the turbidity and so on. In many of these sites the effect of the dredging seemed to be very local, which is expected when considering small-scale dredging sites. Although several small-scale dredging sites might have a cumulative effect. The sedimentation and release of harmful substances (environmental toxins or heavy metals) previously embedded in the sediment can also influence on a bigger scale. In general, more species and a higher cover of vegetation was observed outside of the dredged area, as expected.