Rapport nr 163: Bottenfaunan i Ålands skärgård 2022
Pykäri, Janina (2022)
Pykäri, Janina
Editori
Cederberg, Tony
Åbo Akademi, Husö biologiska station
2022
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-12-4247-2
https://urn.fi/URN:ISBN:978-952-12-4247-2
Tiivistelmä
In the summer of 2022, a study of benthic fauna was conducted in the Åland archipelago. The aim was to compare the benthic macroinvertebrate communities between 2013 and 2022 at 39 sites, some of which have been sampled for benthic fauna since 1994, and to explain the observed changes with sampled environmental factors. The stations were located around the main island of Åland, and the depths ranged from 3–35 meters.
Since the latest study in 2013, a new invasive polychaete Laonome xeprovala had arrived to Åland islands and was present at four sites in 2022. L xeprovala has potential to spread further in Åland islands and occupy new suitable locations in the future as well as to reach higher densities. The effect of the invasive polychaete on the local benthic fauna remains still unknown.
The recruitment of the Baltic clam (Macoma balthica) in 2022 was approximately only half of that of 2013, but the effect of one bad year on the Baltic clam population will likely be small. Differences in length distributions of M. balthica between 2013 and 2022 were highly variable among sites, and recovery from several years of failed recruitment was observed at some sites while M. balthica seemed to slowly disappear from other sites.
The main reason for failed M. balthica recruitment as well as worsened ecological status, that was observed for several stations, was likely oxygen depletion, that was observed at the bottom water at several sites. Even though the Baltic Sea is slowly recovering from eutrophication, oxygen depletion is still locally common in some areas of the Åland archipelago.
Based on the results of this and the previous study from 2013, three stations, where only little change in benthic macroinvertebrate community has been observed, were recommended to be removed from this monitoring to balance the amount of exposed and sheltered sites. In addition, the level of identification of taxa was documented in more detail in this study and changes to the procedure of collecting and analyzing sediment samples for organic matter content were proposed to allow for even better comparisons between different years’ data in the future.
Since the latest study in 2013, a new invasive polychaete Laonome xeprovala had arrived to Åland islands and was present at four sites in 2022. L xeprovala has potential to spread further in Åland islands and occupy new suitable locations in the future as well as to reach higher densities. The effect of the invasive polychaete on the local benthic fauna remains still unknown.
The recruitment of the Baltic clam (Macoma balthica) in 2022 was approximately only half of that of 2013, but the effect of one bad year on the Baltic clam population will likely be small. Differences in length distributions of M. balthica between 2013 and 2022 were highly variable among sites, and recovery from several years of failed recruitment was observed at some sites while M. balthica seemed to slowly disappear from other sites.
The main reason for failed M. balthica recruitment as well as worsened ecological status, that was observed for several stations, was likely oxygen depletion, that was observed at the bottom water at several sites. Even though the Baltic Sea is slowly recovering from eutrophication, oxygen depletion is still locally common in some areas of the Åland archipelago.
Based on the results of this and the previous study from 2013, three stations, where only little change in benthic macroinvertebrate community has been observed, were recommended to be removed from this monitoring to balance the amount of exposed and sheltered sites. In addition, the level of identification of taxa was documented in more detail in this study and changes to the procedure of collecting and analyzing sediment samples for organic matter content were proposed to allow for even better comparisons between different years’ data in the future.