Photo: Essi Keskinen
In all, 19 macrozoobenthic species were considered threatened in the HELCOM Red List assessment. One species, an amphipod Haploops tenuis, was categorised as Endangered (EN) and eighteen species as Vulnerable (VU). Most of the threatened species are restricted to the western part of the HELCOM area with many occurring mainly in the Kattegat.
Nine species were classified Near Threatened (NT) and 23 species as Data Deficient (DD). Altogether, 51 species were red-listed in this assessment.
Of the almost 1 900 species included in the Baltic Sea checklist, 627 (33%) were left unevaluated (Not Evaluated). For these species the information required for the assessment was missing, for example due to the fact that the species never or only occasionally become sampled in normal monitoring.It is quite likely that eutrophication has played a significant role in the negative development for many of the red-listed benthic invertebrates. In the western HELCOM area, to which most of the red-listed species are restricted, the detrimental changes caused by eutrophication are the same as elsewhere in the Baltic Sea region, for example increased sedimentation and anoxia in bottom habitats.
Another important factor behind the declines is bottom trawling, which is very intense in some areas. Bottom trawling has a direct impact on benthic fauna on the actual site of trawling and causes turbidity and increased sedimentation over much larger areas.
Various construction activities, especially on the coast, have also had detrimental effects on bottom fauna. This includes sea defence or coast protection works, land reclamation, the construction of wind farms and dredging to deepen waterways, for example, as well as boulder fishing, which has decreased the amount of hard bottom habitats considerably in some areas in past decades.