Algae report number 5, 2025

Abstract

The stations in the Skagerrak and Kattegat varied in both species richness and total cell counts. At both stations in the Skagerrak, species richness was high, while in the Kattegat, only the coastal station showed similarly high species richness. Total cell counts were also high, except at Anholt E, the offshore station in the Kattegat, where
they were lower. The species Dactyliosolen fragilissimus and Skeletonema marinoi were particularly common. The genus Chaetoceros was also frequently observed and was especially dominant in the large fluorescence peak found in the Sound. The coccolithophore Emiliania huxleyi was very common at all stations except Anholt E. All integrated chlorophyll values were within the normal range in the Skagerrak. However, the integrated chlorophyll values (0–10 m) were above normal at the coastal station in the Kattegat, while the offshore station had lower chlorophyll concentrations than what is considered normal.

The diversity and cell abundances of phytoplankton were generally low in the Baltic Sea. The toxin producing Dinophysis acuminata was present at all stations and quite common at several stations. Various species of colony forming cyanobacteria were present at several stations and especially common in the south western part of the Baltic Sea. All Stations integrated chlorophyll concentrations were within normal for the month.