Algae report number 4, 2025

Abstract

The stations along the west coast were quite different regarding species diversity and total cell numbers. The outer most station, Å17, in Skagerrak had low cell numbers and mainly small cells were found. At the rest of the stations the cell numbers and biodiversity were higher and diatoms dominated. Two species that occurred in high cell numbers were Thalassionema nitzschioides and Skeletonema marinoi. The genus Chaetoceros was also common and especially dominant in the plenty full fluorescens maxima found along the coast.

The diversity and cell abundances of phytoplankton varied greatly in the Baltic Sea. The chain-forming diatom S. marinoi, commonly found during the spring bloom, was observed at most stations and was highly abundant in several samples. Particularly at station BY15, high cell counts of S. marinoi were recorded, where the species
dominated the phytoplankton community. The dinoflagellate Peridiniella catenata, also characteristic of the spring bloom in the Baltic Sea, was observed at most stations as well, although in low abundances.

Chlorophyll diagrams and maps are not included in this report due to delays in the analysis