Algae report number 4, 2026

Abstract

Species diversity was normal but cell abundance was high along the Swedish west coast. The only exception was the outer most station in Skagerrak, Å17, where the cell abundance and biodiversity was low. Small to medium sized flagellates dominated all samples except at Å17. The most numerous taxa found was difficult to get to a scientific name but might belong to the order prymnesiales as some cells seemed to have a short haptonema. A live sample was collected the day after sampling at Släggö by Kristineberg center and they had a better shape but were still difficult to name to any scientific entity. The integrated chlorophyll concentrations (0-10 m and 0-20 m) were above the normal range for the month at all stations except at Å17 where they were below normal.

Diversity and cell abundances of phytoplankton were generally moderate in the Baltic Proper. The spring bloom was ongoing at most stations, with varying amounts of typical spring bloom species such as the diatoms Skeletonema marinoi, Pauliella taeniata and Melosira arctica, but also the dinoflagellate Peridiniella catenata. However, at BY2 Arkona the spring bloom was completely over. The integrated chlorophyll concentrations were within the normal range for this month at all stations.