Algae report number 5, 2026

Abstract

The bloom of a small prymnesiales* species was observed in the Skagerrak and Kattegat areas. The chlorophyll fluorescence peaks in the Skagerrak were partly caused by the same prymnesiales*, but the presence of an unidentifyed dinoflagellate was obvious at the Släggö peak, and at Å13 and P2 the number of diatoms was large. A relatively high species diversity at Släggö, was dominated by diatoms in moderate cell numbers. The integrated chlorophyll concentrations were low for this month at Å13 and Å17 and normal at all other stations.

Phytoplankton diversity and cell abundances were generally moderate in the Baltic Proper. The typical spring bloom dinoflagellate Peridiniella catenata was common at several stations, while diatoms occurred only in low numbers and did not constitute a spring bloom. Diatoms observed included Skeletonema marinoi, Pauliella taeniata and Thalassiosira gravida. At BY2 Arkona the community was dominated by pico sized unicells, small flagellates and ciliates. The ciliate Mesodinium rubrum was common to very common at all stations. The integrated chlorophyll concentrations were within the normal range for this month at all stations.