Algae report number 8, 2025

Abstract

The species diversity and the total cell numbers were low in Kattegat but a bit higher in the Skagerrak. The highest cell counts were found at Släggö at the Skagerrak coast. The diatom Pseudosolenia calcar-avis was found in high abundance at all stations along the Swedish west coast. The integrated chlorophyll concentrations (0–20 m) in the Skagerrak were within normal except for the upper integrated depths (0–10 m) at Släggö where it was above normal. All integrated chlorophyll concentrations in the Kattegat were within normal for this month.

At BY2 in the Southwestern Baltic Proper, the species diversity was relatively high and dominated by diatoms. At all of the other phytoplankton stations, both diversity and cell numbers were low with enhance cell counts of small species only. At three stations, BY15, BY29 and BY39, there were enhanced amounts of the filamentous
cyanobacterium Aphanizomenon flosaquae. The integrated chlorophyll concentrations (0–10 m and 0–20 m) were within normal for this month.