Algae report number 6, 2023

Type: Report
Author: Maria Karlberg, Marie Johansen


The diversity was quite low at all stations along the Swedish west coast. The cell numbers were however normal and almost high at Å17 with a dominance of diatoms. All stations had high cell numbers of Dactyliosolen fragilissimus which is normal for summer. Small cells were common and
Emiliania huxleyi was common at all stations except Å17. The integrated chlorophyll concentration (0-10 and 0-20 m) were generally normal at all stations.

The diversity and cell numbers of phytoplankton were normal at all Baltic Sea stations with a presummer bloom community. Several dinoflagellate taxa were present in quite high cell numbers at all stations, such as Gymnodiniales and Heterocapsa rotundata, and a few cells of the toxin producing Dinophysis norvegica* and D. acuminata*. Of the summer blooming filamentous cyanobacteria Aphanizomenon flosaquae was very common, mainly in the northern and eastern parts of the Baltic
Sea, but was found in all samples. Also, smaller amounts of Nodularia spumigena* were present at all stations. The integrated chlorophyll concentration (0-10 and 0-20 m) were generally over the normal range for this month at several stations, except at the southern stations where the
concentration was normal. The fluorescent peaks sampled displayed a similar species composition as the hose sample (0-10 m) but with significantly lower amount of filamentous cyanobacteria.