Algae report number 7, 2023

Type: Report
Author: Marie Johansen


The diversity was overall low to moderate at most stations along the Swedish west coast. The larger cells were represented by the dinoflagellate genus Tripos together with Proboscia alata at some stations. The smaller cells were represented by the coccolithophore Emiliania huxleyi. Worth mentioning is that at Anholt E, in Kattegat, the small centric diatom genus Cyclotella was also found in high cell numbers.
Fluorescens maxima at different depths and of different intensity was found at most stations. In Kattegat Tripos dominated in the maxima. In Skagerrak. at the most remote station, it was a mixture of the genus
Tripos but also the genus Pseudo-nitzschia. Closer to the coast both the Tripos spp. and Proboscia alata was represented in the maxima.
No clear surface accumulations of cyanobacteria were found in the Baltic Sea during this expedition. This was most likely due to relatively high wind speed and waves that mixed the water. Many stations had the same amount of filaments in surface samples compared to the integrated (0-10 m) sample indicating that the filaments were dispersed a bit in the water column. The absence of surface aggregations was due to the wind and as soon as the wind decreases there is potential for surface accumulations in almost all parts of the Baltic Proper. The cruise initiated in Kalmar and samples from the western part contained many filaments but most likely
they were dispersed into the water due to the wind. The amount of filaments increased going northward, between Öland and Gotland, and some grains could be seen especially in the north western part. At the
eastern part alongside the east coast of Gotland the amounts of filaments decreased going southward. At the south eastern part, close to Poland, only moderate amounts of filaments appeared in the surface sample. The surface samples taken in the southern part contained more filaments which corresponded well with satellite analyses BAWS (Baltic algal watch system) but no surface aggregations were seen.