Original paper

Cyanoprokaryotes in the Baltic Sea ice and winter plankton

Laamanen, Maria

Abstract

The occurrence of cyanoprokaryotes in the ice interior and also of winter plankton was studied in the Gulf of Bothnia (Baltic Sea), during March-April 1995. Chlorophyll α concentrations were measured correspondingly, showing three to five times higher concentrations within ice than in water. Altogether 17 cyanoprokaryotic taxa were recorded, 15 taxa belonging to the order Chroococcales and two to the order Nostocales. The majority of the chroococcal taxa were colonial and minute-celled or gomphosphaerioid species. The abundance of cyanoprokaryotes was in the order of 100 counting units per l both in plankton and within ice. Seven taxa were found only in the ice interior but not in water, and one taxon only in water. The sum of occurrences of cyanoprokaryotic taxa was higher in ice than in water. Consequently, the ice-trapped cyanoprokaryotes are likely to be important contributors to the spring cyanoprokaryotic community. The majority of the cyanoprokaryotes were found in the intermediate layers of the ice, while they were virtually absent from the layers adjacent to the water column. According to a comparison of salinities and chlorophyll a concentrations of brine extracted from ice with those of the melted ice cores, only a minor fraction of material leaves the ice with brine water.

Keywords

Cyanoprokaryotescyanobacteriacyanophytesthe Baltic Seasea iceice interior habitatbrineoverwinteringChroococcalesNostocales