Observations on surface accumulation of blue-green algae have increased since last week in the Finnish sea areas. Cyanobacteria occur still in moderate amounts, mainly mixed in the water column, but small coastal accumalations have been found in the southern Bothnian Sea, Archipelago Sea and eastern Gulf of Finland. Calm and warm weather conditions might increase the occurrence of surface blooms. The surface water temperature is 14-19 (C) degrees in the Gulf of Bothnia, 17-18 (C) degrees in the Archipelago Sea, and 16-19 (C) degrees in the Gulf of Finland. A small increase of cyanobacterial blooms is expected to occur during the coming week, especially in ´the western Gulf of Finland.
Cyanobacteria occur still in moderate amounts, mainly mixed in the water column, but small coastal accumalations have been found in the southern Bothnian Sea, Archipelago Sea and eastern Gulf of Finland.
The surface temperatures have not changed significantly during the past week in northern and southern Baltic Proper. The water temperature is mostly between 17-18 (C) degrees. The surface water temperature is 14-19 (C) degrees in the Gulf of Bothnia, 17-18 (C) degrees in the Archipelago Sea, and 16-19 (C) degrees in the Gulf of Finland.
In the Gulf of Finland and the Archipelago Sea the blue-green alga Aphanizomenon-flos-aquae* is still dominating, trichomes of Anabaena* spp. and Nodularia spumigena* are very few. The dinoflagellate Heterocapsa triquetra has increased to bloom concentrations especially in the central Gulf of Finland, while also Dinophysis acuminata* is rather abundant in the western Gulf of Finland. The haptophycean Chrysochromulina* spp. and the cryptophycean Plagioselmis prolonga and Teleaulax spp. dominate the nanoplankton fraction.
In the northern and central parts of the Baltic Sea still occurs moderate amounts of Aphanizomenon flos-aquae* trichomes, while Nodularia spumigena* and Anabaena* spp. are scarce. Small colonial blue-green algae are abundant. The dinoflagellate Heterocapsa triquetra has increased and Dinophysis* spp. have decreased in abundance. The haptophycean Chrysochromulina* spp. and the cryptophycean Plagioselmis prolonga and Teleaulax spp. dominate the nanoplankton fraction.
In the southern Baltic Sea the filamentous blue-green algae have vanished, only Aphanizomenon-flos-aquae* occurs in minor amounts. Nanoflagellates (haptophytes and cryptophytes) dominate the species composition.The diatoms Chaetoceros impressus, Nitzschia paleacea ja Cyclotella choctawhatcheeana are moderately common.
In the Mecklenburg Bight diatoms (Proboscia alata, Cerataulina pelagica, Dactyliosolen fragillissimus, Chaetoceros spp.) are moderately abundant, filaments of blue-green algae are very scarce. The dinoflagellate Ceratium tripos is relatively common. Chrysochromulina* spp. and Plagioselmis prolonga are the most abundant nanoflagellates.
(*potentially harmful species)
In case the winds will be weak during the coming week, an increase of cyanobacterial blooms is to be expected especially in the western Gulf of Finland and in the Archipelago Sea.
Scientist Seija Hällfors, SYKE Marine Centre, 'fistname.lastname@ymparisto.fi', tel. +358 40 1823179
