Cyanobacterial surface accumulations have strongly increased in marine waters around Finland since last week as a result of warm and calm weathers. Extensive surface accumulations have been recorded in the open Gulf of Finland and Bothnian Sea. In the open Bothnian Sea off City Pori, algae occur abundantly or very abundantly. In the Archipelago Sea, algae mainly form patchy stripes in the surface water. Surface water temperature is above 17 ˚C in the southern and south-western sea areas. Under warm and calm weather conditions, cyanobacterial surface accumulations are expected to continue.
Cyanobacterial surface accumulations have strongly increased in marine waters around Finland since last week as a result of warm and calm weathers. Extensive surface accumulations have been observed in the open Gulf of Finland and Bothnian Sea, but also in the main basin of the Baltic Proper in the mouth of the Gulf of Finland. In the open Bothnian Sea off City Pori as well as in the NW coastal waters of Estonia, algae occur abundantly or very abundantly. Instead, in the coastal areas between the Cities of Porvoo and Kotka, and in the Archipelago Sea, algae mainly form patchy stripes in the surface or are mixed in the water, but in some places algae also form surface accumulations. Additionally, algae have been recorded abundantly in few bays of Åland. Some observations originate from the northern Bothnian Bay.
In Helsinki sea areas and in the western Gulf of Finland, water temperature is 17 ˚C and 17.7 ˚C, respectively. In the northern and central Baltic Sea as well as in the Arkona Sea, water temperature ranges between 17.2 and 17.7 ˚C. In the Mecklenburg Bay it is 18.8 ˚C.
In the southern Archipelago Sea, the dominating species include the cyanobacteria Nodularia spumigena and Aphanizomenon species. Nodularia spumigena has increased in abundance since last week as a result of warm and calm weathers. Heterocapsa triquetra is the most common and abundant dinoflagelate species. Dinophysis acuminata and Protoperidinium species are less abundant. Other species small in numbers are, inter alia, the diatom Chaetoceros wighamii and unspecified cyanobacterial species of the Chroococcales order.
In the Gulf of Finland off Helsinki, the cyanobacteria Nodularia and Anabaena dominates. The dinoflagellates Heterocapsa triquetra and Dinophysis acuminata are still abundant. Cryptophytes and Prymnesiophytes are most abundant of small flagellates.
In the eastern Gulf of Finland between the City of Kotka, the Islands of Haapasaari and Suursaari, there are hardly no observations of surface algal accumulations, excluding a small Nodularia accumulation recorded near the Island Suursaari. Small numbers of the cyanobacterial species Anabaena lemmermannii, Aphanizomenon flos-aquae and Nodularia spumigena are mixed in the water. The dinoflagellate Dinophysis acuminata is abundant, but Heterocapsa triquetra observed abundantly westwards is very small in number.
Cyanobacterial surface accumulations are expected to occur in the western and central Gulf of Finland, in the Archipelago and Åland Sea as well as in the open southern Bothnian Sea in the coming week if the warm and calm weather conditions continue. Strong cyanobacterial blooms are likely to occur especially in the NW coastal areas of Estonia and in the main basin of the Baltic Proper north east of Gotland.
Scientist Pirkko Kauppila, SYKE Marine Centre, 'firstname.lastname@ymparisto.fi', tel. +358 400 148 530
