General: The chlorophyll a level in the Gulf of Finland based on measurements collected on April 20th is 14.4 µg/l, and seems to be rising. In the nortehrn Baltic Proper the development of the spring bloom has levelled at 10 µg/l. The chlorophyll concentrations in vary in the Gulf of Finland between 6 and 31 µg/l and in the northern Baltic Proper between 6 and 24 µg/l. The bloom timing is over a week later than usual, generally the bloom begins in late March – early April.
The Chlorophyll concentration in the Arkona Basin has stayed at the level of 3 to 4 µg/l, in other words no massive spring bloom has developed. In the south-western corner of the Baltic, the Bay of Mecklenburgh, the bloom peak was situated in the beginning of March, after which some smaller blooms have ocurred. At the moment the chlorophyll concentration is rising again.
The surface water temperature is rising. Temperatures were measured to be between 1 and 2.5 ˚C in the open parts of the Gulf of Finland, between 2 and 3.5 ˚C in the northern Baltic Proper, between 3 and 5 ˚C in the southern Baltic and the Arkona Basin and between 4 and 7 ˚C in the Mecklenburg Bight. The salinity was normal; in the western Gulf of Finland between 5 and 6 ‰ and in the Baltic Proper between 6 and 8 ‰. In the Bight of Mecklenburg the salinity was 15 ‰.
Nutrients: The nitrate- and nitrite-nitrogen (NO3+NO2-N) is used up in the entire Baltic Proper and the opening of the Gulf of Finland. In the central Gulf of Finland the concentration has decreased aswell since last week, measured now at 2 to 5 µmol/l. The phosphate-phosphorus (PO4-P) concentrations have decreased, being in the northern Baltic Proper between 0.2 and 0.3 µmol/l and in the Gulf of Finland 0.2 to 0.5 µmol/l. The silicate-silicon (SiO4-Si) concentration varies between 8 and 10 µmol/l.
Phytoplankton community: Mainly small flagellates (Dictyochophyceae, Chrysophyceae, Dinophyceae) occur in the Mecklenburg Bight. Diatoms have almost disappeared in southern Baltic Sea. In the central parts of the Baltic Sea Chaetoceros spp. are moderately common. Skeletonema costatum coll. Chaetoceros spp., Achnanthes taeniata and Thalassiosira spp. are very common in the Baltic Proper and in the Gulf of Finland. The dinoflagellates Woloszynskia halophila and Peridiniella catenata are abundant in the Gulf of Finland.
Forecast: The phytoplankton community is still expected to expand in the Gulf of Finland. The low amount of NO3+NO2-N in the northern Baltic Proper is already slowing the growth, so the peak of the spring bloom is expected in a few days. After the peak the chlorophyll concentration will decrease in a few weeks to 2 to 3 µg/l, after which the situation usually is stable until July.
Within the Baltic Sea Portal:
Most recent results of the state of the Baltic Sea (algae, blue-green algae, nutrients, water temperature, salinity)
Present situation compared to 10-year average (chlorophyll \a\, temperature, salinity, nutrients)
Taxonomic reports
Ice situation
Forecasts provided by the Finnish Institute of Marine Research:
Wave forecast
