Rapport nr 92: Uppföljning av växtplankton utvecklingen, med tyngdpunkt på blågrönalger i åländska vattentäkter och skärgårdsvatten sommaren 1995
ÖHMAN, P (1995)
ÖHMAN, P
Åbo Akademi, Husö biologiska station
1995
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Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:951-650-745-X
https://urn.fi/URN:ISBN:951-650-745-X
Tiivistelmä
The phytoplankton development in drinking water reservoirs and archipelago areas on Aland was monitored in July-September 1995. Special emphasis was layed on potentially hazardous algae, especially cyanobacteria. The water quality (hydrography and plankton) in eight water reservoirs were investigated three times and in the archipelago area samples were taken at different places throughout the summer.
Among many, Anabaena spp. were the most common cyanobacteria in the water reservoirs. Microcvstis spp. were abundant in Tjudö träsk, but the amounts in the other lakes were quite small. Planktothrix agardhii, a species that has caused problems in earlier years, was only found in small amounts. In Borgsjön a heavy bloom af Anabaena sp. occurred in the beginning af September. The bloom was non-toxic. In Toböle träsk Ceratium hirudinella and C. furcoides formed a bloom in August-September. The amounts af plankton and chlorophyll a in the drinking water was checked at several occasions. The water from Leviksfjärden contained high amounts of phytoplankton, mostly green algae but also a lot of cyanobacteria. The chlorophyll a value was in average 1, 73 µg/l. Chlorophyll a and phytoplankton cells were also found in the drinking water from Borgsjön (Sundets vatten), but in smaller amounts. Phytoplankton cells were found in the water from Lavsböle träsk (Bocknäs vatten) but no chlorophyll a was detected.
In the archipelago blooms of cyanobacteria were observed mostly in July and August in the Mariehamn-area. In the Northwestern archipelago the amounts of cyanobacteria were high from the end of July to October, although only a few surface blooms were observed. The most common species were Aphanizomenon sp.,
Nodularia spumigena and Anabaena lemmermannii.
In the waters around Mariehamn, especially in Svibyviken, heavy blooms of Heterocapsa triquetra. caused red water in July-August.
Among many, Anabaena spp. were the most common cyanobacteria in the water reservoirs. Microcvstis spp. were abundant in Tjudö träsk, but the amounts in the other lakes were quite small. Planktothrix agardhii, a species that has caused problems in earlier years, was only found in small amounts. In Borgsjön a heavy bloom af Anabaena sp. occurred in the beginning af September. The bloom was non-toxic. In Toböle träsk Ceratium hirudinella and C. furcoides formed a bloom in August-September. The amounts af plankton and chlorophyll a in the drinking water was checked at several occasions. The water from Leviksfjärden contained high amounts of phytoplankton, mostly green algae but also a lot of cyanobacteria. The chlorophyll a value was in average 1, 73 µg/l. Chlorophyll a and phytoplankton cells were also found in the drinking water from Borgsjön (Sundets vatten), but in smaller amounts. Phytoplankton cells were found in the water from Lavsböle träsk (Bocknäs vatten) but no chlorophyll a was detected.
In the archipelago blooms of cyanobacteria were observed mostly in July and August in the Mariehamn-area. In the Northwestern archipelago the amounts of cyanobacteria were high from the end of July to October, although only a few surface blooms were observed. The most common species were Aphanizomenon sp.,
Nodularia spumigena and Anabaena lemmermannii.
In the waters around Mariehamn, especially in Svibyviken, heavy blooms of Heterocapsa triquetra. caused red water in July-August.