Växtplankton i Storvänern 2023

The seasonal average biovolumes for 2023 were higher than the year 2022, however, normal for the period 1979-2023. As expected in April and May, the species composition of diatoms dominated in the lake, except in Dagskärsgrund, which had no clear dominance of any phytoplankton group. In June, bio volumes were again markedly higher than normal in all sampling points and thus above the long-term average for the month. In June, the golden algae were again a major component of the biomass at all sample sites. August biomass was low across the lake and the chryptophytes dominated in the lake, however with low percentages. Status assessments of the water quality with regard to nutrient impact give a high status for the total biovolumes both for the last three years and for the entire period from 1979. The plankton trophic index PTI, on the other hand, generally gives a slightly worse status than the total biovolume.