Diatoms as indicators of the present and past ecological state in Karelian Pyhäjärvi – an oligotrophic transboundary lake on the Finnish-Russian Border

Kukkonen, Minna; Simola, Heikki; Niinioja, Riitta; Luotonen, Hannu

doi:10.1080/03680770.2006.11903035

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“…This is also the case in Lake Pyhäjärvi, where a biomass maximum at 7-8 metres has been reported . Some differences have been reported between the loaded and pristine basins of Lake Pyhäjärvi in the zooplankton communities (Rahkola-Sorsa et al, 2004) and the sedimented diatoms (Kukkonen et al, 2006). The changed zooplankton community in the northern part of the lake and the diatom species composition of the loaded bay areas agree particularly well with the spatial differences in phytoplankton.…”

Section: Discussionmentioning

confidence: 71%

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Spatiotemporal and long-term variation in phytoplankton communities in the oligotrophic Lake Pyhäjärvi on the Finnish-Russian border

et al. 2008

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As part of the joint Finnish-Russian research and development project ''Assessment of the ecological state of the transboundary waters'', seasonal and spatial variations in the phytoplankton communities of Lake Pyhäjärvi were studied in order to identify possible long-term changes and to present recent data (since 2002) on phytoplankton biomass and species composition. Some changes in both phytoplankton biomass and species composition, particularly in the littoral zone and northern basins of the lake, were obvious at the end of the 1980s; in particular, the density of blue-greens increased during that period. Biomasses increased five-fold in 1980, decreased after 1990 and have remained low (0.14 mg l -l ) to the present time. The effective water protection measures applied, especially reducing the phosphorus load from municipal wastewaters and airborne pollution, can now be seen to have improved the water quality. Although no significant temporal differences were found in phytoplankton biomass during the intensive biweekly sampling in 2002, considerable spatial variation was seen within the lake. An obvious change in the species composition of phytoplankton and an increase in biomass were seen even in the loaded parts of the lake. Despite the spatial differences in phytoplankton biomass and community structure, the changed species composition in the northern part of the lake indicated a clear recovery from the blue-green and Chrysophyceae dominated high biomass of the 1980s.

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Section: Discussionmentioning

confidence: 71%

“…The main loading of Lake Pyhäjärvi derives from diffuse sources such as forestry and agriculture, but there are also point source loads from small villages (Kukkonen et al, 2006). Lake Pyhäjärvi is composed of several separate basins.…”

Section: Study Area Materials and Methodsmentioning

confidence: 99%