THE PROBLEMS OF RESTORING LARGE, SHALLOW LAKES.

The problems of restoring eutrophic, shallow lakes are discussed using examples from three lakes with different surface areas, e.g., L.Neagh (N. Ireland), L.Balaton (Hungary) and L.Suwa (Japan). The water quality in each lake has undergone marked deteriorations during this century and all of them were considered hypertrophic by the late 1970's. Improved sewage treatment was installed and although they all showed some initial recovery (max. chl a down by 25 - 33% by 1984), since then further improvement has been much slower. Two of the main reasons for this are internal recycling and the in-wash of nutrients from non-point sources. In considering the restoration plans for the three lakes, it is important to include inshore areas. Each of these lakes has been lowered and their annual water level fluctuations controlled. To highlight the major ecological problems associated with such changes, L.Neagh, which has a largely 'undeveloped' shoreline but where rare post-glacial habitats are endangered, is compared to L.Balaton, now one of Central Europe's most popular resorts.Article信州大学理学部付属諏訪臨湖実験所報告 7: 9-19(1991)departmental bulletin pape

Contribution of grazing in phytoplankton overall losses in a shallow French lake

Based on data for 14C-primary production and biomass changes in the small, shallow Creteil Lake, overall phytoplankton losses were calculated through an annual cycle (November 1985-October 1986). Summer 1986 is compared with summer periods in 1985 and 1980, these two years corresponding to extreme levels of algal biomass. Independent from the trophic state of the lake, phytoplankton populations were dominated by small-sized species (<20 μm); their high growth rate (maximal in May and June: 0.8 day-1) was characteristic of nanoplanktonic natural populations. The positive correlation between phytoplankton losses and production indicates a close coupling between growth and loss processes. With a high filtering rate (0.22 day-1 as an annual average), zooplankton impact is considerable at any time of the year but especially in late summer, when grazing losses exceeded primary production. The persistence of small algae throughout the year implies that a great part of the phytoplankton production was harvested by grazers which led to a recycling of organic matter within the water column. -from AuthorsSCOPUS: NotDefined.jFLWNAinfo:eu-repo/semantics/publishe