Some changes in the flora and vegetation of algae in freshwater environments

Abstract

Changes in the flora and vegetation of algae are discussed with regard to the following aspects: (1) Changes in the distribution of an individual taxon (new colonizations and extinctions); (2) Changes within one group of algae over some decades (examples: desmids of two nature reserves between 1925 and 1980, and charophytes in the region of Berlin since 1800) or over longer periods of time (for example: analysis of diatom frustules in lake sediments since the glacial periods); (3) Changes in the algal flora within a region (for example: the phytoplankton of a small lake in Berlin in 1909 in connection with the restoration of this lake by R. Kolkwitz as compared with the phytoplankton in 1983, or the attempt to show the development in the algal flora in Berlin (West) by a survey of all data available and by planned investigations). - The interpretation of these data often proves difficult due to the problems regarding nomenclature, taxonomy and determination as well as the discontinuity in research, and the different methods applied. Finally, the importance of old reports and the need for modern research are emphasized. "Red Lists" of algae point to the urgent necessity of maintaining as many natural ecosystems as possible. © 1988 Biologische Anstalt Helgoland.