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Type microscope slides and material from Ghana from which Foged described nine new Surirella taxa in the 1960's were reinvestigated. Although these taxa have not been reported in the literature afterwards, the results of our study confirm the identity of six species: Surirella agonaensis, S. bonsaensis, S. examangensis, S. nagbogensis, S. sorriensis and S. takoradiensis. They constitute an important element of the endemic diatom flora of West Africa. The study of Surirella takoradiensis var. suhinensis resulted in its proposed synonymy with the nominate variety. Surirella delicatissima var. ghanaensis is transferred to the genus Stenopterobia: Stenopterobia delicatissima var. ghanaensis (Foged) Cocquyt & Lisner comb. nov. Valves resembling Foged's drawing of Surirella dodowaensis could not be detected on the holotype slide; however, two observed frustules in girdle view are in agreement with the description of this taxon.
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The water column of Lake Kyaninga is permanently stratified (meromictic) below 100 m depth. Above this depth, mixing frequency varies from daily (down to 8-12 m depth) over at least once per year (down to 39-47 m depth), to once in several years or decades (between 39-47 and ca. 100 m depth).Nutrient and chlorophyll concentrations as well as phytoplankton data classify the lake as low in aquatic productivity (oligotrophic). Its pelagic, open-water phytoplankton community is dominated by Cyanobacteria (blue-green algae) and Chlorophyta (green algae). Bacillariophyta (diatoms) contribute only a minor part of total phytoplankton biomass in both wet and dry seasons, and are characterized by an assemblage of small Nitzschia species. Epiphytic and epipelic diatoms are relatively few, because steep rocky crater slopes limit the littoral zone even though water-column transparency is hugh. The composition of recently deposited diatom assemblages preserved in offshore surface sediments gives a good, annually integrated representation of the present-day pelagic diatom community. The documented species richness of the diatom flora of Lake Kyaninga is moderate with about 150 taxa. Only ca. 17% of these are biogeographically restricted to tropical Africa; and most of these belong to the genus Nitzschia.
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