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BR Staff Publications [a] (paper in international, peer reviewed journal) --- lakes --- Bacillariophyta = Diatoms = Diatomeae

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This study aims to evaluate the seasonal and interannual variability in the importance of the microbial food web in Lake Tanganyika. Phytoplankton, bacteria and protozoa (heterotrophic nanoflagellates and ciliates) were monitored at two contrasting pelagic sites (Kigoma and Mpulungu) during 3 consecutive years. In addition, spatial variation was studied along 3 north-south transects during contrasting seasons. The study period covered a wide range of limnological conditions, with mixing depth ranging from 13 to >100 m and euphotic depth from 14 to 65 m. The consistently high bacterial biomass (up to 62 µg C l-1) and the high contribution of small phytoplankton (<5 µm) to total phytoplankton biomass (on average 50 % in Kigoma and 84 % in Mpulungu) point to an important role of the microbial food web in the lake throughout the year. Total phytoplankton biomass increased during periods of low water column stability, with an increased biomass of small eukaryotic phytoplankton (2 to 5 µm) at both stations, together with autotrophic prokaryotic picoplankton at the southern station Mpulungu and diatoms at the northern station Kigoma. Heterotrophic bacteria, heterotrophic nanoflagellates (0.06 to 11.01 µg C l-1) and ciliates (up to 8.16 µm C l-1) did not show this seasonality. The main seasonal and spatial variability in the importance of the microbial food web seems therefore primarily linked to the contribution of the small phytoplankton, which may be better adapted to lower average light intensities and higher N:P ratios during periods of deep mixing

BR Staff Publications [a] (paper in international, peer reviewed journal)

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BR Staff Publications [a] (paper in international, peer reviewed journal) --- heterogeneity --- lake Tanganyika

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There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom dataset, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere

BR Staff Publications [a] (paper in international, peer reviewed journal) --- Bacillariophyta = Diatoms = Diatomeae