Cyanocystopsis kitagatae gen. et sp. nov. (Cyanoprokaryota/ Cyanobacteria) from the tropical lake Kitagata (Uganda, Africa)

peer reviewedThe paper describes a new genus and new species of Cyanoprokaryota, referred to Pleurocapsales incertae sedis – Cyanocystopsis kitagatae gen. et sp. nov. The new taxon is characterized by the presence of two different stages (filamentous, formed by spherical cells and stalked bundles of claviform cells). The branching of filaments, which leads to the formation of clusters of claviform cells, is caused by cell division, which slightly resembles the true-branching of cyanoprokaryotes. However, this division is peculiar by its subsequent character and excentric disposition of the daughter cells, which leads to the formation of specific tetrads, from which the claviform cells develop. Spores (aplanospores) and vegetative reproductive stages of the alga have been observed. The new species was found as a dominant in a fixed phytoplankton sample from the small, hypertrophic and hypersaline tropical crater lake Kitagata (Uganda, Africa). The pigment marker analysis of the same sample proved the high (ca 96%) cyanoprokaryote contribution to the phytoplankton biomass.HIP

Phytoplankton abundance and diversity in the Congo river at high and low waters

The Congo river is the second largest in the World in terms of freshwater discharge (1457 km3 y-1) and in terms of drainage basin (375106 km2). In this study we sampled the Congo river mainstem and major tributaries along the 1700 km stretch from Kisangani to Kinshasa, during the high water and low water periods. Phytoplankton was analysed using a combination of microscopy with HPLC analysis of marker pigments. During high water, phytoplankton biomass in the mainstream was low (mean Chl a = 0.8 mg m-3). Most tributaries presented lower Chl a, with some exceptions, as the Oubangui river (3.6 mg m-3). At low water, phytoplankton development in the R. Congo mainstem was higher (Chla 1.1-7.7 mg m-3). Phytoplankton was essentially composed of green algae (mostly coccal green algae and some desmids), diatoms (mostly Aulacoseira spp.) and filamentous cyanoprokaryotes. In some samples euglenophytes (mostly Strombomonas spp.) and chrysophytes appeared with greater abundance and diversity. In the low water period, phytoplankton was, as typical in most large rivers, dominated by diatoms, whereas the high water phytoplankton was dominated by coccal green algae, both in the main river and tributaries