Plankton composition,biomass, phylogeny and toxin genes in Lake Big Momela,Tanzania

Lake Big Momela, one of the East African soda lakes in Northern Tanzania characterised by highly saline-alkaline conditions, making them inhospitable to a range of organisms, although supporting massive growths of some adapted planktonic microorganisms that serve as food for birds, such as Lesser Flamingo. The temporal dynamics of plankton, with an emphasis on cyanobacteria, were examined in 2007 using morphological traits and ribosomal genetic markers (16S and 18S rRNA). Cyanobacterial genes encoding for hepatotoxins (mcyE and ndaF) were also screened. Rotifers and copepods dominated the zooplankton, whereas cyanobacteria, such as Anabaenopsis elenkinii and Arthrospira fusiformis dominated the phytoplankton community, and these being related to representatives in other East African soda lakes. The cyanobacteria community also showed distinct seasonal patterns influenced by environmental parameters, mainly salinity, pH and nitrate. Significant positive correlations were found between phytoplankton abundance and nitrate concentrations (r = 0.617, p = 0.033). No signals of the hepatotoxin synthetase genes mcyE and ndaF were retrieved from cyanobacteria during the whole year. In general, our data illustrate the presence of rich planktonic communities, including some unique and potentially endemic cyanobacteria.     

The effect of environmental factors of the coking plant on the enzymatic activity of rabbit oral mucosa.

Histochemical methods were used to investigate the activities of some intracellular enzymes in the oral mucosa of the rabbits which had been kept in selected work-stands of a coking-plant for 3 months. The findings were compared with the results for the enzymatic activity of the oral mucosa of control rabbits. The epithelium of the oral mucosa of the experimental rabbits was found to be proliferated acanthotically; moreover, there occurred some other morphological changes of the mucosa which often resembled precancerous states of leukoplakia type. In comparison with the control group, the activities of the studied enzymes, i.e. reduced NAD dehydrogenase (NADD), glucose-6-phosphate dehydrogenase (G6PD), lactate dehydrogenase (LDS), succinate dehydrogenase (SD), cytochrome oxidase (CO), and phosphorylase a+b in the epithelium and the connective-tissue cells of the studied mucosa of the experimental animals were as a rule markedly lowered, this decline being especially pronounced for the three last-mentioned enzymes. It was only the proliferating stratum basale of the experimental rabbit epithelium that frequently exhibited enhanced activities of NADD and LDS. Besides, the activities of NADD, G6PD and LDS were of a markedly diverse intensity in the cells of the chaotically proliferating stratum spinosum of the experimental rabbit mucosa. The results point to the noxious modifying effect of chemical and physical agents of the investigated environment on the oral mucosa of the animals studied.