Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.     

Seasonal dynamics of cell numbers and biodiversity of marine heterotrophic bacteria inhabiting invertebrates and water ecosystems of the Peter the Great Bay,Sea of Japan

The annual changes in bacterial numbers and diversity of the heterotrophic microflora in invertebrates and ambient water were studied. During the whole period of observation, bacterial cell numbers were higher in invertebrate specimens than in the ambient water. The highest number of bacterial cells was detected in trepangs and sea urchins, while the lowest number of cells was detected in starfish. Based on the results of phenotypic analysis and analysis of fatty acid composition of bacterial cell lipids, 487 strains (out of the total of 502 isolates) of heterotrophic bacteria were identified to the genus level. Morphological differences between the winter and summer isolates of vibrios and halomonads were analyzed. The seasonal dynamics of the cell numbers of vibrios and halomonads was revealed. The gram-positive microflora was most often present in animals during the winter, fall, and spring periods. The diversity of heterotrophic bacteria was greater in the water column than in animal tissues.