PubMed · 4654721
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M Wilfert, D Beckmann. 1972. [An improved roto-compressor].. https://pubmed.ncbi.nlm.nih.gov/4654721/
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The content of uranium, thorium, radium, lead, polonium, and plutonium in bottom sediments and algae from two locations at the Bulgarian Black Sea coast have been determined. Some parent:progeny ratios for evaluation of the geochemical behavior of the nuclides have been estimated as well. The extractable and total uranium and thorium are determined by two separate radiochemical procedures to differentiate the more soluble chemical forms of the elements and to estimate the potential hazard for the biosphere and for humans. No distinct seasonal variation as well as no significant change in total and extractable uranium (also for 226Ra) content is observed. The same is valid for extractable thorium while the total thorium content in the first two seasons is slightly higher. Our data show that 210Po content is accumulated more in the sediments than 210Pb, and the evaluated disequilibria suggest that the two radionuclides belong to more recent sediment layers deposited in the slime samples compared to the silt ones for the different seasons. The obtained values for plutonium are in the lower limits of the data cited in literature, which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio 238Pu:239 + 240Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural radionuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling locations for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed.
The Glaucocystophyta (e.g., Cyanophora paradoxa) form a morphologically distinct group of photosynthetic protists that is primarily distinguished by its cyanelles (= plastids). To elucidate their evolutionary relationships, we determined nuclear-encoded small-subunit ribosomal RNA (SSU rRNA) coding regions for four taxa classified in the Glaucocystophyta (C. paradoxa, Glaucocystis nostochinearum, Glaucosphaera vacuolata, Gloeochaete wittrockiana; sensu Kies and Kremer), and these sequences were positioned within the eukaryotic phylogeny. Maximum likelihood, maximum-parsimony, and neighbor-joining phylogenetic analyses show that the Glaucocystophyta is a relatively late-diverging monophyletic assemblage within the "crown" group radiation that forms a sister group to cryptophyte algae. Glaucosphaera vacuolata is a red alga and lacks some cyanelle (e.g., bounding peptidoglycan wall) and host cell (e.g., cruciate flagellar roots) characters typical of glaucocystophytes. Our data are consistent with a monophyletic origin of the cyanelle in the glaucocystophytes. The distribution of photosynthetic taxa within the glaucocystophytes/cryptophytes and other lineages such as the filose amoebae/chlorarachniophytes and heterokont protists provide clues to the origin of plastids with four bounding membranes. We speculate that multiple, likely independent, secondary endosymbioses gave rise to these plastids.