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Microcystis Blooms (Microcysti + bloom)

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Life Sciences	100%

Selected Abstracts

Bioaccumulation of the hepatotoxic microcystins in various organs of a freshwater snail from a subtropical Chinese Lake, Taihu Lake, with dense toxic Microcystis blooms

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007
Dawen Zhang
Abstract In this paper, we describe the seasonal dynamics of three common microcystins (MCs; MC-RR, MC-YR, and MC-LR) in the whole body, hepatopancreas, intestine, gonad, foot, remaining tissue, and offspring of a freshwater snail, Bellamya aeruginosa, from Gonghu Bay of Lake Taihu, China, where dense toxic Microcystis blooms occur in the warm seasons. Microcystins were determined by liquid chromatography electrospray ionization mass spectrum. Microcystin (MC-RR + MC-YR + MC-LR) content of the offspring and gonad showed high positive correlation, indicating that microcystins could transfer from adult females to their young with physiological connection. This study is the first to report the presence of microcystins in the offspring of the adult snail. The majority of the toxins were present in the intestine (53.6%) and hepatopancreas (29.9%), whereas other tissues contained only 16.5%. If intestines are excluded, up to 64.3% of the toxin burden was allocated in the hepatopancreas. The microcystin content in the intestine, hepatopancreas, and gonad were correlated with the biomass of Microcystis and intracellular and extracellular toxins. Of the analyzed foot samples, 18.2% were above the tolerable daily microcystin intake recommended by the World Health Organization (WHO) for human consumption. This result indicates that public health warnings regarding human ingestion of snails from Taihu Lake are warranted. In addition, further studies are needed to evaluate the occurrence by Microcystis in relation to spatial and temporal changes in water quality. [source]

Impact of the fish Garra on the ecology of reservoirs and the occurrence of Microcystis blooms in semi-arid tropical highlands: an experimental assessment using enclosures

FRESHWATER BIOLOGY, Issue 8 2009
TADESSE DEJENIE
Summary 1.,Many man-made reservoirs in the semi-arid highlands of Northern Ethiopia (Tigray) are characterised by the occurrence of intensive blooms of cyanobacteria and a dominance of small riverine fishes belonging to the genus Garra. 2.,We carried out enclosure experiments to test for the effect of these small fish on abiotic characteristics, phytoplankton biomass and zooplankton community structure in the pelagic of two reservoirs (Gereb Awso and Tsinkanet). Two experiments were carried out in each of the reservoirs, one at the end of the rainy season (highest water level) and one at the end of the dry season (lowest water level). 3.,The presence of Garra in general increased the amount of suspended matter, nutrient concentrations (total nitrogen and total phosphorus), phytoplankton and Microcystis biomass (including the proportion of Microcystis in the phytoplankton community), and reduced water transparency. The positive effect of the presence of Garra on nutrient concentrations and phytoplankton productivity indicate that Garra has the potential to affect food web functioning indirectly through bottom-up effects, by enhancing nutrient concentrations through sediment resuspension and excretion of nutrients. Indeed, population densities of the cladoceran zooplankton taxa Ceriodaphnia and Diaphanosoma also showed an overall increase in enclosures with Garra. 4.,However, our data also provide some evidence for a potential of Garra to exert top-down control on large bodied daphnids (Daphnia carinata, D. barbata), although such effect varied among experiments. The limited capability of Garra to control zooplankton communities mainly reflects the low efficiency of these small, riverine and benthos-oriented fish in foraging on zooplankton and suggests the existence of an unoccupied niche for zooplanktivorous fish in the majority of the reservoirs. 5.,Although the main effects of Garra on the pelagic food web seemed to be mediated by bottom-up mechanisms, our results also indicate that one of the key variables, the relative abundance of Microcystis, was impacted by Daphnia -mediated trophic cascade effects. [source]

POPULATION DYNAMICS AND THE TOXICITY OF BLUE-GREEN ALGAE IN THE NAKTONG RIVER, KOREA

JOURNAL OF PHYCOLOGY, Issue 2001
Article first published online: 24 SEP 200
Lee, J. A.1, Choi, A. R.1, Park, J. H.1 & Chung, I. K2 1Department of Environmental Science, Inje University, Kimhae 621-749, Korea; 2Departement of Marine Science, Pusan National University, Pusan 609-735, Korea Seasonal and spatial variations of phytoplankton community were monitored at 16 sites along the Naktong River. Blue-green algae appeared from May through November with dominant genera of Microcystis, Anabaena, Oscillatoria and Gomphosphaeria. Frequency and biomass of the genera became greater at lower reaches. The Microcystis were observed from May to October up to 85,750cells/ml. Six species of Microcystis were identified with morphological characteristics and M. aeruginosa was most dominant. There were significant relationships between biomass of Microcystis and NO -3, TP and pH in water column. However, NH4+, PO4 -3 and N/P were not critical in successions to the Microcystis dominated community. Microcystis blooms were notable at water temperature higher than 25°C. Microcystis density in sediment was 3 orders of magnitude higher than water column. Anabaena density ranged up to 11,220cells/ml. Four species of Anabaena were identified and A. flos-aquae was most dominant. Anabaena biomass was not related to temperature, NO3 - , TN, PO4 -3, TP and N/P of water column and the frequency of trichome with akinete and/or heterocyte were not related to these parameters. Microcystins were detected from May to November with yearly fluctuations. Microcystin-RR was most dominant. Total 84.2% of algal materials with Microcystis exhibited toxicity of microcystin with maximum of 3,292,g/g dry wt. Total 12.5% of water column with Microcystis exhibited dissolved microcystin up to 3.3,g/l. Microcystin concentrations were positively related to Microcystis biomass and pH of water column. Anatoxin-a was determined by FD-HPLC analysis with NBD-F and all concentrations were below the detection limit of 0.1,g/l. [source]