The principal response curve analysis revealed that the main trend of the effects was a dose-dependent population decrease. increase was likely an indirect effect due to interspecies interactions. At 500-5000 Gy, one or three taxa died out and populations of two or three taxa decreased over time, while that of Tolypothrix sp. At 100 Gy, populations were not affected in any taxa. and Philodina sp.) and a ciliate protozoan (Cyclidium glaucoma) as consumers and more than four species of bacteria as decomposers. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producers an oligochaete (Aeolosoma hemprichi), rotifers (Lecane sp. Organoselenium compounds such as selenomethione may thus contribute disproportionately to Se bioaccumulation and toxicity in aquatic organisms.Įffects of acute gamma-irradiation on the aquatic microbial microcosm in comparison with chemicals.įuma, Shoichi Ishii, Nobuyoshi Takeda, Hiroshi Miyamoto, Kiriko Yanagisawa, Kei Doi, Kazutaka Kawaguchi, Isao Tanaka, Nobuyuki Inamori, Yuhei Polikarpov, Gennady GĮffects of acute gamma-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. Selenium added as selenomethionine was bioaccumulated preferentially compared to that added as selenite or selenate. Daphnids accumulated highest concentrations of Se, followed by periphyton and macrophytes.

Loss rates of dissolved Se residues were more rapid than rates reported from mesocosm and field studies, suggesting that sediment: water interactions are more important in microcosms than in larger test systems. Selenium lost from the water column accumulated primarily in sediments, but volatilization was also an important pathway for loss of Se added as selenomethionine. When each Se species was labeled separately, selenomethionine was lost from the water column more rapidly than selenate or selenite. Sulfate did not affect the distribution and bioaccumulation of 75Se over the range 80â€“180 mg SO4 literâˆ’1. A mixture of dissolved 75Se species (selenate, selenite and selenomethionine) was sorbed more rapidly to fine-textured, highly organic pond sediments than to sandy riverine sediments. Distribution and bioaccumulation of Se varied among sediment types and Se species. La Point, Thomas W.Ĭlosed-system microcosms were used to study factors affecting the fate of selenium (Se) in aquatic systems. Plant bioconcentration and microbial biodegradation are the main processes involved in the IPU decay in our outdoor aquatic microcosms.ĭistribution and bioaccumulation of selenium in aquatic microcosmsīesser, John M. Our data show that bioconcentration does not occur in mollusks but is important in photosynthetic organisms. The observed plant bioconcentration factors are higher than those predicted by usual numerical models, probably due to the specific binding of IPU on one protein of the photosynthetic apparatus. A high variability of the IPU concentration was observed in exposed plants, with bioconcentration factors ranging from 100 to 1,200 with large coefficients of variation. This relatively fast decrease was also confirmed in 1995, but it reached a constant value after two months. A first-order kinetic decrease in IPU concentration was observed in 1994, with half-life ranging from 15 to 35 d, depending on the microcosms. The IPU concentration was determined in the water column and in different species (mainly plants) of the microcosms. In each case, the initial concentration of IPU contamination was set at 10 microg/L. Three different types of ecosystems were tested in 1994 and one type of ecosystem was selected and repeated in 1995 with three replicates. All the experiments were conducted during the summer over two years. To gain information concerning the ecotoxicity of isoproturon (IPU) on aquatic ecosystems, six experimental ponds of 5 m3 each were studied. Merlin, Gerard Vuillod, Maryline Lissolo, Thierry Clement, Bernard Fate and bioaccumulation of isoproturon in outdoor aquatic microcosms.

Example of microcosm