Atsushi Takagi

Tohoku University, Sendai-shi, Miyagi-ken, Japan

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Publications (2)0 Total impact

  • Source
    Hideyuki Doi, Atsushi Takagi, Eisuke Kikuchi
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    ABSTRACT: The impacts of mining activities on aquatic biota have been documented in many stream ecosystems. In mining streams, point-source heavy metal pollution often appears in the stream. We hypothesize that this pollution is toxic to macroinvertebrates owing to high concentrations of metals and therefore affects macroinvertebrate community structure. We investigated macroinvertebrate community structure in mountain streams, including heavy metal-polluted sites and neutral-pH streams, to determine the relationship between community structure and environmental factors such as low pH and heavy metal concentrations. Based on multidimensional scaling ordination, the macroinvertebrate community at heavy metal pollution sites was remarkably different from that at the other sites. Inductively coupled plasma mass spectrometry revealed high concentrations of aluminum and iron in surface water at the polluted sites. Macroinvertebrate community structure at the metal pollution sites was significantly different from that at other sites in the same stream and in neutral-pH streams. Thus, point-source metal pollution may reduce the density and diversity of in situ macroinvertebrates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 05/2007; 92(3):258 - 266.
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    ABSTRACT: We estimated the food sources of macroinvertebrates using carbon, nitrogen, and sulfur stable isotopes in a headwater stream. Stream food webs, including macroinvertebrates, rely on production from autochthonous and allochthonous photosynthesis. We found that a freshwater grazer, the snail Semisulcospira libertina, may assimilate different food sources, based on stable carbon and nitrogen isotope evidence from snail muscle and the much lighter sulfur isotope signature than those of other associated macroinvertebrates. Previous studies have shown the importance of methanotrophic and sulfur bacteria in reductive environments (clay and organic-rich sediments) as food sources for macroinvertebrates. Our results show that the production by chemoautotrophic bacteria contributes to the food sources of a snail in a stream. Thus, the chemoautotrophic bacteria are important in the freshwater food webs, even in mostly aerobic habitats. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 11/2006; 91(6):501 - 508.