Moderate Impact by an Insecticide Increases Species Richness in a Zooplankton Community : Results Obtained in Experimental Ponds

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概要

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• The insecticide carbaryl at nominal concentrations of 0 (control), 10 (low dose) and 100 μg 1{ 1 (high dose) was applied repeatedly to experimental ponds containing predacious larvae of the midge Chaoborus and to ponds without the predator, and the effect of the chemical on species richness of the zooplankton community was analyzed. Cladocerans dominated the ponds without Chaoborus, but were kept at very low densities in the ponds with Chaoborus due to predation. In the Cladocera-dominant ponds, the treatment with high-dose carbaryl reduced the species diversity of the cladoceran community to just one : only the small cladoceran Bosmina fatalis survived. Rotifers established large populations in the ponds with Chaoborus because they were released from competition with the superior competitor cladocerans, which were suppressed by the Chaoborus predation. In these ponds, the species richness of the rotifer community became higher in the high-dose ponds than in the control and low-dose ponds during and after the period of insecticide application. The chemical treatment seemed to suppress, but not eliminate, the dominant rotifer species, allowing the species inferior in competition but more tolerant to the insecticide to coexist with the competitively superior species. The moderate impact of carbaryl might have increased the species richness. These results suggest that the impact of human influence such as insecticide contamination does not always reduce biodiversity in organic communities.

著者

• Hanazato T

  Research And Education Center For Inlandwater Environment Shinshu University

• Hanazato Takayuki

  Suwa Hydrobiological Station Shinshu University

• HANAZATO Tayuki

  Suwa Hydrobiological Station, Shinshu University

関連論文

• Moderate Impact by an Insecticide Increases Species Richness in a Zooplankton Community : Results Obtained in Experimental Ponds
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