Waters are more polluted than tests say

http://www.eurekalert.org/pub_releases/2015-11/tuom-wam113015.php

Public Release: 30-Nov-2015
Waters are more polluted than tests say
Standard toxicity analyses come up short
Technical University of Munich (TUM)

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If a small crustacean does not grow properly, this can affect its reproduction. And if it is no longer able to move normally, it cannot flee from predators or from changing temperatures, which eventually has a fatal outcome. In scientific research, these effects are referred to as "sublethal effects". However, worldwide standard methods of pesticide analysis and the risk assessments associated with them only consider the lethal (deadly) effects. For the first time, three studies published in "Ecotoxicology", "Environmental Science and Pollution Research" and "Environmental Toxicology and Chemistry" demonstrate the sublethal effects on swimming behavior and growth, caused by widely used pesticides on the animals being studied. Moreover, the results indicate that the substances influence the underwater world for weeks, even if they are no longer detectable using standard methods.

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Another factor is the mix of pesticides: "We looked at the insecticides not individually, but as a mixture, in order to investigate their interaction with one another", explains lead author Dr. Simone Hasenbein. "In addition, we observed several species in the contaminated water body, including the less standard species for these tests, such as mini-snails and copepods."

The tests took place over a period of ten days in the laboratory and also for six months in the field. Eventually, significantly negative effects resulting from the combined pesticide pollution in the water were found for twelve of the 15 small invertebrates and ten of the 16 zooplankton species. "Another point that was considered was how long the insecticide remained detectable in water", was Dr. Hasenbein's explanation of the method - "thus, one of the three substances was still detectable after six weeks."

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The negative effects on aquatic ecosystems could only be pinned down once all the results were combined. Since the microorganisms being studied can be influenced by the pesticides for much longer than these substances remain detectable, this also leads to the conclusion that bodies of water are far more polluted than all previous research had demonstrated.

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