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Waters are more polluted than tests say

Standard toxicity analyses come up short

Date:
November 30, 2015
Source:
Technical University of Munich (TUM)
Summary:
Bodies of water are 'sinks', and thereby bind contaminants particularly well. If even slightly toxic concentrations in water are to be detected, the growth and swimming behavior of small crustaceans and copepods should be used for ecotoxicological assessments. This was the conclusion of a scientist who carried out a number of studies on the subject. She also confirmed that it is more informative to test several substances on various aquatic species, rather than carrying out individual toxicity tests.
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Bodies of water are "sinks," and thereby bind contaminants particularly well. If even slightly toxic concentrations in water are to be detected, the growth and swimming behavior of small crustaceans, mini-snails and copepods should be used for ecotoxicological assessments. This was the conclusion of a scientist from the TUM, who carried out a number of studies on the subject in cooperation with the University of California in Davis. She also confirmed that it is more informative to test several substances in parallel on various aquatic species, rather than only carrying out individual toxicity tests.

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.

Pesticides become more toxic as a combined package

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."

A clear result delivered by a combination of study series

- Firstly, the laboratory tests provided an indication of the concentrations at which the contaminants influence the growth and swimming behavior of the organisms.

- The field studies proved the long-term effects on an entire ecosystem, its food web and its community structures.

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.

Sublethal effects as alarm signals

The changes in the animals which are detectable from their swimming behavior, growth or weight, and which eventually lead to their death (sublethal), are an important indicator of this. To date, however, there is no valid scale showing the point from which, for example, a delay in growth has a fatal outcome for the animal. Therefore, study author Dr. Hasenbein is advocating this approach in particular: "Sublethal endpoints need to be integrated into the methods used in ambient water monitoring, to allow long-term negative effects on aquatic ecosystems to be detectedreliably, even when the pesticide concentrations in the water are low," says the scientist. "A crustacean population which is exposed to low-level contaminant pollution could be more susceptible to invasive species, changes in water temperature or different salt concentrations, because the permanent, low-level pesticide contamination increases stress on the animals." This is an important aspect, especially in the light of climate change, and should therefore be taken into consideration in future ecotoxicologic assessments.


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Materials provided by Technical University of Munich (TUM). Note: Content may be edited for style and length.


Journal References:

  1. Simone Hasenbein, Sharon P. Lawler, Juergen Geist, Richard E. Connon. A long-term assessment of pesticide mixture effects on aquatic invertebrate communities. Environmental Toxicology and Chemistry, 2015; DOI: 10.1002/etc.3187
  2. Simone Hasenbein, Richard E. Connon, Sharon P. Lawler, Juergen Geist. A comparison of the sublethal and lethal toxicity of four pesticides in Hyalella azteca and Chironomus dilutus. Environmental Science and Pollution Research, 2015; 22 (15): 11327 DOI: 10.1007/s11356-015-4374-1
  3. Simone Hasenbein, Sharon P. Lawler, Juergen Geist, Richard E. Connon. The use of growth and behavioral endpoints to assess the effects of pesticide mixtures upon aquatic organisms. Ecotoxicology, 2015; 24 (4): 746 DOI: 10.1007/s10646-015-1420-1

Cite This Page:

Technical University of Munich (TUM). "Waters are more polluted than tests say." ScienceDaily. ScienceDaily, 30 November 2015. <www.sciencedaily.com/releases/2015/11/151130135010.htm>.
Technical University of Munich (TUM). (2015, November 30). Waters are more polluted than tests say. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/2015/11/151130135010.htm
Technical University of Munich (TUM). "Waters are more polluted than tests say." ScienceDaily. www.sciencedaily.com/releases/2015/11/151130135010.htm (accessed March 28, 2024).

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