SETAC Globe - Environmental Quality Through Science
  13 September 2012
Volume 13 Issue 9

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Berlin World Congress Session Brief: Risk Assessment, Pest Management and Phytoremediation

Gertie Arts, Alterra Wageningen University and Research Centre, Silvia Mohr, German Federal Environment Agency and Udo Hommen, Fraunhofer Institute for Molecular Biology and Applied Ecology

During the 6th SETAC World Congress in Berlin, the session “Plants and Chemicals in the Environment” was organized by the SETAC Aquatic Macrophyte Ecotoxicology Group (AMEG). Plants are key components of ecosystems. By performing photosynthesis, they produce O2 and organic material. Plants therefore form the basis of many aquatic and terrestrial food webs. The session focused on how plants interact with chemicals. The current risk assessments for chemicals consider risks for aquatic primary producers based on standard tests with algae and free-floating Lemna species. Contrary to this, sediment-rooted aquatic macrophytes with lower growth rates are not tested for standard risk assessments. Besides the fact that chemicals can affect plants, plants can also accumulate and biodegrade chemicals and thus contribute to lowered exposure concentrations. This ability of plants is potentially useful for phytoremediation and mitigation purposes. Both aspects were covered by this session. Six platform presentations focused on risk assessment and phytoremediation and also addressed terrestrial and marine plants besides aquatic ones. The poster corner covered ecotoxicology, test development and phytoremediation.

Session Highlights
Effects of chemicals on plants may be detected in the laboratory; however, field trials are very important for validation of approaches to extrapolate effects observed in the laboratory to the population and ecosystem level in the field. In a terrestrial field study, the buttercup Ranunculus acris was an important indicator plant for detecting herbicidal drift effects. The ability of plants to flower was the most sensitive endpoint for this species. Another study showed that the effects of a herbicide mixture in multispecies tests with several aquatic macrophytes were predictable from effects observed in single-species tests. Species sensitivity distributions (SSDs) for aquatic macrophytes showed that for the compounds considered, the standard test species in risk assessment—including the Eurasian water milfoil Myriophyllum spicatum—are protective for the effects on other aquatic macrophyte species. By combining algae and aquatic macrophyte data, the method is applicable even with low availability of macrophyte tests. As another higher-tier tool for aquatic macrophyte risk assessment, the first steps in modeling are currently being undertaken. A toxicokinetic/toxicodynamic model was presented for calculating the effects of pesticides on Myriophyllum spicatum considering the internal concentration in the plants. The study showed that the modeled data were in good agreement with laboratory test results. The model will be further refined. A new and important topic was the finding of intracellular uptake of hydrophobic substances in aquatic macrophytes. This research showed that macrophytes indeed bioconcentrate hydrophobic substances and thus can be used for phytoremediation. A last presentation discussed the application of marine plants in constructed wetlands to remediate nutrient-rich waste water from aquaculture facilities.

The poster corner addressed some topics in addition to the main platform session. The potential allelochemical influence of Myriophyllum was discussed. Several posters presented test designs for species that have recently been proposed as new regulatory test species, i.e. Myriophyllum species and the reed mannagrass, Glyceria maxima. Also several posters addressed phytoremediation by plants. Aquatic macrophytes not only adsorb chemicals but they also influence their chemical environment, for example, by changing the pH and O2 conditions and producing dissolved organic carbon. This might have effects on the fate of chemicals. Also the rhizosphere might be important for both aquatic and terrestrial plants to contribute to adsorption and degradation and therefore to phytoremediation.

Take-home Message
In current risk assessment schemes, aquatic macrophytes are being addressed more and more. New regulatory species have been proposed and the development of laboratory tests and guidelines is in process. Higher-tier risk assessment for terrestrial and aquatic plants receives more attention and effects on the higher levels of populations and ecosystems are studied and discussed. However, guidance on how to perform such tests is still needed. Phytoremediation is a promising field in which aquatic and terrestrial plants might help to decrease environmental concentrations of toxicants.

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