Aquatic macrophytes are important primary producers of aquatic ecosystems that must be protected from adverse chemical effects in order to maintain important ecosystem structure and functions. Macrophytes fulfil several critical functions in aquatic ecosystems including conversion of solar energy and carbon dioxide into organic matter; production of oxygen; sequestration of carbon dioxide; cycling and retention of nutrients; stabilization of sediments; and provision of food and habitat resources for aquatic fauna (Wetzel 2001). Thus, aquatic macrophytes, and the ecosystem services that they provide, must be protected on a local and global basis.
Currently, the only aquatic macrophyte used in risk assessment of plant protection products (e.g., herbicides and plant growth regulators) under the European Regulation (EC 2009) is the standardized growth inhibition test with duckweed (Lemna spp.; EC 1997). Additional data with other aquatic plant species may be required on a case-by-case basis (EC 2002). In other regulatory frameworks, macrophytes are not obligatory in the risk assessment, e.g., in the risk assessment of chemicals in the context of the Water Framework Directive (Lepper 2005). Lemna is a small, floating, non-sediment-rooted monocotyledon with a short generation time and is rather atypical in growth form and traits compared with many other aquatic macrophytes; therefore, concerns have arisen that risk assessments based on Lemna and its endpoints may not be protective of other macrophyte species due to potential differences in exposure route, recovery rate, or sensitivity to chemicals with specific toxic modes of action (Brock et al. 2000; Hanson and Arts 2007; Vervliet-Scheebaum et al. 2006).
In January 2008, 41 macrophyte experts from academia, regulatory authorities, and business from Europe and North America discussed the current state and potential options for refinement of aquatic macrophyte risk assessment procedures at the workshop “Aquatic Macrophyte Risk Assessment for Pesticides” (AMRAP), which was organized under the auspices of SETAC-Europe (Society of Environmental Toxicology and Chemistry). During the workshop, an overview of the current European regulatory framework for the risk assessment of aquatic macrophytes was discussed, and the uncertainties and areas for improvement within the regulatory framework were identified. Conclusions and recommendations of the AMRAP workshop have been published (Maltby et al. 2010). Four working groups evolved from the workshop and were charged with the following tasks:
Developing and testing a proposal for a modified aquatic macrophyte Tier 1 Risk Assessment scheme for Plant Protection Products in the EU, including criteria when an additional macrophyte must be tested (Fig. 1);
Drafting and testing a protocol for a laboratory toxicity test with Myriophyllum spp. (Myriophyllum spicatum and Myriophyllum aquaticum) to be ring-tested in 2010;
Compiling an overview of laboratory toxicity methods for testing aquatic macrophytes other than Lemna;
Compiling data and developing guidance for the use of species sensitivity distributions (SSDs) in aquatic macrophyte risk assessment.
A SETAC Advisory Group on aquatic macrophytes was considered to be the optimal platform to facilitate the ongoing discussions regarding these tasks; the future dissemination of results of these working groups; and to provide a forum for participation by all those interested in these matters. In general, SETAC Advisory Groups have been and still are successful as a scientific forum (see as an example of another recently established SETAC Advisory Group: Preuss et al. 2009). In addition, an Advisory Group on aquatic macrophytes allows the original scope of AMRAP on the registration of plant protection products in Europe to be extended to other risk assessment schemes and legislative backgrounds in other countries (e.g., the Water Framework Directive; USA Clean Water Act).