SETAC Globe - Environmental Quality Through Science
 
  20 June 2013
Volume 14 Issue 6
 

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Aquatic and Terrestrial Plant Ecology, Ecotoxicology and Risk Assessment

Gertie Arts, Alterra Wageningen University and Jo Davies, Syngenta

Author names and numbers cited refer to abstracts from the meeting, which can be found at meetings.setac.org/glasgow_abstracts.

The SETAC Aquatic Macrophyte Ecotoxicology Advisory Group (AMEG) held a session at the SETAC Europe 23rd Annual Meeting in Glasgow, Scotland, titled “Aquatic and Terrestrial Plant Ecology, Ecotoxicology and Risk Assessment.” This session highlighted recent scientific developments in the field of plant ecotoxicology and risk assessment for chemicals. Several topics, including toxicity, uptake and bioaccumulation studies in plants, phytoremediation studies and the management of aquatic plants, were covered by 18 platform presentations and more than 35 poster presentations.

Effect and Recovery Studies with Aquatic Plants and Algae

Several papers used species sensitivity distributions (SSDs) to investigate differences in sensitivity to chemicals between the taxa of primary producers (Arenas 328; Christl 339; Larras 340). One author used SSDs to demonstrate that herbicide risk assessments based solely on toxicity data for the standard regulatory test species (Lemna spp.) may not be fully protective of all primary producers (Arenas 328). Another study used SSDs to compare the sensitivity of dicotyledonous and monocotyledonous species (Christl 339). The author of this study concluded that, given the high uncertainty of the lower limit of the HC5 derived from these SSDs, this parameter should not be recommended for use in herbicide risk assessments. SSDs with benthic diatoms and mixtures showed that SSDs generated using data for species from specific localities may underestimate risk, while SSDs generated using data for generic species may overestimate risk (Larras 340). The author concluded that risk assessments should, therefore, consider a range of species.

Recovery studies of Lemna spp. were discussed in a number of platform presentations. Hanson (341), for example, demonstrated the ability of Lemna spp. to recover following exposure to toxic concentrations of diuron. Other studies investigated the effects of mixtures of herbicides on Lemna minor (Tagun 343) and the use of Lemna spp. for studying metals (e.g., uranium) in plants (Horemans 402). Another presentation (Brain 3420) demonstrated the use of aquatic plant data, combining SSD approaches with recovery and mesocosm data for several algal and aquatic plant species in a regulatory risk assessment for atrazine.

Uptake and Bioaccumulation Studies with Terrestrial and Aquatic Plants

Several plant uptake studies were presented that considered the uptake of organic compounds, either from a modeling approach (Limmer 399), or from an experimental approach in aquatic plants (Diepens 400) or terrestrial plants (Mueller 464), including vegetables (Gan 463). An important similarity was drawn between plant roots and blood vessels, contributing to the understanding of how chemicals move through the root before entering the central xylem transport system. A number of chemical characteristics were identified as being important to the easy uptake of chemicals in plants, including hydrophobicity (log Kow), the number of hydrogen receptors, and acceptors and pKa values.

The potential use of plants for remediation was discussed, specifically the use of Elodea nutalliito to remove mercury and methyl-mercury from a contaminated lake (Cosio 401).

Management of Aquatic Macrophytes, Especially Invasive Weed Species in Water Courses

In UK water courses, several invasive aquatic plant species occasionally form at such high densities that water flow is impeded and the management of aquatic vegetation is required. Options for management include both mechanical and chemical strategies. While only one herbicide (glyphosate) is registered for aquatic use, the mechanical removal of vegetation is labor-intensive, non-selective and not always effective. Therefore management strategies frequently need to encompass a combination of methods and appropriate guidance is required (Tarrant 403). Several methods have been used to manage an invasion of floating pennywort (Hydrocotyle ranunculoides) on the River Soar, with varying degrees of success (Harding 404). During the AMEG open meeting, an additional platform presentation evaluated the need to manage Crassula helmsii and investigated the effects of freezing on its subsequent growth and competitive abilities as a potential means of control.

Risk Assessment for Terrestrial Plants

A number of presentations were dedicated to risk assessment for terrestrial plants (Geilen 460; Ochoa-Acuna 461; Solga 462; Geraskin 465). Pesticide risk assessment for terrestrial plants is mostly based on a germination test or effects on juvenile plants. In one study, seed production and quality were also evaluated, but proved less sensitive than the standard parameters typically measured in juvenile plants (Ochoa-Acuna 461). Another study presented a higher-tier test design for non-target terrestrial plants under semi-field conditions. This higher-tier test resulted in a reduction of required mitigation measures compared to the results of a standardized greenhouse study (Solga 462).

Additional Topics Presented in Posters

While a large number of posters covered the topics addressed above, others addressed additional topics, including new developments in the risk assessment of pesticides (e.g., new mesocosm approaches), new test systems and methods for testing aquatic plants, effects and risk assessment of chemicals in algae, effects of metals on algae and macrophytes, and studies with marine plants.

Conclusions

The number of presentations submitted to this session demonstrates an increased interest in aquatic and terrestrial plant ecotoxicology and risk assessment. The results and outcomes of research in this field contribute to a better understanding of plant ecotoxicology and to improved risk assessments for chemicals.

Authors' contact information: Gertie.Arts@wur.nl, jo.davies@syngenta.com

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