Helena Crosland and Amy Brooks have co-authored a journal article on aquatic macrophyte growth periods that was published this month in the SETAC IEAM journal. A summary of the article is provided below:
Journal article authors: Helena Crosland1, Amy Brooks1, Michael Hackett1,2, Johannes Witt3, Thomas Preuss
1Cambridge Environmental Assessments; 2At time of preparation of underlying report; 3Bayer AG
Aquatic organisms including aquatic plants (i.e. macrophytes) may be exposed to pesticides via the surface water in which they reside through spray drift or run-off from agricultural applications. A risk assessment may therefore be required to demonstrate the safe use of pesticide products. For macrophytes, pesticides with herbicidal Modes of Action (MoAs) are of particular concern. If an unacceptable risk to macrophytes is highlighted during the risk assessment, possible refinements to demonstrate an acceptable risk include additional species testing and mitigation (e.g. buffer zones).
However, some herbicidal MoAs are only effective on plants which are actively growing (e.g. acetolactate synthase (ALS) inhibitors such as sulfonylureas). In these cases, a standard risk assessment approach could be argued to be overly conservative. This is because standard toxicity studies with macrophytes are performed under conditions where plants are actively growing to maximise the detection of effects (both in climate-controlled labs, and usually also for mesocosms which are often performed over the Spring/Summer months). This may be suitable when exposure to a pesticide is likely to occur during the growth season, but may not be realistic when exposure to a pesticide is predicted to occur outside of the growth season. This can occur even when a pesticide is applied during the growth season, e.g. as a result of winter drainage events.
The aim of this journal article was therefore to use available literature to identify the main active growth period of aquatic macrophytes in natural freshwater bodies. The focus was centered on freshwater bodies in climates relevant to the Central zone and the Northern zone of the European Union. A systematic literature review was performed using text mining to identify potentially relevant literature sources. A screening process was performed, and growth seasons were extracted from papers which were considered to be suitably relevant and reliable. The findings from all citations which were deemed to be suitable are summarised in Table 3 of the publication, but are also available in an alternative format for convenience.
In general, the 43 collated growth periods from 25 relevant publications provides a strong basis to conclude that general trends in growth periods of aquatic macrophytes in Central and Northern Europe (and areas with similar climates) are consistent. The data supports a growth period for aquatic macrophytes in CZ and NZ EU beginning in April and ending in September. This period represents most species reviewed, and most growth that occurred for each species. The implication for the risk assessment and authorization of PPPs which only affect macrophytes when they are actively growing is that it may be possible to conclude a low risk for aquatic macrophytes if the predicted surface water exposure period for these PPPs is demonstrated to be outside the periods of active growth. This would require the support of exposure modeling or data to demonstrate when the aquatic macrophyte exposure period realistically occurs for a particular proposed use.
You can read the full open-access article on the IEAM website.
A poster summarising the main results of this work is also available, which was previously presented at a past SETAC Europe conference.
You can find all of our publications from conferences and links to journal articles we have authored on our library page.
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