SETAC Spotlight: Incorporating macrophyte health measurements into higher tier risk assessments

CEA presented 1 platform and 9 posters at SETAC Seville in May 2024. We will be showcasing each of these presentations in a series of ‘SETAC Spotlight’ articles. This week it is:

SETAC Spotlight: Incorporating macrophyte health measurements into higher tier risk assessments

Authors: Marie Brown¹, Zoe Parker-Crosse¹ Ellie Welch¹, Katie Smith¹, Hanna Schuster¹, Nadine Taylor¹,

¹Cambridge Environmental Assessments, RSK ADAS, Boxworth, UK

Current guidelines recommend that at least 8 sensitive/vulnerable taxa, with acceptable minimum detectable difference (MDD) values, should be tested within a mesocosm study, however, there is little guidance on the selection of appropriate endpoints for macrophytes that will provide regulatory acceptable data. In addition, many assessment methods for macrophytes are considered subjective such as visual determination of chlorosis and necrosis. The lack of standardized methods and challenges associated with using this subjective and ordinal data to derive statistically meaningful endpoints can lead to questions over reliability and relevance in the risk assessment of PPPs. Despite this, these measures are useful in supporting the assessment of potential effects on macrophytes and as a weight of evidence approach for the derivation of suitable overall endpoints. The considerations for macrophyte studies should include ecological relevance as well as the practical implications of ensuring good growing conditions and appropriate assessment methods to achieve robust and reliable data. The unique sloped mesocosm employed at CEA allows a wider range of macrophytes to be planted within the mesocosm and methods have been optimised to assess macrophyte growth and health, increasing valid data collection throughout the study. The endpoints have been specifically developed for each species, in order to maximise the quality and quantity of data collected. These include height measurements, number of stems, number of nodes per cm, counts of leaves and flowers as well as visual assessments of aerial coverage (cm²) and percentage of chlorosis and necrosis. On completion of the test period, measurements of wet and dry weight of each species are determined, however by measuring additional parameters throughout the study, this data can be used to contextualise the wet/dry weight results, assess short term effects and recovery, and determine the overall community effect of the test item.

By sharing our considerations for macrophyte endpoint evaluation in mesocosm studies we aim to highlight the relevance of mesocosm studies, particularly within the future of risk assessment for macrophyte communities.