Why choose CEA for mesocosm studies?

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Why choose CEA for mesocosm studies?

Aquatic freshwater mesocosms are higher tier studies designed to increase the realism of ecotoxicology testing by determining the effects of a chemical on a community, in a system replicating the natural environment in an edge-of-field waterbody. CEA offers bespoke mesocosm studies at our facility in Cambridgeshire, UK, uniquely designed to meet your higher-tier regulatory testing needs. All our studies are run to GLP and in accordance with regulatory guidelines.

Our mesocosm design has evolved over the years in accordance with EFSA guidance, such that the results meet the requirements for 8 sensitive/vulnerable taxa with acceptable Minimum Detectable Difference (MDD) values, in order to maximise regulatory acceptability. We have the in-house expertise to taxonomically identify the organisms in our systems and interpret these complex data sets, determining the true effects of a Plant Protection Product (PPP) on the aquatic community.

Our mesocosm design

Our flat bottomed mesocosms are used to assess insecticides and fungicides, employing a wide range of sampling methods and traps to collect abundance data on the whole community of aquatic macroinvertebrates. Each trap targets different types of organisms: sweep nets are used to capture fast-moving pelagic organisms, whereas colonisers are left in-situ to allow benthic organisms to enter the trap, and emergent traps capture organisms in their adult stage. At CEA we have specifically designed our sampling techniques to maximise organism sampling, thus increasing the reliability of the data collected to derive robust endpoints. 

Our unique sloped mesocosm design allows a wide range of macrophytes to be included, from Veronica beccabunga that thrives in the shallows (less than 10 cm deep) to Potamogeton natans that prefers deeper waters (50 cm). The slope provides varying depth and light levels accommodating different habitat niches, ensuring all macrophytes tested have ideal growing conditions. Furthermore, the sloped design enables species interactions, replicating true community effects. This is especially important as the recovery of communities following exposure to a PPP is highly influenced by intra and interspecific interactions, and these systems allow for more realistic recovery endpoints to be evaluated. This is a rarity as, in general, herbicide studies often grow macrophytes in individual plant pots or at a single water depth. We have developed methods to assess macrophyte health and growth throughout the study, including chlorosis, necrosis, plant height and the number of stems. By increasing the number of parameters measured for each plant, more relevant and robust data can be obtained to accurately monitor the effect of the herbicide on aquatic macrophytes over time.

What we monitor

In our mesocosm studies we monitor the whole community and have the ability to collect data on freshwater zooplankton, phytoplankton, periphyton, macrophytes, macroinvertebrates and emergent insects.  This means that PPPs can be tested under realistic conditions at the population and community levels, containing multiple interacting species and relevant biotic and abiotic processes. We collect supporting data to contextualise effects observed, such as water quality and nutrients, and have the expert knowledge to relate community changes to organism physiology and seasonality.

The process

As spring approaches, our mesocosms are cleared and re-established for the experimental phase of studies to be completed in the summer. This establishment period is critical to seed and plant the mesocosms with a healthy community of plants and organisms in order to establish comparable communities between replicates and reduce variability in the collected abundance or growth data.

Long term seasonal studies require planning several months before initiation, so now is an ideal time for reviewing existing data packages and getting your tailored study design underway.

To find out more about our mesocosm studies, or any other aspect of our aquatic testing services, please contact Nadine Taylor on +44(0)1954 268320 or


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