EPT taxa (Ephemoptera; mayflies, Plecoptera; stoneflies and Trichoptera; caddisflies) are used as biological indicators of water quality and have been shown to be sensitive to environmental pollutants such as PPP’s. These taxa are also particularly vulnerable as their long aquatic larval stages mean that individuals are potentially exposed to PPPs in water bodies for extended time periods. The life histories of EPT taxa make them inherently problematic for ecotoxicology testing as they are generally low in abundance in the natural environment and typically have a 1 to 2 year life cycle. This means that full life cycle culturing in the laboratory is labour intensive and costly, and the development of standardised tests using lab-cultured organisms would be very challenging to achieve. It is possible to perform laboratory toxicity tests using field collected organisms, selecting organisms based on size or life stage. This approach often results in higher variability in comparison to using lab-cultured organisms, due to the lack of synchronicity associated with using field collected organisms of a particular size range. It can also require additional work to determine the most sensitive life-cycle stage(s) to use in toxicity tests. It is also difficult to assess long term effects on emergence and reproduction in the laboratory, due to the lengthy generation times of these taxa, though surrogate sublethal endpoints can be measured e.g. growth, feeding. Mesocosm studies offer an alternative approach, however EPT taxa are often considered to be under-represented in static systems. However, there are some E and T taxa that thrive in static water habitats, such as the mayfly Cloeon dipterum and Caddisfly taxa Phryganeidae. One of the major challenges for mesocosm studies is achieving consistently high abundances of organisms to allow sufficient statistical power to detect significant differences. EPT taxa often yield low abundances and highly variable data, which can result in uncertainties in the detection of treatment-related effects.
Here we present our findings for determining the optimum experimental conditions to provide improved endpoint measures for EPT taxa in (i) laboratory systems, including techniques for the measurement of sub-lethal endpoints with species where it is not possible to test full life cycles and (ii) static mesocosms by comparing the abundances of EPT taxa in historical control data with mesocosms of different design.
To find out more about this work, please download our poster 'Ecotoxicology testing experiences with EPT taxa'.
In addition to this topic, CEA also presented six other posters at the SETAC virtual conference (SETAC SciCon, May 2021). These are available for download here.
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