Under Regulation (EC) 1107/2009, it is increasingly difficult to demonstrate acceptable risks to aquatic organisms at Tier I. Therefore, it is often necessary to turn to higher-tier approaches, with one such tool being mesocosm studies. Under the current aquatic guidance document (EFSA 2013), two types of endpoint can be generated from mesocosm studies: no observed effect concentration (NOECs) and no observed adverse effect concentration (NOEAC). The NOEAC represents a concentration at which aquatic communities will experience transitory effects but can recover within a period of time. The acceptable length for this recovery period is dependent upon the magnitude of effects observed i.e. a small effect can last for months, a medium effect can last for weeks, a large effect can last for days.
Regulatory authorities are sometimes cautious about using NOEAC endpoints in the risk assessment due to concerns that recovery in real waterbodies may not occur, particularly in physically isolated waterbodies that do not benefit from unaffected areas upstream acting as a source for recolonization. In such situations, the time required for an impacted community to recover may be longer, which could influence whether an effect is considered acceptable under EFSA (2013). Individual species traits outside of their sensitivity to pesticides, such as dispersal ability, timing of dispersal and generation time, play an important role in their ability to recover; these factors may also determine whether a species is present in isolated water bodies prior to a disturbance event. One important aspect of this discussion that can be assessed with available data is the degree of isolation of water bodies in heavily agricultural landscapes.
Our aim was to first examine the occurrence of isolated waterbodies in agricultural landscapes; if waterbodies are rarely isolated, this may help contextualise the concerns of regulatory bodies that isolated waterbodies may not recover following disturbance. As a case study, we investigated the extent of waterbody isolation within agricultural landscapes in England and Wales based on analysis of open GIS datasets, including a database of UK lakes.
The main conclusion from the analysis was that highly isolated ponds (i.e. >301 m from other water bodies) are uncommon within highly agricultural landscapes. In fact, 90% of ponds identified were within <301 m of another water body. Based on a further review of ponds considered highly isolated it was also concluded these ponds did not generally occur in local landscape settings likely to result in high exposure to pesticides.
These investigations provide useful information to help regulators contextualise the issue of recovery in isolated water bodies and thus to make more informed decisions on recovery endpoints. Future work could examine the effect of isolation on biodiversity and species identity and how this in turn affects recovery. This could potentially be conducted using existing datasets from the UK or wider Europe.
This work was recently presented at SETAC Brussels, with the poster being available for download here.
If you have any comments or questions about this work, please contact Michael.Hackett@cea-res.co.uk.
In addition to this poster, CEA also presented a further 6 posters and 3 platform presentations at SETAC Brussels, with the rest being available for download at: