Amy Brooks

Sublethal effects and predator-prey interactions: Implications for ecological risk assessment

Ecological risk assessments tend to focus on contaminant effects on single species in isolation. However, additional effects from interactions between species (e.g., predator-prey interactions) may also occur in natural systems. The present study investigated the consequences of sublethal contaminant effects in prey on predator-prey interactions, particularly the interaction between prey behavioral changes and predation by predators with different hunting strategies. Ambush (Ischnura elegans Vander Linden [Insecta, Odonata]) and active (Notonecta glauca Linnaeus [Insecta, Heteroptera]) predator species were used in conjunction with three prey species (Asellus aquaticus Linnaeus [Crustacea, Isopoda], Cloion dipterum Linnaeus [Insecta, Ephemeroptera], and Chironomus riparius Meigen [Insecta, Diptera]). Immobilized prey demonstrated the importance of prey behavior for determining predation rates for both single- and multiple-prey species. Chironomus riparius was less responsive following exposure to cadmium, becoming more vulnerableto attack by the active but not the ambush predator. Some evidence was also observed for reduced general activity in C. dipterum following cadmium exposure. Sublethal exposure of prey did not affect the prey choice of active predators, possibly because of prey behavioral changes being insufficient to influence their relative availabilities. However, cadmium exposure of prey did alter their susceptibility to ambush predators. There was a reduced proportion of C. dipterum and an increased proportion of A. aquaticus in the diet of ambush predators, possibly because of reduced activity in C. dipterum affecting their relative encounter rates with predators. Sublethal exposures can therefore result in reduced prey survival that would not be predicted by single-species toxicity tests.

Importance of prey and predator feeding behaviors for trophic transfer and secondary poisoning.

Hydrophobic contaminants accumulate within aquatic sediments, hence pelagic predators may have limited direct contact with such compounds, but can be exposed via their benthic prey (i.e., via dietary exposure). Here we examine the importance of feeding behaviors of both prey (sediment ingesters or noningesters) and predators (piercers or engulfers) in determining the extent of dietary exposure and toxic effects. A freshwater macroinvertebrate system was used, consisting of two predator species, a piercer (Notonecta glauca) and an engulfer (Ischnura elegans), and three prey species, a sediment noningester (Cloëon dipterum) and two sediment ingesters (Asellus aquaticus, Chironomus riparius). Predators were fed prey previously exposed to artificial sediment dosed with 30 microg/g of 14C benzophenone. The piercer predator accumulated more benzophenone from sediment ingester compared to sediment noningester prey, whereas the engulfer predator accumulated a similar concentration for all three prey species. Toxic effects, in terms of reduced feeding rate, were only observed with the engulfer feeding on sediment noningesters, probably due to the interaction between the narcotic mode of action of benzophenone and predator hunting strategy. The importance of dietary exposure in risk assessments may therefore depend on exposure pathways of prey, feeding behaviors of predators, and the contaminants toxic mode of action.

Reflections on bird and mammal risk assessment for plant protection products in the European Union: Past, present, and future

The use of plant protection products on agricultural crops can result in exposure of birds and mammals to toxic chemicals. In the European Union, the risks from such exposures are assessed under the current (2009) guidance document from the European Food Safety Authority (EFSA), designed to increase the realism of the theoretical risk assessments in comparison to its predecessor (SANCO/4145/2000). Since its adoption over 7 yr ago, many plant protection products have been evaluated successfully using the 2009 EFSA guidance document. However, there are still significant areas of improvement recommended for future revisions of this guidance. The present Focus article discusses experiences to date with the current scheme, including levels of conservatism in input parameters and interpretation by regulatory authorities together with proposals for how the guidance document could be improved when it is revised in the not too distant future. Several areas for which further guidance is recommended have been identified, such as the derivation of ecologically relevant bird and mammal reproductive endpoints and the use of modeling approaches to contextualize risk assessments. Areas where existing databases could be improved were also highlighted, including the collation of relevant focal species across Europe and expansion of the residue database for food items. To produce a realistic and useable guidance document in the future, it is strongly recommended that there is open and constructive communication between industry, regulatory authorities, and the EFSA. Such collaboration would also encourage harmonization between member states, thus reducing workloads for both industry and regulatory authorities. Environ Toxicol Chem 2017;36:565-575.