Effects of intra- and interspecific competition on the sensitivity of aquatic macroinvertebrates to carbendazim

Interaction between stress induced by competition, predation, and an insecticide on the response of aquatic invertebrates

“…In the interspecific experiment it was clear that intraguild predation of A. aquaticus by D. pulex decreased as chlorpyrifos concentration increased (Supplemental Data, Figure S2). Similar interactive responses were observed for other pesticides by Blockwell et al and Del Arco et al . In the present study, predation could have allowed for release from food limitation at lower concentrations whereby G. pulex survival increased despite chlorpyrifos stress.…”

“…Such an approach often disregards side effects caused by chemical pollution as a result of ecological interactions. Species interactions such as competition or predation are susceptible to chemical stress (e.g., Foit et al , Del Arco et al ), possibly leading to population or community changes and impacts on several ecosystem functions and processes (e.g., nutrient cycling, food chain provision). The literature shows that intraspecific competition can increase the sensitivity of insect larvae to insecticides (e.g., Liess ), result in higher population survival rates as a result of increased availability of resources (e.g., Postma et al ), or temporarily affect the structure of aquatic populations .…”

“…For instance, Liess and Foit showed that Daphnia magna exposed to the insecticide fenvalerate experienced delayed population recovery, whereby the level of intraspecific competition determined the length of time needed for the recovery of population structure. Laboratory experiments have shown that interspecific competition may lead to population decreases in less fitted species or in species with the highest sensitivity to the toxicant , whereas others have observed an adaptive behavior encompassing changes in feeding strategies to overcome food resource limitations . As is often seen in microcosm and mesocosm experiments, interspecific competition generally leads to an increase of the least sensitive competing species because of increased availability of resources and a slower recovery of the most sensitive one .…”

“…Two sets of species were selected. The first set was formed by the amphipod Gammarus pulex , which competed over food resources with the isopod Asellus aquaticus , also showing intraguild competition . The second set of species was formed by the cladoceran Daphnia pulex (focal species), a rotifer that competed over the same food resource, and an external predator that predated on D. pulex .…”

Is the chronic Tier-1 effect assessment approach for insecticides protective for aquatic ecosystems?

“…A comparative assessment of its chronic sensitivity to the main insecticide groups with Tier‐1 standard test arthropods has not yet been performed. Nevertheless, some studies have indicated that G. pulex could be considered as an interesting species not only to evaluate its direct chronic sensitivity, but also to investigate toxicity mechanisms (Xuereb et al ), to evaluate individual‐level effects under particular exposure patterns (Ashauer et al ), multiple stress conditions (e.g., starvation, competition) (Nyman et al ; Del Arco et al ), and to assess effects on reproduction (Cold and Forbes ) and meta‐population poststress recovery using mechanistic effect modeling (Galic et al ).…”