Effects of chlorpyrifos on individuals and populations of Daphnia pulex in the laboratory and field

Abstract

Effects of the insecticide chlorpyrifos (cpf) on young (<1 d old) and adult (7–9 d old) Daphnia pulex and the ability of D. pulex to recover after exposure were tested in the laboratory. Populations of D. pulex exposed to cpf were studied in the laboratory and field. In the field, cpf was applied in a single dose. The effects of that dose on D. pulex populations were tested and compared with the effects of a simulated single dose and its ensuing decay on populations in the laboratory. The lowest no‐observed‐effect concentration was about 0.05 μg/L (actual concentration). Chlorpyrifos immobilized D. pulex several days before death. Juveniles became immobilized faster than adults. Even when no longer exposed, D. pulex immobilized by cpf died. In the laboratory and field, observed population dynamics and effects of cpf on these dynamics were very similar. The median effective concentration for population size after 2 and 7 d of exposure did not differ between the laboratory and field (2 d, 0.38 and 0.31 μg/L, respectively; 7 d, 0.25 and 0.34 μg/L, respectively). Effects of cpf on single‐species Daphnia populations in the laboratory and field can be predicted from effects observed in tests with individuals.

Genetic differentiation in pesticide resistance between urban and rural populations of a nontarget freshwater keystone interactor, Daphnia magna

“…For example, evolved chlorpyrifos resistance in Daphnia pulex prevented the development of a noxious algal bloom and impacted amphibian survivorship (Bendis & Relyea, 2016b ). Although impacts of field exposures to pesticides seem predictable from ecotoxicological laboratory exposures (van der Hoeven & Gerritsen, 1997 ), future research on toxicant resistance in urban freshwater communities should specifically include targeted transplant experiments of focal species and communities (Brans et al, 2020 ). This enables to assess in situ to what extent evolution in multiple species in response to a multi‐stressor (warming, pollution, disturbance) anthropogenic environment leads to costs of adaptation or can ultimately stabilize ecosystem properties (water clarity, biodiversity), which will feed back to society via socio‐eco‐evolutionary feedbacks (Des Roches et al, 2020 ).…”

Response of Daphnia magna to pulsed exposures of chlorpyrifos

“…These experiments indicate that daphnids could survive (or recover from) CPF toxicity if sufficient time elapsed between exposures, so that the critical body burden was not reached. Others have shown that once affected (i.e., immobilized), daphnids did not recover from CPF exposure [35].…”