title: Competition increases toxicant sensitivity and delays the recovery of two interacting populations.
abstract: We investigated how persistent competitive pressure alters toxicant sensitivity and recovery from a pesticide pulse at community level. Interacting populations of Daphnia (Daphnia magna) and Culex larvae (Culex pipiens molestus) were pulse-exposed (48 h) to the pyrethroid fenvalerate. The abundance and biomass of the populations were monitored by non-invasive image analysis. Shortly after exposure, Daphnia showed a concentration-response relationship with the toxicant with an LC₅₀ of 0.9 μg/L. Culex larvae were slightly less sensitive with an LC₅₀ of 1.7 μg/L. For both species, toxicant sensitivity increased with the population biomass of the respective species before exposure, which is explained by intraspecific competition. Several weeks after exposure to the highest treatment concentration of 1 μg/L, the slight differences in sensitivity between the two species were amplified to contrasting long-term effects due to interspecific competition: high interspecific competition impaired the recovery of Daphnia. Subsequently, Culex larvae profited from the slow recovery of Daphnia and showed an increased success of emergence. We conclude that, in natural systems where competition is present, such competitive processes might prolong the recovery of the community structure. Hence, natural communities might be disturbed for a longer period by toxic exposure than predicted from single-species tests alone.
authors: Helmholtz Centre for Environmental Research - UFZ, Department of System Ecotoxicology, Permoserstrasse 15, D-04318 Leipzig, Germany. kaarina.foit@ufz.de
authors: Kaarina
authors: K
authors: Foit
authors: Oliver
authors: O
authors: Kaske
authors: Matthias
authors: M
authors: Liess
mesh_terms: D000818:Animals; D044822:Biodiversity; D001686:Biological Phenomena / Q000187:drug effects*; D003163:Competitive Behavior / Q000187:drug effects*; D003465:Culex / Q000502:physiology*; D003621:Daphnia / Q000502:physiology*; D009570:Nitriles / Q000378:metabolism; D010575:Pesticides / Q000633:toxicity; D011157:Population Dynamics; D011722:Pyrethrins / Q000378:metabolism; D018570:Risk Assessment; D013312:Stress, Physiological; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D009570:Nitriles; D010575:Pesticides; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; C017690:fenvalerate