Influence of temperature on Cd accumulation by species of the biomonitor Chaoborus
Limnol. Oceanogr., 47(2), 2002, 505-514 | DOI: 10.4319/lo.2002.47.2.0505
ABSTRACT: We exposed larvae of several species of the phantom midge Chaoborus to the trace metal cadmium (Cd) to determine whether Cd accumulation rates varied with ambient temperature. Because this predator is known to accumulate its Cd mainly from food rather than from water, we presented the Cd in food, that is, Cd-rich copepods taken from a lake near a metal smelter. Rates of Cd accumulation by larvae of Chaoborus americanus, C. flavicans, and C. punctipennis were measured at three temperatures (5, 14, and 228C) covering the seasonal range encountered by these animals. The rates at which all species accumulated Cd increased with temperature. To explain these results, we fit our experimental data to a bioaccumulation model that allowed us to estimate Cd assimilation efficiency, Cd-efflux rate, and larval growth rate. Temperature-related changes in Cd accumulation rates were best explained by changes in the rate at which Chaoborus larvae ingested prey as well as the efficiency with which they assimilated Cd from their food. Neither the rate of larval growth nor the rate at which larvae lost Cd was influenced by temperature. Extrapolations of our laboratory results to the field suggest that our model results provide a realistic representation of the processes involved in Cd accumulation by larvae of this common aquatic insect.