Experimental studies of reproduction and feeding for two Arctic-dwelling Calanus species exposed to crude oil

Copepods of the genus Calanus are keystone species in the transfer of energy from lower to higher trophic levels of the Arctic/sub-Arctic food web. We performed experimental tests on the reproduction and feeding of Calanus spp. exposed to the water-soluble fraction (WSF) of crude oil. Fecal pellet and egg production were examined for females of C. glacialis exposed to WSF (16 EPA) concentrations of 10.4 mu g l(-1) (high treatment; HT), 3.6 mu g l(-1) (low treatment; LT) and 0 mu g l(-1) (control treatment; CT). We observed no significant difference in cumulative egg or fecal pellet production. Egg hatching success was examined for 2 d after transferring eggs from treatment solutions to uncontaminated seawater. Hatching success was significantly lower in the HT compared to the CT. In a second experiment, feeding of C. finmarchicus was examined after exposure for 11 and 18 d to 7.0 (HT), 3.4 (LT) or 0 (CT) mu g l(-1) of WSF (16-EPA). Using algae cell concentrations as a proxy for feeding success, feeding was inhibited for C. finmarchicus specimens exposed to the HT of WSF compared to the CT. Our findings indicate that adult females of C. glacialis may withstand some exposure to crude oil components but the survival of offspring is negatively affected. Reduced feeding efficiency in C. finmarchicus exposed to high concentrations of WSF provides evidence that adult specimens are sensitive to exposure to crude oil. The study expands on the limited body of knowledge of potential changes to key life history traits of Arctic Calanus species resulting from exposure to chemical compounds in crude oil.