PARENT SESSION
5A Assessing and predicting toxicant effects in an ecologically complex world
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/MF183) Short-term effects of chromium enriched seawater on Dinophilus gyrociliatus (Polychaeta) on population level.

Mauri, Marina¹, Crema, Roberto ¹, Simonini, Roberto ¹, ¹

ABSTRACT- In view to highlight the effects of the toxicant exposure on population parameters and to evaluate the capability of the population to maintain stationary the level of its rate of increase, life table response experiments were performed on a laboratory strain of Dinophilus gyrociliatus, a small polychaetous annelid considered a good candidate for laboratory ecotoxicological tests and also a probable target species in polluted marine closed areas as ports and harbours. Survival and reproduction, starting from the deposited egg age class until death, were recorded for control and laboratory treated individuals maintained at 1,1.4, 1.6 Cr/ml in artificial seawater. Starting from the observations, the main population parameters were calculated. As a total, survival and fecundity were significantly reduced by chromium. Fecundity was higher in control groups except at the beginning of the reproductive period, when metal enrichment induced a small reproductive advantage. Yet population growth rate , used as index for population fitness, was higher in the treatments with respect to control groups. The elasticity analyses revealed that:1, is most sensitive to changes in juvenile survival and fecundity; 2, the differences in were almost completely due to life table differences during the early 3 weeks of life. The decomposition analyses measuring age specific survival and fecundity contributions to differences evidenced how the marked decrease in treated groups fecundity was overweighted by the small increase occurred in the early reproductive events. Survival on the contrary gave no contributes to . The complex effect of enhanced environmental chromium highlighted by the demographic analyses make us to propose a practice application to chronic toxicity tests to link individual level responses to population level impacts.

Key words: ecotoxicology, polychaeta, reproduction, chromium