Effects of zinc on the polychaete Dinophilus gyrociliatus: a life table response experiment

A life-table response experiment (LTRE) was performed in order to study the effects of enhanced zinc on the survival, fecundity and demographic indices of Dinophilus gyrociliatus (Polychaeta). A control group and three treated cohorts kept in artificial seawater enriched with nominal concentrations of zinc at 0.25, 0.50 and 1.00 g Zn/ml, respectively, were considered. Zinc marginally affected survival but had a strong impact on the reproduction of D. gyrociliatus. Zinc enrichment had no effect on age at maturity, whereas it induced a slight increase in fecundity during the early reproductive phases at 0.50 and 1.00 g Zn/ml, and a sharp decrease in fecundity from the twentieth day of life at all levels of metal enrichment tested. Treated groups were characterized by a marked reduction of the net growth rate (R0) and a decrease in generation time (T) with respect to the control groups, but no effect on life expectancy (e0) or on population growth rates () was observed. R0 and , which are the most commonly used indices of fitness, were not equally susceptible to zinc.  appears less sensitive to stress induced by metal enrichment with respect to R0 and other life history traits like age-specific fecundity. D. gyrociliatus appears to be an appropriate bioindicator species in LTRE to assess the consequences of environmental heavy metals on individual life-history and population dynamics.