Abstract
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 μg 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 μg Zn/ml, and a sharp decrease in fecundity from the 20th day of life at all levels of metal enrichment tested. Treated groups were characterised by a marked reduction of the net growth rate ( R 0 ) and a decrease in generation time ( T) with respect to the control groups, but no effect on life expectancy ( e 0 ) or on population growth rates ( λ) was observed. R 0 and λ, which are the most commonly used indices of fitness, were not equally susceptible to zinc. λ appears less sensitive to stress induced by metal enrichment with respect to R 0 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.
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