EFFECTS OF SEDIMENT-ASSOCIATED PHENANTHRENE ON SURVIVAL, DEVELOPMENT AND REPRODUCTION OF 2 SPECIES OF MEIOBENTHIC COPEPODS

The lethal and sublethal toxicity of phenanthrene (a polycyclic aromat ic hydrocarbon, PAH) to 2 species of meiobenthic estuarine harpacticoi d copepods (Schizopera knabeni and Nitocra lacustris) was investigated . Individuals of different Life stages (nauplius, copepodite, adult ma le and female) were exposed to sediment-associated phenanthrene in sep arate 10 d bioassays. Overall, N. lacustris (10 d LC50 values ranging from 43 to 105 mu g g(-1) dry wt) was more sensitive than S. knabeni ( 10 d LC50 values ranging from 84 to 349 mu g g(-1) dry wt). Significan t differences in life-stage-specific sensitivity were observed for S. knabeni, with the nauplii being most sensitive, followed by copepodite s, and adults; adult males and females were equally sensitive. For N. lacustris, females were significantly more sensitive than all other st ages; no significant differences were evident among the other stages. Phenanthrene effects on offspring production were investigated in the adult 10 d bioassay. Significant decreases in offspring production occ urred at sublethal concentrations for S. knabeni (as low as 22 mu g g( -1) dry wt), but at concentrations in the same range as the 10 d LC50 values for N. lacustris. In addition, phenanthrene significantly prolo nged embryonic and larval development and decreased egg hatching succe ss for both species. Our results suggest that PAHs have a negative eff ect on the reproduction of meiobenthic copepods at sublethal concentra tions mostly due to a decrease in brood production rate and impairment of hatching. Overall, deleterious effects were manifested in the same range of concentrations for both species, but definite species-specif ic differences in the pattern of responses were evident.