Influence of polycyclic aromatic hydrocarbons on the meiobenthic-copepod community of a Louisiana salt marsh

The influence of sediment contaminated with polycyclic aromatic hydrocarbons (PAHs) on the meiobenthic copepod community of a Louisiana salt marsh was examined with microcosms of sediment containing natural faunal assemblages. Microcosms were dosed with PAH-contaminated sediment that ranged in concentration from 0.3 (controls) to 27 mg PAH/kg dry sediment, and effects were followed for 28 days. Data suggest that highest doses (High-PAH) elicited avoidance behavior by Pseudostenhelia wellsi (Coull and Fleeger) copepods and nauplii, particularly 12 h after contaminants were added (Day 0). Weaker avoidance behavior was indicated in non-P. wellsi species that was manifested as increases in nauplius/copepod ratios. Nematode/copepod ratios were calculated for each of 4 species (P. wellsi, Coullana sp., Enhydrosoma sp., and Onychocamptus mohammed (Blanchard and Richard)); only nematode/P. wellsi ratios were significantly affected by PAH. High-PAH treatments also lead to a higher proportion of females in P. wellsi and Coullana sp. This effect was only observed from Day 7 on and is interpreted as an indication of disproportionately high mortality of males. Collectively, our data demonstrate that relatively low-level PAH contamination may cause many ecologically important impacts on copepod community structure that may not be detected at the level of higher taxon.