Associations between macrofauna and sediment hydrocarbons from treated ballast water effluent at a marine oil terminal in Port Valdez, Alaska.

Sediment-dwelling macrofauna, polycyclic aromatic hydrocarbons (PAH), and abiotic parameters were monitored annually in benthic marine sediments from 1989-2007 in Port Valdez, a period of declining routine discharge of treated marine ballast water containing residual PAH from a major crude oil loading facility. The resulting dataset was used to evaluate associations between macrofauna and environmental characteristics including PAH concentrations. The influences of natural abiotic gradients on macrofauna were stronger than associations between macrofauna and sediment PAH. Though overall associations of PAH with macrofaunal community structure were weak, effects were greater for the tube-dwelling polychaete worms Galathowenia oculata and Melinna cristata which responded negatively to low PAH values near sediment quality criteria (threshold effects concentration: TEC and field-based sediment quality criterion: fb-SQG: ∼300 ng g( -1)). Effects of PAH on benthic fauna may be strongest through poor survival of juveniles and failed recruitment over multiple years. Comparison of measured PAH concentrations to the TEC and field-based fb-SQG suggest that the observed levels of change in Port Valdez are minor and the criteria are ecologically appropriate for environmental monitoring. By demonstrating positive responses of sensitive fauna to reduction of PAH concentration, this study contributes to understanding the temporal change, ecological importance, and size of effects expected on benthic fauna in the presence of continuous exposure to low levels of hydrocarbons.