TRACE-ELEMENT AND BIOTIC CHANGES FOLLOWING A SIMULATED OIL-SPILL ON A MUDFLAT IN PORT VALDEZ, ALASKA

A mudflat in Port Valdez, Alaska, was examined to determine effects of experimental additions of Prudhoe Bay crude oil on metal chemistry and harpacticoid copepod abundance. Hydrocarbon concentrations were at background levels 30 days after final addition of oil. The short residence time of oil added to sediments is attributable to physical removal of oil by tides, low sediment permeability, and low affinity of hydrocarbons for periglacial clay surfaces. Elemental concentrations, except Si, were lower in oiled than in unoiled sediments. Elemental depletion in oil-impacted sediments is attributable to mobilization of metals from oxide/hydroxide sediment phases or to desorption from clay due to lowering of Eh-pH of sediments subsequent to oil addition. In oiled sediments, abundance of the harpacticoid copepods Harpacticus uniremis, Halectinosoma gothiceps, and Heterolaophonte sp. was similar to or higher than values within unoiled plots. The reasons for lack of deleterious effects of oil on copepods in Port Valdez are not yet understood. © 1990.