Meiofaunal recolonization experiment in oiled sediments

To gain insights into long-term studies of the effects of the Exxon Valdez oil spill on the meiobenthos, a coionization experiment was iniciated in 1990. Unweathered Exxoon Valdez crude oil was mixed with azoic sediment to pregare low (26 = 3µg -` tocal aromatica) and high (210 = 12 A-` total aromatica) treatments of oiled sedimenta. The resulting mixtures, and azoie sedíment without oil as a controi, were added io triplicate colonization trays and buried flusti with the surface of two beaches ricar mean low water in Herring Bay, Prince William Sound, Alaska. Hydrocarbon concentrations tended to deciine with time. Trays and ambient sedimenta were sampied by coring and harpaeticoid copepod species enumerateti on days 0, 1, 1_ and 28. Harpacricoids (more than 40 species) were mostly phytai associates from surrounding e--lgrass beds. Colonization was rapiti (approaching, ambient levels in 1-2 d), espedaJly in coniroi and low-oil treatments. High-oil treatments exbíóited sitmifiwrltly reduced densities of toral harpacticoids and of two rapicily colonizing species (Haiecnnosoma sp. and iVfesochra ~aea) especially ori days 1 and 2. Two siower coloni= (,Paralaophonte perpiew and Amphiascus minurus) were unaffecied by oil additions. Detrended correspondenee analysis identified oil effects on che harpacticoid assemblaggi among tbc treatment-:aie cogecrions. Ambient samples from all dares segregateti from experimentals and were tightly clustered- Day 1 and 2 low- and high-oil treatments clustered together as diti contro!, low-, and high-cíl sedimenti; from day 28. Controi day 1 and 2 coilecrions were intermediate. 7rius, results suggest that an oil effect on migration and colonization was detectable, but for fewer than 28 d