A COLD-WEATHER SPECIES' RESPONSE TO CHEMICALLY DISPERSED FRESH AND WEATHERED ALASKA NORTH SLOPE CRUDE OIL

ABSTRACT The University of Alaska Fairbanks (UAF) joined the Chemical Response to Oil Spills: Ecological Effects Research Forum (CROSERF) in 1997. In 1998 and 1999, UAF tested the toxicity of: (1) an oil dispersant, COREXIT®9500; (2) the water-accommodated fraction (WAF) of Alaska North Slope (ANS) crude oil as well as the U.S. Environmental Protection Agency (EPA)-standard, Prudhoe Bay crude oil (EPA); and (3) the chemically-enhanced water-accommodated fraction (CE-WAF) of ANS as well as EPA. Tests also were performed with ANS samples that had been artificially weathered to remove most of the volatile components (weathered ANS). Species tested were a juvenile mysid, Mysidopsis bahia, and the larvae of an estuarine fish, Menidia beryllina. Parallel testing with bacteria using the Microtox® test was performed and results compared. Overall, UAF's procedures and results were consistent with that of other CROSERF labs. These procedures use 25 °C water. In 1998 and 1999, UAF tested the larvae of a crab native to Alaska, the Tanner crab, Chionoecetes bairdi. The crab larvae were tested with COREXIT®9500, ANS, and weathered ANS. During gestation the gravid crabs were kept in fresh seawater at temperatures of 6 to 8°C, and larval testing also was done at those temperatures. The results of the fresh oil tests showed that, for both the WAF and CE-WAF, the crab larvae sensitivity was similar to that of M. beryllina during a spiked exposure, but the crab larvae proved to be more sensitive during a continuous exposure. For weathered ANS, the result was highly dependent on the analysis and reporting techniques. A heavy loading of weathered oil was required to produce a low concentration of WAF because of the relative insolubility of the weathered oil.