Effects of Petroleum Stressors on Life History Development in Fishes

The assessment of cause is a complex process during resource damage assessments because there are a range of anthropogenic and environmental factors contributing to adverse biological responses in urban estuaries.  After the San Francisco Bay Cosco Busan oil spill (CBOS) in 2007, three years of field and laboratory data were compiled using Pacific herring (Clupea pallasi) as an indicator species.  Demonstrating Cosco Busan oil (CBO) or components of the fuel oil were the cause of  adverse developmental effects observed in 2008 required validation that the organisms were exposed to CBO at concentrations sufficient to cause the observed effects.  For example, environmental and other contaminant stressors may cause effects similar to petroleum related effects.  An assessment framework was used to examine the data collected over the past three years relative to the CBOS and Pacific herring.  This framework used an epidemiological approach to evaluate multiple interacting processes to identify whether the CBOS could be established as the cause of observed adverse biological responses. Elements of the causal framework that would implicate CBOS included 1) a chemical exposure signature measured at biologically available concentrations in the exposure media and most importantly also measured in tissue samples, 2) CBO concentrations and biological response signatures comparable to known dose response relationships, and 3) a demonstration that any responses exceeding the measured dose response relationships were due to factors not associated with the CBO source.  The conclusion from the evaluation was that CBO was not the cause of disrupted development and mortalities of Pacific herring observed in the naturally spawned Pacific herring embryos collected after the CBOS in 2008.  The alternative hypothesis that environmental stressors (temperature, UV light, aerial exposure) and condition of donor fish gametes were the most likely cause of the experimental observations of anomalies in developing herring in 2008 and 2009 are supported by this evaluation and the experiments conducted in 2010.