California Sea Grant College Program

Morro Bay in Central California is considered a relatively pristine waterway with little urban or agricultural pollution. In this project, however, scientists show a high incidence of primordial gonadal and liver tumors in arrow goby, Clevelandia ios, collected from the bay’s mudflats. Large tumors were found in about ten percent of 150 arrow gobies sampled from the area. Subsequent testing at UC Davis revealed signs of abnormal liver cell growth, associated with the early stages of liver cancer, in even apparently healthy fish. These tumors are usually indicative of exposure to persistent organic pollutants: chemicals that accumulate in organisms but evade detection through traditional water-quality testing. In the case of the bay, the fish were shown to be riddled with an endocrine disruptor known as nonylphenol, the degraded form of a group of petroleum products known as alkylphenol ethoxylates. Ethoxylates, added to detergents, cosmetics and spermicides, have both hydrophilic and hydrophobic chemical groups, which make them highly effective at dissolving organic chemicals in water.