A tumor can be clearly seen in this arrow goby. The fish are abundant, year-round residents of Morro Bay, making them good indicators of the health of the bay ecosystem.
Cal Poly biology professor Lars Tomanek has received a $30,000 grant to investigate why gobies in Morro Bay are developing cancerous tumors.
Eight percent of 150 arrow gobies recently collected from the mudflats of Morro Bay had large tumors. Subsequent testing at UC Davis showed that even apparently healthy fish had signs of abnormal liver cell growth, which indicates the early stages of liver cancer.
Tomanek believes the tumors are being caused by contaminants in the bay that disrupt the fishes’ endocrine systems. An additional 250 gobies were collected and tested for 40 common persistent pollutants.
Analysis of the fishes’ livers showed high levels of a byproduct of compounds found in detergents that help break down oil and grease, called nonylphenol ethoxylates.
“The question is where is it coming from?” Tomanek said. “We don’t know that, yet.”
These compounds are banned in Europe but are common in the United States. They are found in household cleaners, shampoo and spermicides, Tomanek said.
Arrow gobies are abundant, year-round residents of Morro Bay, making them good indicators of the health of the bay ecosystem. The 2- inch-long fish live in ghost and mud shrimp burrows to evade predators, bringing them in close contact with sediment in the bay.
The grant will be used to establish whether there is a link between nonylphenol and the tumor growth. In laboratory experiments, fish will be exposed to varying levels of the pollutant, and their responses will be compared to the fish collected from the wild.
Tomanek said Morro Bay is relatively uncontaminated. However, pollutants that accumulate in the environment exist in low levels in the water.
“The goby data suggest that existing water testing is overlooking pollutants that exert detrimental effects on marine organisms in the estuary,” he said.
The grant was provided by the Sea Grant College Program, a marine research program with the University of California.
Tomanek is a member of the San Luis Obispo Science and Ecosystem Alliance, a group that works to improve the health and management of Morro Bay.
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