Antionetta Quigg, a marine biology professor at Texas A&M University at Galveston, said based on previous studies, the oil has been found to be toxic.
"Given that plankton is food for high-traffic levels of fish, we think that they then become toxic, too," she told The Galveston County Daily News for a story published Sunday.
And that means fish in the polluted water get a "double hit" from oil both in their physical environment and food sources.
The oil from a barge was released into the water March 22 when the barge and a ship collided in the Houston Ship Channel.
While cleanup efforts have been continuing since then, some of the oil picking up sediment could have sunk to the seabed and could smother or poison animals like shrimp or crabs. Their demise, in turn, affects the food chain of the bay, although Quigg believes the short life span of some animals could help mitigate the damage.
"Plankton divides fairly quickly, so as long as (the oil) keeps being cleaned up and moving offshore, we'll have a new community popping up fairly quickly," Quigg said. "It will be detrimental perhaps for another few weeks, but then life should resume for something close to normality."
Texas A&M-Galveston scientists worried that dolphins living in the ship channel would flee, but they've been seen since the spill following the school's boat during an inspection trip.
State officials late last week issued a seafood consumption advisory for Galveston Bay and the Gulf of Mexico that recommends fish, shrimp or crab from water where oil is present not be eaten.
The cleanup itself has extended down the coast to Matagorda Island, where crews have been using rakes, shovels and buckets to remove oil washed ashore on the 24 miles of beach that line the Matagorda Island State Park.
The effort has been complicated because the island is accessible only by barge or boat.
The Texas Department of Health said some samples taken Friday from Matagorda Bay have been tested and are biological in origin and not related to the spilled oil.
But officials have established a wildlife rehabilitation facility in Port O'Connor in the event birds or marine life are impacted by the spilled oil.
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