Sea creature threatens oysters

A mysterious sea creature ofunknown origins has been found in Indian River Lagoon in Brevard County.

The creature that looks like bunched up bright red daisy petals is an ascidian, better known as a sea squirt. But exactly how it gotinto the lagoon and where it came from has researchers puzzled.

The only thing scientists know for sure is that it is overgrowing native oysters, a keystone organism for the health of the waterway as well as an important part of the local economy. And it may be part of an ugly trend.

University of Central Florida biologist Linda Walters has been monitoring the lagoon and helping to restore its oyster population for the past 14 years. She has since seen three other non-native species invade the lagoon putting it at risk.

Global warming may be partly to blame as water temperatures rise and create inviting environments for species that typically stay in tropical climates farther south. Some states are spending millions of dollars battling invasive marine creatures that use interconnected waterways to spread.

“This is not unique to Florida,” Walters said. “We’re seeing more and more aquatic nonnative species across the United States. They compete with native species and can disrupt the natural ecosystem. And that can have very real consequences.”

In Brevard, for example, if oysters can’t grow because of an invasive species, they can’t clean the lagoon. It’s estimated that one oyster filters five gallons of water a day.

The oysters also provide refuge to native species such as blue crab, shrimp and red fish that locals catch and sell. Without them, many other creatures’ food sources disappear. In the Indian River Lagoon, Walters has identified 149 species that rely on native oysters in a balanced ecosystem.

Eric Hoffman, a UCF evolutionary biologist who specializes in genetic variation of invasive species, is working with Walters. Togetherwith a team of students and other scientists, they are working to trace theorigins of each new species in the lagoon through careful detective work.

It’s essential to figure out each species’ origins if invaders are to be kept from wrecking havoc on U.S. waterways, researchers say – like putting together a giant puzzle over long period of time.
“Each time these organism make it into a new environment, there is a potential for them to establish themselves,” Hoffman said. “Sometimes we don’t see the damage for decades. Other times it is more immediate.”

For example, the zebra mussel has steadily been invading U.S. waterways since the late 1980s when it was found in the Great Lakes region. The mussels, which originated in Europe, attached themselves to cargo ships. Now, they have been spotted across North America, including New York, Illinois and even parts of Canada.