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Post subject: LI's invaders from the deep
 Posted: Sep 28, 2006 - 07:42 PM
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Puffer
Joined: Dec 31, 1969
Posts: 73
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LI's invaders from the deep
BY JENNIFER SMITH
Newsday Staff Correspondent
September 27, 2006
ABOARD THE R/V CONNECTICUT - Setting out for a day's research on Long Island Sound, the team of scientists expected to find colonies of sea squirts blanketing the sea floor.
But an underwater survey yesterday revealed only patchy evidence of the fast-spreading non-native invertebrates. The results only deepen the mystery surrounding the spongy squirts that in recent years have been fouling lobster traps and taking over mussel beds from Prince Edward Island to New York.
The results came as something of a surprise to University of Connecticut researchers who only four months before mapped out nearly seven square miles of sea squirts in eastern Long Island Sound, using a sophisticated robot equipped with underwater cameras.
"The plot thickens," said Bob Whitlatch, a professor of marine sciences at the university, as the 76-foot research vessel Connecticut moved back toward the university's Avery Point dock in Groton, Conn.
Since no previous data existed for the spots visited yesterday, it was difficult to tell just how established the patches were. What they saw could be the first stages of a growing colony, Whitlatch said, but it could also be a mature colony cutting back growth before winter or even fragments of larger groups that had been broken up by churning water from a recent storm.
Still, information recorded on the eight-hour trip will help scientists advance their understanding of where this type of sea squirt occurs, and what allows it to flourish. That's key, because researchers worry that the thick, rubbery mats of sea squirts they have seen on the sea floor east of Fisher's Island could crowd out lobsters and other species that live and develop there, such as flounder and scallops.
What makes these particular sea squirts different from the native species present here is the aggressive way they take over new habitats. Unchecked by predators, they cluster in colonies that can grow to the size of manholes; when the colonies meet they overlap and grow together, like pieces of an afghan.
Peering at shipboard monitors streaming live video from the sea floor yesterday, scientist Rick Osman pointed at a sea squirt colony poised to envelop blue mussels on a boulder. "Once the slit of the shell gets overgrown, it will smother the mussel," said Osman, a senior scientist at the Smithsonian Environmental Research Center in Edgewater, Md.
These tiny invaders are thought to have come from Europe or Asia, perhaps on boats' bottoms. Anecdotal accounts have them sighted in Maine as early as the 1970s; scientists first identified them off the New England coast in 1993. Since then they've cropped up in Maine, Massachusetts, Long Island Sound, Shinnecock Bay and as far south as Delaware.
The sea squirts found in Long Island Sound are believed to be the same kind seen up and down the East Coast, didemnum, although that identification can't be confirmed until researchers finish mapping out their genetic code so that they can compare the different outbreaks.
The R/V Connecticut is scheduled to retrace the steps of the May trip today.
Meet the sea squirt
WHAT THEY ARE: Widely known as "fouling organisms," they are one of many types of invertebrate organisms known as tunicates, which all have globular or cylinder-shaped bodies. They have hearts and nervous systems.
WHAT THEY DO: As adults, they attach themselves underwater to rocks, pilings or fishing traps and don't go anywhere. As juveniles, tadpole-like tails allow them to swim.
WHAT THEY LOOK LIKE: A few inches long, they range in color from cream to white; can look like fat fingers, or, in large colonies, like sheets or carpets.
HOW THEY GOT HERE: Introduced to area from Pacific (apparently by ships emptying ballast water or on bottoms of visiting ships), first documented in 1993. They spread on ocean currents when they are in microscopic form.
THE CONCERN: They can foul commercial fishing traps; scientists also suspect they may have an impact on habitat availability or quality for native marine species; and can prevent valued fish from eating worms on the bottom.
Source: National Undersea Research Center at the
University of Connecticut; University of California, Berkeley
Copyright 2006 Newsday Inc. |
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