Denver -- While there are many known cases of exotic creatures invading the country's rivers and estuaries, scientists have for the first time documented the invasion into U. S. coastal waters of a type of marine microorganism.
In a talk to be given on Thursday, Oct. 31, at the annual meeting of the Geological Society of America in Denver, Doris Sloan and Andrew N. Cohen of the University of California at Berkeley, and Mary McGann of the U.S. Geological Survey in Menlo Park, Calif., report the introduction of a single-celled amoeba-like organism, the foraminifer Trochammina hadai.
Foraminifera or forams, microscopic marine creatures with shells of calcium carbonate, are best known from their abundant fossils, which are found in such profusion and diversity they are used to date sedimentary rocks going back as far as half a billion years.
The organism apparently arrived within the past 10 years from Japan, probably hitching a ride in the ballast tanks of a ship that took on water in a Japanese port and emptied its tanks into western U.S. waters, the scientists say. This exotic foraminifer is a common inhabitant of estuaries and bays in Japan, where it lives in the mud in shallow water.
Alarmingly, the new resident in San Francisco Bay has spread widely throughout the bay and is now found in large numbers at many sampling sites.
The introduction of an exotic organism that spreads as rapidly as T. hadai is a matter of considerable concern, Sloan says. In particular this invasion raises questions about the extent to which other microorganisms are invading the world's ports and estuaries.
It is too early to tell what the impact of this introduction will be on the ecosystem, Sloan says, but at the population levels currently found, it is likely to have a large impact on the native species of foraminifer.
The introduction of exotic species to the estuaries and inland waters of the United States is now a well known problem. Invaders su
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Contact: Doris Sloan
dsloan@violet.berkeley.edu
510-642-3703
University of California - Berkeley
31-Oct-1996