Zebra Mussels Invade the South!
What started out as a Great Lakes problem may ultimately prove to be a bigger headache in the southern reaches of the Mississippi River. Zebra mussels, according to Lousiana Sea Grant researchers, appear to love the warmer southern waters into which they've moved.
Zebra mussel veligers were first reported in Louisiana in 1993. By summer 1994, Louisiana Sea Grant researchers John Lynn, Tom Dietz and Harold Silverman were recording zebra mussel densities up to 200,000 per square meter on hard surfaces in the Mississippi River. By fall, those densities had doubled to around 400,000 per square meter. ( By comparison, last fall in Green Bay, Lake Michigan, the highest measured zebra mussel densities were 356,000 per square meter.)
"Our zebra mussel population has grown by leaps and bounds,' Lynn said. "I'd say we're in the big leagues now."
The population growth most likely was the result of last summer's spawn, Lynn said.
"Not only are the veligers settling, but the settlers are growing up," he added. "We've seen a shift in the mean average size of the zebra mussels from one millimeter to 3.5-4.0 mm in the last three months."
One reason the mussels are thriving is the water flow rate in the Mississippi River, Lynn said.
"We have millions of gallons of water flow per second," he said. "That's a lot of fresh water to provide zebra mussels with a steady food source and to flush away any potential toxins."
Southern conditions also are ideal for reproduction. Though nobody has yet determined exactly how many times zebra mussels can spawn in a year, Lynn said most people believe they spawn more than once.
"I'd even speculate that under optimum conditions of temperature and food supply, they might be able to spawn every three weeks or less," he said.
Louisiana State University researchers also are studying the salinity concentrations mussels can tolerate.
"We've seen long-term mussel survival in water with a sodium chloride concentration as high as 12 parts per thousand," he said. That concentration would translate to a mix of about 30 percent seawater, 70 percent freshwater.
"We've worked on duplicating the chemistry of water in the tidal flats," Lynn explained. "That involves manipulating ion ratios of sodium, potassium, calcium and magnesium. It's the ion ratios that are most critical to the mussels."
Lynn hopes this work will help researchers' understanding of mussels in fresh water, too.
"The common thought is that a high level of calcium is conducive to zebra mussel survival," he said. "That's true in part, though we're finding that it's more specifically calcium in conjunction with magnesium, potassium and sodium that's important. Even then, the ratios must be in the proper balance."
Lynn doesn't believe the mussels will be contained in the Mississippi, either. Over the next year he envisions them continuing to spread in the Atchafalaya basin, possibly invading the Tombigbee River basin and entering Texas waters through the Toledo Bend Reservoir.
- Laurence Wiland
UW Sea Grant to Sponsor Teacher Education Program
Great Lakes region elementary and middle school teachers will gather in June in Milwaukee to study oceanography and coastal processes, and develop ways to pass this knowledge on to their students. The 12-day program, called Operation Pathfinder, will target teachers who are members of a minority or teach in schools with minority populations. Participants must commit to a three-semester-hour graduate course at UW-Milwaukee; develop at least one teacher training workshop or staff development program within their own school or school district; and submit a journal article, present a paper or demonstrate an activity at a state, regional or national education conference. Sea Grant personnel will assist teachers with these tasks. Applications for the program are due March 31. Financial support is available for a limited number of participants. For application materials or further information, contact UW Sea Grant Education Specialist Jim Lubner at (414) 227-3291; fax (414) 382-1705; or email: lubner@csd.uwm.edu.
Bhumralkar Named National Sea Grant Director
The National Oceanic and Atmospheric Administration (NOAA) has named Chandrakant M. Bhumralkar acting director of the National Sea Grant College Program (NSGCP) in Silver Spring, Md.
Bhumralkar had been director of the Program Development and Coordination Staff of NOAA's Office of Oceanic and Atmospheric Research.
A native of India, Bhumralkar received an M.S. in meterology from the University of Hawaii and a Ph.D. in meterology from the University of Miami. Prior to joining NOAA in 1985 as a senior meterologist, he had been an assistant professor of atmospheric physics at Old Dominion University in Norfolk, Va., a senior scientist at the Rand Corporation in Santa Monica, Calif., and director of the Atmospheric Science Center at the Stanford Research Institute in Menlo Park, Calif. Former NSGCP Director David Duane retired Feb. 3.
Weston Donation Benefits Sea Grant
Dr. and Mrs. Carl B. Weston of Madison have donated $10,000 to the Wisconsin Foundation to establish the Carl J. Weston Memorial Scholarship Fund. Income from the fund will support an undergraduate scholarship through the University of Wisconsin Sea Grant Institute.