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Great Lakes
Article:
Zebra mussels still thrive in cool waters of Great Lakes
Article courtesy of the Associated Press
October 25, 2001
MILWAUKEE (AP) -- Spring floods and high summer water
temperatures likely killed trillions of zebra mussels
in the upper Mississippi River, but the plankton-eating
pests still thrive in the cool waters of the Great Lakes,
experts say.
The die-off of zebra mussels is good news, but water
temperatures are rising and the population may not be
quelled for good, the scientists say.
" Although this is a setback (for the species) this year,
we think the levels will become problematic again, " said
John Sullivan, a water quality specialist with the state
Department of Natural Resources.
The mussels likely overtaxed themselves by trying to
filter nonorganic material from last spring' s sediment-filled
Mississippi River floodwaters, Sullivan said.
The river' s summer temperatures, which reached 86 degrees
and above in late August, were too warm for zebra mussels
to prosper, Sullivan said. The Mississippi hasn' t been
that warm since 1995, when there weren' t as many zebra
mussels, he said.
But the zebra mussel population still grows in the Great
Lakes, where the cooler conditions are optimal for the
species, said Phil Moy, a Wisconsin Sea Grant Institute
fisheries and nonindigenous species specialist.
By hitching rides in the bilge of seagoing vessels, the
European-native species has infested U.S. waters, first
appearing in the Mississippi River watershed in 1991 in
La Crosse.
Zebra mussels latch on to native species, hog most of
the food and nutrients in the quart of water they can
filter each day and leave little for fish and other species
that depend on the plankton, said Pam Thiel, a La Crosse
fishery resource office project leader for the U.S. Fish
and Wildlife Service.
The mussels have a life span of just three to four years,
but this year' s death rate was abnormally high, Thiel
said.
Authorities looked at native Mississippi River mussel
beds in fall and found that beds that had zebra mussels
in June were free from the pests.
" They certainly haven' t eliminated zebra mussels, but
it will put a dent in the population, " Thiel said.
On the Net:
DNR zebra mussel information: http://www.dnr.state.wi.us/org/water/wm/glwsp/exotics/zebra.html
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