Alien species problem must remain
Port Clinton News Herald
The growing belief that zebra mussels may be causing a
"dead zone" in Lake Erie provides further evidence
of the importance of efforts to control invasive species
in the nation's waterways.
Researchers are finding that the thumbnail-size zebra
mussel and the Quagga mussel are altering the food chain
and habitat in the lake.
Those researchers think that those changes are behind
the low-oxygen area that is a dead zone in the lake.
High levels of phosphorus are believed to be behind the
dead zone that occurs in the central basin of the lake
between sping and fall. Colder, more dense water stays
at the bottom and cannot be replenished with oxygen, creating
an environment in which it is difficult to sustain life.
Scientists are focusing on three theories on what's causing
the high phosphorus levels: climate, increased phosphorus
releases from farms and sewage treatment plants and internal
changes in the lake.
Many are pointing to changes caused by the mussels that
have replaced tiny animal and plant life that once floated
in the water.
This makes the water clearer, allowing algae to grow
at deeper levels.
The mussel problem is becoming more complicated as the
quagga, which lives in lower temperatures and deeper waters,
has become more dominant than the zebra mussel.
Scientists and public officials have been trying for
years to gain control over the invasive species, fearing
the possible impact on existing species and the Great
Lakes in general.
Most of the dozens of alien species introduced into the
Great Lakes arrive in the water that ships carry in ballast
tanks. Ships take on tons of water in the Caspian or Black
Seas for stability while crossing the Atlantic, and larvae
or baby fish are sucked in. When the ships dump their
ballast in the Great Lakes, they also dump the alien species.
Some introduced species have been devastating. The United
States and Canada spend $15 million a year to control
the lamprey, a snakelike bloodsucker that attaches itself
to larger fish. The lamprey almost drove the native lake
trout to extinction when it first expanded into the Great
The zebra mussel is a fast growing filter-feeder that
clings to boats and pilings and jams water intake pipes.
Combatting the pesky mussel in the Great Lakes costs the
United States $100 million a year.
The cost and the variety of alien species demonstrate
the seriousness of this situation overall.
The importance of Lake Erie and the Great Lakes in general
to our environment, our economy and our quality of life
makes the problem especially serious to us.
Local officials must keep the pressure on to be sure
that this situation is addressed on a national level.