Zebra Mussels
http://www.watershedmanagement.vt.gov/lakes/htm/lp_lczebramon.htm
Description
The zebra mussel is a small freshwater mollusk, native to the Caspian and
Black sea region of Eurasia. Adult zebra mussels attach themselves to firm
surfaces with strong hair-like fibers called byssal threads. Each female
zebra mussel can lay up to one million eggs during the summer months
when water temperatures rise above 50°F. The fertilized eggs hatch into
microscopic juveniles called veligers, which can travel great distances
following water currents or when transported on boats and trailers. These
methods of spread lead to rapid infestation of new waterbodies. Once
settled on a firm surface, the veligers grow rapidly into "D" shaped, one inch
size adult mussels. Colonies of adults can attain densities of up to 700,000
individuals per square meter. Zebra mussels generally live for two years in North American
waters, but can survive for as long as 4-5 years.
Distribution
In 1988 the zebra mussel was first identified in the United States in Lake St. Clair of the Great
Lakes region. It is believed that the emptying of ballast water from commercial transatlantic
ships introduced the mussel into the Great Lakes. Since then, zebra mussels have spread
throughout the interconnected waterways in the eastern U.S. and were confirmed in Lake
Champlain during the summer of 1993. Adult zebra mussels can now be found throughout much
of Lake Champlain and the lower reaches of many of the lake's tributaries. In 1998 adult zebra
mussels were discovered in Lake Bomoseen in Hubbarton and Castleton, Vermont. Adult zebra
mussels have not found in any other Vermont lake or pond.
Impacts
Zebra mussels can clog the intake pipes of industrial and water facilities such as the water
supply plants along Lake Champlain. Similar effects can occur in small lakeside residential
water systems and agricultural irrigation systems. Fortunately, most facilities and home owners
on Lake Champlain averted serious impacts by installing control technologies at the beginning
of the infestation. However, the costs for installing and maintaining such technologies has been
significant. Zebra mussels also attach themselves to the hulls, engines and other submerged
parts of moored boats. Boaters on Lake Champlain must now take special precautions to
prevent damage to their boats and to avoid spreading zebra mussels to other waterbodies when
trailering their boats. Zebra mussel shells are very sharp and swimmers at many of Lake
Champlain's popular swimming areas must now wear protective footwear to avoid painful cuts.
Additionally, Lake Champlain has numerous historic sunken ships and other artifacts which are
at risk of becoming obscured or damaged by colonies of zebra mussels growing on them.
Zebra mussels can have numerous ecological impacts as well. Most significantly, the mussels
are extremely efficient filter-feeders, consuming large portions of the microscopic plants and
animals which form the base of the food chain. Over time, this feeding behavior can affect a
lake's entire ecological balance, causing significant shifts in native species populations. Zebra
mussels can also attach themselves to the shells of native mussels, impeding movement,
feeding and respiration. As the native mussels become heavily encrusted they suffer increasing
stress, losing body weight until they eventually succumb from either starvation, disease, or
osmoregulatory problems. As a result of the invasion of zebra mussels into Lake Champlain,
and their direct impact on our native mussel populations, several native mussels are listed as
endangered or threatened in the state of Vermont.
http://www.youtube.com/watch?v=Gtqb41CjQfc
When and where were zebra mussels first found in the US?
How was the zebra mussel introduced to US waterways?
List the ways in which the zebra mussel is changing the ecosystem of Lake Michigan (as well as Lake
Champlain)?
Why is an increase in lake water clarity a concern of eco-biologists?
How are zebra mussels a threat to native mussels?
What are some ways scientists in NY are working on to restrict zebra mussel populations?
Research the current progress or use of this new treatment.
What can boaters on Lake Champlain do to help control the population of Zebra Mussels?
C. What does Graph 1 tell you about the impact of zebra mussels on the primary
production in Lake Ontario?
Zebra mussels increased rapidly in the early-to mid '90s. Chl a is an indicator of primary
productivity, the concentration of Chl a fluctuates as the rise of zebra mussel densities increased
in Lake Ontario. This shows that zebra mussels were consuming phytoplankton, and removing
Chl a from the water column. As their mussels declined the Chl a concentrations began to rise
again.
D. If you were a scientist that researched Seneca Lake ecology would you be
concerned about the impact of Zebra Mussels? Why or Why not?
Yes, because there are indications that zebra mussels have affected Seneca Lake. The bar
graph shows that the water is more clear now and the concentrations of Chl a have gone
down during the same period of time that zebra mussels invaded Seneca Lake. If Lake Ontario
is a model of what could happen in Seneca Lake then we would expect that primary
productivity in Seneca Lake would decrease and the food web in Seneca Lake would be
affected. In addition, now that light can penetrate deeper in the water column more plants are
able to grow and the lake could become more weedy.
On the other hand, as the article about Cayuga Lake points out (see references below) - there
have been many introduced species into the Finger Lakes and the ecological impacts are not
always so profound.
RISKS/IMPACTS: Ecologically, the zebra mussels cause many problems. One such
problem is that they need to attach to a hard surface to survive, and these hard surfaces could
be anything from many manmade objects to other animals. Zebra mussels will attach to
crayfish, turtle shells as well as other mussels. When a native mussel has zebra mussels
attached, the native mussel loses its ability to move, feed, breath, and breed. Eventually this
will lead to the death of the native mussel. In Lake St. Clair and Lake Erie, the native mussel populations
have been severely reduced due to the dense populations of zebra mussels. This dramatic drop
happened only two years after the zebra mussel was discovered in the Great Lakes. This sends up a red
flag for Indiana managers. With many of Indiana’s native mussels already on state or federal
endangered and threatened species list, zebra mussels could spell eventual extinction.
Zebra mussels have the ability to filter up to 1 liter of water per day. They eat the
phytoplankton that is suspended in the water, which is in competition with the nearly
microscopic animals called zooplankton. The food chain is very delicate and the zebra
mussels could be disrupting it by taking out the very bottom link, the phytoplankton.
This affects all the higher organisms including the fishes
Because zebra mussels filter large amounts of water, infested lakes have become
clearer. While this may sound like a good thing, this can cause problems as well. With
clearer water, sunlight penetrates to deeper water; this allows for more vegetative growth.
This vegetation can become so thick that it could hinder swimming and boating.
While zebra mussels feed on phytoplankton, they do not eat blue-green algae.
Because the blue-green algae are not being eaten, there is a competitive advantage over
other algae resulting in a blue-green algae bloom. Such blooms occur in Lake Huron and
Lake Erie much more frequently than ever before. Some forms of blue-green algae
produce toxins. If enough blue-green algae toxin is produced, harm can occur to fish,
waterfowl and any other animals that drink the water, including humans.
Yet another ecological impact that the zebra mussels impose on our native fauna
is the fact that they are bioaccumulators. Any contaminant in the water is multiplied up
to 10 times the water concentration in the zebra mussels. When the mussels are eaten, the
contaminant concentration increases through the food chain. As zebra mussels become
more prevalent more animals will eat them increasing the chance that higher levels of
toxins will be accumulated throughout the food chain.
The zebra mussel is also economically detrimental. The mussel’s need to attach
to hard surfaces creates problems. Water intake structures are prime locations for
attachment. These intakes provide a continuous flow of water and protection from
predators. Once inside a pipe the zebra mussels layer on top of each other eventually
causing reductions in pumping capabilities and even complete blockages. Industrial
water pipes are not the only ones at risk. While zebra mussels feed on phytoplankton, they do not eat
blue-green algae.
Because the blue-green algae are not being eaten, there is a competitive advantage over
other algae resulting in a blue-green algae bloom. Such blooms occur in Lake Huron and
Lake Erie much more frequently than ever before. Some forms of blue-green algae
produce toxins. If enough blue-green algae toxin is produced, harm can occur to fish,
waterfowl and any other animals that drink the water, including humans.
Yet another ecological impact that the zebra mussels impose on our native fauna
is the fact that they are bioaccumulators. Any contaminant in the water is multiplied up
to 10 times the water concentration in the zebra mussels. When the mussels are eaten, the
contaminant concentration increases through the food chain. As zebra mussels become
more prevalent more animals will eat them increasing the chance that higher levels of
toxins will be accumulated throughout the food chain.
The zebra mussel is also economically detrimental. The mussel’s need to attach
to hard surfaces creates problems. Water intake structures are prime locations for
attachment. These intakes provide a continuous flow of water and protection from
predators. Once inside a pipe the zebra mussels layer on top of each other eventually
causing reductions in pumping capabilities and even complete blockages. Industrial
water pipes are not the only ones at risk.