Invaders
in the Bay
The
arrival of non-native species, species that do not naturally
occur in a certain area, is not a new problem for the
Chesapeake Bay. Researchers at the Marine
Invasion Research Laboratory
at the Smithsonian Environmental Research Center (SERC)
have reconstructed the pattern of invasions over the past
four centuries, beginning with European colonization.
The researchers have now identified approximately 160
species that are nonindigenous to the Chesapeake Bay,
and scores of other species that are of unknown origin.
Today,
the global movement of ships has increased the distribution
of species all over the world. Non-native species don't
just swim across the ocean; they can conveniently ride
with large cargo vessels that are crossing the ocean from
port to port.
"All
aboard!"
When
cargo ships are not carrying a load, they need to carry
other weight in order to remain stable and be able to
adjust the balance of the ship for optimal steering and
propulsion. So after ships deliver their cargo at a port
and head home, they fill up enormous tanks on the ship
with water from the port or coastal region.
Picture:
Researchers
taking a sample of the ship's ballast water.
With
the ballast water, as it is called, the ships also pump
up the animals and plants that are in the water. When
the ships then get to the next port to load cargo, they
release the water (with the animals and plants in it),
either in the port or along the coast. As a result, the
ships pick up, transport, and release marine organisms
around the world.
Researchers
at SERC's Marine Invasion
Research Laboratory
measure the supply and fate of these foreign species in
the Chesapeake Bay and elsewhere in the United States.
SERC researchers examine many different htmlects of the
big journey of these organisms from their origin to the
waters of the Chesapeake Bay.
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Picture:
Researchers
at SERC's Marine Invasion Research Laboratory examine
many different htmlects of the big journey of the invasive
species from their origin to the waters of the Chesapeake
Bay and elsewhere in the United States.
The
researchers, for example, track where the ships are coming
from, what percentage of the animals and plants survive
the trip, which creatures can actually reproduce after
they arrive in the Chesapeake Bay, and how many new invasions
are discovered.
Although
the effects of many introductions remain unmeasured, it
is clear that invasive species can have significant economic
and ecological impacts, as well as human-health consequences.
Invaders like the zebra mussel in the U.S. Great Lakes,
toxic dinoflagellates in Australia, and the oyster parasite
MSX in the Chesapeake Bay have had tremendous ecological
and economic impacts.
Is
there a way to stop this worldwide transport_
The
only effective way at the moment to reduce the risk of
introducing more invasive species is called "ballast
water exchange."
Ballast
water exchange means that ships on their way to the next
port release the coastal water they pumped up and replace
it with open-ocean water. Although this measure is not
perfect, it at least reduces the number of potentially
invasive species in the ballast tanks and replaces them
with oceanic organisms that are less likely to survive
in the near-shore waters of the next port where the ship
will dock.
Although
alternate methods to treat ballast water are not yet available,
the researchers at SERC are carrying out extensive laboratory
and field tests to examine the many possible treatments.
Picture:
A ship is exchanging
its coastal ballast water with water from the open ocean
to reduce the chance of transporting any invasive species
to the next port.
References
and further reading...
For
more information about invasive species and ballast water
exchange, visit the web pages of the SERC
Marine Invasion Research Laboratory.
(Pictures
courtesy of SERC's Marine Invasion Research Laboratory.)
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