Picture by John Southern

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Marine Invasive SpeciesMonitoring Program
National Park Service U.S. Department of the
Interior Glacier Bay National Park and Preserve
European Green Crab
What is an invasive species? Invasive species
come from other parts of the world and can be
harmful to the environment, natural resources,
humans, and the economy. Invasive species are
transferred between regions by people
intentionally or accidentally. For marine
invasive species, common forms of transfer
include ships ballast water, hull fouling, and
aquaculture. "Invasive species have large
effects on native biodiversity, cause hundreds of
billions of dollars in economic damages, and
complicate the management of natural ecosystems
around the world." (Strayer, 2006)
(Carcinus maenas)
Why are they a problem? As their name suggests,
this species is native to European waters. Over
time it has been introduced to multiple new
habitats, including the Atlantic and Pacific
coasts of North America. Although green crabs
have been detected only as far north as
Vancouver Island in British Columbia thus far,
models indicate that the species will be able to
survive in coastal Alaskan waters. European
green crabs are aggressive predators, eating
clams, mussels, marine worms, and crustaceans
that are important foods for native marine
animals. If green crabs invade Alaskan waters,
they could be a serious threat to native crabs
and fisheries.
What should you do if you find one? If you find
a green crab, dont throw it back in the water!
Keep it in a container with information about
where and when you found it. Then put it into a
freezer or preserve it with alcohol. Contact
1-877-INVASIV for more information.
Invasive tunicates documented in Pacific waters
Botrylloides violaceus, Botryllus schlosseri,
Styela clava, Didemnum sp., and Ciona
intestinalis.
The green crabs distinguishing features are 5
spines, or teeth, on each side of its fan shaped
shell and 3 rounded lobes between its eyes. The
two backmost legs are flattened. The abdomen
(underside) color ranges between green, orange,
and red, and the dorsal (top) side of its shell
is a mottled dark green with yellow patches.
Picture by John Southern
Tunicates
What aboutGlacier Bay? So far, no invasive
green crabs or tunicates have been detected in
Glacier Bay through our monitoring efforts. For
green crabs, we set out traps once a month during
the summer in the lower intertidal area of
Bartlett Cove. For tunicates, we suspend
settlement plates from our three docks quarterly
to detect whether any tunicates colonize the
surfaces. Atlantic Salmon are the only marine
invasive species detected within park waters to
date. We will continue collaborating with
partner agencies to detect marine invasive
species.
What is a tunicate? Tunicates, or sea squirts,
are marine invertebrates (lacking a back bone)
that grow attached to surfaces. They might be
confused with a sponge, but they are more
resistant to touch. They can range in color,
including orange, red, yellow, black,
translucent, cream, and blue. They can be
solitary (completely independent and generally
fairly large) or colonial (congregations of
zooids that aggregate by budding, like corals).
Tunicates filter feed by siphoning plankton from
the water. Tunicates belong to the Phylum
Urochordata, which are more closely related to
vertebrates (including humans) than any other
invertebrate group. There are a number of native
species in Alaskan waters however, several
non-native species have been detected.
Botrylloides violaceous (orange morph) an
invasive colonial tunicate. SERC
Ciona intestinalis an invasive solitary
tunicate. SERC
Why are they a problem? Tunicates are a fouling
organism that can smother other marine organisms
and coat surfaces, such as boats and docks. They
filter out the waters phytoplankton, thus
depriving other species of their nutrition.
Since larval tunicates can be transported in
ballast water and adults can foul boat hulls,
tunicates can easily disperse to new waters,
where they can readily establish in the absence
of natural predators. In the coastal Pacific
waters of North America, the Smithsonian
Environmental Research Center (SERC) coordinates
a monitoring program ranging from Tijuana Slough,
CA to Port Valdez, AK.
Smithsonian Environmental Research Center (SERC)
For more information Whitney Rapp, Invasive
Species Coordinator, Glacier Bay National Park
and Preserve, Gustavus, AK 99826
whitney_rapp_at_nps.gov, 907-697-2603