What are Marine Bioinvaders?
Marine Bioinvaders are organisms that have been introduced into
a new marine ecosystem, and thrive within their new environment.
In their home environments, these organisms live in balance with
their predators, and are controlled by diseases and other ecosystem
interactions. The invaders often thrive in their new ecosystem,
where controls may not exist to keep populations in check.
Styela clava, a
tunicate native to the Pacific Ocean, lies on a dock in New
What are their impacts?
These invading species (also known as aquatic nuisance, non-indigenous,
exotic, or alien species) can cause complex changes within the structure
and function of their new ecosystem. Impacts include restructuring
established food webs, importing new diseases to the new surroundings,
and competition with indigenous organisms for space and food.
Other ecological changes may occur when the invading organisms
reproduce with native species, possibly altering the gene pool.
This may lead to hybridization and homogeneity, which reduces biodiversity,
the primary element associated with an ecosystem's adaptability
to natural or human-induced changes.
Introduction of new species can also directly impact society and
human health. Invading organisms can replace harvested native species
through competition or predation. New diseases, moving beyond their
normal geographic range or brought by invading hosts, may eliminate
native species. Pathogenic organisms can cause the build-up of toxins
in wild-harvested fish and shellfish, raising serious human health
concerns. These concerns then have to be addressed by society, typically
resulting in large governmental spending.
Where are they?
Invading species are now found all around the world, inhabiting
ecosystems where they do not naturally occur. They are especially
common in ports and other locations where they "jump ship" from
the vessel that has transported them (see "How do they get here?"
below). Here in Massachusetts it is easy to find invading species
all along the coast.
In August 2000 and 2003, a group of expert taxonomists surveyed
a number of sites around New England, where they found fouling communities
(groupings of marine plants and animals which cling to surfaces
and larger objects such as rocks, ships, docks, or sometimes even
whales). There they identified macroalgeae and macroinvertebrates
(plants and animals visible to the naked eye). Although the studies
were limited in time and habitat type, over 500 organisms were identified,
and of these, 34 were introduced species, and 37 were cryptogenic
(of unknown origin). For more information on these Rapid Assessment
Surveys, see the RAS Fact Sheet.
A report on this study is available for download
(2.2MB PDF file).
The locations where each species was sighted were entered into
a database, which is available through our interactive map (see
link below). Descriptions of the species and their geographic range
are also provided.
Rapid Assessment Survey Maps:
Introduced and Cryptogenic Species
The species maps and lists have been updated (March 2004) to include
data from the 2003 survey, and to reflect current taxonomic classifications.
Hitchhikers Guide to Exotic Species
We are recruiting the public to help us locate additional sightings
of non-native species through the The Hitchhikers
Guide program. This field guide allows beachcombers, students
and other interested individuals to identify non-native species in the field
and to report them to us through the Hitchhikers Guide webpage.
New sightings submitted by sceintists and verifiable information
from the public will be added to our database, maps and reports.
Information from these reports will be used to support efforts by
the state and federal agencies to prevent, manage and control introductions
of exotic species.
How do they get here?
A primary method of alien species introduction has been in the
ballast water of shipping vessels.
In order to maintain stability during transit along coasts and on
the open ocean, ships fill their ballast tanks with water. Taken
from coastal port areas, this water (and associated sediments) is
home to multiple marine organisms. The ships, loading ballast, also
load living organisms, ranging in size and phyla from tiny microorganisms
to larger species, including schools of fish! Scientists estimate
that as many as 3,000 alien species per day are transported in ships
around the world, however, not all transported species survive the
trip and their new home.
Invading organisms are also introduced through the culture of
marine species, including fish, shellfish, and marine flora (seaweeds).
Through aquaculture, nonindigenous
species can provide sources of recreation and inexpensive food for
human communities. Conversely, these species, escaping from enclosed
pens, or released - intentionally or not - into regional waters,
can impact the coastal and marine ecosystem in ways previously mentioned.
Another way in which invasive species are introduced to new environments
is through the live and fresh seafood
trade. Non-native aquatic and marine species purchased as seafood
and then dumped or released into local water supplies can bring
diseases, parasites, and hitchhikers. They can also establish themselves
within their new environment and become invasive. MIT Sea Grant
has recently developed a multi-lingual educational pamphlet Live
and Fresh Seafood: Into the pan, not into the wild to raise
awareness on proper seafood handling and disposal practices which
minimize the chance of invasive species introductions through the
live seafood vector.