MIT Sea Grant Center for Coastal Resources

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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
Styela clava, a tunicate native to the Pacific Ocean, lies on a dock in New England

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 of Massachusetts
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.



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  this page last updated on: 7 December, 2009