What Are Invasive Species?
Countries around the world are the recipients of unwanted visitors each year – invasive species. The National Invasive Species Information Center defines an invasive species as a species that is: “non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”
Invasive species can be plants, animals or other organisms such as microbes. They are introduced into new habitats primarily by humans.
Impacts of Invasive Species
The impacts of invasive species can be widespread and extremely damaging to native species and environments, humans, and the economy. A study published in 2000 found that the environmental and other costs caused by the estimated 50,000 invasive species that have been introduced into the U.S. could be over $137 billion per year. This is more than any other natural disasters combined.
Invasives in the Marine Environment
Marine invasives, also known as “marine bioinvaders,” or "non-indigenous aquatic species," are organisms that have been introduced into a new marine environment and flourish there. In these species’ native environments, there are natural “controls,” such as predators, that keep the species in check. In their introduced environment, these controls may not exist.
When marine species move into a new environment, they can restructure the food web, introduce diseases, and compete with and prey on native organisms. They can also impact humans by destroying populations of commercially-valuable native species (e.g., wild-harvested fish and shellfish) and cause toxins to build up in native species, impacting those who eat them.
How Are Marine Bioinvaders Introduced?
- Ballast water - Large ships often take on extra water (sometimes millions of gallons) into their ballast tanks to maintain stability when transiting in the open ocean. The water may be discharged when the ship gets into a new port, discharging new organisms in the water along with it. This is the primary method that these species are transported.
- Aquaculture – Species such as fish, shellfish and seaweeds raised in pens may escape or be released into local waters.
- Seafood trade- Species purchased as seafood may be later dumped or released into local waters. These species can carry diseases, parasites and other organisms.
Examples of Marine Bioinvaders
- Chinese Mitten Crab
- Red Lionfish
- European Oyster
- European Green Crab
- Colonial Tunicates (e.g. Didemnum sp.)
What is Being Done to Stop Marine Bioinvaders?
It appears that the world is becoming more aware of invasive species and their associated threats. Since each invasive species can be so different, there are often different approaches needed to control them. These approaches in the marine world can include putting a “bounty” on a species to encourage fishermen to capture them, using volunteers to track the spread of invasives, or figuring out how to use invasives as a food source.
Since the costs of invasive species can be so great, there is an intense need for better systems to detect invaders early on, build better systems to prevent invaders and to track and control invasives that are already in an area.
Sources:
- Chase, C., Reilly, C. and J. Pederson. 2008. “Marine Bioinvaders Fact Sheet: New England Marine Bioinvaders.” Massachusetts Institute of Technology (Online). Accessed September 4, 2008.
- MIT Sea Grant: Marine Bioinvasions
- NBII Invasive Species Information Node
- National Invasive Species Information Center
- Pimentel, D., Lach, L., Zuniga, R., and D. Morrison. 2000. Environmental and Economic Costs of Nonindigenous Species in the United States. BioScience 50(1):53-65. (Online) Accessed September 4, 2008.
