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10 Invasive Marine Species (North America)

An invasive species is an organism which has been introduced to an area outside of its native range, typically by humans, which then have a negative impact on the introduced area. The negative impacts are typically economic, ecological or related to human-health. Here, we will introduce some impactful and interesting marine invasive species found in North America.

Despite broad interconnection of the world’s oceans, the number of marine invaders has always been somewhat limited by natural processes (such as currents and winds). In recent decades, the number of marine invaders has rapidly increased due to improved nautical travel by humans.

10 Invasive marine species

1. Green crab

European green crab
European green crab | image by Tim Binns via Flickr | CC BY-SA 2.0

Scientific name: Carcinus maenas

The green crab is native to European and North African coastlines, but can now be found on both coasts of North America. The main impact by green crab is its predatory habits.

Although their diets are broad, they are known to prey upon native North American clams, which detriments local native populations, but also local commercial and recreational fisheries.

2. Killer algae

Killer algae
A killer algae | image by Coughdrop12 via Wikimedia Commons | CC BY-SA 4.0

Scientific name: Caulerpa taxifolia

Killer algae, native to tropical waters of the Indian and Pacific Ocean, is a widely spread invasive species that outcompete native plants for resources, ultimately stripping local marine life of any food and habitat. Killer algae was detected in California in 2000, where it was eradicated via chlorine bleach and other chemicals at huge national costs. The possession, transport, sale and release of killer algae is now illegal within California ever since its detection.

3. The Asian sea squirt

Stalk sea squirt
Stalk sea squirt | image by predomalpha via iNaturalist | CC BY 4.0

Scientific name: Styela clava

The Asian sea squirt is native to the northwest Pacific Ocean, but is now widely distributed as an invasive species throughout the world, including North America. Mainly, the Asian sea squirt outcompetes and displaces native species, and further impacts aquaculture production.

Specifically, they grow in dense aggregations around aquaculture gear and equipment, and even smother scallop and mussel species ultimately impacting local harvests.

4. The carpet tunicate

Tunicate colony of sea vomit
Tunicate colony of sea vomit | image by U.S. Geological Survey/photo by Dann Blackwood (USGS) via Wikimedia Commons

Scientific name: Didemnum vexillum

Native to Japan, the carpet tunicate (also known as sea vomit!) can be found on the coasts of North America, Europe and New Zealand. Similar to the Asian sea squirt, this species grows in dense clumps which smother native benthic species.

Beside these direct effects on native organisms, the carpet tunicate is also known to change habitat structure, further impacting native species. Ultimately, this species can cause both ecological and economic harm to North American coastlines.

5. The veined rapa whelk

The veined rapa whelk
The veined rapa whelk | image by Katy via Wikimedia Commons | CC BY-SA 2.0

Scientific name: Rapana venosa

The veined rapa whelk is a large predatory sea snail native to the Northwest Pacific region. This species is a voracious predator which is known to decrease populations of both economically and ecologically important North American species – such as clams, mussels, oyster and scallops. Additionally, they outcompete native whelks for space and food resources, further impacting native species.

6. Lionfish

Red lionfish in clear water
Red lionfish in clear water | image by Bernard DUPONT via Flickr | CC BY-SA 2.0

Scientific name: Pterois volitans

Originally from the Indo-Pacific region, lionfish have become one of the most prolific invasive species on the East coast of the United States. These are another voracious predator, with an extreme generalized diet which allows them to prey upon dozens of native North American marine fish species.

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In fact, lionfish can consume up to 460,000 prey fish per acre! To make it even worse, female lionfish can produce up to 2 million eggs per year!

The lionfish is a particularly awful invasive species because it ticks all of the negative invasive species impact boxes. They eat native organisms causing ecological harm, and in turn, reduce fishery harvests and thus impact the local economy.

But the lionfish also possesses several venomous spines which cause local swelling and discomfort if stung, ultimately impacting human health as well.

7. Northern Pacific seastar

Northern Pacific seastar
Northern Pacific seastar

Scientific name: Asterias amurensis

As the name suggests, the northern Pacific seastar originates from the northern Pacific region. Similar to the lionfish, the issue with this invasive species is owed to its varied appetite.

The northern Pacific seastar is known to eat just about anything, including several species of bivalves, molluscs, crustaceans and even other echinoderms. A recurring theme with many of the invasive species on this list, the seastar also has huge impacts on local ecology and the economy due to its predatory lifestyle.

8. Devil’s tongue weed

Devil’s tongue weeds on the shore
Devil’s tongue weeds on the shore | image by Jymm via Wikimedia Commons | CC BY-SA 4.0

Scientific name: Grateloupia turuturu

Originating from the northwest Pacific, the devil’s tongue weed is a known invasive species in the northeastern United States. It grows and thrives in shallow subtidal zones, just like several important species of native North American marine plant species.

Due to its extreme growth and size, the devil’s tongue weed restricts native species’ ability to access sunlight and other resources. As a result, this species reduces local biodiversity where it is introduced.

9. Asian shore crab

Asian shore crab
Asian shore crab | image by LeBourgmestre via Wikimedia Commons | CC BY-SA 4.0

Scientific name: Hemigrapsus sanguineus

The Asian shore crab is native to the western Pacific Ocean, but has been detected along the eastern coast of the United States for several decades. This species has caused detrimental ecological changes to intertidal communities.

The Asian shore crab is able to reproduce at an alarming rate, and they actively prey upon native crustacean species and outcompete for local resources. This has specifically impacted local populations of blue crabs, rock crabs and lobsters, thus leading to negative ecological impacts also.

10. Wakame

Wakame on wood
Wakame on wood | image by Voctir via Wikimedia Commons | CC BY-SA 4.0

Scientific name: Undaria pinnatifida

Wakame is a species of kelp native to the northwest Pacific Ocean. This species thrives in non-native areas due to their large temperature tolerance and the ability to attach and grow on a range of available substrates, such as rocks, oyster reefs, wood, rope and boat hulls. Wakame causes both economic and ecological harm to its introduced environment by fouling aquaculture equipment and outcompeting native algal species for local resources.