Aquatic Invasive Species: Plants, Animals & Examples

Instructor: Amanda Robb

Amanda has taught high school Biology & Physics for 8 years. She received her M.Ed. from Simmon's College and M.S. from Tufts in Cellular and Molecular Physiology.

In this lesson, we'll be looking at the fierce world of invasive species. Here, we'll focus on aquatic plants and animals and learn how they've invaded new ecosystems and what adaptations make them cause havoc on the current inhabitants.

What Are Invasive Species?

Imagine being part of a secret operation mission. Dressed in black, identical to your teammates, you sneak behind enemy lines in the night. With your high tech gear, you're far more suited to the environment than the enemy and easily overtake them, winning the fight.

Although there typically isn't a war raging on in a natural ecosystem, sometimes enemies do sneak in that aren't meant to be there. Invasive species are species that are not native to an area, and compete with native animals for food and other resources.

Invasive species are typically brought in through human activity. Sometimes humans keep them as pets, and then they get released into the wild. Other times invasive species hitch a ride on a boat or other form of transportation and wind up in places they shouldn't.

They can take over the ecosystem and often have no natural predators. This disrupts the delicate balance of the environment and can cause population crashes, where species die off.


Zebra Mussels

Zebra mussels are aptly named for the dark and light stripes on their shells. These tiny creatures, growing up to only about five centimeters in length, have found a home in America's waterways, particularly, the Great Lakes.

Ships sailing to America in the 1980s brought zebra mussels with them in their ballast water inside the ships. These unintentional passengers that come from the Caspian and Black seas were an excellent fit for the Great Lakes and other waterways in America. But, they were too good of a fit. The zebra mussel population exploded in America, and soon, they were crowding out native species. With their large population zebra mussels are eating all of the food for native species, and even growing on the shells of native clams and larger mussels.

Zebra mussels growing on a native mussel
zebra mussels

Zebra mussels aren't just bad for other animals though; they are also a big problem for humans. Zebra mussels clog waterways that clear sewage water as well as the pipes that bring cooling water to power plants. They also damage ships and buoys. Millions of dollars are spent trying to eradicate the zebra mussel population.

Sea Lamprey

Most of us know that vampires aren't real, but one invasive species is similarly frightening. The sea lamprey looks like a combination between a snake and an eel. This fish has a long, cylindrical body with dorsal fins. In place of a mouth, these animals have a circular jaw filled with tiny teeth that they use to attach onto their prey, sucking blood for food.

The mouth of a sea lamprey
sea lamprey mouth

Sea lampreys are a species that originated from the Atlantic Ocean, but through human activity, they have found their way to the Great Lakes. They have had devastating effects on the local fish populations, decimating lake trout and whitefish populations before large-scale control efforts were implemented. In its relatively short adult life (less than 2 years), a sea lamprey can kill about 40 pounds of fish. With the Great Lakes being a major fishery, the introduction of the sea lamprey has cost the community billions of dollars.


Water Hyacinth

Deep in the jungles of South America, the streams and tributaries of the Amazon River appear to be covered in a green carpet. Upon closer examination, the carpet is actually a plant called the water hyacinth. This beautiful aquatic plant floats in the water and produces large purple flowers.

Water hyacinths have beautiful purple flowers
water hyacinth

It has been brought to the United States as an ornamental plant for gardens due to its pretty flowers and water cover. However, it is incredibly resilient and is outgrowing native species, particularly in the tropical waters of Florida, although it can be found throughout waterways of the United States.

The water hyacinth grows in dense patches on the surface, blocking light from getting to other plants. It grows so densely it can also interfere with human activities, such as irrigation, recreational activities and water cooling for power plants. The dense mats also create a breeding ground for mosquitoes, potentially causing an increase in the spread of disease.

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