Invasive Aquatic Plants That Impact Manatees | Discover Crystal River

Invasive Aquatic Plants That Impact Manatees

The introduction and invasion of non-native plant species can wreak havoc on the delicate ecosystem that serves as a home to many incredible species, such as the manatee.

The Crystal River area is well known for its beautiful aquatic plant life, free-flowing waterways, and marshlands, but native and non-native plants can impact our delicate ecosystem. 

Four main invasive aquatic plants that impact manatees: lygnbya, water hyacinth, water lettuce, and hydrilla.


Lyngbya grows by attaching itself to other seagrass and rocks along the bottom of the riverbed. As they mature, the strands of lyngbya begin to accumulate together and form mats. Once they’ve fully matured, the mats float to the surface, which blocks the sun from reaching anything below them.

As we all know, sunlight is an essential part of photosynthesis; without it, the eelgrass that our manatees love so much cannot thrive. This can have disastrous effects on their feeding grounds and, in turn, the manatee's ability to call Crystal River home.

The most effective way to remove lyngbya is with a large vacuum system. These devices can suck algae up through a long hose into net bags. Once filled, the bags are removed and emptied at ecologically appropriate locations where the algae decomposes harmlessly. Removing this harmful algae allows native eelgrass to once again thrive, and we’re supplementing native eelgrass with robust planting plans.

To date, over 50 acres of seagrass have been planted and restored in the Crystal River area, and we don’t plan to stop there. Types of seagrass that have been planted so far include “Rockstar” and “Salty Dog,” with both serving as primary food sources for the manatees! It also allows other sea creatures–like scallops, fish, and invertebrates–a place to call home.

As we’re sure you have gathered by now, planting seagrass is a pivotal part of our plan to keep manatees and the Nature Coast ecosystem safe and happy. However, it’s not the finish line! It’s just the starting point. Outside of regular planting of new seagrass, we must also work to ensure the grass planted grows and stays healthy. Needless to say, we’ve got our work cut out for us, but we’re confident we can do it together!

Water Hyacinth

Did you know that invasive aquatic plants, more often than not, hitch a ride on a boat? They can inadvertently be transferred to non-native areas in the ballast water of traveling sea vessels. This is how water hyacinth and its relative water lettuce made their way to the Crystal River area.

Since first being introduced to St. Johns River in 1890, this invasive plant has choked waterways and altered local ecosystems. You may find yourself asking, “How?” Well, as they mature, their dense greenery blocks light from reaching the vegetation below.

Luckily, manatees love to snack on water hyacinth, and with manatee populations on the rise, they’re doing quick work of leveling the playing field.

Water Lettuce

A primary difference between water hyacinth and water lettuce is their leaf coverage. While hyacinth reaches up to 3 feet in height and produces flowers like its land-dwelling cousin, water lettuce forms a dense cover over the surface of our waterways. This cover not only hinders light from reaching the native plant life below but it can also get tangled up in boats and other watercraft as they traverse our waters.


If you’ve ever had an aquarium at home, then Hydrilla might look familiar. This invasive plant is native to Asia but has spread worldwide thanks to the aquarium trade. Even though manatees will eat hydrilla, it’s particularly invasive due to the quick growth cycle of just a single piece of the plant.

These non-native, invasive aquatic plants can easily crowd out and overpower native plants, which results in an imbalance in our local ecosystem, but through education and the hard work of restoration groups like Save Crystal River and the Homosassa River Restoration Project, we can remove these threats and restore our native plant life and ensure a pristine local ecosystem.


Discover Crystal River
Official Guide to Crystal River in Citrus County, Florida