Seagrasses form important ecosystems in coastal areas around the world. They are highly productive and rich in biodiversity. Seagrass ecosystems provide nursery habitat for small fishes and invertebrates, and food for a wide variety of animals. They stabilize sediments and help maintain water clarity.
The park contains extensive seagrass beds throughout Biscayne Bay and on the reef tract. Most of the recreationally and commercially important fish, crustaceans and shellfish spend a portion of their lives in seagrass habitat.
Three seagrass species are commonly found in the park.
- Turtle grass (Thalassia testudinum) has wide leaf blades and a deep root structure. It forms most of the large, lush seagrass meadows found in the park. Sea turtles and some fish like parrotfish feed on turtle grass.
- Manatee grass (Syringodium filiforme) is recognized easily because of its cylindrical leaves. Like its name suggests, manatees feed on this type of seagrass.
- Shoal grass (Halodule wrightii) is an early colonizer of disturbed areas and usually grows in very shallow water. The leaves are generally smaller than the other two species.
Other seagrass species include star grass (Halophila englemanni) and paddle grass (Halophila decipiens).
Numerous species of macroalgae are found in park marine habitats. Macroalgal species are often called marine plants, however these species are non-vascular precursors to true plants. Although not exhaustive, the following list includes commonly observed species of macroalgae. Very few species of marine macroalgae have widely recognized common names, so only scientific names are provided.