Seagrass Mapping

Your Questions Answered 

November 2020

Q: What are seagrasses?
A: Seagrasses are flowering plants that colonized the ocean some 70 to 100 million years ago. Seagrasses have leaves, flowers, seeds and roots. Unlike land plants, seagrasses do not have strong stems to hold themselves up. Instead they are supported by the buoyancy of the water surrounding them. Another unique characteristic of seagrasses is that they are “halophytes,” meaning they only grow in saltwater. Of the approximately 52 species of seagrasses that exist worldwide, there are only seven species found in Florida, six of them along Florida’s Gulf Coast.

Q: Where do seagrasses grow?
A: Seagrasses typically grow in protected bays and lagoons but can also be found in the deeper waters of the Gulf of Mexico. The depth to which seagrasses grow is most often determined by the amount of light reaching the bottom. In most of our Gulf Coastal estuaries you can find seagrass meadows between 6-10 feet of water. But off the Springs Coast just north of Tampa Bay, seagrasses can grow at depths of 30 feet or more! Overall, Florida has about 2.5 million acres of seagrass, more seagrass than anywhere else in the continental United States.

Q: Why are seagrasses so important?
A: Seagrasses provide critical habitat in Florida estuaries. They help improve water clarity, reduce nutrient pollution, and even help combat climate change. Approximately 70% of commercially and recreationally important fish spend at least part of their lifecycle within seagrass meadows. Seagrasses are very important to Florida’s economic health, contributing approximately $20 billion annually to the state’s economy.

Q: How and why does the District map seagrass habitat?
A: Seagrasses are sensitive to environmental change and therefore make very good indicators of estuarine health. For this reason, District scientists have been mapping seagrass habitat along the west-central and southwest Florida coast since 1988 as a way to take the pulse of the estuary. District scientists collect digital aerial photographs from an aircraft flying at an altitude of approximately 10,000 feet.

Q: When does the District map seagrass and when is the next map expected?
A: The District maps seagrasses along two regions of west-central and southwest Florida, the Springs Coast and the Suncoast. The Suncoast includes all the estuaries from Tampa Bay south to Charlotte Harbor and is mapped every two years. The Springs Coast extends from Waccasassa Bay near Cedar Key south to the mouth of the Anclote River. This region is mapped every four years. The most recent photography was flown between November 2019 and February 2020. At this time, photo interpreters are hard at work mapping both the Suncoast and Springs Coast estuaries with an expected release in early 2021.

Q: How are seagrasses doing in our estuaries?
A: The good news is that mapped acres of seagrass over the past 25 years have significantly increased in most of our estuaries peaking in 2016. For example, in Tampa Bay, seagrass acreage is greater today than it was in the 1950s. These long-term gains are a direct result of better water quality, largely due to improvements in how we treat our wastewater and manage our stormwater runoff. However, since 2016, seagrass acreage has remained relatively steady and has even declined in some of our Suncoast estuaries. Seagrass loss can be caused by a number of reasons. Hurricanes, red tide, and other significant events all effect the overall health of our seagrass habitat. What will the 2020 maps show us? We will soon find out.

Q: Who else monitors seagrasses in my estuary?
A: The District’s maps provide an excellent systemwide estimate of seagrass coverage over time. But that’s not the whole story. To complete the seagrass habitat picture, more site-specific information needs to be collected. That’s where our local partners come in. These partners, including county and city governments, National Estuary Programs, and citizen volunteer groups work very hard to collect critical site-specific seagrass data, that when used in conjunction with the District’s seagrass maps, gives us a comprehensive look at this critical undersea habitat.

Q: How can I find out more information about seagrasses in my estuary?
A:  The District seagrass maps are available for download via our geospatial open data portal ( The University of South Florida Water Institute’s open data portal also hosts many of the District’s seagrass maps (

Chris Anastasiou, Ph.D.
Chief Environmental Scientist