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May 30, 2020

This page last modified:
March 21, 2001

Monroe County Leads State In Seagrass Damage

by Pam Wingrove

University of Florida/Monroe County Cooperative Extension

Florida Bay Education Project

Imagine an underwater meadow where leaves wave back and forth and animals cavort in near weightless abandon. This is the scene in the underwater world of seagrass habitats. As of 1995, approximately 1,452,800 acres of seagrass were found in the waters of Monroe County. Supporting hundreds of animals including fish, crustaceans and waterfowl, this habitat is in danger from the constant onslaught of prop dredging. In a 1995 report, the Florida Department of Environmental Protection estimated boat propellers damaged 30,000 acres of seagrass. The month of May has been designated "Seagrass Awareness Month" by the Board of County Commissioners in recognition of the importance of and risk to this critical marine resource. Monroe County Cooperative Extension Service will highlight seagrass habitats and resources in this column for the month of May.

Seagrass habitats are the cradle of recreational and commercial fishing resources, often called nurseries, because many juvenile fish and invertebrates spend their early life stages there. The seagrass beds of Monroe County are important to the Caribbean spiny lobster, pink shrimp, stone crab and numerous other animals.

Approximately 120 water bird species found in South Florida rely on seagrass beds for foraging. The osprey or fish hawk, great blue heron, roseate spoonbill and of course the bald eagle are only a few of the exotic, colorful and majestic species who make the Florida Keys their home. They feed on the fish, crustaceans and microscopic organisms residing in shallow seagrass habitats.

In addition to providing shelter and food for animals, seagrass beds also help to stabilize the bottom through their root systems. Seagrass dieoffs and destruction from boat propellers have resulted in more exposed sediment in near shore waters. Currents and waves generated by storms cause this sediment to move up into the water column which in turn decreases the clarity of the water. Excessive turbidity decreases the amount of light reaching seagrasses and interferes with its ability to produce its nourishment. With the recent severe storms and hurricanes in the Florida Keys the benefits of seagrass habitats in reducing wave energy and trapping sediment are easy to appreciate.

Unlike the grass in our lawns, which seems to grow right in front of our eyes, seagrasses take a long time to recover when damaged or cut. The actual recovery time is different for the seven species of seagrass found in the Florida Keys and depends on the type of growth each species has, the degree of damage, water quality conditions and sediment characteristics. Turtle grass, a common species locally, may take anywhere from 3 to 6 years to fully recover.

Seagrasses are damaged when props gouge the bottom tearing through root systems and digging up plants. A single engine vessel can leave a long trail of mud and uprooted seagrass when attempting to power through a shallow area. Vessels have been known to do acres of damage and become stranded. It happens to experienced operators and beginners alike.

The key to avoiding prop dredging and grounding is having local knowledge gained from experience on the water. Every vessel operator should carry and be able to use a detailed navigational chart of the area. These charts have marked channels and depth readings to assist the operator. Always stay within marked channels. They indicate areas known to be deep enough for your vessel to navigate. Don't operate your vessel in water less than 3 feet deep. Finally, learn to read the water. The angle of the sun can make this a challenge. Remember the rhyme, "blue blue, sail on through; white white you just might; green green, nice and clean; brown brown, run aground!" The destruction of seagrass can be stopped. It's up to you!

For more information on this research, contact the Florida Bay Education Project at 305-852-3592. Additional information on a variety of topics is available from the University of Florida/Monroe County Cooperative Extension Service, 5100 College Road, Stock Island or call at 292-4501; fax: 292-4415; email: or visit our web site Our services are free and available to all without regard to race, color, sex, or national origin.

The Florida Bay Education Project is an archived site. For more information go to NOAA's South Florida Ecosystem Education Project at