St. Martins Marsh Aquatic Preserve - Management and Protection of Seagrasses

Seagrass beds are one of the most productive habitats found in the world. The rich biodiversity that make up seagrass habitats plays a critical ecological and environmental role to Florida’s coastal com­munities. Seagrasses improve water clarity by stabilizing bottom sediments and absorbing nutrients from the water column. They reduce coastal erosion by helping to diffuse wave energy during storm events. Economically, seagrass beds are of critical importance to Florida’s commercial and recreational fisher­ies. Florida’s juvenile fish and invertebrates (red drum, shrimp, bay scallops, sea trout, mullet, and stone crabs) depend on these rich nurseries for food and protection. Manatees, wading birds, and sea turtles also utilize these areas for foraging.

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Seagrass monitoring is an integral part of mapping the total acreage of Florida’s seagrasses. Accord­ing to FWC’s Seagrass Integrated Mapping and Monitoring (SIMM) report for the State of Florida, there are approximately 396,100 acres of sea­grass coverage in the Springs Coast region and 2.48 million acres in Florida’s coastal waters. The five species of seagrass found in St. Martins Marsh Aquatic Preserve are shoal grass, manatee grass, turtle grass, widgeon grass, and star grass. In addition to the five seagrass species, eighteen species of green macroalgae have been documented during annual seagrass surveys in St. Martins Marsh Aquatic Preserve. Macroalgae not only plays an important role in reducing nutrient loading in estuarine environments but are also pioneer species and help to stabilize prop scars from continuous scouring. One of the major threats to seagrasses in the state is from prop scarring. Repetitive scouring of prop scars prevents re-colonization of new grass and often requires restoration. Another threat to seagrass is nutrient loading from rivers which can decrease water clarity and shade out sunlight that grasses need for photosynthesis. Natural threats, like hurricanes, can cause fragmen­tation of seagrass beds that can take years to heal.

To help protect this valuable resource, St. Martins Marsh Aquatic Preserve staff have developed and implemented a Seagrass Monitoring Plan for the aquatic preserve that maintains a strategic, long-term seagrass monitoring project to include water quality indicators, percent coverage of seagrass and macroalgae species, macroalgae identification, density, epiphyte loading, and sediment depths.

St. Martins Marsh Aquatic Preserve staff are also working to promote the importance of seagrass habitats through a variety of outlets that target recreational, commercial, and scientific user groups operating in aquatic preserve, such as updating brochures, new educational signage at boat ramps and marinas, and participating in education and outreach events throughout the area.