Seagrass meadows are home to an astounding array of ocean life. Manatees and turtles nourish themselves on the swaying blades. Young fish begin life there, and shrimp and crabs find shelter.
These marine grasslands are among the most important and valuable ecosystems on Earth. They capture the sun’s energy to generate food and oxygen for animals; provide habitat for fish and shellfish that feed people and form the backbone of coastal businesses; stabilize sediments; and absorb the power of waves, helping to stave off erosion and protect coastlines from storms. They also soak up climate-changing carbon and polluting runoff.
But these essential underwater grasslands are disappearing around the globe at the rate of two football fields an hour, pushed beyond their limits by a range of chronic and acute threats.1 Some are battered by storms, floods, droughts, disease, invasive species, and warming waters while others are ripped from the sand by trawls, dredges, propeller blades, and anchors. Still others are stressed by shifting water levels from runoff and other discharges from land, or they wither under the shade of suspended sediment and smothering algae fueled by pollutants flowing from cities and farms, particularly nitrogen-rich fertilizers.
Protecting seagrass is vital to the health of the oceans as well as businesses and coastal economies.
Seagrasses, which resemble prairies on land, are mostly found in the clear shallow waters of bays, lagoons, and estuaries, where they can receive the sunlight they depend on. Worldwide, there are more than 70 species of seagrass, with at least one found on every continent except Antarctica.
Seagrasses are flowering plants with blades, roots, and rhizome networks that spread and anchor to the seafloor or sediment, forming dense beds that can extend for miles. They are not seaweed or algae, and although they are similar in many ways to plants found in marshes and wetlands, they differ significantly from those terrestrial plants because they live fully submerged in salty water.
Like corals, seagrasses form structures where animals find homes, food, and nursery areas.2 These undersea communities are filled with a variety of species, such as bay scallops, crabs, seahorses, corals and sponges, snappers and groupers, salmon, sharks, dolphins, and birds ranging from pelicans to herons. Some animals eat the grass, and others feast on small organisms that grow on the blades and roots. Still others, such as small schooling fish like pinfish, anchovies, and smelts, hide from predators among the blades.
Healthy seagrasses also sustain activities that boost coastal economies, such as duck hunting, wildlife watching, and fishing for tarpon, stripers, salmon, and crabs.
Seagrass is a valuable ecosystem that provides varied services in the water and on land.
Along the Florida coastline, seagrass meadows bolster economic activity by nurturing commercially important fish, stone crabs, and shrimp and by drawing tourists from around the world for manatee watching, scalloping, fishing, snorkeling, and paddle sports. The state’s seven species of seagrass span more than 2.5 million acres13 and give Florida the nation’s most diverse seagrasses and two of its largest contiguous seagrass beds: Florida Bay at the southern tip of the state and the Big Bend, between the mouths of the Suwannee and Apalachicola rivers along the Gulf Coast.
Florida is also home to the first and only marine plant listed under the Endangered Species Act: Johnson’s seagrass.14
The approximately 400,000-acre habitat along the Nature Coast—which encompasses the shorelines of Citrus, Hernando, and Pasco counties bordering the Gulf of Mexico north of Tampa—is one of the healthiest seagrass habitats in the state.15 Here, seagrass mingles with mangrove islands, salt marsh, naturally occurring algae, sponges, and corals to provide habitat for recreationally and commercially important marine species that are the lifeblood of the region’s economy. The area is home to the “Manatee Capital of the World” and hosts world-class fishing and recreational opportunities that draw hundreds of thousands of tourists, support thousands of jobs, and generate millions of dollars annually.
Florida’s seagrasses are threatened by stormwater runoff, failing septic tanks, agricultural nitrogen pollution, coastal development, disease, warming waters, and a host of other problems.
During the 20th century, Florida’s seagrass experienced large acreage declines as well as changes in species, density, and size of beds. Recent efforts to improve water quality and clarity have increased seagrasses in a few Florida estuaries, but total seagrass coverage in coastal waters continues to decline along most of the state’s shoreline.
Although excellent water quality along the Nature Coast has generally kept the region’s seagrass habitats healthy and stable, the lush beds are showing increasing signs of thinning.21 Many of the threats to Nature Coast seagrass are shared by meadows in other locations around the state and country, but two issues stand out along the Nature Coast:
Some of the worst damage to the state’s seagrass has occurred in the Indian River Lagoon on the east coast and in Florida Bay to the south. Polluted sediments and nitrogen-laden runoff have fueled repeated toxic algae blooms that have received national attention, and water quality has become so poor that sometimes just being close to the water has made people feel sick.26 Under these harsh conditions, seagrass coverage in the lagoon has decreased more than 80 percent during the past decade, a loss of more than 42,000 acres.27
As the lagoon’s health has deteriorated, so have the economic benefits of tourism, fishing, and recreational activities, which support local businesses supplying everything from bait to gas. Commercial fisheries in the area have declined precipitously, including a 72 percent reduction in shellfish landings and a 54 percent drop for finfish since 1996.28 Despite a 12 percent increase in the local population during that time, boater registrations, primarily for small inshore and coastal vessels, fell 11 percent, indicating a decrease in overall fishing and recreational boating, which could jeopardize the $1.2 billion in annual consumer spending generated by these and other water-related activities.29
Florida Bay, the marine gem of the world-famous Everglades National Park, also has experienced significant seagrass die-offs. A prolonged drought and high temperatures in the summer of 2015 damaged more than 40,000 acres of seagrass, followed two years later by Hurricane Irma, which swept through the region, further damaging the seagrasses and delaying recovery of beleaguered meadows.30
Understanding the causes and consequences of seagrass loss is vital, because the most successful conservation efforts have been those that prevent, lessen, or remove threats and allow seagrasses—and the vital coastal economies they support—to recover and thrive.
Using funds from the Deepwater Horizon oil spill legal settlements, Gulf Coast leaders, including state and federal officials, university faculty members, and local citizens, are focusing on seagrass restoration, especially in Panhandle estuaries. In other parts of Florida, networks of federal, state, and county officials, nongovernmental organizations, and local communities are working together to find long-term solutions that can stem further declines of seagrass and set the stage for recovery.
Seagrasses play a vital role in coastal ecosystems and support activities and businesses that power economies. But as chronic and acute threats increase in duration and frequency, these productive and diverse habitats are at growing risk. Given the right environmental conditions, seagrasses can recover from damage resulting from pollution, boat propellers, storms, warming ocean waters, and other stressors. Urgent action on the part of state marine resource managers, elected officials, and others can help protect, conserve, and restore these special habitats.