Seagrass Monitoring

a puffer fish among seagrass blades
Seagrass provides important habitat to many forms of sealife, like this scorpionfish. Photo: NOAA

While Florida Keys National Marine Sanctuary is known for the beautiful coral reefs, it is also home to over a million acres of seagrass habitat. These large seagrass meadows serve as a critical habitat and nursery areas for many economically and ecologically important fishes and invertebrates, and feeding grounds for sea turtles, manatees, and herbivorous fish and invertebrates. Seagrasses also play a key role in trapping sediment and nutrients and preventing them from reaching the reef. Through photosynthesis, seagrasses produce oxygen, help sequester carbon dioxide, and provide a critical step in minimizing ocean acidification.

Seagrass populations throughout the Florida Keys are threatened by a host of stressors such as increased sea surface temperatures, reduced freshwater inputs, elevated salinity, and increased nutrients. In some locations, fleshy macroalgae is replacing the seagrass, and this is contributing to the loss of some of the important functions provided by seagrass beds. In addition, the direct loss of seagrass habitat has occurred as a result of dredging, coastal development, and boating impacts. More than 300 groundings are reported within Florida Keys National Marine Sanctuary each year, with nearly 80% of these incidents impacting seagrass habitat.

The Seagrass Monitoring Program measures the status and trends of seagrass communities across the sanctuary, which encompasses part of the largest contiguous seagrass meadow on Earth. Measuring the spatial extent and species composition of seagrasses provides information about nutrient levels in the water. Low nutrient conditions, which are predominant in most sanctuary waters, favor the growth of turtle grass. In contrast, high nutrient conditions result in the loss of such seagrasses in favor of nutrient-loving algae that are indicative of deteriorating water quality. This monitoring effort can detect water quality driven changes in seagrass meadows even before there has been any significant loss of this vital habitat.

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