Submerged Aquatic Vegetation

Aquatic grasses provide critical habitat to key species and can improve water clarity. Seagrasses are submerged plants found in shallow waters and are a critical part of the water that provide a number of benefits like buffering coastal communities from storms, removing pollution from the water, and providing shelter for animals.

See the results for submerged aquatic vegetation in the Northern Estuaries, Lake Okeechobee, or Southern Coastal Systems.

Photo credit: South Florida Water Management District.

How is it measured?

Submerged aquatic vegetation is measured in the Northern Estuaries, Lake Okeechobee, and Southern Coastal Systems.

For the Northern Estuaries, submerged aquatic vegetation is measured in all three subregions.

In the St. Lucie Estuary, seagrass cover and abundance is measured at seven 1-2 acre polygon sites. This data is used calculate the Braun-Blanquet cover and abundance scores per site, which are used as the thresholds for this indicator. The sites for the St. Lucie Estuary are actually located in the southern Indian River Lagoon.

In the Caloosahatchee River Estuary, seagrass cover and abundance is measured at six 1-2 acre polygon sites. This data is used calculate the Braun-Blanquet cover and abundance scores per site, which are used as the thresholds for this indicator. Braun-Blanquet cover and abundance scores are expected to be different based on conditions in the upper, middle, and lower Caloosahatchee River Estuary, and are scaled appropriately. 

In the Loxahatchee River Estuary, seagrass is measured using the fixed polygon method, with 24 - 32 random points sampled within each 1 meter squared quadrat. This data is used to calculated seagrass occurance which is a presence absence measure. Data from 2008-2018 was used to determine the threshold, which is the Historical Optimum (the highest recorded average occurance percent). The Historical Optimum was calculated for each individual site. 

For Lake Okeechobee, nearshore submerged aquatic vegetation coverage is mapped every year. The thresholds for this indicator are based on the Performance Measure and the Interim Goal.

For the Southern Coastal Systems, submerged aquatic vegetation is measured in Biscayne Bay and Florida Bay.

In Biscayne Bay, submerged aquatic vegetation is monitored as part of the Integrated Biscayne Bay Ecological Assessment and Management project. The thresholds are based on the presence weights of different species groups and the site cover divided by the maximum cover per site. 

In Florida Bay, submerged aquatic vegetation is sampled in 19 individual basins within Florida Bay. The thresholds and scoring are based on the stoplight indicator. The scoring is a composite referred to as seagrass abundance Index A and includes spatial extent (percent of all sampling locations where seagrass was present) and abundance (average density of seagrass cover where seagrass is present).