Florida Bay: Beneath the Surface

By Jenn Sweatman - August 06, 2012

Florida Bay consists of mud banks so intertwined it takes an experienced boater (or a great GPS chart tracker, if you’re me) to successfully navigate across the bay. Because flow is somewhat restricted by these mud banks, the basins have developed into unique habitats making each dive of the FCE-LTER seagrass sampling project quite different. At each of the LTER sites within Florida Bay, we estimate percent cover of all seagrass species and many calcareous green algal species, as well as red, brown, and other green algae. We monitor water quality over time via nutrient analyses in seagrass and calcareous green algal tissue, and we collect data on salinity, temperature, light penetration, and water turbidity. Data are located at www.fiu.edu/~seagrass.

Sprigger Bank is our monitoring site located at the western border of the bay where salinity is more stable than that of eastern regions. Sprigger Bank is characterized by dense turtle grass (Thalassia testudinum) and manatee grass (Syringodium filiforme); abundant calcareous green algae (Halimeda sp., Penicillus sp., and Udotea sp.); diverse red and brown algae (e.g., Laurencia sp. and Dictyota sp., respectively); and, brightly colored sponges. Mangrove snapper, grazing shrimp, amphipods and isopods, and megafauna such as sharks and a resident Loggerhead turtle (affectionately named “Spriggy”) inhabit this diverse habitat.

Sprigger Bank seagrass and algae (on a clear day).

Mangrove snappers cruising around Sprigger Bank.

Alex and Chris diving Sprigger Bank. The tide was really low, but it is easier to dive than snorkel these shallow sites because we don't have to worry about dunking our snorkels!

Bob Allen Key is located in central Florida Bay, is deeper than Sprigger Bank, and has fewer submerged plants. Turtle grass is the only seagrass at Bob Allen Key, and the seagrasses are smaller than those at Sprigger Bank. Duck Key is located in eastern Florida Bay. Bob Allen and Duck Key are very similar in depth (about 6 feet) and submerged plants. Compare these two sites in the photos below.

Bob Allen Key

Duck Key

Seagrass beds are important nursery habitats because they provide a safe place for juvenile fish, crabs, and shrimp to live until they become adults. Some animals live in seagrass beds their entire life, and others will use the seagrasses while they are young and migrate to other habitats (such as coral reefs) when they are older. Seagrasses also help clear up the water by trapping suspended sediments and excess nutrients. See below some animals that call seagrasses home!