The health of estuaries in south Florida is regularly monitored as part of the Comprehensive Everglades Restoration Plan.  The Eastern oyster (Crassostrea virginica) is a filter-feeding bivalve that provides critical habitats for estuarine animals and cleans the water passing through it.  Oysters can be harmed by poor water quality, freshwater releases, and toxic algal blooms, so they are used as a measure of estuary health by the South Florida Water Management District (SFWMD).

Sophisticated sonar arrays are used to survey the underwater habitats in estuaries, and the sonar reflections are used to estimate the density and health of oysters.  The resulting maps of oyster coverage, density, and health must be checked for accuracy.  The SFWMD contracted with EAI to perform a ground-truthing survey of oyster habitats in the Caloosahatchee River and Estuary.  In mid-September, EAI Senior Scientist Matt Scripter and Biologist Joseph Pessolano visited 150 stations to perform in-water assessments of oyster habitats. At each site, Dr. Scripter would enter the water with a quarter-meter quadrat and underwater camera to document oyster coverage, percent live oysters, benthic substrate, and sedimentation.  Oyster clumps were brought to the surface to search for newly-settled oyster spat since an oyster reef cannot thrive without new recruits.  The ground-truthing survey provided valuable corrections to the side-scan sonar maps since some of the mapped “oyster” habitats were actually a rare gastropod reef, natural rocks covered in mussels, or recently dead clams lying on the river bottom.  Surveying the many healthy oyster beds in the Caloosahatchee River and Estuary was an encouraging task that more than made up for the time spent in dark tannin-stained water, long days, and challenges that go hand-in-hand with in-water survey work.