Seagrass Monitoring


What types of grasses occur within Choctawhatchee Bay?

Choctawhatchee Bay has two main types of seagrass. Shoal Grass, or Halodule wrightii, is the most commonly found species in the bay and thrives in areas with higher salinity levels. It has long narrow strands and can form carpet-like beds. Widgeon grass, or Ruppia maritima, is often said not to be a "true" seagrass because it tolerates both freshwater and marine water. It has thin leaves that grow from branched stems, and can have small buds or blooms.   

                      

 

 

 

 

 

 

Why are seagrasses important?

Seagrasses have important biological and physical functions that contribute to a healthy estuarine ecosystem. A healthy Choctawhatchee Bay is the foundation for our local economic well-being.

Seagrass Sampling

In 2009, CBA began a seagrass monitoring program designed to cost-effectively determine the abundance and distribution of seagrasses in Choctawhatchee Bay. That year, CBA staff and interns sampled over 100 sites within the Bay. Because the newly-formed monitoring program was designed to be linked to photo interpretation of Landsat 5 TM satellite imagery, each sampling site needed to be 30 meters by 30 meters square, the resolution of the Landsat photos. At each square, CBA samplers recorded map coordinates for the site, along with the estimated percent coverage of sea grass, water depth and clarity, and sediment type.

CBA then collaborated with University of Florida graduate student Jenney Lazzarino, who used Landsat 5 TM Imagery and the information collected by CBA to generate a seagrass map for Choctawhatchee Bay. Mrs. Lazzarino created an algorithm that interpreted, or “read,” color and reflective signatures in the Landsat satellite imagery of Choctawhatchee Bay to pinpoint seagrass presence in the bay.  Using the reference points collected during CBA’s seagrass sampling, Mrs. Lazzarino was able to ground-truth her photo interpretation methods and determine that the earliest version of the model predicted the presence of sea grass with a 70% accuracy. In subsequent years, CBA’s sampling confirmed that model’s accuracy had improved to close to 90% accuracy. This combination of modeling and sampling has proven a cost-efficient way to routinely sample seagrass abundance and distribution in Choctawhatchee Bay.