An attempt was made to visualize seagrass change in select regions of St Andrew’s Bay using Sentinel 2 imagery.
The imact of Hurricane Michael seems apparent, but then the question is: what happened in 2021?
Two areas of seagrass loss between 2020 and 2024 were manually identified using the IMaRS SIMM project seagrass .tif files.
Sentinel images were cloudmasked and the mean was taken from within these areas using this GEE script.
The resulting values were downloaded as a .csv and imported into this gsheet.
The visualizations there were screenshotted into Inkscape and manually annotated.
More on Seasonality
The apparent seasonality in the series is could be explained by seagrass growth patters, water quality changes, and changing optical properties. To explore this further an offshore area was selected to use as a baseline reference region. A small modification was made to the previous GEE script to create a script which extracts the deep water region.
The NDSVI extracted from the deep water region was subtracted from the seagrass area NDSVI.
The resulting “corrected” signal retains strong seasonality. The “hurricane Michael” event is more prominent in this series.
The same method was applied for an area of “deepish” water from within the sound. This baseline reference area should include changes in optical properties and water quality.
The remaining seasonality indicates that the seasonal signal of the seagrass area is stronger than the seasonality a nearby area of “deepish” water. In this series the “hurricane Michael” event is characterized by a sudden drop in NDSVI during the hurricane, followed by a missing winter peak.