Researchers monitor seagrass in Caloosahatchee

The scientists couldn't see their feet in the meter-deep water of the Caloosahatchee River last week — tannins from freshwater runoff had turned the river a deep reddish brown.

But Mark Thompson and RIck Bartleson of the Sanibel-Captiva Conservation Foundation Marine Laboratory had a job to do: Go underwater with masks and snorkels and document the density of shoal grass (often known by its genus name, Halodule) on the river bottom near Iona.

In a study dating back to 2004, marine lab researchers are looking at the effects of high freshwater flows on the river's seagrass species (shoal grass, turtle grass and manatee grass).

During the dry season, little rain falls, so little fresh water is added to the flow of the Caloosahatchee; during the wet season, rain falling on the Caloosahatchee watershed between the mouth of the river and Lake Okeechobee runs into the river, lowering salinity the estuary.

As Okeechobee fills during the rainy season, water managers release fresh water down the river to prevent flooding in the communities surrounding the lake.