Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Will We Get a Rainy Season This Year?

August 23, 2023
cooter on shore of high salinity pond

August is already half over and we aren’t seeing the usual standing water in ditches on the side of the road nor temporary wetlands filled with calling frogs and wading birds.

“We are wondering if we will get a wet season on par with most years,” said Wildlife & Habitat Management Director Chris Lechowicz. “Summer rains are critical to the success of many wildlife species, as well as certain plant communities, especially this year.”

Typical ephemeral (temporary) wetlands will be vitally important for wildlife this season as available freshwater is sparse. So far, we aren’t seeing any.

The inundation of freshwater bodies, both natural and manmade, with saltwater from Hurricane Ian has certainly had its effects on those wildlife communities from the loss of freshwater fish, frogs, and turtles, as reported by residents due to high salinity.

Many impounded manmade lakes in housing communities were dug over the last half century and filled naturally with freshwater from rainfall. These deep-water bodies were infiltrated by a variety of aquatic and semi-aquatic species that saw them as an oasis to exist in over the long dry season.

The American alligator (Alligator mississippiensis), especially, migrated to these lakes as they are much deeper, on average, than the natural wetlands that can mostly dry up in some years. Now, with a decrease in prey items due to high salinity in these lakes, alligators and other predators appear to be moving around searching for lower-salinity waterbodies.

Heavy and sustained rainfall will drop the salinity in these impounded lakes, although it will not remove the salt. This rain will also fill many natural ephemeral wetlands that are dormant at this time.

The control structure at Tarpon Bay Road separates the east basin of the Sanibel River from the west basin. Salinities in the two basins were very different after the hurricane, with the east basin at 15 ppt (parts per thousand) and the west at 24 ppt.

“These temporary wetlands provide habitat for small live-bearing fish, frogs, and aquatic invertebrates that depend upon freshwater to reproduce,” said Lechowicz.

Their offspring, such as fry, tadpoles, and nymphs, provide food for a plethora of vertebrate species that need prey resources, as well as the continued sustainability of those prey species on the island.

The Sanibel River and the connected wetlands are essentially a reservoir for excess water that can be released into the bay if water levels on the island get too high.

“The recovery of the freshwater wetlands will take many years, but many wildlife taxa need the process to start now with a heavy and sustained rainy season,” he added.


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