Among the most visible residents of the hard-bottom habitats of the Florida Keys, sponges are not plants. They’re animals. They attach to hard surfaces and continuously filter large volumes of water through their pores to capture food, removing particulate matter such as plankton. Essential to healthy marine ecosystems, sponges alter water chemistry by cycling nutrients and they provide nursery habitat for species such as spiny lobster, stone crab and bonefish. More than 70 species of sponges live in the Florida Keys, offering a home to brittle stars and several species of shrimp. Snapping shrimp, known to inhabit open spaces within some sponges, make a loud popping sound with their claws, which may attract other species seeking habitat.
In recent years, a series of harmful algal blooms has impacted Florida sponge habitats, changing the balance of marine ecosystems. Many sponges have died over wide areas of the Middle and Upper Keys in Florida Bay. Since sponges grow slowly and are limited in dispersal during their larval stage, there is a lengthy recovery time for sponge communities after die-offs.
Elliot Hart of the Florida Fish and Wildlife Commission laying out sponge cuttings in the Sandfly Key nursery. ©Jennifer Stein
The Nature Conservancy and researchers from University of Florida, Old Dominion University and Florida Fish & Wildlife Conservation Commission (FWC), Bonefish and Tarpon Trust, and the Florida Keys Environmental Fund have partnered to study sponge community restoration. The partners have propagated sponges both at natural sites and nurseries. In natural sites, existing sponges are cut and monitored for recovery and the pieces are placed locally, then monitored for growth. In underwater nurseries, seven species are grown. They were collected locally, then will be transplanted in the future on degraded areas of Florida Bay.
After transplantation, sponges are monitored for benefits to water quality, including impacts on plankton and nutrient cycling; creation of habitat for other species; ability to become self-sustaining and improvement of reproductive success. Since the program began in 2015, thousands of sponge pieces have been placed in natural habitats, and thousands more are growing in four sponge nurseries. The program is led by the FWC's Fish and Wildlife Research Institute, Dr. Mark Butler of Old Dominion University and researchers from Florida SeaGrant and FWC. The objective is to determine the potential effectiveness of large-scale sponge restoration.
Researchers continue to expand existing nurseries and evaluate their success to develop the most effective and productive methods for sponge growth.