Restoring Florida Bay: Sponges the foundation for thriving ecosystem

Vase sponge

A healthy vase sponge can grow to over 1 meter in length, and may be decades old. Sponges pump and filter large quantities of sea water, and provide shelter for a wide variety of tiny marine creatures. (Florida Sea Grant photo)

Prior to the 1990s the Florida Keys sponge community was a lively underwater city for fish and invertebrates. Curious divers could hear the snap, crackle and pop of snapping shrimp. The noisy bottom was a sign of health for the organisms that provide nursery habitat to juvenile marine species.

But now when divers plunge to the bottom, it’s as if the sponge community is on mute. There is no hustle and bustle of creatures foraging for their next meal, only silence.

Major phytoplankton, or algae blooms in the 1990s caused massive die-offs of the crucial species. More than 500 square miles of sponges in the Florida Keys suffered, representing an area bigger than the size of Los Angeles.

Because these sponges are a foundation species, their losses are having severe impacts on the ecosystems they support. A team of researchers, however, is testing transplant techniques to restore the community before it is too late.

Researchers at the University of Florida and Old Dominion University, along with more than 40 volunteers from around the world have joined together for an ecosystem intervention. John Stevely, a sponge researcher and Florida Sea Grant agent emeritus, said transplanting sponge cuttings is a way to speed up nature so the ecosystem doesn’t reach a point of no return.

“Our work has shown that sponge communities can take decades to recover,” Stevely said. “When the sponges go away, they don’t just come back in a few years. The project provides us with an opportunity to speed up the recovery process and conduct basic research that will expand our understanding of sponges in the ecosystem.”

Marine sponges are not only a valuable commercial asset to the state, they are also critical to Florida marine life. Researchers suspect that the biotic sounds caused by the inhabitants that occupy the sponges may help guide the larva of fish and invertebrates to safe habitat, similar to coral reef communities.

Their porous bodies, a complicated maze of canals and chambers, also serve as water filtration systems that regulate the water chemistry, and provide homes to juvenile fish and invertebrates. Research has also shown that compounds from sponges also show promise for drug development to enhance human life. The cancer-treating drug cytosine arabinoside was made from a Caribbean sponge, Cryptotethya cripta.

When sponges face stressors that wipe them out in mass quantities, they need help becoming re-established due to slow growth and low rates of larval dispersal. After piecing together various aspects of sponge biology and ecology, the research team found that cuttings of several sponge species can be successfully transplanted to restoration sites and after a few years, new populations begin to emerge.

In the Keys, where diving for sponges is prohibited, fishermen harvest sponges by using a hook on a long pole to tear a sponge free from the bottom. Off the Gulf Coast near Tarpon Springs, sponges are found in deeper water and diving gear is allowed. Photo by Florida Sea Grant

In the Keys, where diving for sponges is prohibited, fishermen harvest sponges by using a hook on a long pole to tear a sponge free from the bottom. Off the Gulf Coast near Tarpon Springs, sponges are found in deeper water and diving gear is allowed. (Florida Sea Grant photo)

But the team’s mission is not complete. The next step is determine whether the restoration sites can become the thriving and diverse ecosystems they once were.

By test planting a variety of sponge species, the researchers will be able to see if additional species are viable transplant candidates. The team has seen success in four species so far: the loggerhead sponge, vase sponge, brown branching sponge and the yellow rope sponge. These species were chosen because of their large adult size and their role as major filter feeders. However, these four species represent less than 10 percent of the naturally-occurring species in the Florida Keys.

The team says with additional funding they will be able to test more species to see whether they can be regrown and transplanted. Each sponge species that is successfully restored brings the team one step closer to reviving this thriving underwater community.

Stevely said the initial results have been very successful, but he is eager to see what lies ahead.

“We don’t know the whole story or what the long-term impacts will be, but that is something we’re hoping will be positive and help aid in restoring the ecosystem,” Stevely said.

New In Print: Sponges: The Key to the Keys. A brief fact sheet that describes how researchers and volunteers in the Keys are working together to restore lost sponge habitats.

Note: Florida Sea Grant is hosting a shallow-water sponge forum on Monday, Aug. 9, from 6-9 pm in Marathon, Fla. Contact Shelly Krueger, (, Florida Sea Grant agent, UF/IFAS Extension, Monroe County.

Editor’s note: Nov. 10, 2014 − The original version of this article stated that unregulated commercial fishing pressure and negative effects of shrimp trawling were among the factors causing sponge die-offs in the Florida Keys. Researchers attribute the die-offs to phytoplankton, or algae, blooms. Commercial sponge fishing is indeed highly regulated and conducted at a sustainable level. Shrimp trawls are not believed to impact shallow-water sponge communities in the Keys. The article has been corrected for accuracy.

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