Sponges play two important roles in the Florida Keys shallow water ecosystem -- improving water and providing critical habitat for juvenile spiny lobsters and stone crabs, two of the state's most important commercial fisheries.
They are made up of a complicated maze of canals and chambers, are remarkable pumping machines and can pump water as much as 10,000 times their own size in one day. A sponge the size of a gallon milk container can pump enough water to fill a small swimming pool within one day, according to John Stevely, who has been conducting sponge research off the Florida Keys since the 1970s.
"They filter a phenomenal amount of water," Old Dominion University professor and sponge researcher Mark Butler said. "Sponges filter the entire Florida Bay in a matter of days."
Harmful algal blooms in the early 1990s, 2007 and 2013 caused massive sponge die-offs throughout large areas of the Middle and Upper Keys. More than 500 square miles of sponges in the Florida Keys were decimated. As a foundation species, sponge loss has major impacts on the ecosystems they support.
Prior to the 1990s, the sponge ecosystem was so healthy divers could hear the crackle and popping of snapping shrimp. The sound would draw the larger fish into sponge ecosystem to feed and may be a signal for fish and crab larva to sink to bottom to begin next life stage into adults. But the symphony of the shrimps has since been silenced and there is no ruckus of fish foraging for their next meal.
Florida Sea Grant and Old Dominion University have joined forces to bring the music back by growing sponges. The team is testing revolutionary transplanting techniques. Sponges need help becoming re-established due to slow growth and low rates of larval dispersal.
The agencies have 14 transplant and restoration sites spread across more than 200 miles off the Florida Keys.
Sea Grant research show that sponges have a remarkable way of regenerating themselves, not unlike the way stone crabs regrow their claws. If sufficient amount of sponge tissue is left attached to the bottom, the sponge can survive and regenerate, Stevely and Butler said.
In the northern Gulf, divers historically used knives to tear sponges free from the bottom, but the industry has gradually moved to cutting sponges from the ocean floor. Sea Grant studies show survival rates for sponges can be as high as 71 percent for cut sponges versus 41 percent for those hooked. In the Keys, where diving for sponges is prohibited, hooked sponges grow back about one-third of the time, Stevely said.
Based on the industry's embrace of the cutting practice and Sea Grant recommendations, the Florida Fish and Wildlife Conservation Commission (FWC) passed regulations that now require sponge divers to harvest sponges by cutting. This insures that the sponge can grow back, and produce another harvestable sponge, Stevely said. Monroe county does not allow cutting or diving, only collect by hooking.
Sea Grant and Old Dominion University's work involves a sponge being cut into pieces, attached to a concrete disk, and then grown into a full-size sponge. The sponges are then transplanted back into Florida Bay.
"It's truly a sustainable resource," said Jim Cantonis, whose family has owned Acme Sponge and Chamois Co, in Tarpon Springs for decades. "The little piece you leave behind will grow back."