CORTEZ – John Stevely holds up a two-toned, blue kitchen pot scrubber.
“This is not a sponge,” he declares.
The manmade commercial product is not as absorbent, durable or sustainable as the real thing, the retired Florida Sea Grant marine biologist told listeners at the Florida Maritime Museum on Wednesday.
Stevely, a board member of FISH (the Florida Institute for Saltwater Heritage), will give short Dock Talks on marine-related subjects at the Cortez Commercial Fishing Festival the weekend of Feb. 16-17.
His talk on sponges was the highlight of the museum’s recent display of sponges from Tarpon Springs, the epicenter of sponge diving in Florida.
The reason natural sponges work better than artificial ones is that they are built to force water into and out of themselves – that’s how they feed, Stevely said. A sponge could fill a residential swimming pool in a day with the amount of water it pumps, all to get about one ounce of nourishment.
Natural sponges can be broken off without killing the whole animal, much like stone crabs can survive having a leg removed.
It doesn’t get more renewable than that, he said.
Sponges are the skeletons of animals, Stevely said, and also are a place where other animals live.
Gold-brown when dead, living sponges have vivid colors, including purple, orange and yellow, and give the water its color variations, he said.
Natural sponges are the preferred tool for window washers, horse groomers and ceramics makers, who use them to shape the wet clay, he said, noting that they also are better bath sponges than anything else.
Before World War II, sponges were the most productive fishery in Florida, Stevely said, with nearly 600,000 pounds of sponges produced in 1906 (think about how light a sponge is to picture that, he said).
But a sponge disease devastated the crop in Florida in 1938, followed by a red tide in 1947.
Then, synthetic sponges began taking over.
In the 1990s, blue-green algae killed many Florida sponges. Today, both blue-green algae and red tide – both harmful algal blooms (HABs) – continue to threaten the sponge population, even more than hurricanes, he said.
Sponges take years to rebound from these events, he said, naming water quality as their primary threat.
Few sponges live in local waters, but they flourish in west central Florida waters around Tarpon Springs and in southern waters off the Florida Keys. Sponge harvesting is now prohibited in the Keys.