Researchers to share data from sponge program
July 12, 2017
ISLAMORADA — There is no distinguishing a sea sponge’s front from its back or the blob-shaped organism’s left from its right. Researchers say a sponge’s beauty lies deep within its obscurely-patterned pores and caverns; in its remarkable ability to filter thousands of gallons of water a day while providing vital habitat for sea life.
A panel of sponge experts will be hosting a forum next week at Founders Park to share data collected through a multi-agency effort to bolster declining numbers of sea sponges in the Florida Bay by propagating sponges and testing different growth strategies in four Middle Keys nurseries before transplanting them to nine experimental sites in the bay to study their development.
The long-term goal is to conduct a major out-planting of sponges in the bay as part of a large-scale restoration effort.
The multi-year program is led by professor Mark Butler and doctoral candidate Marla Valentine of Old Dominion University, Florida Fish and Wildlife Research Institute scientist Elliot Hart, and bonefish researcher and professor Jennifer Rehage of Florida International University.
Their data, in part, highlights the significant role sponges play in the Florida Keys’ marine ecosystem’s health.
According to Valentine, a single 2-pound sponge filters about 6,340 gallons of seawater a day, cycling rich nutrients into surrounding waters and provides habitat for species like spiny lobster and snapping shrimp.
These unusual organisms have been around for eons. Scientists have discovered chemical traces from sponges in rocks beneath glacial deposits from an ice age that ended about 635 million years ago.
“They are one of the simplest organisms with only a cellular organization, so they don’t have true tissues or organs or digestive systems like other animals,” Hart said. “It’s one of the reasons they can be cut up into many small pieces and each of those pieces can grow into a new sponge.”
Sponges have a network of canals through which water is pumped. They filter tiny bacteria-sized food particles for sustenance and expel the filtered water. This network of canals also provides a place for animals to live and even contribute to the underwater soundscape by hosting snapping shrimp.
“Listening for snapping shrimp is a neat ecological function included in our restoration. These shrimp are a good indicator of hard-bottom health,” Hart said.
Researchers record the number of snaps over a 10-second span with a hydrophone, or they cut open the sponge to count the shrimp.
The shrimp’s “snap, crackle, pop” noises serve a helpful purpose ecologically by attracting larvae of fish and other species to safely settle in the sponge, where they’re protected.
Valentine, who has been working with sponges since 2013, said they are not only important as habitat but also remove toxic ammonium from the water, which benefits fish and other sea life.
She said sponges in local waters have dramatically declined due to algae blooms — especially the bloom of 1991 — and not because of commercial spongers plying the waters with their pronged hooks.
Valentine described the small Keys commercial sponge market as “artisanal,” saying the practice has minimal effect on sponge populations. The hook spongers use leaves the sponge base intact, so it can regenerate, she added.
The Keys’ strict regulations have helped to preserve sponges as a fishery. Of the 5,000 sponge species found throughout the world, the Keys host 70 — of which only a few have commercial value: sheepswool, yellow, glove and grass sponges mainly.
Chris Bergh, South Florida program manager of The Nature Conservancy, said developing effective and productive methods for growing sponges here is important.
“There is an effort going on to bring back sea sponges that is ecologically meaningful,” he said. “It’s important to bring sponges back to contribute to water quality improvement.”
Rehage says sponges are key to a healthy Florida Bay.
“Through their role as the largest and most abundant filter feeders in the bay, sponges are critical to good water quality,” she said. “They provide key habitats for prey that many recreational fish depend on. Their role may be particularly important now post the 2015 seagrass die-off, since algal blooms may be expected.”
Hart said about a dozen volunteers helped with the 7,000 transplants last year. It’s easy to do, he said.
“Take a sponge, cut into bits, zip-tie it to a paver and grow as many sponges from it,” Hart said. “You can create a sponge factory, if you will.”
The transplants adhere to the paver within two weeks.
Florida Sea Grant, the University of Florida, The Nature Conservancy, Bonefish & Tarpon Trust, and the Florida Keys Environmental Fund have also supported the sponge propagation and transplanting project.
The Backcountry Sponges and Fisheries Forum is to begin at 6 p.m. Tuesday, July 18, at Founders Park, mile marker 87, bayside. Admission to the forum and entrance to the park is free.