What are sponges?
Marine invertebrates called sponges make up a critical component of Florida’s submerged marine and coastal ecosystems. It’s easy to think that sponges are not living creatures, but in fact, they are sessile (attached and cannot move), bottom-dwelling animals that live their entire lives in one spot, filtering water.
Globally, sponges live in coastal areas surrounding all seven continents, though they are found in higher numbers in tropical and sub-tropical areas. Roughly 9,000 have been documented. More than 70 sponge species can be found on Florida’s Coral Reef and surrounding habitats.
Ecological benefits
Sponges attach and live in hardbottom communities, including coral reefs. They play important roles in these ecosystems. One role includes serving as habitat for fish and invertebrates. Brittle stars, octopus, shrimp and crabs can hang out in sponge chambers, providing refuge from predators. In particular, Loggerhead sponges host juvenile Caribbean spiny lobster, an important recreational and commercial fishery species. Studies show that fish and invertebrate populations are higher in areas with sponges than areas with bare hardbottom.
Of particular importance is sponge filter feeding capabilities. Sponges are capable of removing bacteria, viruses, phytoplankton and cyanobacteria from the water. Filtration rates differ based on sponge species. A basketball-sized Loggerhead sponge could filter 304 gallons of water in an hour. It’s easy to see how effective sponges can be at helping to maintain or improve local water quality.
Sponge restoration
Numerous events have impacted sponge populations in south Florida. These include algal blooms, seagrass dieoffs, and hurricanes. Sponge restoration efforts have been taking place throughout the state for the past 15 or so years, with the intent of bringing back sponge species in affected areas. Since sponges can reproduce asexually, this process is fairly simple and involves fragmenting donor sponges into smaller pieces-a technique commonly employed in the coral restoration world. Sponge propagation methods are fairly simple: 1) find the appropriate sized donor sponge, 2) harvest about 50% of the sponge (this will allow the donor sponge to regrow in place on the seafloor, 3) fragment the piece into as many fist-sized pieces as needed, 4) tether to a paver, 5) monitor survival and growth. I would be remiss if I did not mention that all of these activities require at least one, if not two or more permits. Sponges can begin attaching themselves to the pavers pretty quickly, and depending on species, can show good growth within the first two years.
Our project
This year, my colleague Dr. Lisa Krimsky and I finally got to join the efforts of sponge restoration. We are part of a multi-partner sponge restoration project which aims to advance the field of sponge restoration and identification. Our part of the project entails setting up a pilot sponge nursery in south Biscayne Bay, in an area that was once home to a commercial sponge fishery. We are targeting six species for restoration: Brown branching sponge, Glove sponge, Loggerhead sponge, Sheepswool sponge, Vase sponge, and Yellow sponge. After receiving training from the Florida Fish and Wildlife Conservation Commission in propagation techniques, I’m pleased to share that last week, we placed 400 sponge fragments in our nursery.
We will monitor the fragments monthly through the summer and continue growing the nursery next winter. We will be comparing survival between sponges fragged on the boat versus sponges fragged underwater on SCUBA. In addition to survival, we will be examining water quality parameters in the nursery to see what effects the sponges’ filtration has on the area. I look forward to seeing this project come to fruition and expanding the great work happening around Florida.
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