What are sponges?
Marine sponges are invertebrate animals that are a vital part of Florida’s coastal and underwater ecosystems. Although they may appear plant-like, sponges are living, sessile organisms, meaning they attach to the seafloor and remain in one place for their entire lives, constantly filtering water to feed.
Volunteer Terry Helmers attaches Loggerhead sponge fragments to brick pavers while on SCUBA. Photo: Ana Zangroniz
Sponges are found in marine environments around all seven continents, with the greatest diversity in tropical and subtropical regions. Globally, about 9,000 species have been documented, and more than 70 species occur along Florida’s Coral Reef and nearby habitats.
Ecological benefits
Sponges primarily inhabit hardbottom areas such as coral reefs, where they play several key ecological roles. They provide shelter and habitat for a variety of marine life: brittle stars, shrimp, crabs, and even octopus use sponge cavities as refuge from predators. Notably, Loggerhead sponges serve as important nursery habitat for juvenile Caribbean spiny lobster, a species of commercial and recreational importance. Research shows that areas with sponges support greater abundance of fish and invertebrates compared to bare substrate.
Another critical function of sponges is their ability to filter water. They remove bacteria, viruses, phytoplankton, and cyanobacteria, helping maintain and even improve water quality. Filtration rates vary by species; for example, a basketball-sized Loggerhead sponge can filter over 300 gallons of water per hour, illustrating their substantial impact on the marine environment.
Sponge restoration
Sponge populations in South Florida have declined due to events such as harmful algal blooms, seagrass die-offs, and hurricanes. Over the past 15 years, restoration initiatives have aimed to reestablish sponge communities in affected areas.
Sponges reproduce asexually, making them well-suited for restoration through fragmentation, a method similar to coral restoration. The basic process includes selecting a healthy donor sponge, harvesting up to half of it (allowing it to regrow), cutting it into smaller fragments, attaching those pieces to a substrate such as a paver, and monitoring their growth and survival. These efforts require appropriate permits and oversight. Once placed, fragments typically attach quickly and can show measurable growth within the first couple of years.
Our project
This year, my colleague Dr. Lisa Krimsky and I joined a collaborative sponge restoration effort focused on advancing restoration techniques and species identification. Our role involves establishing a pilot sponge nursery in South Biscayne Bay, an area that historically supported a commercial sponge fishery.
Yellow sponges fragmented on SCUBA are counted before being placed in the nursery. Photo: Ana Zangroniz
Made possible by an EPA grant awarded in 2024, we are focusing on six species: Brown branching, Glove, Loggerhead, Sheepswool, Vase, and Yellow sponges. After receiving propagation training from the Florida Fish and Wildlife Conservation Commission, we successfully deployed 400 sponge fragments in the nursery.
We will conduct monthly monitoring throughout the summer and expand the nursery next winter. Our work will compare survival rates between fragments cut onboard versus those fragmented underwater using SCUBA. Additionally, we will track water quality in the nursery to evaluate the effects of sponge filtration. We are excited to contribute to ongoing restoration efforts and build on the important work happening across Florida.
