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Sponges on Florida Coral Reefs: Demographics and Impacts on Water Quality

Principal Investigator: Dr. Joseph Pawlik, UNCW

Co-Principal Investigator: Dr. Christopher Finelli, UNCW
Training: August 9 — 13
Mission: August 17 — 26

Demography of Reef Sponges

Sponges are now the dominant habitat-forming animals on most Caribbean coral reefs. Unlike corals and some macroalgae, sponges do not have calcified skeletons, and are less likely to be affected by ocean acidification due to global climate change. The Caribbean barrel sponge, Xestospongia muta, is a large and common member of the Florida coral reef community and has been called the “redwood of the deep”. Despite its prominence, high biomass and importance to habitat complexity and reef health, few data existed regarding the basic biology of this massive sponge prior to our research, including rates of mortality and recruitment, reproduction, growth and age. Like reef corals, this sponge is subject to bleaching, diseases, and subsequent mortality. Additional threats to this and other sponge species include fishing line debris, which can cleanly slice through sponges during storm events and in high-flow environments. Using the Aquarius habitat beginning in 1997, Dr. Pawlik and students established and began monitoring 9 permanent circular plots (16 m diameter) at Conch reef containing over 600 marked X. muta to document sponge mortality, recruitment, bleaching, growth, disease, and damage by debris. Using repeated digital photographs of sponges taken over 6 years, we have modeled growth to estimate ages of large sponges within our plots at >100 years, and very large X. muta at other sites at over 2000 years old, placing these sponges among the oldest animals on earth. We applied stage-based matrix modeling to our long-term monitoring data to study the demographics of X. muta, and determined that populations of this important species are increasing on Florida’s reefs. For this Aquarius mission, we will extend our monitoring program to include staking, tagging and photography of two additional species of prominent reef sponges within our permanent plots, Geodia neptuni and Agelas conifera.

Pumping Rates of Sponges and Water Quality

Dr. Finelli and his students have preliminary data that specimens of X. muta filter water at a rate of 97 ml-H2O h-1 ml-tissue-1, or about 100-times their own volume every hour. With sponges ranging in size from < 100 ml to > 200,000 ml, potential population filtration rates are considerable and demographic changes in sponge populations could have profound effects on reef water quality. For this Aquarius mission, pumping and clearance rates of healthy and diseased X. muta, G. neptuni, and A. conifera across a range of sizes will be measured to estimate population filtration rates and the effects of disease on filtration. These data will ultimately be useful in determining the overall effect of sponges on reef water quality.

Monitoring for Oil Spill Impacts

Conservation and management efforts require basic long-term monitoring data on reef sponges to establish baseline demographic information. These data may also be critically important for understanding future effects of the Gulf of Mexico Deepwater Horizon oil spill on the reef communities of the Florida Keys. In addition to the decade-long monitoring database on X. muta, Pawlik’s group has survey data and tissue samples from the sponge community on Conch Reef, and this Aquarius mission will include additional surveys of sponges, corals and fishes.