M.S. Marine Biology
David Gilliam, Ph.D.
Jose Lopez, Ph.D.
Charles Messing, Ph.D.
Xestospongia muta, the giant barrel sponge, is a key component of coral reef benthic communities in Southeast Florida and the Caribbean. Xestospongia muta increases habitat complexity and stability, and filters large volumes of water, enhancing water quality and facilitating nutrient cycling. Therefore, it is important to investigate trends in the X. muta population on Southeast Florida reefs in response to anthropogenic stressors, changing environmental conditions and acute disturbances and how these events affect its ecological role in the benthic community. This study identified trends in X. muta population density, volume, and size class distribution over time and across reef habitats on the Southeast Florida Reef Tract (SEFRT). Density and volume changes were also investigated following acute physical disturbance caused by Hurricane Irma in September of 2017. Images and demographic data collected at 41 permanent sites from two long-term monitoring projects, The Southeast Florida Coral Reef Evaluation and Monitoring Project (SECREMP) and the Broward County Biological Monitoring Project (BC BIO), were used to evaluate the X. muta population trends. My analysis of the data from 2003 to 2018 shows that Xestospongia muta densities and volume increased over time regionally on the SEFRT and increased on the nearshore, middle, and outer reefs of the SEFRT. Xestospongia muta was found to be more abundant on the SEFRT compared to other locations including the Bahamas, the Florida Keys, Colombia, Belize and Saba. Highest mean density on the SEFRT was 0.35 individuals m-2 ±0.04 SEM, which was higher than the mean densities between 0.21 and 0.29 individuals m-2 at the Caribbean sites previously mentioned. Xestospongia muta individuals were categorized into size classes by volume to investigate density distribution of size classes on the SEFRT. Greater abundances in the smallest of five size classes (≤143.13 cm3) drove the increasing density trends. Despite the increasing trends from 2003 to 2017 with a peak in density and volume in 2017, Hurricane Irma caused a region-wide decline in population density and volume as well as a loss of individuals within the largest size class by volume (>17383.97 cm3). These results indicate that the X. muta population is exhibiting increasing long-term trends on the SEFRT, but also demonstrate that acute physical disturbances have a significant impact on the demographics of the population. Because of this sponge’s multiple roles in the reef communities, these trends have implications for structural complexity, nutrient cycling, water filtration, as well as carbon sequestration on the SEFRT.
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Alanna D. Waldman. 2019. Spatial and temporal trends in the Xestospongia muta (giant barrel sponge) population on the Southeast Florida Reef Tract. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (514)