Effects of anthropogenic stressors on tropical sponge ecology

The impacts of coastal development, ocean acidification, and temperature increases on sponge ecology were investigated, with an emphasis on community-wide impacts. At three locations with varying degrees of coastal development and sediment supply, field surveys were used to assess existing sponge abundance, diversity, species richness and community composition in Jamaica. Sediment accumulation rate, total suspended solids and other water quality parameters were quantified. The community-wide consequences of coastal development and increased sediment supply were also investigated by monitoring the annual and seasonal recruitment, as well as community succession over 6 years and 30 months, respectively. Of the adult (existing) populations surveyed, the location with the lowest degree of coastal development and sediment supply had higher sponge abundance, diversity, species richness and a distinct community composition than the other two locations with higher coastal development. Sponge seasonal recruitment was similar in diversity and percent cover across all locations; however, the diversity and percent cover of sponges assessed annually was lowest at the location with the most coastal development and sediment supply, suggesting that post-settlement mortality was higher at this location. After 30 months, the location with the highest sediment supply had statistically more bare space, which is indicative of an overall lack of recruitment; this provides further evidence that post-settlement mortality is occurring and propagating community trajectory changes. Although the exact mechanism is unclear, this study provides correlative evidence that even moderate coastal development is influencing sponge communities on reefs along the northern coast of Jamaica

To determine the effects of industrialization and increasing atmospheric CO2 on sponges, two studies were performed to evaluate how 1) ocean acidification affects the interactions between a bioeroding sponge, Cliona varians , and a coral, Porites furcata and 2) how increasing temperature and decreasing pH affect sponge erosion of living and dead coral substrate. The results of the first study indicated that acidification had no negative physiological impacts on C. varians, and no significant impact on the survival of either coral or sponges. However, exposure to end-of-century levels of pH reduced calcification in P. furcata and led to a significant increase in sponge-mediated erosion. The second study provided a more comprehensive evaluation of the relevant interactions between sponges and living corals and evaluated the differential impacts of bioeroders on living and dead coral substrate under acidification and warming scenarios. The findings of this study suggest differential impacts of temperature, pH and sponge bioerosion for living and dead corals. Living coral calcification was significantly reduced by temperature and sponge treatments, with no significant effect of pH, while dead coral dissolution was primarily driven by pH, regardless of sponge presence or seawater temperature. The results of this study suggests that future acidification and warming studies should include ecologically relevant time scales, adequate acclimation periods, interactions, and multiple levels of community organization to better understand and predict ecosystem-level response to future environmental conditions. This dissertation represents an effort to understand how anthropogenic stressors are affecting sponge communities, and the subsequent implications for reef community structure and function.

Stubler A. D., 2015. Effects of anthropogenic stressors on tropical sponge ecology. PhD thesis, State University of New York at Stony Brook, 235 p. Thesis (restricted access).

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