M. S. Thesis
Coral reefs are one of the most diverse ecosystems in the world and this diversity is largely due to the abundance and range of invertebrate taxa that live within the reef. Stony corals and sponges are two benthic taxa that provide numerous benefits to coral reef communities that can be affected by anthropogenic disturbances. This thesis is comprised of two studies that address the ecological or physiological implications of anthropogenic disturbances on shallow coral reef communities. The first study took an ecological approach by addressing two morphologically distinct sponge species (Ircinia campana and Niphates digitalis) and their associated fauna, in St. John, US Virgin Islands, following two category five hurricanes. N. digitalis was 52% more abundant (individual m-2) on the reefs of St John then I. campana. Hurricanes effects did not significantly decrease density of either sponge, but they did decrease sponge size for both species. N. digitalis housed more invertebrate fauna (Ophiothrix suensoni, and Pelia mutica) per unit length, then I. campana but this epifauna-host relationship did not appear to be obligate and changed over time. The second study took a physiological approach by measuring, for the first time, the metabolic scope of two corals, Pocillopora verrucosa and Acropora pulchra, that are important components of the resilient reefs of Mo'orea, French Polynesia. Using a metabolic uncoupler to elicit the maximum metabolic rate (MMR), and starvation to elicit the basal metabolic rate (BMR), I described the gradient of metabolism and placed the metabolic rates associated with polyp expansion and digestion along this gradient. The metabolic scope ([MMR-BMR]/BMR) was ~136% for P. verrucosa and ~251% for A. pulchra, with metabolism increasing with expansion ~48-94%, and ~18-43% with digestion. I also explored size dependent metabolism and assessed if scaling differs based on organismic activity. The metabolic scaling exponents differed significantly among several treatments (b = 0.2 to 1) and differed from the exponents (b = 0.67 to 1) proposed by the metabolic level boundary (MLB) hypothesis. Variation in the scaling exponent was potentially caused by behavioral differences among the polyps. Together the results from Mo'orea, French Polynesia, and St. John US Virgin Islands, demonstrate the importance of studies that address the extent to which scleractinian and non-scleractinian taxa are being impacted by natural disturbances. They also highlight the need for ecological and physiological studies on coral reefs to determine how these stressors effect coral reef community structure and function.
Thesis or Dissertation
Department of Biology, CSU Northridge