Bochum, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Bochum, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Bochum, Universiẗat, Diss., 2002.

The symbiotic jellyfish, Cassiopea andromeda (Cnidaria: Scyphozoa) often sit upside-down on the benthic of shallow water regions, with constant pulsation behavior of its umbrella which brought water currents flowing through its oral arms to enhance prey capture and material exchange with surrounding water. However, little is known about the influence of pulsation on its heterotrophic behavior and symbiotic relationship with endosymbiotic zooxathellae. Current study focused on the potential effects of animal size, illumination, diel cycle, prey availability and starvation on the pulsation rates of the jellyfish. Our result revealed that the pulsation rates decreased at larger animal size, absence of prey, prolonged starvation and dark environment, and vice versa. Animals receiving natural light illumination showed significant diel cycle pattern of pulsation in the 24 hr period, which is not observed in the group dark treatment. Meanwhile, we also conducted the clearance rates of the upside-down jellyfish through its ontogenetic growth, and found that the clearance rates significantly increased as they grow. Based on the results obtained from this study, its is likely that the smaller meduae might rely more on the energy provided by the symbiotic algae, and can exhibit more significant habit selecting behavior.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Not available / text

Coastal marine ecosystems are among the most impacted globally, attributable to individual and cumulative effects of human disturbance. Anthropogenic nutrient loading is one stressor that commonly affects nearshore ecosystems, including seagrass beds, and has positive and negative effects on the structure and function of coastal systems. An additional, previously unexplored mechanistic pathway through which nutrients may indirectly influence nearshore systems is by driving blooms of benthic jellyfish. My dissertation research, conducted on Abaco Island, Bahamas, focused on elucidating the role that benthic jellyfish have in structuring systems in which they are common (i.e., seagrass beds), and explored mechanistic processes that may drive blooms of this taxa. To establish that human disturbances (e.g., elevated nutrient availability) may drive increased abundance and size of benthic jellyfish, Cassiopea spp., I conducted surveys in human-impacted and unimpacted coastal sites. Jellyfish were more abundant (and larger) from human-impacted areas, positively correlated to elevated nutrient availability. In order to elucidate mechanisms linking Cassiopea spp. with elevated nutrients, I evaluated whether zooxanthellae from Cassiopea were higher from human-disturbed systems, and whether Cassiopea exhibited increased size following nutrient input. I demonstrated that zooxanthellae population densities were elevated in human-impacted sites, and that nutrients led to positive jellyfish growth. As heightened densities of Cassiopea jellyfish may exert top-down and bottom-up controls on flora and fauna in impacted seagrass beds, I sought to examine ecological responses to Cassiopea. I evaluated whether there was a relationship between high Cassiopea densities and lower benthic fauna abundance and diversity in shallow seagrass beds. I found that Cassiopea have subtle effects on benthic fauna. However, through an experiment conducted in a seagrass bed in which nutrients and Cassiopea were added, I demonstrated that Cassiopea can result in seagrass habitat modification, with negative consequences for benthic fauna. My dissertation research demonstrates that increased human-driven benthic jellyfish densities may have indirect and direct effects on flora and fauna of coastal marine systems. This knowledge will advance our understanding of how human disturbances shift species interactions in coastal ecosystems, and will be critical for effective management of jellyfish blooms.