Sponge Community Biocomplexity, Competition, and Functional Significance in Hard-Bottom Habitats of the Florida Keys, FL (USA)

Sponges can have powerful effects on ecosystem processes in shallow, tropical marine ecosystems and are an integral component of the bentho-pelagic cycle of nutrients, via filtering of dissolved and particulate organic matter from the water column. The diversity of marine communities is thought to play a determining role in intensity of ecosystem processes; thus the loss of taxa alters community function and by extension ecosystem processes. Coastal sponge populations worldwide are increasingly exposed to declining water quality that in several regions has resulted in mass sponge mortalities and reduced sponge diversity. In the Florida Keys (Florida, USA), for example, frequent cyanobacteria blooms have decimated coastal sponge communities. There were two objectives for this research. First, to experimentally establish the baseline effects of Florida Keys sponges, at ecologically relevant biomass levels, on various shallow water ecosystem processes and functions, and richness on water column properties. The results of this work demonstrated the importance of sponge biomass and species-specific filtration rates on the intensity of water column nutrient cycling, and its constituents. The second objective of this research was to develop an understanding of how sponges might interact in the wild, ultimately affecting the ecosystem processes and functions measured previously. The results of field manipulations, and sponge measurements plus water column sampling, conducted at multiple sites within Florida Bay showed clearly that the sponges of these back-water lagoons competed intensely for food, particularly in areas of higher biomass and slower water movement. Overall, this dissertation highlighted how reductions in the abundance and diversity of sponges in coastal ecosystems can drastically alter water column properties

Characterization of Epibenthic and Demersal Megafauan at Mississippi Canyon 252 Following the Deepwater Horizon Oil Spill

Increased demand for new sources of oil and gas has resulted in an expansion of drilling into deeper waters. With this exploratory drilling come increased risks, which were realized on April 20, 2010 when the blow out preventer on the Macondo Well failed, resulting in the release of a large quantity of oil and gas into the Northern Gulf of Mexico from a bathypelagic source. This unprecedented environmental disaster was coined the Deepwater Horizon Oil Spill by the popular news media. In the months that followed the spill, the lack of knowledge about the pre-spill condition of deep-sea communities in this area of the Gulf of Mexico became apparent. This made it difficult to determine the effects of the spill on deep-water megafauna. The objective of this study was to characterize the epibenthic and demersal megafaunal community immediately following and one year after the spill. Remotely operated vehicles conducted a series of video surveys over an extended time series (11 surveys Aug 4 – Nov 1, 2010) of a site located 750 m to the Southwest of the Macondo Well and at five additional study sites during August and September 2010: 2000m north, west, south, and east, and 500m north of the Macondo well. The 750 m Southwest site was revisited in July of 2011 to determine what, if any, changes had occurred in the deep-water megafaunal community. These study sites were dominated by demersal fishes and mobile benthic invertebrates both in 2010 and 2011. The results indicate both diversity and densities of organisms declined over time in 2010, while densities appeared to increase in 2011 to levels similar to those observed immediately following the spill. The presence of carcasses of pyrosomes, salps, and crabs in 2010 indicated some short-term or acute mortality following the spill. It is hoped that these data will be used as a post-spill baseline against which future surveys of diversity and abundance of deep-water megafauna can be compared