An interdisciplinary project to explore the physical, chemical and biological factors that promote the growth of Sargassum blooms in the Tropical Atlantic and investigate the factors that may have changed in recent years (last decade). A novel combination of ecological approaches, remote sensing products, physical modeling, and oceanographic work at sea will be used to investigate and resolve the mechanisms that drive the onset of Sargassum blooms in the Central Tropical Atlantic and their growth and development in waters of the Western Tropical North Atlantic.
Coral reefs have tremendous environmental, economic, and cultural value but are in dramatic global decline. Over the last 4 decades, coral cover on Caribbean reefs has declined by ~80% and on Pacific reefs by more than 50%. Declines are being driven by a host of anthropogenic stresses including global change, overfishing, pollution, and disease spread, but all of these stresses generally result in losses of corals, increases in seaweeds, and then a loss of reef resilience as seaweeds dominate and suppress corals.
The characterization of sediment biogeochemistry at high spatial and temporal resolution is a necessary step in predicting the overall pathways and extent of hydrocarbon degradation in areas affected during and after an oil spill. However, geochemical data for sediments from deeper environments are scarce, and most studies do not measure the full suite of terminal electron acceptors involved in sediment diagenesis.
Plastic marine debris or the plastisphere impacts marine organisms through ingestion, entanglement, and as a source of toxic chemicals. The plastisphere could also have a major impact on biogeochemical cycles in the oceans. Plastics are transported via major ocean currents to central gyres, where they reside for decadal time scales. The amount of plastic waste is large, exceeding 2 kg/ km2 in central gyres. Even the most recent ocean surveys cannot account for the amount of debris estimated to enter the ocean, with inputs and outputs differing by orders of magnitude.
The sustainability of human civilization and its evolving lifestyle depends fundamentally on a sustainable food and energy supply. This can largely be linked to the availability of reactive nitrogen (Nr), phosphorus (P) and trace-element nutrient availability for natural and managed ecosystems. Nr, P and Fe are known to stimulate productivity while other elements, like Cu and Mn, can be toxic for ecosystems. Nr is also a critical link for the carbon cycle, and directly/indirectly impacts climate and human/ecosystem health.
The exponential growth of human populations in the Mekong-South China Sea (SCS) system, the eutrophication of estuarine and coastal waters by excess nutrients transported by the Mekong River, and the rapid sinking of the Mekong Delta are fundamentally changing the biological productivity and biodiversity of the system, with uncertain implications these aquatic resources. In the near future, larger forcings will alter the linkages between the Mekong system and the SCS basin.
Deep subsurface methane hydrate-bearing sediments contain microbial communities that are distinct from shallow marine sediments and hydrate-free environments. DNA evidence suggests that novel bacterial phyla (e.g. Atribacteria) are highly enriched in methane hydrate-bearing sediments. Recent genome assemblies by the Glass group at Georgia Tech are providing insights into the metabolic potential of samples drilled from gas hydrate stability zone 70 mbsf below Hydrate Ridge (IODP Leg 204).
Geochemical time series from remote Pacific atolls have provided long records of climate variability that extend into the pre-industrial era. Recent studies document a wide range of geochemical variability in corals growing on the same reef, ostensibly of the same genus. Deciphering which fraction of coral geochemistry variations are driven by changes in physical environment versus physiological differences between corals is key to constructing more robust records of past climate variability.
The student will work jointly between the labs of Drs. Frank Stewart (Biological Sciences) and Kostas Konstantinidis (Biological Sciences, Civil and Environmental Engineering) to characterize a globally important marine bacterial group (SAR11). A collaboration between these labs recently described how SAR11, the world’s most abundant organismal group, has adapted to the unique chemical and physical environment of anoxic oxygen minimum zones (OMZs). This work (Tsementzi et al.
Single-celled marine algae are especially chemically rich, producing toxins that kill fish, marine mammals, and seabirds, contaminate shellfish, and threaten human health. Many predators of these algae – copepods – selectively consume less toxic algae, which in turn sense copepods via an excreted blend of copepod-specific molecules. These algae then become up to 20X more toxic when they sense copepod cues in the open ocean.
