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 urbanization of the coast is generating significant environmental issues, including increasing nutrient runoff that promotes eutrophication and hypoxic conditions in estuaries. At the same time, the excessive input of nutrients is also responsible for an increase acidification of coastal waters, as denitrification in sediments typically generates acidity.
Seaweeds create toxic compounds to deter consumers (fish) and poison competitors (corals). However specific fishes resist these toxins, and some corals also are resistant to their effects. These tolerances may be due to unusual microbes in the gut microbiomes of fishes and in coral mucus coverings. GT has an unusual mixture of marine ecologists, chemists and microbiologists to address these issues.
CO2 emission will continue exaggerating, as fossil fuels will most likely remain the major source of energy in next couple decades. The increased carbon in the atmosphere moves into marine ecosystems, making the world’s oceans more acidic. The rate of ocean acidification (OA) today is faster than any time in the past 300 million years.
Native microbial communities (microbiomes) of the vertebrate gut exert vital effects on host ecology, physiology, and evolution. This project explores the potential that the gut microbiome of herbivorous fish plays a vital role in biochemically degrading algal toxins consumed by the host fish, and therefore structuring diet choice and ecology. The student will work jointly between the labs of Drs. Mark Hay and Frank Stewart to test this broad hypothesis, likely focusing on the microbiomes of specific coral reef herbivores.
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.
