Doctor of Philosophy (PHD)
Marine and Atmospheric Chemistry (Marine)
Date of Defense
First Committee Member
Dennis A. Hansell - Committee Chair
Second Committee Member
Rana Fine - Committee Member
Third Committee Member
Donald Olson - Committee Member
Fourth Committee Member
Joseph Prospero - Committee Member
Fifth Committee Member
Jia-Zhong Zhang - Outside Committee Member
Atmospheric nitrogen deposition to the ocean has more than doubled in the past 150 years due to anthropogenic activity, reaching levels comparable with nitrogen fixation in the subtropical North Atlantic. Previous studies have suggested that atmospherically deposited N may increase export production, decrease surface water phosphate levels, and substantially impact geochemical estimates of nitrogen fixation. This dissertation reports on the magnitude and biogeochemical fate of soluble N and P deposition in the subtropical North Atlantic. Aerosol and wet deposition time-series samples were used to determine the fluxes, sources, and N:P ratios of atmospheric nutrient deposition. Based on the magnitudes of total soluble N and P deposition, atmospheric nutrients are estimated to supply ~10-50% of allochthonous N to the North Atlantic subtropical gyre. Samples gathered in Barbados, the Canary Islands, and Miami indicate that atmospheric N sources are primarily anthropogenic (and thus, increasing) and that P sources are primarily natural (and thus relatively steady). Because inorganic nutrient concentrations in surface waters are in the low nM range, increasing P stress in surface waters may occur as a result of increasing N deposition. This assessment is supported by modeling studies, which also indicate that deposition would enhance surface P depletion. Inorganic N contributes nearly all (85-87%) of atmospherically deposited soluble N; the majority (~60%) of the remaining soluble organic N is comprised of an incompletely characterized pool of volatile basic organic N. Water soluble organic P contributes ~20-50% of soluble P. Because organic P contributes a relatively higher portion of soluble P as compared to organic N, the inclusion of organic matter in deposition estimates could both enhance the expected level of export production and reduce the predicted levels of P stress induced by atmospheric deposition. Further modeling studies indicate that the fate of atmospheric nutrients in the subtropical North Atlantic is controlled by non-Redfieldian processes, and that atmospheric nutrients eventually accumulate in the main thermocline. The research presented here suggests that future increases in atmospheric N emissions could have long-term impacts on surface ocean biology and nutrient cycles in the subtropical North Atlantic.
Nutrients; New Production; Global Change
Zamora, Lauren Maria, "Inputs and Biogeochemical Impacts of Nutrient Deposition on the Subtropical North Atlantic" (2010). Open Access Dissertations. 477.