Tracking the Evolution of Water Column NO3-+NO2- δ15N & δ18O from the South Atlantic, Through the Gulf of Mexico, and to the North Atlantic

• Other Authors: Howe, Samantha Paige (authoraut)
• Format: Bachelor Thesis
• Language: English
• Published: 2018
• Subjects: North Atlantic
• Online Access: https://diginole.lib.fsu.edu/islandora/object/fsu%3A621060/datastream/TN/view/Tracking%20the%20Evolution%20of%20Water%20Column%20NO3-%2BNO2-%20%CE%B415N%20%26%20%CE%B418O%20from%20the%20South%20Atlantic,%20Through%20the%20Gulf%20of%20Mexico,%20and%20to%20the%20North%20Atlantic.jpg

The Gulf of Mexico is known for the biogeochemical impacts of significant riverine nutrient inputs on the ecosystem. However, it is unclear whether nutrients delivered to the Gulf of Mexico are subsequently exported from the Gulf, further influencing the chemistry of the North Atlantic. The nitrogen and oxygen isotopic composition of nitrate (NO3-) have been increasingly used to track nitrogen fluxes to, from, and cycling within the ocean. Here, we report the first dual isotopic composition measurements of NO3- from the Gulf of Mexico and Florida Straits, and compare these with prior measurements from the South and North Atlantic, and identify potential processes consistent with the observed shifts. The nitrogen and oxygen isotopic composition of nitrate in the Gulf of Mexico and Florida Straits is very similar to that previously measured in the Sargasso Sea. There is little evidence for riverine or submarine groundwater NO3- directly influencing the isotopic composition of NO3- exported from the Gulf of Mexico. These results are consistent with recent modeling work suggesting that the majority of riverine nutrients delivered to the Gulf of Mexico are retained in the near-shore region. Keywords: nitrate isotopes, Gulf of Mexico, nutrient cycling, nitrate concentration