Subtropical North Pacific variability in primary production and nutrient utilization inferred from compound specific isotopes in Hawai'ian deep-sea coral gorgonin.

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The project will investigate whether the compound-specific isotope signature of amino acids in deep-sea proteinaceous corals can be used to interpret changes in the upper ocean ecosystem and its biogeochemical cycling. As these corals feed on particulate material (POM) derived from the surface they potentially can be used to deconvolute the factors that combine to drive bulk isotope change, and may provide an important expansion of proxy tools for examining longer-term changes in ocean productivity and particulate production and cycling. It is hypothesized that the compound-specific analysis can indicate both the average trophic position of exported POM as well as original signature at the base of food webs, creating independent records of both factors. Additionally, it is proposed that the results will allow a measure of relative microbial alteration, and a direct record of the average C signature of exported production. An archived set of proteinaceous coral (Gerardia) samples from contrasting regions of the subtropical North Pacific Ocean will be analyzed and the information used to construct records of trophic structure, and C and N signatures at the base of the food webs over 100-2000 years. Such information will allow examination of the validity of current interpretations from bulk isotope records, as well as provide additional details. The research will develop and validate a potentially important paleoceanographic tool using proteinaceous coral archives.The scientific merits and broader impacts of the project are clear and far-reaching, and will impact not only Chemical Oceanography but also the other branches of the marine community. The approach could be generalized and used to understand different processes and ecosystems once it has been properly demonstrated. The project will train a graduate student and will involve additional training of undergraduates and has an additional outreach component.