CAREER: Nitrogen Biogeochemistry during Oceanic Anoxic Events

Syracuse University, Syracuse NY

Investigators

Abstract

CAREER: Nitrogen Biogeochemistry During Oceanic Anoxic Events Christopher Junium, Syracuse University How the Earth and life have interacted through time is central to our understanding of the Earth system, particularly during significant transitions such as mass extinctions and intervals of rapid climate change. Oceanic Anoxic Events (OAEs) were extraordinary disturbances in Earth's climatic and ecological balance, initiated by rapid increases in the concentrations of greenhouse gases. The Earth system responded to rapid warming by sequestering added carbon dioxide as organic carbon rich shales deposited in anoxic marine environments. The key link between greenhouse gas induced warming hand productivity is in how nutrients, particularly nitrogen, phosphorus and biolimiting trace metals, are cycled and redistributed in marine environments. Indeed, what we know about how the N and P cycles respond during OAEs makes it clear that nutrient cycling was drastically different during OAEs than for much of Earth's history. Over the course of the coming centuries the extent of marine anoxia is likely to expand as a direct result of warming and increased agricultural nutrient runoff. The future trajectory of marine anoxia is best constrained by examining intervals of the past, such as OAEs, where warming and the expansion of anoxia are linked and life in the ocean was directly impacted. This study will address this research challenge through development and application of nitrogen and carbon isotope techniques focused on the Cretaceous, Cenomanian-Turonian OAE 2 and Syracuse-region anoxic lakes as principal study areas. The educational component of this project will involve undergraduate students from traditionally underrepresented groups in field research during the early stages of their STEM education. Opportunities for hands-on research transcend what can be accomplished in the Earth science classroom, and increases the likelihood that students will continue in STEM fields. This CAREER project will aim to resolve outstanding issues that remain regarding how marine productivity and Oceanic Anoxic Events are linked. The primary questions addressed in this study are: Why are nitrogen isotope values anomalously low during Phanoerozoic OAEs' How do marine food webs and ecology respond to rapid warming and expansion of water-column anoxia? How does the depth of the oxic/anoxic transition (the chemocline) affect the ecology of marine communities? This work will be achieved by analyzing stable carbon and nitrogen isotopic composition of trace organic constituents in the shells of marine macroinvertebrates, the tests of foraminifera and organic microfossils. Field research and education will be focused on the extraordinary, meromictic Fayetteville Green Lake, just a few miles from the Syracuse University campus. Through collaboration with the Upstate Louis Stokes Alliance for Minority Participation and Onondaga Community College we will host summer research interns through the duration of the project and will run a short course that focuses on the geochemistry of Fayetteville Green Lake for STEM students from Onondaga Community College.