Local versus remote controls on the nitrogen cycle in the Indonesian Throughway over the past 500 ka

Abstract

The feedback between the biological conversion of inert atmospheric N2 to organic nitrogen (nitrogen fixation) and the biological reduction of nutrient species of nitrogen to N2 (denitrification) controls the budget of bioavailable nitrogen, essential to primary productivity and carbon export in the world’s oceans. Nutrient delivery from coastal runoff stimulates nitrogen fixation and may disrupt this feedback, but not much is known about this mechanism. The Indonesian Throughflow (ITF) is the gateway where Pacific and Indian Ocean waters exchange and is an ideal location to study the interaction of multiple geochemical triggers. In the ITF, IODP Site U1483 sits nearby the northwest Australian upwelling zone and downstream of coastal runoff controlled by a highly variable hydroclimate. Pacific waters flowing through the ITF carry the signal of remote pelagic denitrification, also influencing the geochemistry at U1483. Each of these factors varies with global climate change, yet with distinct pacings. I will leverage the temporal differences within a newly generated 500 kyr record of foraminiferal bound nitrogen isotopes to examine the dominant controls on productivity and nitrogen cycling in the ITF from the mid Pleistocene through to the Holocene.

Biography

I grew up on the New Jersey coastline playing in the marshes and mud, inspiring me to learn as much as I could about the natural world. I completed a B.S. in Environmental Science at the University of Rochester, where my interest in geochemistry and paleoclimate ignited while taking classes and conducting independent research on carbon isotopes from foraminifera in Arctic methane seeps. My growing love of forams led me to work with Dr. Rebecca Robinson at the University of Rhode Island Graduate School of Oceanography. My dissertation work focuses on nitrogen cycle changes in the southwest Indian Ocean on different geologic timescales. I am excited for my work with the Schlanger Fellowship to take me to the other side of the Indian Ocean, where I will examine nitrogen fixation and productivity at another ocean gateway and work on creating a more complete picture of the Indian Ocean nitrogen cycle. I look forward to connecting with other geochemists as I complete the program.