Weight percent nitrogen from Bering Sea IODP Site 323-U1342

Here, we present a high-resolution paleo-productivity record of weight percent nitrogen (wt % N) from IODP Expedition 323 Site U1342 (818 m depth) in the Bering Sea from 0-1.2 Ma. Sediment cores were sampled at ~3 cm intervals with in massive sediments and 1 cm intervals within laminated sediments, yielding an average sampling frequency of ~1 sample/kyr. Unwashed sediment samples were freeze-dried and crushed using a mortar and pestle. Bulk sediments (unacidified) were analyzed for weight percent total nitrogen (wt % N) on a Carlo Erba 1108 elemental analyzer, interfaced to a Thermo Finnigan Delta Plus XP IRMS, at the University of California, Santa Cruz. Low correlation between nitrate utilization proxy presented in this study (Knudson et al., 2016, Geophysical Research Letters, doi:10.1002/2015GL066317) and paleo-productivity proxies, including wt% N, provide evidence that fluctuations in primary productivity were not the main control over nitrate utilization at Site U1342 over the past 1.2 Myrs. Together, these results imply that enhanced physical water column stratification was likely the most important mechanism controlling nitrate utilization on orbital (glacial-interglacial) timescales.