Nitrogen fixation rates in a cyclone-anticyclone eddy pair in the North Pacific Subtropical Gyre (Cruise KOK1607)

Surface N2 fixation rates were measured in the center of a cyclonic eddy (23.74°N, 157.39°W), an anticyclonic eddy (22.94°N, 155.95°W), and an additional station between the two eddies (23.44°N, 156.78°W) during May 2016. Seawater was collected from 25 m and sampled into 4.4 L bottles, spiked with 15N2-enriched seawater, and incubated in surface-seawater cooled, flow-through, deck-board incubators fitted with screening to reproduce in situ light conditions. These incubations were conducted during the day (10 h incubation, 08:00-18:00 local time) and at night (6 h incubation, 22:00-04:00 local time), using seawater from separate CTD casts prior to each incubation. Times provided are the average time of each incubation. Details on 15N2-enriched seawater preparation and other methodological details for the rate measurements are provided in Böttjer et al. (2017, Limnology and Oceanography, doi: 10.1002/lno.10386).

Additional physical and biogeochemical data collected on cruise KOK1607 are available online: http://scope.soest.hawaii.edu/data/hoelegacy/data/