Primary productivity measurements from the Hawaii Ocean Time-Series (HOT) project from 1988-2021 at Station ALOHA

Primary productivity measurements from the Hawaii Ocean Time-Series (HOT) from 1988 to 2021. The 14C-radiotracer method was used to measure the assimilation of dissolved inorganic carbon (DIC) by phytoplankton as an estimate of the rate of photosynthetic production of organic matter in the euphotic zone. All incubations from 1990 through mid-2000 were conducted in situ at eight depths (5, 25, 45, 75, 100, 125, 150 and 175m) over one daylight period using a free-drifting array as described by Winn et al. (1991). Starting October 2000 (HOT-119), samples were collected from only the upper six depths while the lower two depths were modeled based on the monthly climatology. During 2015, all incubations were conducted in situ on a free floating, surface tethered array. Integrated carbon assimilation rates were calculated using the trapezoid rule with the shallowest value extended to 0 meters and the deepest extrapolated to a value of zero at 200 meters.