HOT-294 - KM1708 - 14C Net Primary Production and Chlorophyll

These Simons Collaboration on Ocean Processes and Ecology (SCOPE) data products were produced by the University of Hawaiʻi at Mānoa with support from the Simons Foundation. The HOT-294 cruise on the R/V Kilo Moana was performed from June 19th-23rd, 2017 at Station ALOHA (22.75, -158) north of Oahu, Hawaii. Standard HOT protocols were used to measure in vitro primary productivity (PP) via the 14C radiotracer method [Karl et al., 1996]. Water samples were collected from ~5m before dawn and incubated on deck in incubators screened to ~50% of surface irradiance and plumbed with flow through surface seawater for temperature regulation. Duplicate 500-ml bottles were incubated in the incubator for ~12hr and 24hr, light bottles were paired with dark bottles. A time zero sample was taken at each station to ensure acidification was complete. Following dawn to dawn incubations, each sample was filtered onto a 25mm glass fiber filter. Filters were acidified with 1 ml of 2N hydrochloric acid in a fume hood for 12 hr to remove inorganic 14C after which 10 ml of Ultima Gold scintillation fluid was added to each sample. Radioactivity was determined using a Perkins Elmer 2600 liquid scintillation counter. The rate of PP was calculated by multiplying the percent of carbon labeled by the total carbon available for photosynthesis (e.g. dissolved inorganic carbon, DIC, calculated from SST and salinity measured at each station as per Lee et al. [2006]) and dividing by incubation time (t = 1 day). Rate measurements in light bottles were corrected to remove the rate measured in parallel dark bottles. All rates are in units mg C m-3; ‘stdev’ refers to the standard deviation of duplicates for each incubation type. These samples are paired with chlorophyll data for normalization. Fluorometric chlorophyll were collected from rosette niskin bottles at specific depths and filtered at low vacuum through a glass fiber filter. Samples were then flash frozen in liquid nitrogen and stored in a histoprep capsule at -80°C until analysis. Post cruise, the filters were extracted using 90% acetone for a total of 48 hours in a -20°C freezer, covered to prevent the photodegradation of pigments. Upon extraction samples were centrifuged to settle filter particulates and gently poured into a glass cuvette. Samples were then run on a Turner 10-AU Fluorometer. Data was corrected for average glass fiber filter blank values and is reported as the average of triplicate samples. The timestamp is in UTC.