Underway System (MET/SCS)
Primary productivity incubation experiment: at local apparent noon (LAN; ~11:30-12:20), each day of the cruise, a primary productivity incubation experiment is started with seawater samples collected from the CTD cast. Eighteen samples are drawn from six calculated light-level depths determined by the Secchi depth. Each seawater sample is inoculated with C14 and incubated from LAN to civil twilight at 6 different light levels, simulated 6 different ocean depths. Primary production is determined by C14 uptake by phytoplankton in these samples. Chlorophyll and phaeophytin concentrations are determined from 24hr cold acetone extraction fluorometric measurements of duplicate seawater samples. Nutrients are measured with an auto-analyzer. All 14C radioisotope work is done in a certified, isolated, radioisotope van; all areas are wipe tested multiple times before, during and after the cruise by SIO technical staff.