PRODUCTION AND RESPIRATION IN THE 1989 NORTH-ATLANTIC SPRING BLOOM - AN ANALYSIS OF IRRADIANCE-DEPENDENT CHANGES

Gross and net O-2 production rates at 47 degrees N, 20 degrees W over 13 days during the 1989 JGOFS North Atlantic (Spring) Bloom Experiment were measured. Gross O-2 production was measured by H-2 O-18 uptake o r calculated from C-14 assimilation, and net O-2 production was measur ed by Winkler 2 titration. Production versus irradiance P-B(I) curves were constructed from gross O-2 production rates (determined with in s itu incubations) normalized to chlorophyll a concentration for the fiv e days of highest total irradiance. Magnitudes of P-m(B), alpha and be ta were high during the bloom. Chlorophyll-normalized gross O-2 produc tion, integrated over the euphotic zone, was observed to be linearly r elated to integrated incident irradiance. This linear trend can be sim ulated with an algorithm using average values of P-m(B), alpha and bet a parameters. 24 h O-2 respiration rates for each day appeared to cons ist of two components: one proportional to the production rate and inv olving respiration of carbon fixed during the same day's photoperiod, and the other independent of the production rate and respired carbon f ixed prior to the day's photoperiod. Integrated over time and depth, t hese respiration components were of comparable magnitude, and together equalled about 60% of gross O-2 production. POC turnover times ranged from two days for near-surface waters up to about two weeks at the ba se of the euphotic zone.