DISSOLVED ORGANIC PHOSPHORUS CONCENTRATIONS IN THE NORTHEAST SUB-ARCTIC PACIFIC-OCEAN

Shipboard determinations of dissolved organic P (DOP) concentrations were made for NE subarctic Pacific Ocean samples with three different oxidation-hydrolysis methods: UV irradiation, acid persulfate digestion, and a rigorous method that combines the UV and persulfate treatments (combination method). The UV technique was 71 +/- 9% and the persulfate technique 83 +/- 9% efficient relative to the combination method for these coastal and open-ocean surface samples. Combination method results indicate that levels of DOP in the mixed layer of the NE Pacific during August and September ranged from 0. 17 to 0.38 mum. These values are comparable to those found for the NW Atlantic in a previous study with similar methodology. A significant inverse correlation (r2 = 0.76) was found between DOP, measured by the combination method, and apparent oxygen utilization. Analysis of a small number of samples by crossflow ultrafiltration showed that 75-85% of DOP in surface seawater was comprised of < 10,000 nominal molecular weight (NMW) material. However, samples taken from 100- and 1,000-m depths were relatively enriched in colloidal (> 10,000 NMW) fractions, which formed 33-100% of the total DOP in these waters.