FREEZING AS A METHOD OF SAMPLE PRESERVATION FOR THE ANALYSIS OF DISSOLVED INORGANIC NUTRIENTS IN SEAWATER

It is often desirable or necessary to store collected seawater samples prior to analysis for dissolved inorganic nutrients. It is therefore important to establish preservation and storage techniques that will e nsure sample integrity and will not alter the precision or accuracy of analysis. We have performed a series of experiments on the storage of nutrient samples collected at the oligotrophic North Pacific benchmar k Station ALOHA, using both standard autoanalyses and low-level techni ques. Our results reveal that for oligotrophic oceanic waters, the imm ediate freezing of an unfiltered water sample in a clean polyethylene bottle is a suitable preservation method. This procedure is simple, it avoids potentially contaminating sample manipulations and chemical ad ditions, and it adequately preserves the concentrations of nitrate + n itrite, soluble reactive phosphate, and soluble reactive silicate with in a single water sample.