THE OCEANOGRAPHY SOCIETY PACIFIC BASIN MEETING, July 1994, p.62

Freezing as a method of preservation for seawater dissolved nutrient and organic carbon samples

T. Houlihan, J.E. Dore, L. Tupas, D.V. Hebel, G. Tien and D.M. Karl

The successful preservation of seawater samples for later analyses is highly desirable given the rigors of at-sea chemical determinations. Of the many potential preservation techniques, freezing is particularly simple and minimizes sample manipulation and thus potential contamination aboard the research vessel. We report here on experiments to determine the applicability of this preservation method to analyses of dissolved nitrate, nitrite, ammonium phosphate, silicate and organic carbon. We present results of experiments designed to elucidate any potential "freezing effect" and also comparisons of at-sea analyses of fresh samples versus later laboratory analyses of samples maintained in frozen storage. Where possible, both standard and low-level analytical methods have been used to make such comparisons. With certain caveats, we endorse freezing as a method of sample preservation for the above constituents.