Scripps Institution of Oceanography

Satellite imagery is now being used to estimate the near-surface chlorophyll concentration for large ocean areas. To assess the accuracy and precision of these remote sensing techniques, contemporaneous ship and satellite data for the determination of oceanic chlorophyll concentrations have been collected. Since chlorophyll fluorometry is a widely used technique for the determination of chlorophylls at sea, our analyses have led us to review the literature of fluorometry in order to re-examine the assumptions and approximations made when using this field technique.

This report gives a summary of the general concepts of fluorometry, examines important assumptions, presents an outline of an established fluorometer calibration technique, and estimates the accuracy and precision of this methodology. Also included are field observations of the discrete chlorophyll to fluorescence ratio, of the variability of discrete chlorophyll determinations using various particle collecting filters, and of diurnal fluorescence ratio comparisons.

The launch of the Nimbus-7 satellite in October 1978 carrying the Coastal Zone Color Scanner (CZCS) has made possible optical measurements of the oceans from space. Algorithms are presently being developed to relate these optical spectral measurements to the chlorophyll present in the water. Our purpose is to outline our own consistent methodology of along track shipboard fluorescence for the concurrent comparison with satellite derived values of chlorophyll. This report is not intended as a definitive statement on fluorometric techniques, but rather a working document describing our field techniques. Hence, although the theory is general, the specifics apply to the Turner and Turner Designs fluorometers.