ON THE CHLOROPHYLL-A RETENTION PROPERTIES OF GLASS-FIBER GF F FILTERS/

Extensive comparisons of the retention properties of glass-fiber GF/F and 0.2-mu m membrane filters show that these two filter from 46 degre es N to 28 degrees S, including waters from the equatorial divergence, the low latitude subtropical gyres, and higher latitudes. These resul ts contradict a recent report that suggests that in some cases GF/F fi lters underestimate chlorophyll concentration by 4-fold when compared with 0.2-mu m membrane filters. The data set also allowed examination of latitudinal gradients in integrated chlorophyll. Previously observe d latitudinal gradients in the North Pacific were present but were muc h weaker than those found in the South Pacific.