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 degrees N to 28 degrees S, including waters from the equatorial divergence, the low latitude subtropical gyres, and higher latitudes. These results contradict a recent report that suggests that in some cases GF/F filters 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 observed latitudinal gradients in the North Pacific were present but were much weaker than those found in the South Pacific.