DETERMINING CHLOROPHYLL ON THE 1984 CALCOFI SURVEYS

Two sources of error may be relevant to the 1984 CalCOFI chlorophyll data set. These are discussed and their magnitude estimated. The first error is due to the use of GF/C glass fiber filters, which do not completely retain the smallest phytoplankters. This error is important mainly in more oligotrophic waters, where its relative bias is of the order of -15%. The second error arises from the incomplete recovery of chlorophyll from the filter when the filter is not ground in acetone but is allowed to extract in acetone for 24 hours. The relative bias introduced is about -8%. Taking into account both of these errors, the most accurate estimate of the true chlorophyll concentration falls in the range 1.1 to 1.3 times the observed concen