Hawaii Ocean Time-series (HOT)
in the School of Ocean and Earth Science and Technology at the University of Hawai'i at Manoa
» Home » Analytical Results » Fluorometric Pigments

Fluorometric Pigments

Chlorophyll Filtration
FTP View Data
Methods View Method
To assist in the interpretation of the data, it can be displayed using the Hawaii Ocean Time-series Data Organization & Graphical System (HOT-DOGS©).

Sampling Procedure

Samples for Chlorophyll a (chl a) and pheopigments were collected onto glass fiber filters (Whatman GF/F, 25 mm diameter) and measured fluorometrically on a Turner Designs Model 10-AU flourometer with 100% acetone as the solvent using standard techniques (Strickland and Parsons, 1972). It is known that this method will underestimate chlorophyll a in the presence of chlorophyll b (Welschmeyer 1994). The average precisions during 2022 determined from triplicate analyses are presented in the Table below.


Chlorophyll a Pheopigments
Cruise CV (%) SD (µg/l) N CV (%) SD (µg/l) N
335 1.7 0.003 5 6.3 0.016 5
336 9.4 0.024 4 7.6 0.026 4
337 19.3 0.031 4 17.5 0.042 4
338 4.8 0.010 4 11.7 0.026 4
339 6.3 0.010 4 6.7 0.023 4
Mean 8.3 0.016 5 10.0 0.027 5

Results

A contour plot of chlorophyll a concentrations measured using standard fluorometric techniques from 0 to 200 dbar during 1988-2022 is shown in Figure 45. A chlorophyll maximum with concentrations up to about 0.3 mg m-3 is observed at approximately 110m depth. The magnitude of this feature exhibits significant interannual variability, with a pronounced period of low chlorophyll concentration lasting from 1992-1998. Chlorophyll a concentrations at depths shallower than 50m display an annual cycle with winter maxima and summer minima.