Hawaii Ocean Time-series (HOT)
in the School of Ocean and Earth Science and Technology at the University of Hawai'i at Manoa

Fluorometric Pigments

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

Analytical Method

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 2018 determined from triplicate analyses are presented in the Table below.


Chlorophyll a Pheopigments
Cruise CV (%) SD (µg/l) N CV (%) SD (µg/l) N
299 5.2 0.011 4 6.6 0.028 4
300 1.7 0.003 7 6.3 0.004 7
301 4.0 0.008 8 3.8 0.010 8
302 1.2 0.002 4 3.1 0.013 4
303 5.5 0.007 6 6.0 0.016 6
304 3.7 0.005 6 6.8 0.013 6
305 6.6 0.005 6 5.7 0.008 6
306 5.5 0.005 6 3.0 0.006 6
307 7.9 0.004 6 5.3 0.012 6
308 4.4 0.010 2 5.5 0.009 2
Mean 4.6 0.006 10 5.2 0.012 10

Results

A contour plot of chlorophyll a concentrations measured using standard fluorometric techniques from 0 to 200 dbar during 1988-2018 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.