Hawaii Ocean Time-series (HOT)
in the School of Ocean and Earth Science and Technology at the University of Hawai'i at Manoa
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Chlorophyll a, b and c by TD-700

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 Chlorophyll Filtration
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Sampling Procedure

In mid-2000 we started measuring chlorophyll a, b and c on a Turner Designs TD-700. Samples were filtered onto 25 mm GF/F glass fiber filters and put into 100% acetone similar to the standard fluorometric method. Samples were analyzed using the wavelength filters shown in Table 1 below. The average precisions during 2006 determined from triplicate analyses are presented in Table 2. Figure 50 shows the relationship between chlorophyll a measured using the TD-700 and chlorophyll a measured using the 10-AU as well as chlorophyll a, b and c measured by HPLC during 2006.


Table 1: Wavelength filters used for TD-700 Chlorophyll analyses

Chlorophyll Ex Em
a 436 680
b 480 650
c 450 630

Table 2: Precision of TD-700 Chlorophyll analyses during 2006

Chlorophyll a Chlorophyll b Chlorophyll c
Cruise CV (%) SD (µg/l) N CV (%) SD (µg/l) N CV (%) SD (µg/l) N
177 0.9 0.002 4 11.3 0.007 4 7.4 0.001 4
178 5.7 0.003 6 13.9 0.009 6 9.5 0.001 6
179 2.7 0.004 6 28.4 0.020 6 6.5 0.001 6
180 1.5 0.003 6 16.9 0.005 6 5.4 0.001 6
181 3.8 0.005 6 9.1 0.004 6 6.7 0.001 6
182 3.2 0.006 6 10.5 0.010 6 6.7 0.002 6
183 2.7 0.003 6 14.8 0.005 6 10.8 0.003 6
184 3.3 0.006 6 18.0 0.008 6 4.2 0.001 6
188 2.2 0.005 6 16.9 0.010 6 6.6 0.001 6
Mean 2.9 0.004 9 15.5 0.009 9 7.1 0.001 9

Results

Contour plots of TD-700 analyzed chlorophylls a, b and c from 0 to 200 dbars are shown in Figure 51. For every pigment, a maximum is observed at approximately 120 meters. Chlorophyll a concentrations by fluorometry show an annual cycle with winter maxima and summer minima. During HOT-116 (June 2000), chlorophyll a concentrations increased dramatically in the upper 45 m of the water. This feature appears associated with a large bloom of diatoms, as evidenced from the shap increases in chlorophyll c, particulate silica (Figure 69) and fucoxanthin (Figure 48).