Database for time-series stations K2 and S1

Phytoplankton pigment data were obtained from water samples collected with Niskin bottles and include ancillary CTD observations at stations K2 and S1. The pigment data include concentrations of total and size-fractionated ( ＞10 µm, 3–10 µm, 1–3 µm, and ＜ 1 µm) chlorophyll a, and concentrations of accessory pigments measured by high-performance liquid chromatography (HPLC). The data are arranged in one MS Excel file for each cruise.

Phytoplankton pigments were determined on board ship by both conventional fluorometry and HPLC. The fluorometric determination was made with a fluorometer (model 10-AU; Turner Designs, Inc.) by the acidification method (Holm-Hansen et al., 1965) and the non-acidification method (Welschmeyer, 1994). Quantification of phytoplankton pigments by HPLC (Waters Corp. or Agilent Technologies, Inc.) was based on the C8-column method with pyridine in the mobile phase (Zapata et al., 2000).
For fluorometric determinations, water samples (0.15−0.5 L) were filtered through a Whatman GF/F filter (25-mm diameter), and pigments were extracted immediately in N,N-dimethylformamide at –20 °C for 24 h (Suzuki and Ishimaru, 1990). Size-fractionated samples for fluorometric measurements were obtained by sequential filtration of a 1-L water sample through 10-µm, 3-µm, and 1-µm pore size polycarbonate filters (47-mm diameter) and Whatman GF/F filters (25-mm diameter). For HPLC, aliquots of 2–5 liters of water were filtered through a Whatman GF/F filter (47-mm diameter), then dehydrated by vacuum-drying (Furuya et al., 1998), and extracted in N,N-dimethylformamide using the same protocol as the fluorometric assay. Analytical conditions for the fluorometric determination are listed in Table 1. Size-fractionated samples were assayed only with the non-acidification method of Welschmeyer (1994).
The fluorometer was calibrated with a commercially available chlorophyll a standard (Anacystis nidulans, Sigma Chemical Co.). The HPLC system was calibrated with the following pigment standards obtained commercially: chlorophyll a, chlorophyll b, chlorophyll c2, chlorophyll c3, divinyl chlorophyll a, pheophytin a, chlorophyllide a, pheophorbide a, [3,8-Divinyl]-protochlorophyllide, peridinin, fucoxanthin, 19'-butanoyloxyfucoxanthin, 19'-hexanoyloxyfucoxanthin, neoxanthin, prasinoxanthin, violaxanthin, diadinoxanthin, antheraxanthin, alloxanthin, diatoxanthin, zeaxanthin, lutein, crocoxanthin, ß,ɛ-carotene and ß,ß-carotene (Sigma Chemical Co., DHI Co. and WAKO Ltd.).
Zeaxanthin and lutein were not well separated in the chromatogram, especially if the lutein concentration was extremely low compared to the zeaxanthin concentration. Similarly, neoxanthin and violaxanthin were not well separated from other pigments.

Table 1. Analytical conditions of “Non-acidification method” and “Acidification method” for chlorophyll a with Turner Designs fluorometer (10-AU-005).

The following is an explanation of the indicated columns of data.

• Holm-Hansen, O., Lorenzen, C.J., Holmes, R.W., strickland, J.D.H., 1965. Fluorometric determination of chlorophyll. J. Cons. Cons. Int. Explor. Mer. 30, 3-15.
  
• Welschmeyer, N.A., 1994. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnol. Oceanogr. 39, 1985-1992.
  
• Zapata, M., Rodríguez, F., Garrido, J.L., 2000. Separation of chlorophylls and carotenoids from marine phytoplankton: a new HPLC method using a reversed phase C8 column and pyridine-containing mobile phases. Mar. Ecol. Prog. Ser. 195：29-45.
  
• Suzuki, R., Ishimaru, T., 1990. An improved method for the determination of phytoplankton chlorophyll using N, N-dimethylformamide. J. Oceanogr. 46, 190-194.
  
• Furuya, K., Hayashi, M., Yabushita, Y., 1998. HPLC determination of phytoplankton pigments using N,N-dimethylformamide. J. Oceanogr. 54 (2), 199-203.