Phytoplankton pigments composition and concentrations measured with HPLC methods in water samples collected in Europen Arctic in 2000-2022

Sea water samples were collected in the Arctic region, usually from the surface, the deep chlorophyll a maximum layer, and below the euphotic zone. Samples were obtained during cruises on RV Oceania in summer seasons between 2000 and 2022 (AREX expeditions), as well as on RV Akademik Ioffe (spring 2002 and summer 2003), RV Polarstern (spring 2003), RV DANA (summer 2021), and RV Maria S. Merian (summer 2022).

Immediately after collection, seawater samples were filtered through Whatman GF/F glass-fibre filters (f = 25 mm) under gentle vacuum and stored in liquid nitrogen (-196 °C) until laboratory analysis to improve extraction efficiency and minimise pigment alterations. Measurements were performed in the land-based laboratory at the Institute of Oceanology Polish Academy of Sciences (IO PAN), Sopot, Poland. Pigments were extracted from cells by mechanical grinding and sonication (2 min, 20 kHz, Cole Parmer, 4710 Series) in darkness conditions at 4 ºC for 2 hours using 90% acetone solution (Parsons et al. 1984). After centrifugation (20 min., 4 ºC, 3210xg, Beckman, GS-6R) to remove the filters and cellular debris, extract was subjected to the chromatographic analysis. The chromatographic system HP1200 (Agilent, Perlan Technologies) was equipped with diode array absorbance detector, fluorescence detector and C18 LichroCART™LiChrospher™ 100 RP18e (Merck) analytical column (dimension 250 x 4 mm, particle size 5 μm and pore size 100 Å). Pigments separation, qualification and quantification was performed according to methodology described in Stoń-Egiert and Kosakowska (2005) using a gradient mixture of methanol, 1 M ammonium acetate and acetone used as a mobile phase. Pigments detection was based on their retention time and absorbance spectra, while quantification base on an external standardization equation combining the chromatographic parameters of individual pigments with their concentration. Calibration of chromatographic system was performed using commercially available chlorophylls and carotenoids standards (The International Agency for 14C Determination DHI Institute for Water and Environment in Denmark). The documented measurement precision was 2.9% ± 1.5% and a recurrence error was 9.7%±6.4% (Stoń-Egiert et al., 2010).

Parsons TR, Maita Y, Lalli CA (1984) A manual of chemical and biological methods for seawater analysis. Pergamon Press, Oxford

Stoń-Egiert J, Kosakowska A (2005) RP-HPLC determination of phytoplankton pigments – comparison of calibration results for two columns. Mar Biol 147:251–260.