Spectrophotometric measurements of absorption coefficients by phytoplankton during RV POLARSTERN cruise PS121 from 11 Aug to 10 Sep 2019

Water samples were taken during North Sea to Fram Strait expedition PS121 with RV Polarstern from 11 Aug to 10 Sep 2019. Water samples were collected from CTD Niskin bottles at five to six different depths from the upper 100 m and additionally from the ship's seawater supply pumped through teflon tubing from about 11m depth during underway as described in Liu et al (2018). All collected samples were filtered through 25 cm Whatman GF/F filters, respectively, under low-vacuum pressure (below 200 mbar). Blank filters were collected by soaking them in 0.2um filtered seawater. Measurements for particulate and non-algal (NAP) absorption were performed directly after filtration the quantitative filtration techniques-intergrative cavity measurement device and procedure from Röttgers et al. (2016) as described in Liu et al. (2018). Phytoplankton absorption (aph) was derived by subtracting the NAP (Bracher et al. 2021) from the particulate absorption.