DOI: 10.48457/iopan.2025.388
title: Particulate absorption spectra (350-750 nm) collected in the Woodfjorden (Spitsbergen) in August 2024.

description: This data sets contains spectra of the light absorption coefficients of particles (ap(λ), m-1), detritus (ad(λ), m-1) and phytoplankton pigments (aph(λ), m-1). Samples were collected on during the AREX-2024 cruise on r/v Oceania, in the leg dedicated to a Horizon Europe SeaQuester project in the Woodfjorden, Northern Spitsbergen, between 20-26 August 2024. Water samples were collected at three depths, at the surface, at the Deep Chlorophyll-a Maximum (DCM) and below it. The depth at which the DCM was located was determined from chlorophyll-a fluorescence profile measured by the standard fluorometer attached to the CTD rosette. Collected water samples were filtered onboard using Whatman filters (GF/F, 25 mm). Filters with the retained material were stored in liquid nitrogen or in deep-freeze conditions until the measurements. Measurements were performed in the land based laboratory in the Institute of Oceanology Polish Academy of Sciences, Sopot, Poland, using a Perkin-Elmer Lambda 650 spectrophotometer equipped with an integrating sphere with a diameter of 15 cm.. The spectra of light absorption coefficients were measured in the spectral range of 350-750 nm according to the methodology described by Tassan and Ferrari (1995, 2002) and Woźniak et al. (2011). Transmission and reflectance (T-R) measurements were performed for filters with suspended particles and again after bleaching with 2% sodium hypochlorite NaClO2 (Meler et al., 2020). To account for the optical path extension of light on the filter with suspension in relation to the same suspension in water, the beta factor correction was applied according to formulae developed by Stramski et al. (2015). This allowed to determine the spectra of the light absorption coefficient by all particles, ap(λ), as well as the absorption by bleached and mineral particles, (detritus -both organic and mineral), ad(λ). The light absorption coefficients by phytoplankton pigments aph(λ) were then calculated as the difference between ap(λ) and ad(λ) coefficients.
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