Absorbance measurements of total particulate and non-algal particulate matter during Heincke cruise HE448 in Sognefjord and Trondheimsfjord, Norway

NAP Abs spectra were measured using the same filters upon bleaching with 90% sodium hypochlorite solution. Water samples were collected from near-surface (4m) and subsurface (close to observed deep chlorophyll maxima (DCM) depths.

Near-surface samples were collected from Ferry-Box system (4HJena, Germany) and the DCM samples were collected from a SBE 911plus CTD system (SeaBird, USA). Water samples of varying volume (0.25 - 0.75 l), depending on water turbidity, were filtered onto 47 mm, pre-combusted, 0.7 μm glass fiber filters (Whatman, GF/F) under low vacuum. Absorbance was measured following the Quantitative Filter Technique (QFT) using a spectrophotometer with integrating sphere (Cary 4000, Agilent Technologies, USA).