Absorbance of particles retained on GF/F (0.7 µm) filters was measured using a Varian Cary 100 spectrophotometer equipped with an integrated sphere. Absorbance and reflectance spectra were measured by placing a sample filter in front and back of an integrating sphere, respectively (so-called Transmittance-Reflectance or T-R method; Tassan & Ferrari 1995; doi:10.4319/lo.1995.40.8.1358). An appropriate beta factor specific to the geometry of the instrument was used to calculate absorption coefficients of particles (Tassan & Ferrari 2002; doi:10.1093/plankt/24.8.757).
Empty cells = NA