README_NAAMES_IOPs

Water samples for the particulate absorption coefficient were collected in 2L Dark Nalgene bottles, filtered onto 25-mm-diameter Whatmann GF/F glass fiber filters, and were immediately frozen in liquid nitrogen until analysis. Particulate absorption coefficient spectra, ap(λ), were determined using the quantitative filter technique (Mitchell et al., 2000). Optical density spectra (350–700 nm) were made with the Lambda 18 spectrophotometer, a blank baseline (Milli-Q) was subtracted, and the resulting baseline-subtracted optical density spectra were corrected for multiple scattering effects with a beta correction determined using methods described in Nelson et al. (1998) and Morrison and Nelson (2004). Detrital particulate absorption, ad(λ), was estimated using the same procedure after extracting these filters in methanol for a minimum of 4 h at room temperature (Mitchell et al., 2000). The phytoplankton absorption coefficient spectrum, aph(λ), was determined as the difference between ap(λ) and ad(λ).

Reported data include the particulate absorption spectrum (ap), the detrital absorption spectrum (ad), the phytoplankton absorption spectrum (aph), the phytoplankton specific absorption spectrum (a*ph), particulate absorbance and the standard deviation from multiple measurements on the same filter pad (abs_ap and abs_ap_sd, respectively), and the detrital absorbance and respective standard deviation made from multiple measurements of the same filter pad (abs_ad and abs_ad_sd). 

References:

Mitchell, B. G., A. Bricaud, K. Carder, J. Cleveland, and G. Ferrari (2000), Determination of spectral absorption coefficients of particles, dissolved material and phytoplankton for discrete water samples.

Morrison, J. R., and N. B. Nelson (2004), Seasonal cycle of phytoplankton UV absorption at the Bermuda Atlantic Time-series Study (BATS) site, Limnology and Oceanography, 49(1), 215–224, doi:10.4319/lo.2004.49.1.0215.

Nelson, N. B., D. A. Siegel, and A. F. Michaels (1998), Seasonal dynamics of colored dissolved material in the Sargasso Sea, Deep Sea Research Part I: Oceanographic Research Papers, 45(6), 931–957, doi:10.1016/S0967-0637(97)00106-4.