Direct contribution of phytoplankton-sized particles to optical backscattering in the open ocean
Giorgio
Dall'Olmo, Department of Botany and Plant Pathology, Oregon State University, giorgiod@science.oregonstate.edu
(Presenting)
Toby
Westberry, Department of Botany and Plant Pathology, Oregon State University, westbert@science.oregonstate.edu
Michael
Behrenfeld, Department of Botany and Plant Pathology, Oregon State University, mjb@science.oregonstate.edu
(Presenting)
Emmanuel
Boss, School of Marine Sciences, University of Maine, emmanuel.boss@maine.edu
Wayne
Slade, School of Marine Sciences, University of Maine, wayne.slade@gmail.com
Light scattering properties of the open ocean have been suggested as a better index of phytoplankton biomass than chlorophyll-a concentration (chla) because they are insensitive to physiological forcings, such as light and nutrients, that alter the intracellular concentration of pigments. The drawback of particulate scattering is that it is not unique to phytoplankton. Nevertheless, field studies have demonstrated that variations in the beam-attenuation coefficient (cp) closely track variations in phytoplankton abundance. The relationship between cp and the particulate backscattering coefficient (bbp), the property retrievable from space, has not been fully evaluated, largely due to a lack of open-ocean field observations. Here, we present extensive data on inherent optical properties from the surface Equatorial Pacific and demonstrate a remarkable coherence in bbp and cp. Coincident measurements of particle size distribution (PSD) and optical properties of size-fractionated samples indicate strongly that this covariance is due to both the
conserved nature of the PSD and a greater contribution of phytoplankton-sized particles to bbp than predicted by Mie theory. Importantly, these findings imply that satellite derived bbp could be used to derive information on phytoplankton carbon biomass and physiology in the open ocean.
NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster: