Inversion of spectral absorption in the optically complex coastal waters of the Mid-Atlantic Bight

Abstract

Recent advances in hydrologic optics offer the potential for quantitative maps of inherent optical properties, which can be inverted into optically significant constituents. During summer experiments in the Mid-Atlantic Bight (MAB) a procedure to invert bulk absorption measurements from off-the-shelf technology was developed. The inversion provides optical concentration estimates of phytoplankton, colored dissolved organic matter (CDOM), and detritus. Inversion estimates were validated against chlorophyll fluorescence, filter pad absorption, and phytoplankton pigment measurements. The inversion could account for up to 90% of the observed variance in particulates, CDOM, and detritus. Robust estimates for phytoplankton community composition could be achieved but required constraints on the inversion that phytoplankton dominate the red light absorption. Estimates for the composition, as indicated by spectral slopes, for CDOM and detritus were not robust. During the summer months in nearshore waters of the MAB, total absorption was almost equally associated (±10%) with phytoplankton, detritus, and CDOM, and the regions of variability were associated with major frontal boundaries. The variance between particulates, CDOM, and detritus varied spatially and with year; which precluded robust correlations. Copyright 2004 by the American Geophysical Union.