Bio-optical properties and ocean color algorithms for coastal waters influenced by the Mississippi River during a cold front

Abstract

During the passage of a cold front in March 2002, bio-optical properties examined in coastal waters impacted by the Mississippi River indicated that westward advective flows and increasing river discharge containing high concentrations of nonalgal particles contributed significantly to surface optical variability. A comparison of seasonal data from three cruises indicated spectral models of absorption and scattering to be generally consistent with other coastal environments, while their parameterization in terms of chlorophyll (Chl) alpha concentration showed seasonal variability. The exponential slope of the colored dissolved organic matter (CDOM) averaged 0.0161+/-0.00054 nm(-1) and nonalgal absorption averaged 0.011 nm(-1) with deviations from general trends observed due to anomalous water properties. Although the phytoplankton specific absorption coefficients varied over a wide range [0.02 to 0.1 m2 (mg Chl)(-1) at 443 nm] being higher in offshore surface waters, values of phytoplankton absorption spectra at the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) wave bands were highly correlated to modeled values. Particulate scattering characteristics were similar to observations for other coastal waters, while backscattering ratios were on average lower in phytoplankton-dominated surface waters (0.011+/-0.003) and higher in low Chl near-bottom waters (0.0191+/-0.0045). Average percent differences in remote sensing reflectance Rrs derived from modeled and in-water radiometric measurements were highest in the blue wave bands (52%) and at locations with more stratified water columns. SeaWiFS estimates of Chl and CDOM absorption derived using regional empirical algorithms were highly correlated to in situ data.

Optical properties of size fractions of suspended particulate matter in littoral waters of Québec

“…In this study, dimensionless Chl / SPM ratios varied between 3.9 × 10 −5 and 1.8 × 10 −3 with a median of 1.1 × 10 −4 and an arithmetic mean of 2.7 × 10 −4 . These values are commonly lower than those reported in coastal waters of the Gulf of Mexico by D'Sa et al (2006) (∼ 10 −3 ), and is consistent with the relatively high a SPM * values obtained in SLS-SF waters.…”

“…This is remarkable given the large diversity of methodologies used by different research teams for estimating a SPM * values (e.g., pad technique, ac-s, integrating sphere). In general, the lowest a SPM * values (i.e., 0.01-0.02 m 2 g −1 at λ = 440 nm) commonly corresponded with samples obtained in very turbid environments (i.e., > 100 g m −3 , Mississippi River and Delta, Gironde River) (Bowers and Binding, 2006;D'Sa et al, 2006;Doxaran et al, 2009). These low values could be overestimated due to an increase on particulate absorption associated with an incomplete removal of multiple scattering effects.…”

Chromophoric Dissolved Organic Matter and Dissolved Organic Carbon from Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), Moderate Resolution Imaging Spectroradiometer (MODIS) and MERIS Sensors: Case Study for the Northern Gulf of Mexico

“…Semi-analytical (SA) inversion models have been developed for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) to derive CDOM and detritus absorption coefficient as a single component (CDM) [11][12][13][14], as both exhibit similar spectral shape and slope in the visible light spectrum [15]. In order to investigate carbon cycling in coastal and estuarine waters (Case-2 waters) where optically active constituents often do not co-vary with chlorophyll-a, knowledge of CDOM's distribution and dynamics is required [16][17][18]. Empirical algorithms, also known as band ratio algorithms, are based on statistical relationships between R rs band ratios and the concentration of seawater constituents [18][19][20][21][22][23].…”

“…In order to investigate carbon cycling in coastal and estuarine waters (Case-2 waters) where optically active constituents often do not co-vary with chlorophyll-a, knowledge of CDOM's distribution and dynamics is required [16][17][18]. Empirical algorithms, also known as band ratio algorithms, are based on statistical relationships between R rs band ratios and the concentration of seawater constituents [18][19][20][21][22][23]. For example, Kahru and Mitchell [19] developed a relationship between a CDOM (300) and SeaWiFS R rs (443)/R rs (510) at the CalCOFI site in southern California.…”

A portable fiber optic system for measuring particle absorption using the quantified filter technique (QFT)

“…In particular, there is great interest in estimating phytoplankton spectral absorption as it often serves as a critical component of bio-optical models of water column production (Sosik 1996;Lohrenz et al 2002;Marra et al 2007;Yoshikawa and Furuya 2008;Lutz et al 2009), remote sensing algorithms (Stramska et al 2003;D'Sa et al 2006;Cannizzaro et al 2008;Wang et al 2008) and radiative transfer models (Zaneveld 2005;Liu et al 2006). The most widely used protocol for measuring particle absorption is to concentrate particles onto optically diffuse glass fiber filters in the field by filtration and measure the absorbance of filter-bound particles (living and detrital) in a laboratory using a dual-beam spectrophotometer.…”