Impacts of a recurrent resuspension event and variable phytoplankton community composition on remote sensing reflectance

Abstract

[1] In order to characterize the impact of turbidity plumes on optical and biological dynamics, a suite of environmental parameters were measured in southern Lake Michigan during the springtime recurrent sediment plume. In-water measurements of inherent optical properties (IOPs) were entered into the Hydrolight 4.2 radiative transfer model and the output was compared with measured apparent optical properties (AOPs) across a wide range of optical conditions. Hydrolight output and measured underwater light fields were then used to clarify the effects of the sediment plume on primary production, phytoplankton community composition, and nearshore remote sensing ocean color algorithms. Our results show that the sediment plume had a negligible effect on the spectral light environment and phytoplankton physiology. The plume did not significantly alter the spectral quality of available light and did not lead to light limited phytoplankton populations compared to non-plume conditions. Further, the suspended sediment in the plume did not seriously impact the performance of ocean color algorithms. We evaluated several currently employed chlorophyll algorithms and demonstrated that the main factor compromising the efficacy of these algorithms was the composition of phytoplankton populations. As phycobilin-containing algae became the dominant species, chlorophyll algorithms that use traditional blue/green reflectance ratios were compromised due to the high absorption of green light by phycobilin pigments. This is a notable difficulty in coastal areas, which have highly variable phytoplankton composition and are often dominated by sharp fronts of phycobilin and non-phycobilin containing algae.

Coastal Sediment Dynamics and River Discharge as Key Factors Influencing Coastal Ecosystem Productivity in Southeastern Lake Michigan

“…We summarize results from a combined approach using in situ optical measurements and remote sensing to characterize sediment distributions and properties during resuspension events, we track algal distributions, and we assess basin-scale temporal and spatial patterns in primary production. Our (Millie et al, 2003;Bergmann et al, 2004;Chen et al, 2004;Vanderploeg et al, 2007).…”

Deriving in situ phytoplankton absorption for bio‐optical productivity models in turbid waters

“…Most satellite algorithms are based on case 1 waters where the in situ absorption and water-leaving radiance (Lw) signal in the blue wavelengths are dominated by chlorophyll absorption while Lw in the green wavelengths is relatively insensitive to chlorophyll concentrations [Gordon and Morel, 1983]. Inaccuracies in this approach arise in coastal waters that contain significant amounts of other absorbing/ scattering compounds such as dissolved organics, detritus, and even variable phytoplankton communities [Morel and Prieur, 1977;Bergmann et al, 2004]. These errors directly impact the utility of optical techniques for estimating primary production and in turn impacts our understanding of carbon flux and nutrient recycling in nearshore ecosystems and their relation to ecosystem function [Jickells, 1998;Cloern, 2001].…”

Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

“…Both scattering and backscattering coefficients are primarily controlled by mineral concentration (TSS) as reported by several authors [45,63,[65][66][67][68]. Increasing TSS concentration yielded positive and significant (p <0.05) correlation with b p (660) , b bp (660) , and a p (440) .…”