You are here:
Spatio-temporal dynamics of inherent optical properties in oligotrophic northern Gulf of Mexico estuaries
Citation:
Sari Austuti, I., D. Mishra, S. Mishra, AND B. Schaeffer. Spatio-temporal dynamics of inherent optical properties in oligotrophic northern Gulf of Mexico estuaries. Continental Shelf Research. Elsevier BV, AMSTERDAM, Netherlands, 166:92-107, (2018). https://doi.org/10.1016/j.csr.2018.06.016
Impact/Purpose:
Estuaries are complex coastal systems where freshwater meets seawater making this?? environment a productive, suitable habitat, and source of food for numerous aquatic organisms?? (Levinton, 1982; Carlton, 1989; and Ma, 2005). Estuaries also provide social and economic? services including tourism, recreational activities, and port facilities (Pendleton, 2010). The connection with terrestrial environments make estuaries prone to anthropogenic disturbances.?? Nutrient over-enrichment is a widespread threat to coastal estuaries because eutrophication?? impacts reduce the benefits of the water body. Eutrophication impacts include changes in algal populations and species composition, decreased light availability, reduced oxygen supply, and ?? increased organic matter production (Murrell et al., 2007). Increased anthropogenic activities ?? near coastal and estuarine environments lower the ability to provide fisheries stock, and nursery?? habitats (Barbier et al., 2011). Coastal areas in Florida have undergone rapid development and?? are in need of continuous and real-time monitoring of water quality for improving coastal ?? management practices. Traditional in situ monitoring is time consuming, resource intensive, and still only provides limited spatial and temporal coverage. Remote sensing offers a powerful alternative to provide information about the water quality of these estuaries in a synoptic, rapid,?? near real-time, and inexpensive way. With these advantages, coastal managers may benefit by?? integrating satellite remote sensing into existing monitoring protocols for studying the water?? quality in these estuarine environments (Schaeffer et al., 2012; Jolliff et al.; and Keith et al.,?? 2014). The northern Gulf of Mexico Florida estuaries are one of these areas experiencing rapid?? development. Previous studies in these estuaries focused on the hypoxic condition in Pensacola?? Bay (Hagy and Murrell., 2007), and nutrients and productivity in Escambia Bay (Murrell et al.,?? 2007) indicates these estuaries are subject to physical factors such as flow, wind and tides.?? Rapid development in the surrounding watersheds will likely further impact the estuarine water quality, and integration of satellite remote sensing with traditional assessments can lead to a rapid monitoring tool to quantify changes.
Description:
Coastal and estuarine ecosystems provide numerous economic and environmental benefits to society. However, increasing anthropogenic activities and developmental pressure may stress these areas and hamper their ecosystem services. Satellite remote sensing could be used as a tool for monitoring water quality parameters, including inherent optical properties (IOP) in coastal regions. Spatio-temporal information on IOP variability will help in understanding the dynamics of the water quality of estuaries. The objective of this research was to develop a novel hybrid model by combining and parameterizing existing quasi analytical and semi-analytical algorithms to estimate IOPs in four oligotrophic northern Gulf of Mexico Florida estuaries. The hybrid model was applied to above surface remote sensing reflectance data representing the Medium Resolution Imaging Spectrometer (MERIS) and Sentinel-3's Ocean and Land Colour Instrument (OCLI) bands. The hybrid model produced a root means squared error (RMSE) of 0.32 m−1 (13.95% NRMSE) for total absorption (at), 0.21 m−1 (7.61% NRMSE) for detritus-gelbstoff absorption (adg), and 0.09 m−1 (22.77% NRMSE) for phytoplankton pigment absorption (aphi). Results showed that absorption by detritus and gelbstoff (adg) dominates the water in these estuaries. Monthly IOP variability in 2010 revealed that compared to other estuaries, magnitudes of IOPs was the highest in Pensacola Bay and therefore the highest attenuation. Findings also indicated that river discharge and precipitation predominantly govern the IOP variations in all four estuaries, showing an increase in IOP values following the high flow period. The hybrid model improved IOP retrieval in these low chlorophyll-a (Chl-a) estuaries where the existing spectral decomposition models did not perform satisfactorily.
URLs/Downloads:
DOI: Spatio-temporal dynamics of inherent optical properties in oligotrophic northern Gulf of Mexico estuaries