Spatial Interpolation of Two-Wavelengths Bio-Optical Models to Estimate the Concentration of Chlorophyll-a in A Tropical Aquatic System

Igor Ogashawara,Petala Bianchi Augusto-Silva,Enner Herenio De Alcântara,José Luiz Stech,Claudio Clemente Faria Barbosa

doi:10.5539/ep.v2n3p52

Abstract

Bio-optical models have been used to estimate and map the concentration of chlorophyll-a (chl-a) in aquatic systems. Bio-optical models’ algorithms try to infer the concentration of optically active components in water from their inherent optical properties (IOPs). We proposed the use of two single wavelengths to retrieve chl-a concentration in a tropical aquatic system. The results were compared to in situ measurements of chl-a. To spatialized the results of the bio optical modeling, we tested the spatial interpolation following two methods: (1) ordinary kriging technique was used to spatialize the calculated values of estimated chl-a for each model; (2) ordinary kriging was used to spatialize the estimated Rrs from 470nm and 700nm then the two wavelengths models were calculated by a map algebra using the spatialized Rrs. We generated four different spatial interpolations of chl-a concentration. They were compared to the spatialized reference based on the in situ chl-a collected in the reservoir of Itumbiara–Goias in the same period. The comparison was performed through the Spatial Language for Algebraic Geoprocessing (LEGAL) implemented at SPRING software. Results showed a better accuracy for the procedure using the spatialization of Rrs and map algebra of them. Thus the spatializaton of proximal remote sensing measurements in order to retrieve the optically active components in water should be performed through the interpolation of the Rrs.

Highlights

Chlorophyll-a has been use as a parameter to calculate the trophic state index (TSIs) of an aquatic system
To spatialized the results of the bio optical modeling, we tested the spatial interpolation following two methods: (1) ordinary kriging technique was used to spatialize the calculated values of estimated chl-a for each model; (2) ordinary kriging was used to spatialize the estimated Rrs from 470nm and 700nm the two wavelengths models were calculated by a map algebra using the spatialized Rrs
Stability is one of the various factors contributing to the stratification and mixing of an aquatic system. It is a measure for physical forcing on phytoplankton communities. These results demonstrate the importance for a parameterization of a bio-optical model for tropical complex aquatic systems

Summary

Introduction

Chlorophyll-a (chl-a) has been use as a parameter to calculate the trophic state index (TSIs) of an aquatic system It has been use as an indicator of photoautotrophic biomass which could be related to primary productivity (Huot et al, 2007). It is the responsible to cause severe oxygen depletion which causes fish mortalities It is the responsible for the death of cattle and other animals from ingestion of cyanotoxins (Melack, 2000). Phytoplankton blooms interferes in the decrease of light penetration through the water column (Boyer, Kelble, Ortner, & Rudnick, 2009). This process could depress seagrass growth and productivity

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