<title>Remote estimation of chlorophyll concentration in polluted marine waters in Haifa Bay, Southeastern Mediterranean</title>

Abstract

Chlorophyll distribution in Haifa Bay was estimated in a period ofveiy high chlorophyll concentrations (up to 70 mg/rn3) using remotely sensed data. Radiometric measurements with spectral resolution of2 urn in the range from 400 to 850 mu, were taken simultaneously with samples for chlorophyll concentration, turbidity and Secchi disk transparency. Prominent features of the reflectance spectra were a wide minimum from 420 to 500 urn, a maximum at 550-570 urn, a minimum at 676 nm and a maximum reflectance showed near 700 nm.High spectral resolution data were used for the selection of the most suitable spectral bands for remote estimating ofchlorophyll concentration. The magnitude and position of the peak near 700 urn were highly correlated with chlorophyll concentration. The reflectance height at 690 nm above the base line from 670 to 850 nm and area above the base line were used as sensitive indicators of chlorophyll concentration. The best model enabled estimation of chlorophyll concentration with an error of less than 4.3 mg/rn3. For the purpose of chlorophyll mapping in Haifa Bay, the use of three relatively narrow spectral bands was sufficient.Radiomethc data were also used to simulate radiances in the channels of TM Landsat and to find the algorithm for chlorophyll assessment. The ratios TM3/TM1 and (TM2-TM3)/TM1 were used and enable chlorophyll estimation with an error ofless than 8 mg/rn3.

Use of Remote Sensing and GIS in Monitoring Water Quality

“…Hyperspectral sensors have been considered as the future sensors to measure chlorophyll concentration in water. The reflectance height at 690nm above the base line from 670nm to 850nm was a sensitive indicator for chlorophyll concentration (Gitelson et al, 1995). Figure 3 shows a Chlorophyll a map of Pensacola Bay Estuary, Florida derived from Landsat 7 ETM+ (Luoheng and Karen, 2005).…”

Comparing Unmanned Aerial Multispectral and Hyperspectral Imagery for Harmful Algal Bloom Monitoring in Artificial Ponds Used for Fish Farming

“…Simultaneously with the water sampling, a handheld fluorometer (FluoroProbe, BBE Moldaenke Inc., Schwentinental, Germany) was used. FluoroProbe is a highly sensitive measuring instrument for the analysis of chlorophyll with algae class determination [12,13]: green algae, blue-green algae/cyanobacteria, diatoms/dinoflagellates, and cryptophytes. It uses six excitation lasers, allowing discrimination of algae groups and correcting the results according to the presence of dissolved organic matter and the turbidity level (of mineral origin) in the waters.…”

“…It is worth noting that almost all of the fifteen most robust models utilized narrow bands between 660 and 730 nm, highlighting the importance of an ideal sensor having at least two bands covering both the absorption peaks at ~660-680 nm and the reflectance maximum at ~700-730 nm from Chl-a [78]. Several studies have tested and confirmed the efficiency of bio-optical models using spectral bands at those wavelengths to estimate Chl-a in continental waters [12,13,41,[79][80][81][82][83][84]. It is worth mentioning that the authors of [13] concluded that there is no universal model for estimating Chl-a, as most models perform better for specific concentration ranges and/or water types and/or for a given location, but not for another set of conditions.…”

“…However, this technique is less feasible in inland waters due to the significant influence of other optically active components (OACs), such as total suspended solids (TSS) and colored dissolved organic matter (CDOM), at these wavelengths. Consequently, narrow bands of intense Chl-a absorption at 660-680 nm and reflectance at 700-720 nm have been used with satisfactory results for monitoring this parameter in inland waters [4,12,13]. For cyanobacteria, the main spectral feature of PC is the absorption effect at 620-630 nm.…”