Synoptic Measurements of Chlorophyll- a and Suspended Particulate Matter in a Transitional Zone from Polluted to Clean Seawater Utilizing Airborne Remote Sensing and Ground Measurements, Haifa Bay (SE Mediterranean)

Abstract

The hyperspectral Compact Airborne Spectrographic Imager (CASI) sensor was implemented to monitor water quality in a transitional zone from polluted to clean seawater, in Haifa Bay and adjacent river estuaries, at the northern part of the Mediterranean coast of Israel. Synoptic measurements of optical data acquired from the airborne scanner were used to map chlorophyll- a (chl- a) and suspended particulate matter (SPM) concentrations in surface waters in the study area. This airborne hyperspectral scanner was found as an expedient monitoring tool for the relatively small geographic area of the current study, as it enabled to reveal the patchy distribution, and sharp concentration changes of the mapped water characteristics. The distribution of SPM concentrations in Haifa Bay was mainly dictated by the polluted riverine inputs, with concentrations between 1 and 3 mg l −1 at its seaward border and higher by more than 1 order of magnitude at the river estuaries. The chl- a concentrations mapped and measured in this survey were unusually low (<2 μg l −1) due to a long-period intermission of anthropogenic phosphate and nitrate input to the bay. SPM and chl- a spatial distributions along the lower rivers system exhibit variations which could be plausibly explained by the hydrological structure and geochemical impacts on the riverine water sources. The correlation between SPM and some particulate heavy metal concentrations was found as a useful tool for monitoring such environmental hazardous substances.