Characterization and Detection of HABs in the Arabian Gulf

Abstract

Harmful Algal Blooms (HABs) are one of the most significant pollutants that have frequently observed in the Arabian Gulf in the last three decades. Presence of these pollutants can affect the quality of the water and human health, kill the fish and the aquatic habitats, and damage the water intake and treatment systems of desalination plants, and in some extreme cases cause the closure of the desalinations plants for extended period. Monitoring and prompt response to HAB outbreaks is becoming a high priority for the public as well as for governmental and nongovernmental organizations in the region. Satellite-based monitoring is becoming an effective and indispensable tool for monitoring water quality parameters over large water bodies. The use of remote sensing technology in HABs detection and monitoring has increased recently due to the unique characteristics and features currently available on numerous remote sensing platforms such as the high temporal and spatial resolutions, which allow covering large areas of oceans, seas, and lakes. Ocean colors Satellites (MODIS, MERIS) data have been successfully used for water quality monitoring and mapping worldwide. However, the application of these tools in the Arabian Gulf region requires a special attention and further adaptation due to its unique climate and water properties: turbid and shallow waters and dusty atmosphere. This thesis covers two scientific fields, which are: 1) the biological science, and 2) applied remote sensing. In terms of the biological science, an intensive effort has been made to have a full characterization and understanding of species involved in the HAB events that have occurred in the region. Several field campaigns with intensive sampling and lab work were performed as part of this study. HAB species have been collected during outbreak events and went through full biological, chemical and physical analysis. The lab work included analysis of algal species, including morphology, their physical and chemical medium and their toxicity level using advanced lab technologies such as the fluorimeter, HPLC, and electronic microscope. This lab work complemented other in situ measurements, including the measurement of spectral properties of the water and the overlying atmosphere. These bio-optical measurements have been matched with satellite images acquired within 6 hours interval with timing of the field measurements. Then, in-depth bio-optical modeling was performed to calibrate, validate existing ocean color models and propose new formulations more adapted to our region of study. These models were also supported with atmospheric modeling taking into consideration the specific dusty conditions in the Gulf region to reduce the effect of atmosphere on the satellite-retrieved water properties. Accurate ocean color models are required to detect these HABs in the Arabian Gulf and Sea of Oman due to their turbid water and atmosphere. These models can be based on the fluorescence or Chlorophyll-a. For this purpose, unique field data, such as bio-optical, physical, chemical and spectral, was collected between 2013 and 2016 in the Arabian Gulf and Sea of Oman. Based on this data, we have developed a regionally-adapted and more precise model than the conventional ocean color models to detect HABs accurately using the MODIS fluorescence even in turbid atmospheres. In addition, a robust MODIS Chlorophyll-a driven model was also developed, taking the turbid atmosphere and water into account.

Date of Award	Dec 2016
Original language	American English
Supervisor	Mohamed Hosni Ghedira (Supervisor)