The relationship between algal blooms, fish kill incidents, and oxygen depletions along the omani coast

A persistence of hypoxia is a common feature for the Sea of Oman, and the western Arabian Sea. By using historical data complemented by ongoing measurements, the relationship between the frequency of harmful algal blooms, fish kill incidents, and oxygen depletions, was investigated. In the Sea of Oman, the seasonal pattern exhibited a tendency of fish kill incidents to increase, from January to November. In the western Arabian Sea, the pattern was different- maximal occurrence of fish kill incidences was observed in December and January. In 1988-2011, the number of harmful algal blooms accompanied by fish kills was 4 times higher for the Sea of Oman (N= 91) compared to the Arabian Sea coast (N= 22), whereas the total number of fish kill incidents was about the same (22 versus 25). This means that the Arabian Sea coast faced more frequent harmful blooms than the Sea of Oman. The Sea of Oman coastal time series of the dissolved oxygen concentration implied a steady decline throughout the year, from January to December. The fish kill incidents in this region were mainly driven by oxygen depletions, whereas in the Arabian Sea these incidents were mediated by the harmful algal blooms along with the oxygen depletions. In analyzing the Omani coast as a whole, the Ridge Multiple Regression Analysis implied the dissolved oxygen concentration and monthly occurrence of algal blooms as the two variables explaining 75% of the seasonal variations in fish kill incidents.