Spatiotemporal variability of secchi depths of the North Arabian Gulf over the last two decades

Abstract Secchi Disk Depth is an important water quality measurement linked to many aspects of coastal and marine ecosystems. Understanding the role of this important indicator at regional scale requires synoptic observations through ocean color sensors, such as Moderate-Resolution Imaging Spectroradiometer (MODIS). In this study, the spatial and temporal distributions of Secchi depths were mapped over the North Arabian Gulf (NAG) from 2003 to 2020 using a regional Secchi depth model. Spatiotemporal patterns and trends of Secchi depths within the NAG were also investigated using time series analysis. Generally, the MODIS SDD retrievals revealed that NAG Secchi depths increased toward south and offshore waters of the study area. The northern areas exhibited very low Secchi depths with monthly means less than 1.7 m, whereas the middle and southern areas had the highest Secchi depths in all seasons with monthly means higher than 9 m. The Secchi depths were lower during the fall and winter seasons while higher during the spring and summer seasons with a general peak in June. The time series analysis approach used in this study can be a systematic guideline for the future remote sensing studies of Secchi depths and other water quality indicators over different geographical locations.