Role of atmospheric nutrient pollution in stimulating phytoplankton growth in small area and shallow depth water bodies: Arabian Gulf and the sea of Oman

Abstract

Limited investigations into the role of dust deposition in enhancing phytoplankton growth in small and shallow water areas have been reported in the remote sensing literature. In this work, we show that phytoplankton growth was stimulated by nutrients supplied by dust deposition over sea water following three major dust storms that blew over the Arabian Gulf (AG) and the Sea of Oman (SO). Shallow water conditions, as those found in the AG and SO, limit convection and the role of mixing processes in supplying nutrients and in mediating bloom growth. Using satellite data, we analyzed three major dust events over the AG and SO in 2009, 2012, and 2015, and the phytoplankton bloom enhancement that ensued. We used the Mixed Layer Depth model to simulate water mixing and convection currents during and after the high dust events. We also applied the Regional Climate Model RegCM 4.5 to derive dust depositions patterns over AG and SO following the dust outbreak. Additionally, we computed potential requirement versus supply of nitrogen, phosphorus, and iron nutrients to support the observed phytoplankton growth using published nutrient data. Carbon to nitrogen to phosphorus, and carbon to chlorophyll ratios were obtained from in situ measurements in the AG and SO. Shallow depth mixed layers can likely still supply phosphate, but not enough nitrate and iron, leading to potential nitrate and dissolved iron limitations. Our work shows that dust storms are playing a significant role in providing nitrate supplies to support phytoplankton growth in shallow waters such as the AG and SO.