Response of Dissolved Trace Metals to Dust Storms, Sediment Resuspension, and Flash Floods in Oligotrophic Oceans

Abstract

Trace metals (TM) delivered by atmospheric dust play a key role in oceanic biogeochemical cycles. However, the impact of short-term environmental perturbations such as dust storms and sediment resuspension events on the oceanic water column is poorly constrained due to the low temporal sampling resolution and episodic nature of these events. The Gulf of Aqaba (GoA), Red Sea, is a highly accessible deep oligotrophic water body featuring exceptionally high atmospheric deposition fluxes that provide the main source of TMs to the GoA surface water. Here, we present a 2-year time series of dissolved manganese, cobalt, nickel, copper, zinc, cadmium, and phosphate concentration profiles sampled in the GoA. The study focuses on daily time scale dust storms and episodes of sediment resuspension to quantify the immediate impact of these events on dissolved TM cycling. Counter-intuitively, upper mixed layer TM inventories decrease with increasing aerosol loads, with the effects of aerosol-induced TM scavenging and dissolution peaking 5–6 days after aerosol deposition. Dust storms promote intense TM scavenging, with TM inventories decreasing by up to 44%, but seldom lead to TM enrichment. Similarly, sediment resuspension and flash flood events triggered significant TM scavenging. These findings highlight the potential dual role of atmospheric deposition in the oceans as a long-term source of dissolved TMs and a short-term sink. The in situ observations presented here may be used to understand and quantify the global impact of abrupt environmental events on oceanic chemical compositions.