Abstract
Natural and anthropogenic aerosols are a significant source of trace elements to oligotrophic ocean surface waters, where they provide episodic pulses of limiting micronutrients for the microbial community. However, little is known about the fate of trace elements at the air-sea interface, i.e. the sea surface microlayer. In this study, samples of aerosols, sea surface microlayer, and underlying water column were collected in the Florida Keys during a dusty season (July 2014) and non-dusty season (May 2015) and analyzed for the dissolved and particulate elements Al, Fe, Ni, Cu, Zn, and Pb. Microlayer samples were collected using a cylinder of ultra-pure SiO2 (quartz glass), a novel adaptation of the glass plate technique. A significant dust deposition event occurred during the 2014 sampling period which resulted in elevated concentrations of trace elements in the microlayer. Residence times in the microlayer from this event ranged from 12 to 94 minutes for dissolved trace elements and from 1.3 to 3.4 minutes for particulate trace elements. These residence times are potentially long enough for the atmospherically derived trace elements to undergo chemical and biological alterations within the microlayer. Characterizing the trace element distributions within the three regimes is an important step towards our overall goals of understanding the rates and mechanisms of the solubilization of trace elements following aeolian dust deposition and how this might affect microorganisms in surface waters.
Highlights
Atmospheric deposition is an important source of bioactive trace elements to the surface ocean and can play a large role in marine primary productivity (Boyd et al, 2010; Baker et al, 2016)
In summary, this study investigated dissolved and particulate trace element concentrations in the sea surface microlayer, underlying water column, and atmospheric aerosols during “dusty” (July 2014) and “non-dusty” (May 2015) periods in the Florida Keys
Residence times of dissolved and particulate trace elements in the microlayer ranged from a few minutes to a few hours
Summary
Atmospheric deposition is an important source of bioactive trace elements to the surface ocean and can play a large role in marine primary productivity (Boyd et al, 2010; Baker et al, 2016). Defined as 10 to 1,000 μm in thickness (Cunliffe et al, 2013), the microlayer is enriched in organic compounds that create a semi-rigid film-like layer over the surface ocean. Due to this organic enrichment, the microlayer has physicochemical and biological properties that are different from the underlying water column (Hardy, 1982; Liss and Duce, 2005; Cunliffe et al, 2013), making it a unique environment
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