Abstract
The northern Red Sea (NRS) is a low-nutrient, low-chlorophyll (LNLC) ecosystem with high rates of atmospheric deposition due to its proximity to arid regions. Impacts of atmospheric deposition on LNLC ecosystems have been attributed to the chemical constituents of dust, while overlooking bioaerosols. Understanding how these vast areas of the ocean will respond to future climate and anthropogenic change hinges on the response of microbial communities to these changes. We tested the impacts of bioaerosols on the surface water microbial diversity and the primary and bacterial production rates in the NRS, a system representative of other LNLC oceanic regions, using a mesocosm bioassay experiment. By treating NRS surface seawater with dust, which contained nutrients, metals, and viable organisms, and “UV-treated dust” (which contained only nutrients and metals), we were able to assess the impacts of bioaerosols on local natural microbial populations. Following amendments (20 and 44 h) the incubations treated with “live dust” showed different responses than those with UV-treated dust. After 44 h, primary production was suppressed (as much as 50%), and bacterial production increased (as much as 55%) in the live dust treatments relative to incubations amended with UV-treated dust or the control. The diversity of eukaryotes was lower in treatments with airborne microbes. These results suggest that the airborne microorganisms and viruses alter the surface microbial ecology of the NRS. These results may have implications for the carbon cycle in LNLC ecosystems, which are expanding and are especially important since dust storms are predicted to increase in the future due to desertification and expansion of arid regions.
Highlights
Aerosols impact marine ecosystems by delivering macro- and micronutrients to surface seawater upon deposition [1,2,3]
We investigated the role of dust-associated airborne microbes on primary and bacterial production using the northern Red Sea (NRS) as a model ecosystem
Our results show that microbial diversity is altered by bioaerosols and that while the rates of primary productivity decline, the rates of bacterial production increase in response to the deposition of bioaerosols
Summary
Aerosols impact marine ecosystems by delivering macro- and micronutrients to surface seawater upon deposition [1,2,3]. These nutrients typically induce an increase in phytoplankton abundance and bacterial biomass and activity [4,5,6,7]. The impact of airborne microbes may be important in low-nutrient low-chlorophyll (LNLC) regions, which make up 60% of the global oceans [15], where or when aerosol deposition rates are high. The Gulf of Aqaba (GOA) in the northern Red Sea (NRS) is a LNLC region with high atmospheric deposition due to its proximity to the Arabian, Sahel, Negev, and Sahara deserts
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