Aerosol Microbiome over the Mediterranean Sea Diversity and Abundance

Esra Mescioglu,Jordan Eizenga,Eyal Rahav,Barak Herut,Adina Paytan,Natalia Belkin,Peng Xian,Ania Vichik

doi:10.3390/atmos10080440

Abstract

Prokaryotic microbes can become aerosolized and deposited into new environments located thousands of kilometers away from their place of origin. The Mediterranean Sea is an oligotrophic to ultra-oligotrophic marginal sea, which neighbors northern Africa (a major source of natural aerosols) and Europe (a source of mostly anthropogenic aerosols). Previous studies demonstrated that airborne bacteria deposited during dust events over the Mediterranean Sea may significantly alter the ecology and function of the surface seawater layer, yet little is known about their abundance and diversity during ‘background’ non-storm conditions. Here, we describe the abundance and genetic diversity of airborne bacteria in 16 air samples collected over an East-West transect of the entire Mediterranean Sea during non-storm conditions in April 2011. The results show that airborne bacteria represent diverse groups with the most abundant bacteria from the Firmicutes (Bacilli and Clostridia) and Proteobacteria (Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria) phyla. Most of the bacteria in our samples have previously been observed in the air at other open ocean locations, in the air over the Mediterranean Sea during dust storms, and in the Mediterranean seawater. Airborne bacterial abundance ranged from 0.7 × 104 to 2.5 × 104 cells m−3 air, similar to abundances at other oceanic regimes. Our results demonstrate that airborne bacterial diversity is positively correlated with the mineral dust content in the aerosols and was spatially separated between major basins of the Mediterranean Sea. To our knowledge, this is the first comprehensive biogeographical dataset to assess the diversity and abundance of airborne microbes over the Mediterranean Sea. Our results shed light on the spatiotemporal distribution of airborne microbes and may have implications for dispersal and distribution of microbes (biogeography) in the ocean.

Highlights

IntroductionProkaryotic microorganisms are found in the air over the global ocean in substantial numbers, with a median abundance of 6.7 × 103 m−3 air [1] and are referred to as ‘airborne microbes’
Prokaryotic microorganisms are found in the air over the global ocean in substantial numbers, with a median abundance of 6.7 × 103 m−3 air [1] and are referred to as ‘airborne microbes’.These airborne microbes can originate from both land [2,3] and the ocean [4,5]
aerosol optical depth (AOD), which includes mineral dust, anthropogenic and biogenic fine aerosol species (ABF), smoke, and sea salt, during the cruise ranged from 0.11 to 0.36, with the lowest values measured during collection of sample 16 and the highest measured during collection of sample 12, both collected from the Western Mediterranean Sea (MS) (Figures 1 and 2, Table 1)

Summary

Introduction

Prokaryotic microorganisms are found in the air over the global ocean in substantial numbers, with a median abundance of 6.7 × 103 m−3 air [1] and are referred to as ‘airborne microbes’. These airborne microbes can originate from both land [2,3] and the ocean [4,5]. Wind can transport microbes over great distances, including across large ocean basins and seas [6,7,8,9,10]. Airborne microbes are deposited with dry (aerosol particles) or wet (rain) atmospheric deposition back onto

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Conclusion