The Impact of Atmospheric Dry Deposition Associated Microbes on the Southeastern Mediterranean Sea Surface Water following an Intense Dust Storm

Eyal Rahav,Timor Katz,Adina Paytan,Chia-Te Chien,Galit Ovadia,Barak Herut

doi:10.3389/fmars.2016.00127

Abstract

This study explores the potential impacts of microbes deposited into the surface seawater of the southeastern Mediterranean Sea (SEMS) along with atmospheric particles on marine autotrophic and heterotrophic production. We compared in situ changes in autotrophic and heterotrophic microbial abundance and production rates before and during an intense dust storm event in early September 2015. Additionally, we measured the activity of microbes associated with atmospheric dry deposition (also referred to as airborne microbes) in sterile SEMS water using the same particles collected during the dust storm. A high diversity of prokaryotes and a low diversity of autotrophic eukaryotic algae were delivered to surface SEMS waters by the storm. Autotrophic airborne microbial abundance and activity were low, contributing ~1% of natural abundance in SEMS water and accounting for 1-4% to primary production. Airborne heterotrophic bacteria comprised 30-50% of the cells and accounted for 13-42% of bacterial production. Our results demonstrate that atmospheric dry deposition may supply not only chemical constitutes but also microbes that can affect ambient microbial populations and their activity in the surface ocean. Airborne microbes may play a greater role in ocean biogeochemistry in the future in light of the expected enhancement of dust storm durations and frequencies due to climate change and desertification processes.

Highlights

Aerosols, including mineral-dust, are regularly transported across marine systems, supplying nutrients and trace metals to the surface water (Prospero et al, 2005)
Variability in aerosol composition and changes in ocean hydrography and ecosystem structure at the time of deposition have been invoked in order to explain the diverse responses (Paytan et al, 2009), another possible explanation is the impact of the airborne microbes delivered with the added dust/dry aerosol deposition
The aerosols collected during early September 2015 had a very high fraction of Ca (20%) and were rich in Mg (4.3%), Fe (6.3%), Mn (945 ppm), Sr (450 ppm), Al (∼67 ng mg−1), and Cu (∼25 ng mg−1; Table 2, Table S1)

Summary

Introduction

Aerosols, including mineral-dust, are regularly transported across marine systems, supplying nutrients and trace metals to the surface water (Prospero et al, 2005). Variability in aerosol composition and changes in ocean hydrography and ecosystem structure at the time of deposition have been invoked in order to explain the diverse responses (Paytan et al, 2009), another possible explanation is the impact of the airborne microbes delivered with the added dust/dry aerosol deposition Such microbes, if viable, may interact with ambient microbial populations in the receiving environment. Airborne microbes can remain viable for decades (Gorbushina et al, 2007), and yet, the full extent of this “biological” addition and the ecological importance of airborne microbes in natural environments are unclear (Hervas et al, 2009; Rahav et al, 2016a) This is because our knowledge about the viability and functionality of airborne microorganisms upon deposition in the ocean is scant (Polymenakou et al, 2008)

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Conclusion