Response of the eastern mediterranean microbial ecosystem to dust and dust affected by acid processing in the atmosphere

Michael D. Krom, Zongbo Shi, Anthony Stockdale, Ilana Berman-Frank, Antonia Giannakourou, Barak Herut, Anna Lagaria, Nafsika Papageorgiou, Paraskevi Pitta, Stella Psarra, Eyal Rahav, Michael Scoullos, Eleni Stathopoulou, Anastasia Tsiola, Tatiana M. Tsagaraki

Research output: Contribution to journalArticlepeer-review


Acid processes in the atmosphere, particularly those caused by anthropogenic acid gases, increase the amount of bioavailable P in dust and hence are predicted to increase microbial biomass and primary productivity when supplied to oceanic surface waters. This is likely to be particularly important in the Eastern Mediterranean Sea (EMS), which is P limited during the winter bloom and N&P co-limited for phytoplankton in summer. However, it is not clear how the acid processes acting on Saharan dust will affect the microbial biomass and primary productivity in the EMS. Here, we carried out bioassay manipulations on EMS surface water on which Saharan dust was added as dust (Z), acid treated dust (ZA), dust plus excess N (ZN), and acid treated dust with excess N (ZNA) during springtime (May 2012) and measured bacterioplankton biomass, metabolic, and other relevant chemical and biological parameters. We show that acid treatment of Saharan dust increased the amount of bioavailable P supplied by a factor of ~40 compared to non-acidified dust (18.4 vs. 0.45 nmoles P mg-1 dust, respectively). The increase in chlorophyll, primary, and bacterial productivity for treatments Z and ZA were controlled by the amount of N added with the dust while those for treatments ZN and ZNA (in which excessive N was added) were controlled by the amount of P added. These results confirm that the surface waters were N&P co-limited for phytoplankton during springtime. However, total chlorophyll and primary productivity in the acid treated dust additions (ZA and ZNA) were less than predicted from that calculated from the amount of the potentially limiting nutrient added. This biological inhibition was interpreted as being due to labile trace metals being added with the acidified dust. A probable cause for this biological inhibition was the addition of dissolved Al, which forms potentially toxic Al nanoparticles when added to seawater. Thus, the effect of anthropogenic acid processes in the atmosphere, while increasing the flux of bioavailable P from dust to the surface ocean, may also add toxic trace metals such as Al, which moderate the fertilizing effect of the added nutrients.

Original languageEnglish
Article number133
JournalFrontiers in Marine Science
Issue numberAUG
StatePublished - 2016
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2016 Krom, Shi, Stockdale, Berman-Frank, Giannakourou, Herut, Lagaria, Papageorgiou, Pitta, Psarra, Rahav, Scoullos, Stathopoulou, Tsiola and Tsagaraki.


  • Atmospheric acid processes
  • Dust
  • Eastern Mediterranean
  • Microcosm experiment
  • Nitrogen
  • Phosphorus
  • Trace metals aluminum

ASJC Scopus subject areas

  • Oceanography
  • Global and Planetary Change
  • Aquatic Science
  • Water Science and Technology
  • Environmental Science (miscellaneous)
  • Ocean Engineering


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