THE ROLE OF VIABLE AIRBORNE MICROBES DELIVERED BY DESERT DUST INTO THE SE MEDITERRANEAN SEA: POTENTIAL ECOLOGICAL IMPLICATIONS

Aerosol deposition may supply a high diversity of airborne organisms including fungi, bacteria and viruses, which can affect surface seawater microbial diversity, abundance and function. We show that these airborne microorganisms may become active upon deposition in seawater and interact (whether positively or negatively) with the ambient microbial populations. Experiments supplemented with dust/aerosol collected during a large Saharan desert dust storm show that airborne microbes caused a specific and rapid decrease in the cyanobacteria Prochlorococcus abundance (max change ~60%, Figure 1). However, other phytoplankton abundances have not declined and primary production and total bacterial production increased (not shown). The addition of UV-killed aerosol resulted in a weaker decrease in Prochlorococcus (max change ~30%, Figure 1), likely due to some chemical toxicity effect. We hypothesize that the rapid demise in Prochlorococcus cells is attributed to airborne viral infection or airborne bacterial predation on the Prochlorococcus cells. Our results demonstrate that dust-born microorganisms can become viable in surface seawater, interact with the surface populations and should thus be considered experimentally and ecologically.