Spatial and temporal diversity of microbial mats in the shallow-water hydrothermal system of Milos Island (Greece)

Monday, 15 December 2014
Donato Giovannelli1, Dionysis Foustoukos2, Nadine Le Bris3, Stefan Manfred Sievert4, Mustafa Yucel5 and Costantino Vetriani1, (1)Rutgers University, Institute of Marine and Coastal Science, New Brunswick, NJ, United States, (2)Geophysical Laboratory, Washington Dc, DC, United States, (3)UPMC, Univ Paris 06, Laboratoire d'écogéochimie des environnements benthiques, Observatoire Océanologique, Banyuls-sur-Mer, France, (4)Woods Hole Oceanographic Inst, Woods Hole, MA, United States, (5)GEOMAR, Kiel, Germany
Shallow-water hydrothermal vents are ubiquitous but poorly studied geothermal environments. The shallow-water hydrothermal system of Milos Island is a unique study site with vents exhibiting steep geothermal gradients in the presence of light that allows the co-occurrence of photosynthesis and chemosynthesis. The active hydrothermal emissions of the Milos hydrothermal system support complex microbial mats, which are fundamental in engineering the environmental niche in which extremophiles thrive. Because of the shallow depth, the mat community is wiped out during every major storm, when swell and wave action increase, and then it reconstitutes itself over a brief period of time (days). While most studies are focused on the diversity of the community residing in the underlying sediments, little information is available on the diversity and functioning of the mat community, and how it responds to abrupt geodynamic events. Here we report the results of a joint geochemical and microbiological survey of the microbial mats of Milos island, and analyze the spatial and temporal evolution of the mat community following a major storm. Our results show that the community is dominated by Epsilonproteobacteria, although significant variability is present within the systemm. The observed variability correlates with spatial profiles and in situ measurement of temperature and sulfide carried out over a 6 days periods, showing that tides, winds, and abrupt geodynamic events generate intermittent mixing conditions lasting for several hours to days. Diversity and metagenomic analyses of the mature mat provide further information on the metabolic potential of the community and on the influence of environmental factors on ecosystem functioning. Our work lays the basis for studies aimed at resolving the spatial and temporal dynamics of chemoautotrophic microbial communities in shallow-water hydrothermal systems.