Discovery and Description of Giant Submarine Smectite Cones on the Seafloor in Eyjafjordur, Northern Iceland, and a Novel Thermal Microbial Habitat

Abstract

With the submersible JAGO and by scuba diving we discovered three remarkable geothermal cones, rising 33, 25, and 45 m from the seafloor at a depth of 65 m in Eyjafjordur, northern Iceland. The greatest geothermal activity was on the highest cone, which discharged up to 50 liters of freshwater per s at 72°C and pH 10.0. The cones were built up from precipitated smectite, formed by mixing of the hot SiO 2 -rich geothermal fluid with the cold Mg-rich seawater. By connecting a rubber hose to one outflow, about 240 liters of pure geothermal fluids was concentrated through a 0.2-m-pore-size filter. Among 50 thermophilic isolates, we found members of Bacillus and Thermonema and a new unidentified low-G؉C gram-positive member of the Bacteria as well as one member of the Archaea, Desulfurococcus mobilis. Analysis of small-subunit rRNA genes PCR amplified and cloned directly from environmental DNA showed that 41 out of 45 Bacteria sequences belonged to members of the Aquificales, whereas all of the 10 Archaea sequences belonged to the Korarchaeota. The physiological characteristics of isolates from different parts of the cones indicate a completely freshwater habitat, supporting the possibility of subterranean transmittance of terrestrial organisms.Since the discovery of hydrothermal activity on oceanic spreading centers in the Eastern Pacific in 1977 and 1979, hot springs have been found at numerous locations on ridge systems (7, 24). The Mid-Atlantic ridge is one of these systems, and Iceland, with its volcanic activity, is the only place where it emerges from the sea. The Eyjafjordur region, in northern Iceland, is one of several localities in Iceland with known submarine geothermal activity. The geothermal activity is in basaltic lava 6 to 12 million years of age (5, 14) and seems to be related to either one or both of two NNE-and NW-trending fault zones with no known surface hot spring activity (4).Oceanic hydrothermal vent fluids originate from seawater, which percolates into the oceanic crust and is heated at the top of magma chambers or in hot rock formations. The hot fluid, discharged from the seafloor, is anoxic and acidic, with salinity varying from 0.1 to 2 times that of seawater and with variable chemical composition (29). Elements dissolved in the hydrothermal fluid precipitate around the vents, commonly forming characteristic chimney-like structures (6, 9). In such an extreme environment, diverse types of thermophilic microorganisms have been detected and isolated (21).Molecular phylogenetic studies on environmental DNA from hydrothermal vent samples have been limited due to low quantity and poor quality of the collected biomass. Part of the problem at submarine hot springs is that they are difficult to access and samples are therefore precious. A variety of sampling devices have been used to collect hydrothermal vent samples for chemical and microbiological analysis. These include samplers for collecting hot fluid, for collecting particles from both warm and hot fluids, and for measuring in situ microbial...

Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland

“…We speculate that exchange occurs by movement of groundwater through the permeable tephra and basalt that underlies western Vatnajökull (Flowers et al, 2003). Unattached cells are readily transported through basalt (Entry and Farmer, 2001;Marteinsson et al, 2001). The high similarity of Sulfuricurvum sequences from all of our samples and enrichments suggests that it derives from a single population beneath Vatnajö kull.…”

“…C-J enrichments had addition of 50 ml of 100Â yeast-acetate medium and were incubated with 80%/20% H 2 /CO 2 and 0.025% final wt v À 1 Na 2 S 9H 2 O. A-J enrichments were the same as C-J, but incubated aerobically with ambient headspace. Additional enrichments used R 2 A medium and 162 Thermus medium (Degryse et al, 1978), both aerobically with ambient headspace, and Thermotoga ('Toga') medium (Marteinsson et al, 1997) and YPS medium (Marteinsson et al, 2001) under pure N 2 headspace. Growth in enrichments was confirmed with phase-contrast microscopy (Olympus BX51).…”

Microbial colonization in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota

“…The high temperature and the casing of the borehole down to 165 m isolates the bottom environment from the upper layers or surface microorganisms (Ólafsson and Jakobsson, 2009). The high sterilizing temperature atop the borehole suggest indigenous subterrestrial microbiota that have probably disseminated from the below faults and cracks of the seafloor in a similar manner as has been reported for other various subterrestrial environments, geothermal boreholes in Reykjavík (Marteinsson et al, 2001a), fresh water hydrothermal vent cones in Eyjafjörður (Marteinsson et al, 2001b) and in subglacial lakes on Vatnajökull (Marteinsson et al, 2013). Furthermore, our results on the microbial diversity support such deep indigenous subterrestrial microbiota speculations as our 16S rRNA gene sequence showed only similarity to uncultivated taxon originated from the deep biosphere.…”

An oligarchic microbial assemblage in the anoxic bottom waters of a volcanic subglacial lake

“…Filters were stored in DNA extraction buffer (0.1 M pH 8.0 Tris buffer, 0.1 M pH 8.0 Na-EDTA, 0.1 M phosphate buffer, 1.5 M NaCl and 0.5% cetyl trimethyl ammonium bromide) at À80 1C. DNA extraction from filters was performed as described by Marteinsson et al (2001b). DNA was also extracted from 1.5 ml of sample that was centrifuged, the pellet re-suspended in lysis buffer consisting of Tris buffer (50 mM, pH 7.6), EDTA (1 mM, pH 8.0), 0.5% Tween-20 (Sigma-Aldrich, St Louis, MO, USA) and 200 mg ml À1 proteinase K, the buffer incubated for 2 h at 55 1C and then heated to 95 1C for 5 min.…”