Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E86

The microbial mats of Vonarskarð

Snædís H. Björnsdóttir (1,2), Sólveig K. Pétursdóttir (2), Andri Stefánsson (1), Nicole S. Keller (1), Haukur Jóhannesson (3), Guðmundur Óli Hreggviðsson (1,2)

1. Háskóli Íslands, 2. Matís, 3. Jarðfræðiþjónusta Hauks Jóhannessonar

Kynnir / Presenter: Snædís H. Björnsdóttir

Tengiliður / Corresponding author: Snædís H. Björnsdóttir (snaedis@hi.is)

The caldera of the Vonarskarð central volcano hosts a geothermal system that is unique in many ways, with unusual abundance of visible microbial mats and geothermal surface features characterized by extremely high runoff of thermal water. The species composition in samples from various hot springs in the area was determined and the estimated diversity was high compared to that of other geothermal sites in Iceland. Diverse and thick microbial mats were observed, many of which were vividly colored due to light harvesting pigments and alteration mineralogy. Three microbial mats were selected for further examination. All formed in neutral steam-heated water of similar origin. However, the sulfur and iron speciation differed between the springs and the appearance of the mats was remarkably different. Most prominent was a thick white sulfur mat that extended downstream for over hundred meters with green intervals at lower temperatures. Scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) revealed irregular structures high in both sulfur and carbon. Dark material consisting of slender filaments, spherical cells and iron sulfide mineralization formed around another outflow and was encircled by a white mat below 73°C, which harbored cells of different sizes. The third examined mat was a photosynthetic mat that formed at oxidized conditions and at a temperature gradient. It was green and orange-red at temperatures below and above 55°C, respectively. SEM-EDS and community analysis revealed the dominance of cyanobacteria and filaments were observed on the surface of the green mat, whereas the surface of the orange mat was covered with sheaths encrusted in iron silicates, composed of amorphous silica and iron oxyhydroxides.