Microbiological activity in thermoglacial karst springs, south spitsbergen

Along the Hornsund fault zone, South Spitsbergen (76°60’ N), thermokarstic springs smell of H₂S and display either growth of, or eject fragments of, organic slime. The temperature in individual springs varies between 4 and 15°C. Their rate of discharge is ∼1 L s^‐1 to 18 m³ s^‐1, corresponding to a minimum temperature of 30°C within the base of the aquifer. The water, which contains a few ppm SO₄ ^2‐, 0.5 ppm S^2‐, and several thousand ppm NaCl, appears to be a mixture of turbid glacial melt water and hot brine. Water chemistry and stable isotopes indicate that the salinity is not the result of simple dilution of modern seawater from the brackish zone beneath the coastal karst aquifer, but rather originates from a deep thermal brine component where concentrations and isotopic composition of various species are controlled by water‐rock interaction in the source area of the brine. A value of δ³⁴S of up to about 30‰ indicates that sulfide is a bioreduction product of sulfate. Scanning electron microscope (SEM) studies revealed bacteria and fungal hypha in the organic slime, and larger spherical particles (∼3.8 μm diameter) that display high concentrations of Fe and S. These findings demonstrate the presence of sutfate‐reducing bacteria within the sub‐permafrost aquifer.

Keywords:

• karst
• Spitsbergen
• subglacial
• subpermafrost aquifer
• sulfur‐metabolizing bacteria
• thermal springs