32 D3. The Geochemistry, Biogeochemistry, and Ecology of Cave and Karst Settings

Sunday, 22 October 2017
1:30 PM - 5:30 PM
Room 612

MICROBIAL TEMPORAL DYNAMICS OF A NOVEL GYPSUM KARST SULFIDIC SPRING

Paper number: 32-4
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Monte Conca Cave is a gypsum karst active sink cave in the Messinian evaporates of central-western Sicily. There is a sulfidic spring located in the lower gallery of the cave which varies in size during the wet and dry seasons. There is no surface water flow during the dry season, isolating tiny lakes that are connected to the sulfidic spring by a stream during the wet season. Previous evaluation of the chemical features of this sulfidic spring provided evidence that there is biological activity at work, which is highlighted in the microenvironment of the sulfidic spring. Water samples were taken from the spring during the wet season (June 20, 2015 and February 6, 2016) and the dry season (July 11, 2015 and August 29, 2015). Samples were taken from Spring Level 1 (surface) which comes from Spring Level 2 (deeper) and flows into Little Stream which sometimes becomes External Water.

16s rRNA and 18s rRNA qPCR show that there is more DNA present in the dry season samples than the wet season ones. Fragment analysis revealed that the microbial community structure does not change significantly (p>0.05) from one location to another but does change significantly (p<0.05) by sampling date. This suggests that water likely flows form one collection site to another in a very short time causing the lack of spatial variation. 16s rRNA sequencing from the same samples shows that this temporal pattern can be broken into the wet season samples which show less species variation and dry season samples which show greater species variation. The most abundant species in these samples varies by date, suggesting turnover of the microbial community.

Sulfide levels in the spring reach as high as 14 ppm during the dry season. During the wet season, they drop to 0-1 ppm as the spring is inundated with rainwater and increased flow. Nitrate, normally absent from this system, is present in the spring water during the wet season. Air and water temperatures in the spring are also higher during the dry season and lower during the wet season. Based on these preliminary findings, we suggest that variation in the microbial ecosystem of the Monte Conca Cave sulfidic spring is driven by changes in hydrological factors.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-300284

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