Harsh environment sensor array-enabled hot spring mapping

We report the design, fabrication, and application of temperature and electrical conductivity sensor arrays for studying the harsh environments of hot springs at Yellowstone National Park. Centimeter-scale measurements are necessary to measure sharp gradients in geochemical parameters across the photosynthetic/nonphotosynthetic transition zone known as the photosynthetic fringe. Platinum, parylene-C, and fused quartz were the critical materials used in fabrication of both sensor arrays. More than 700 temperature and 90 conductivity measurements were taken in the mixing zone, where two geochemically distinct hot spring channels converged. We present a new technique, whereby microscale temperature measurements can be used to predict ion concentrations that represent the bulk ion chemistry via electrical conductivity (or other conservative chemicals) in this mixing zone. High-spatial-resolution data confirm that the strong temperature gradients across these regions largely determine where photosynthetic organisms appear.