Figure 4.

Rate of DIC uptake for chemotrophic and phototrophic assemblages sampled from adjacent sides of the photosynthetic fringe in Nymph Creek (fringe pH = 2.99, Temp. = 52.7°C), Bijah Spring (fringe pH = 7.40, Temp. = 70.0°C), and Dragon Spring (fringe pH = 2.95, Temp. = 46.5°C). Microcosms were incubated both in the light and the dark and rates reflect the difference between triplicate killed controls and triplicate biological controls, for each treatment. For comparative purposes, DIC uptake rates were normalized to grams organic nitrogen present in the chemotrophic or phototrophic biomass used as inoculum (Table 1). All spring water used in the microcosms was sampled from the photosynthetic fringe and all microcosms were incubated in situ at the photosynthetic fringe temperature. Rates of DIC uptake for the phototrophic assemblages sampled from Dragon Spring are indicated as insets on the histogram.