PARENT SESSION
Oral Session # 24: Photosynthesis and Respiration.
Presiding: A Leakey
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 203.
Community composition and photosynthetic rate of photoautotrophs under quartz pebbles in the southern Mojave Desert, California.
Pippen, Jeffrey*,1, Schlesinger, William1, Wallenstein, Matthew1, Klepeis, Debra 2, Mahall, Bruce2, 1 Nicholas School of the Environment and Earth Sciences, Durham, NC, USA2 Department of Ecology, Evolutionary and Marine Biology, Santa Barbara, CA, USA
ABSTRACT- We used 16s rDNA sequences to identify novel species of cyanobacteria beneath translucent quartz pebbles in the desert pavement on an alluvial piedmont of the Coxcomb Mountains in the southern Mojave Desert, California, USA. Transmission of light, as measured with an integrating sphere, was about 0.08% beneath the thickest pieces of quartz (25 mm) harboring these hypolithic autotrophs. The photosynthetic rate ranged from 0.1 to 1.0 micromol m-2 sec-1 in the linear range of its response to light (PAR of 0-50 micromol m-2 sec-1), over which the apparent quantum use efficiency was 0.019. Light-saturated rates of 1.7 to 2.7 micromol m-2 sec-1 were recorded at light intensities of 200 to 400 micromol m-2 sec-1. The hypolithic community has an upper thermal tolerance of > 90 C in laboratory conditions. The quartz pebbles confer a modest greenhouse effect that may be important for photosynthetic activity during cool, wet wintertime periods that prevail in the Mojave Desert.
Key words: Diaphanous rock, Cyanobacteria, Hypolithic environment, Soil biota