The influence of temperature and light penetration on the abundance of the hypolithic algae in the Negev desert of Israel

Abstract

Hypolithic algae were found under flint pebbles in the northern part of the Negev desert in Israel. The algae appeared in the contact area between the stone and the loess soil in which it is partially buried. Two types of flint were found in the research area: dark transparent ones and light opaque ones. A significant difference was found in the distribution of algae in these two types: 46.8% of the dark flints bear algae up to a thickness of 40 mm in the main range of 5 to 15 mm, whereas the respective figure for the light flints was 20.9% up to 30 mm only and in the thickness range of mainly 5 to 10 mm. No significant difference could be shown concerning the temperature underneath the two types of flint stones. The dark flint had a higher extinction coefficient than the light flint and this means that a greater amount of light penetrates to a deeper thickness in the dark flint than in the light. It may be assumed that the differences in light penetration explain the wider distribution under the dark flint than the light flint.

The ecology of sublithic terrestrial algae at the Vestfold Hills, Antarctica

“…The maximum recorded temperature of 12°C was about 40 centigrade degrees lower than that recorded in the Negev Desert (Berner & Evanari, 1978). The mean minimum winter temperature would be at least 20 centigrade degrees below the 0°C recorded in the Negev Desert.…”

“…Vogel (1955) found 0.06 ~o incident light penetration at a depth of 25 mm, the deepest at which algae occurred. Only 0.01 ~ of photosynthetically active radiation penetrated to the deepest algae below 40 mm thick flint stones in the Negev Desert (Berner & Evanari, 1978). At the Vestfold Hills algae were found even deeper below the soil surface, and below stones of greater total thickness, but light penetration was greater.…”

“…Different mineral content and amounts of internal fracturing of the rocks in different regions is probably responsible for the range of results. It has been suggested that lower light levels would be required by antarctic sublithophytes than those in warmer regions (Thompson, 1979) and that heterotrophy could explain their deepest occurrence (Berner & Evanari, 1978).…”

The spatial structures of hypolithic communities in the Dry Valleys of East Antarctica

“…These communities have been reported from many hot deserts including the Mojave (Schlesinger et al 2003;Smith et al 2014), Atacama (Warren-Rhodes et al 2006;Azúa-Bustos et al 2011;Lacap et al 2011), Negev (Friedmann et al 1967;Berner and Evenari 1978;Wierzchos et al 2012) and Namib (Stomeo et al 2013) and in other semiarid and hyperarid regions (Tracy et al 2010;Pointing et al 2007;Wong et al 2010;Weber et al 2013). …”

Hydration status and diurnal trophic interactions shape microbial community function in desert biocrusts

“…Cyanobacteria) within the biocrust (Berner and Evenari, 1978;Davies et al, 2013). To represent light penetration and the diurnal day-night cycle, we express irradiance, I (z; t), as a function of depth z and time t:…”