170
E. IMRE FRIEDMANN AND MARGALITH GALUN
growth. He maintains, with Petersen (1935), that living algae may possibly
be transported into deeper layers of the aphotic zone by rain, and subsist
there with limited metabolic activity for long periods. He argues that the
number of species generally decreases from the surface layer to the depths,
without any species appearing in deeper layers which was not observed
near the surface.
A different view is held by Soviet researchers (Bolyshev, 1968; Gollerbakh, 1953; Sdobnikova, 1956). In Central Asian takyr soils there is a
marked difference in the qualitative composition of the soil flora in different depths. Blue-green algae are dominant in the layers near the surface
and green algae in greater depths. This is attributed to the low level of
tolerance in the latter group to drought and to insolation. Certain species,
such as Chlorella terricola Hollerb., Chlorella vulgar is Beij., and Muriella
magna Fritsch et John, are characteristic of deeper soil layers. In species
such as Chlorococcum humicola (Nag.) Rabenh. and Phormidium autumnale (Ag.) Trevis., which inhabit a wide range of depths, morphological
differences such as cell size exist between forms living near the surface and
those living at greater depths, and these characteristics were found to be
hereditary (Gollerbakh, 1953).
Despite numerous papers on endedaphic algae in deserts, it is difficult
to draw the general characteristics of their floristic composition, mainly
because reports are based on often conflicting nomenclatures. It can only
be stated that coccoid green and filamentous blue-green algae are dominant, and coccoid blue-green algae, Chrysophyceae, and diatoms are
present in lesser numbers. (This, however, is not necessarily a characteristic of deserts, since similar situations also exist in other soil types.) A few
examples from published data may be cited here. Chantanachat and Bold
(1962) isolated from desert soil samples in Arizona, Utah, Chihuahua
(Mexico), Saudi Arabia, and the Negev Desert (Israel) the following
genera: green algae—Bracteacoccus, Chlamydomonas,
Chlorococcum,
Chlorosarcina, Chlorosarcinopsis, Neochloris, Protosiphon, Radiosphaera,
Scenedesmus, Spongiochloris, and Tetraspora; blue-green algae—
Anabaena, Lyngbya, Nostoc, Oscillatoria, and Scytonema; Xanthophycean
algae and diatoms. Sdobnikova (1959) and Shtina and Bolyshev (1963)
report the following algal genera from Central Asian desert soils: bluegreen algae—Synechococcus, Synechocystis, Microcystis, Gloeocapsa,
Amorphonostoc, Sphaeronostoc, Stratonostoc, Anabaena, Scytonema, Calothrix, Tolypothrix, Oscillatoria, Borzia, Phormidium, Lyngbya, Schizothrix,
Microcoleus, and Plectonema; green algae—Chlamydomonas, Coccomyxa,
Chlorosphaera, Actinochloris, Chlorococcum, Dictyococcus, Chlor ochytrium, Macrochloris, Trochiscia, Fernandinella, Chloroplana, Trebouxia,
Chlorella, Pleurococcus, Borodinella, Gloeotila, Ulothrix, Hormidium,
E. IMRE FRIEDMANN AND MARGALITH GALUN
growth. He maintains, with Petersen (1935), that living algae may possibly
be transported into deeper layers of the aphotic zone by rain, and subsist
there with limited metabolic activity for long periods. He argues that the
number of species generally decreases from the surface layer to the depths,
without any species appearing in deeper layers which was not observed
near the surface.
A different view is held by Soviet researchers (Bolyshev, 1968; Gollerbakh, 1953; Sdobnikova, 1956). In Central Asian takyr soils there is a
marked difference in the qualitative composition of the soil flora in different depths. Blue-green algae are dominant in the layers near the surface
and green algae in greater depths. This is attributed to the low level of
tolerance in the latter group to drought and to insolation. Certain species,
such as Chlorella terricola Hollerb., Chlorella vulgar is Beij., and Muriella
magna Fritsch et John, are characteristic of deeper soil layers. In species
such as Chlorococcum humicola (Nag.) Rabenh. and Phormidium autumnale (Ag.) Trevis., which inhabit a wide range of depths, morphological
differences such as cell size exist between forms living near the surface and
those living at greater depths, and these characteristics were found to be
hereditary (Gollerbakh, 1953).
Despite numerous papers on endedaphic algae in deserts, it is difficult
to draw the general characteristics of their floristic composition, mainly
because reports are based on often conflicting nomenclatures. It can only
be stated that coccoid green and filamentous blue-green algae are dominant, and coccoid blue-green algae, Chrysophyceae, and diatoms are
present in lesser numbers. (This, however, is not necessarily a characteristic of deserts, since similar situations also exist in other soil types.) A few
examples from published data may be cited here. Chantanachat and Bold
(1962) isolated from desert soil samples in Arizona, Utah, Chihuahua
(Mexico), Saudi Arabia, and the Negev Desert (Israel) the following
genera: green algae—Bracteacoccus, Chlamydomonas,
Chlorococcum,
Chlorosarcina, Chlorosarcinopsis, Neochloris, Protosiphon, Radiosphaera,
Scenedesmus, Spongiochloris, and Tetraspora; blue-green algae—
Anabaena, Lyngbya, Nostoc, Oscillatoria, and Scytonema; Xanthophycean
algae and diatoms. Sdobnikova (1959) and Shtina and Bolyshev (1963)
report the following algal genera from Central Asian desert soils: bluegreen algae—Synechococcus, Synechocystis, Microcystis, Gloeocapsa,
Amorphonostoc, Sphaeronostoc, Stratonostoc, Anabaena, Scytonema, Calothrix, Tolypothrix, Oscillatoria, Borzia, Phormidium, Lyngbya, Schizothrix,
Microcoleus, and Plectonema; green algae—Chlamydomonas, Coccomyxa,
Chlorosphaera, Actinochloris, Chlorococcum, Dictyococcus, Chlor ochytrium, Macrochloris, Trochiscia, Fernandinella, Chloroplana, Trebouxia,
Chlorella, Pleurococcus, Borodinella, Gloeotila, Ulothrix, Hormidium,