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Question (Bell): What types of biomass measuring techniques have been tried, which work best, and what are some of the confounding factors involved in working with these crusts? Answer: Several methods have been tried. Biomass can be quantified in direct counts using quantitative counting chambers (such as hemacytometer) and fluorescence microscopy. This gives some indication of numbers and kinds of organisms, although only the common cyanobacterial and diatom species can be identified with confidence. Obtaining biovolume estimates can be done with this method but is very laborious. Another direct method is chlorophyll a determination. This is the easiest and fastest method, but has the drawback that lichen phycobionts...
We used microsensors to characterize physicochemical microenvironments and photosynthesis occurring immediately after water saturation in two desert soil crusts from southeastern Utah, which were formed by the cyanobacteria Microcoleus vaginatus Gomont, Nostoc spp., and Scytonema sp. The light fields within the crusts presented steep vertical gradients in magnitude and spectral composition. Near-surface light-trapping zones were formed due to the scattering nature of the sand particles, but strong light attenuation resulted in euphotic zones only ca. 1 mm deep, which were progressively enriched in longer wavelengths with depth. Rates of gross photosynthesis (3.4?9.4 mmol O2�m?2�h?1) and dark respiration (0.81?3.1...
Question (Bell): What types of biomass measuring techniques have been tried, which work best, and what are some of the confounding factors involved in working with these crusts? Answer: Several methods have been tried. Biomass can be quantified in direct counts using quantitative counting chambers (such as hemacytometer) and fluorescence microscopy. This gives some indication of numbers and kinds of organisms, although only the common cyanobacterial and diatom species can be identified with confidence. Obtaining biovolume estimates can be done with this method but is very laborious. Another direct method is chlorophyll a determination. This is the easiest and fastest method, but has the drawback that lichen phycobionts...
The photosynthetic characteristics of the terrestrial cyanobacterium, Nostoc flagelliforme, after complete recovery by rewetting, was investigated to see whether it could use bicarbonate as the external inorganic carbon source when submerged. The photosynthesis?pH relationship and high pH compensation point suggested that the terrestrial alga could use bicarbonate to photosynthesize when submerged. The photosynthetic oxygen evolution rates were significantly inhibited in Na+-free and Na++ Li+ media but were not affected by the absence of Cl?, implying that the bicarbonate uptake was associated with Na+/ HCO3? symport rather than Cl?/HCO3? exchange system. Published in Journal of Phycology, volume 37, issue 5, on...
We describe a population of colonial cyanobacteria (waterwarts) that develops as the dominant primary producer in a bottom-fed, O2-poor, warm spring in the Cuatro Ci�negas karstic region of the Mexican Chihuahuan Desert. The centimeter-sized waterwarts were suspended within a central, conically shaped, 6-m deep well by upwelling waters. Waterwarts were built by an Aphanothece-like unicellular cyanobacterium and supported a community of epiphytic filamentous cyanobacteria and diatoms but were free of heterotrophic bacteria inside. Sequence analysis of 16S rRNA genes revealed that this cyanobacterium is only distantly related to several strains of other unicellular cyanobacteria (Merismopedia, Cyanothece, Microcystis)....