THE ECOLOGY OFNOSTOC

Abstract

Nostoc is a genus of filamentous cyanobacteria that can form macroscopic or microscopic colonies and is common in both terrestrial and aquatic habitats. Much of the success of Nostoc in terrestrial habitats is related to its ability to remain desiccated for months or years and fully recover metabolic activity within hours to days after re‐hydration with liquid water. Nostoc can also withstand repeated cycles of freezing and thawing and, thus, is an important component of extreme terrestrial habitats in the Arctic and Antarctic. The ability to fix atmospheric N2can provide an advantage in nitrogen‐poor environments. Nostoc also has the ability to screen damaging ultraviolet light in terrestrial and shallow benthic habitats. The genus potentially could be important in paddy rice culture because it fixes nitrogen that may later be released and used by plants; it also may play a role in soil formation and may increase nitrogen input to natural aquatic and terrestrial ecosystems. The abilities to survive in terrestrial habitats and fix N2are important in symbiotic interactions with fungi (lichens), liverworts, hornworts, mosses, ferns, cycads, and the angiosperm Gunnera. Nostoc is somewhat resistant to predation; this probably is related to production of large amounts of sheath material, synthesis of microcystin‐like toxins by some strains, and formation of colonies that are too large for many algivores to consume. Some organisms can subsist on Nostoc, although it may not be a preferred food source. Lytic cyanophages also infect Nostoc, but little is known about population control of Nostoc in its natural environment, Late Precambrian fossils resembling Nostoc have been described, and Nostoc possibly has been an important component of many terrestrial and aquatic communities since that time.

The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

“…This may be the result of the physicochemical gradients in the crusts and of the metabolic differences of the organisms themselves (Garcia-Pichel and Belnap, 1996;Jørgensen et al, 1987;Stal, 2000). Due to extremely high irradiation, the surface of the inorganic layer was the harshest microenvironment of the desert crusts and therefore was colonized only with desiccation-tolerant species (S. javanicum and Nostoc flagelliforme) with high UV screening pigments (Dodds et al, 1995;Garcia-Pichel and Belnap, 1996). However, we have not observed the mortality of species of algae.…”

“…It is also worth noting that the possible reason for the domination of Nostoc sp. only at ST5 (0.02-0.05 mm) might be that ST5 is located in a wooded area; 100% shrub coverage would greatly reduced solar irradiation, therefore the requirement for screening radiation is decreased although spherical Nostoc colonies were also well adaptive to variable stresses (Dodds et al, 1995;Potts, 2000). According to Bowker's (2002) research, UV screening pigment is induced by UV irradiation dosage, not just correlated to the number of cyanobacteria.…”

Non-marine algae of Australia:1. Survey of colonial gelatinous blue-green macroalgae (Cyanobacteria)

“…As we have not done any culturing of specimens, we have not had occasion to observe hormogonal mobility. Some specimens, however, have included small attached colonies (or proliferations, see Dodds et al 1995) in sacks at the margins of thalli. Prescott (1951) accepts a number of species (e.g.…”

Effects of light intensity and quality on phycobiliprotein accumulation in the cyanobacterium Nostoc sphaeroides Kützing

“…The thick surface of the thallus has significant shading effects on its inner structure (Raven and Kübler 2002). Dodds et al (1995) reported that 90 % of the incident light is absorbed by the 100 lm-thick algal filament on the surface of Nostoc while the inner algal filament was shown to receive only minimal light (Gao and Ai 2004).…”