abstract
Five Marion Island bryophyte species containing epiphytic cyanobacteria showed acetylene reduction in the laboratory at ca. 20癈. Only Ditrichum strictum exhibited reduction in situ at low (around zero) temperatures. This species occurs as a spherical cushion or ball on cold, windswept, rocky plateaux and contains a band of cyanobacteria a few millimetres below the surface of the cushion. The absence of acetylene reduction in situ for mire bryophyte species containing epiphytic cyanobacteria is ascribed to low temperatures during the incubation and it is thought that during the warm summer months fixation by bryophyte-cyanobacteria associations may significantly contribute towards the nitrogen status of mire habitats.
