ASSOCIATION OF PLEUROCAPSA AND CALOTHRIX (CYANOPHYTA) IN A THERMAL STREAM1, 2

摘要: A crustose, nodular mat, primarily composed of Calothrix sp. and Pleurocapsa sp., occurs in some alkaline hot springs the western United States. Together, these species constituted ca. 71% mat biomass; remainder was partitioned between other cyanophytes bacteria. Their temperature growth ranges culture were 24 to 50 C (Calothrix) 30 55 (Pleurocapsa). Both clonal cultures had maximal rates at 45 (Pleurocapsa, 1.28 doublings/24 h; 2.30). grew approximately twice rate throughout their coincidental range. The relative proportions (42%) (27%) constant a thick (ca. 1 mm) regardless season; however, thin 0.5 contained significantly more (71%) less (5%). Analysis 10 ..mu..m microtome sections showed that dominated innermost region (substrate side) nodule while abundance increased from 3% this 80--96% surface samples 0.8 2.3 mm). Our proposal grazing pressure exerted by an ostracod population accounts for continued coexistence observed spatial relationships appears most consistent withmore » observations.« less