Comparison of Microhabitats of Macroscopic Subalpine Stream Algae

Comparative studies of the microhabitats of the algae Hydrurus foetidus, Monostroma quaternarium and two species of Batrachospermum have disclosed differences which apparently control the specific distribution of these algae within the same subalpine stream beds. Hydrurus attached primarily to sandstones in bright, direct sunlight and exhibited cytological deterioration, decreases in chlorophyll and rates of photosynthesis following 6 days' transfer to the dimmer nearby habitats of Batrachospermum vagum and B. testale. Batrachospermum, which attached to many rock types, grew only in shaded areas and exhibited rapid deterioration such as bleaching, reduction in chlorophyll and photosynthetic rates when moved to the brighter habitats of Hydrurus or Monostroma. Monostromd tolerated a wide range in light intensities, but showed exceptional specificity for iron-rich conglomerates. Monostroma thrived exclusively just below the water surface on the downstream sides of conglomerates with their holdfasts intimately associated with the black iron-rich mineral(s). These findings are documented by laboratory and field measurements and experiments.