Temperature Optima for Algae Inhabiting Cold Mountain Streams

Abstract

Optimal temperatures for photosynthesis were determined for natural populations of algae inhabiting cold mountain streams in the Beartooth Mountains in Montana and Wyoming. Site temperatures at the time of sampling and the predominant organisms present in the samples were as follows: 1°C, Protococcus sp.; 7°C, mixture of Phormidium and Oscillatoria spp.; 12°C, Zygnema sp. Temperatures from 20 to 30°C were optimal for all the samples, regardless of site temperature and the organisms present in the population. Protococcus sp. was obtained in culture, and even after maintenance at low temperature for 2 years, the optimal temperature for photosynthesis was identical to that for the natural population. These microorganisms were, therefore, not optimally adapted to the low temperatures of their habitat.