Role of environmental drivers in phototrophic organisms thriving in the caves of America: a systematic review with quantitative synthesis

Abstract

Caves are an ideal niche for photosynthetic microorganisms with the morphological and physiological adaptations to thrive under extreme conditions. Microclimatic conditions, mainly light, temperature, and relative humidity, vary depending on the location and configuration of these cavities. A systematic review with quantitative synthesis was conducted to identify which environmental and ecological factors favored the growth of algae and Cyanobacteriophyta in cave environments of the American continent. To this end, results of studies from 26 caves, corresponding to 10 countries of the American continent, were analyzed. The species number recorded was 358, of which Bacillariophyceae predominated, followed by Cyanobacteriophyta, Chlorophyta, Rhodophyta, Phaeophyceae, Dinoflagellata, and Glaucophyta. The Shannon index determined that the diversity derived from the compiled literature of algae and Cyanobacteriophyta that thrive in these environments was 4.94, which is remarkably high. Nitzschia and Navicula were the most diverse Bacillariophyceae genera, while Oscillatoria and Phormidium dominated among Cyanobacteriophyta, and for Chlorophyta, Chlorella and Scenedesmus were the most diverse. However, Rhodophyta, Phaeophyceae, Dinoflagellata, and Glaucophyta were less diverse. An exploratory principal component analysis suggests that algal and cyanobacterial thriving is determined more by humidity and cave type than by temperature and photosynthetically active radiation.