Impacts of Climate Change on Cyanobacteria in Aquatic Environments
Hans W. Paerl
from: Climate Change and Microbial Ecology: Current Research and Future Trends (Second Edition) (Edited by: Jürgen Marxsen). Caister Academic Press, U.K. (2020) Pages: 1-36.
Cyanobacteria are the Earth's oldest oxygenic phototrophs and they have had major impacts on shaping its biosphere; starting with the formation of an oxic atmosphere. Their long evolutionary history (>2.5 billion years) has enabled them to adapt to geochemical and climatic changes, including numerous cooling and warming periods, volcanism and accompanying atmospheric physical-chemical changes, extreme dry and wet periods, and recent anthropogenic modifications of aquatic environments, including nutrient over-enrichment (eutrophication), chemical pollution, water diversions, withdrawal and salinization. Combined, these modifications have promoted a worldwide proliferation of cyanobacterial blooms that are harmful to ecological and animal (including human) health. In addressing steps needed to stem and reverse this troubling trend, nutrient input reductions are a 'bottom line' necessity, regardless of other physical-chemical-biotic control strategies that are applied. Cyanobacteria exhibit optimal growth rates and bloom potentials at relatively high water temperatures; hence global warming plays a key interactive role in their expansion and persistence. Additional manifestations of climatic change, including increased vertical stratification, salinization, and intensification of storms and droughts and their impacts on nutrient delivery and flushing characteristics of affected water bodies, play synergistic roles in promoting bloom frequency, intensity, geographic distribution and duration. Rising temperatures cause shifts in critical nutrient thresholds at which cyanobacterial blooms can develop; thus nutrient reductions for bloom control may need to be more aggressively pursued in response to climatic changes taking place worldwide. Cyanobacterial bloom control must consider both N and P loading reductions formulated within the context of altered thermal and hydrologic regimes associated with climate change read more ...