Effects of climate change on aquatic systems and their microbial communities

FERMANI P

Mendoza

Simposio; SAIB (2022). Reunión Anual Edición LVIII.; 2022

SAIB

Climate change is considered one of the most serious threats to ecosystems worldwide. Different stressors, such as land use intensification and global climate change have significant consequences for aquatic resources and their microbial communities. Microorganisms are the most diverse and functionally important organisms on Earth, intricately linked to human health and ecosystem services; however the response to these stressors in different ecosystems are still under debate. Shallow lakes are good sentinels of global climate change because they are sensitive to environmental variations and can integrate shifts in the surrounding landscape and atmosphere. In particular, Pampean lakes experienced changes in land use over the last two centuries, and these variations were reflected in the aquatic communities. Agriculture and livestock activities increasing even more the inherent nutrient contents in nearby water bodies, causing most lakes to change from a pristine clear state to turbid water with high phytoplankton abundance. In many of these shallow Pampean lakes, hypereutrophic conditions do exist, with extremely high chlorophyll-a concentrations and abundances of microorganisms (e.g. bacteria, picoyanobacteria) among the highest recorded in the literature worldwide. The eutrophication increase in these shallow lakes was concurrent with the massive conversion to glyphosate-resistant crops technologies, adopted by major grain producer countries. Glyphosate (N-(phosphonomethyl) glycine) is a broad-spectrum herbicide that is presently among the most widely used agricultural chemicals globally. Several experimental and field studies have shown the stimulatory effect of glyphosate on picocyanobacteria. This tolerance to glyphosate was linked to the presence of the PhnD gene, capable of degrading phosphonates. Data collected shows that long-term agricultural practices relying on glyphosate-based technologies had important effects on freshwater microbial communities, particularly by promoting increases in picocyanobacteria abundance.Furthermore, according to the Intergovernmental Panel on Climate Change, global average temperature has risen by 1.2ºC over the last 50 years; and, if greenhouse gas emissions are not reduced, global warming of 1.5°C and 2°C above pre-industrial levels will be exceeded during the 21st century. For the central region of Argentina, climate change models predict an increase of 2.5-3.5°C in 2100. Temperature is one of the most important environmental variables determining the functioning of aquatic communities. Warming influences microorganism’s growth and physiology. Microcosm studies revealed that interactions between microorganisms are weaker with increasing water temperature and the transfer of matter and energy to the higher trophic levels could be lower. In the area of the Antarctic Peninsula, where the changes are more pronounced, physiological modifications of the microorganisms were observed.