Eutrophication, the cycle in which nutrients overstimulate the growth of potentially harmful plankton and cyanobacterial “blooms” in freshwater lakes, is a problem in more than 60% of the world’s groundwater. The problem is set to worsen due to climate change, and therefore our priority is to further reduce external nutrient inputs to reduce the basis of cyanobacterial bloom outbreaks.
The study of a lake in China, an important source of water for more than 20 million people and for industry, established the mechanisms between heat waves in the lake and potentially toxic cyanobacteria blooms.
The research of Dr. Iestyn Woolway of Bangor University and research colleagues at the Chinese Academy of Sciences, Nanjing, China and Aarhus University, Denmark, published in General Environmental Science studied the heat wave experienced in 2022 in Lake Taihu, one of China’s largest freshwater lakes located in the Yangtze delta, and the associated cyanobacteria blooms. (Cyanobacterial are similar to plankton. Under certain conditions they can thrive in freshwater causing damage to other plants and animals).
Rising surface air temperatures are one of the most recognized consequences of man-made climate change. In lakes, these conditions are exacerbated by “runoff” from other human activities that add nutrients to the lakes, this in turn, helps cyanobacteria to thrive. The increase in surface water temperature of the lake has an effect on the entire environment of the lake.
Woolway says, “In addition to reducing run-off into freshwater as a result of our activities, we must work towards systematic monitoring, prediction and early warning to reduce harmful impact of heat waves on lake ecosystems We need to better understand the mechanisms and triggers of lakes with different levels of nutrients to develop strategies to address and adapt to climate change.
“The whole thing becomes a vicious circle when heat waves occur. An increase in temperature reduces vertical mixing within the freshwater column. This benefits the buoyant cyanobacteria that float and forms dense blooms on the surface. These dense blooms, in turn, slightly increase the temperature of the water.
“The low winds experienced during heat waves also contribute to reduced mixing in the water column and reduced dissolved oxygen in the water. In turn, the low level of dissolved oxygen at the bottom of the lake increases the release of phosphorus from the sediment, which supports the growth of more cyanobacteria.
“Heat waves are predicted to increase eleven-fold this century, and they will have a significant negative impact on the structure, function, and ecosystem services of water systems.”
Na Li et al, Unprecedented 2022 extreme summer heatwaves increase harmful cyanobacteria blooms, General Environmental Science (2023). DOI: 10.1016/j.scitotenv.2023.165312
Provided by Bangor University
Citation: Linking mechanics of lake heat waves and potentially toxic blooms (2023, July 17) retrieved July 18, 2023 from https://phys.org/news/2023-07-linking-mechanics -lake-potentially-poisonous.html
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