Climatically-modulated decline in wind speed may strongly affect eutrophication in shallow lakes

Area of Science:

• Environmental Science
• Limnology
• Ecology

Background:

• Global surface wind speeds have significantly declined.
• The impact of reduced wind speed on shallow, eutrophic aquatic systems remains understudied.
• Lake Taihu, China's third largest lake, is experiencing decreased wind speeds.

Purpose of the Study:

• To investigate the effects of long-term decreased wind speed on Lake Taihu's water quality.
• To understand how wind speed influences nutrient dynamics and phytoplankton biomass in shallow eutrophic lakes.

Main Methods:

• Combined high-frequency monitoring, long-term meteorological and water quality data.
• Conducted laboratory sediment nutrient release experiments.
• Utilized Bayesian functional Linear regression with Sparse Step functions (Bliss) and structural equation models.

Main Results:

• A significant decreasing trend in annual mean wind speed and increased duration of low wind conditions were observed.
• Lower wind speeds enhanced phosphorus release from sediments and increased nitrogen losses via denitrification.
• Decreased wind speed, particularly during spring and summer, significantly increased chlorophyll a concentrations by promoting nutrient release.

Conclusions:

• Declined wind speed, coupled with rising water temperatures, enhances water column stability, increasing internal nutrient loading.
• This internal loading can counteract reductions in external nutrient inputs, hindering overall water quality improvement.
• Reducing external nutrient loading is crucial for improving water quality in Lake Taihu and similar lakes under global change.