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

Jianming Deng; Hans W Paerl; Boqiang Qin; Yunlin Zhang; Guangwei Zhu; Erik Jeppesen; Yongjiu Cai; Hai Xu

doi:10.1016/j.scitotenv.2018.07.208

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

Sci Total Environ. 2018 Dec 15:645:1361-1370. doi: 10.1016/j.scitotenv.2018.07.208. Epub 2018 Jul 23.

Authors

Jianming Deng¹, Hans W Paerl², Boqiang Qin³, Yunlin Zhang⁴, Guangwei Zhu⁴, Erik Jeppesen⁵, Yongjiu Cai⁴, Hai Xu⁴

Affiliations

¹ Taihu Lake Laboratory Ecosystem Research Station, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; University of Chinese Academy of Sciences, Beijing 100049, China.
² Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, NC 28557, United States; College of Environment, Hohai University, Nanjing 210098, China.
³ Taihu Lake Laboratory Ecosystem Research Station, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: qinbq@niglas.ac.cn.
⁴ Taihu Lake Laboratory Ecosystem Research Station, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁵ Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; Sino-Danish Centre for Education and Research (SDC), University of Chinese Academy of Sciences, 100049 Beijing, China.

PMID: 30248859
DOI: 10.1016/j.scitotenv.2018.07.208

Abstract

Surface wind speed has declined significantly globally. However, the response of aquatic systems to decreasing wind speeds has received little attention. We examined the effects of a long-term decrease in wind speed on shallow, eutrophic Lake Taihu, China's third largest lake, by combining high-frequency monitoring, long-term meteorological and water quality data with short-term laboratory sediment nutrient release experiments. The annual mean wind speed showed a significant decreasing trend and the maximum continuous days with wind speed <3 m/s increased significantly from 1996 to 2017. The high-frequency monitoring data showed that bottom water hypoxia occurred occasionally in summer and autumn. The water quality data combined with the experimental results suggest that lower wind speed and longer low wind duration can enhance the release of phosphorus (P) from the sediments and increase nitrogen (N) losses, likely via denitrification, because a longer stability period leads to lower dissolved oxygen concentrations near the lake bottom. The results of Bayesian functional Linear regression with Sparse Step functions (Bliss) indicated that wind speed during spring and summer strongly affected chlorophyll a (Chla) concentrations in the summer by enhancing the release of nutrients from the sediments. The results of the structural equation models indicated that declined wind speed might increase phytoplankton biomass (as Chla) by altering nutrient availability. Increasing water temperatures and decreasing wind speeds synergistically enhance water column stability, which may offset some of the immediate benefits of reductions in external nutrient loading by enhancing internal loading. Given predicted global change, it will become increasingly important to reduce the external nutrient loading for overall improvement of water quality in this and other shallow eutrophic lakes.

Keywords: Atmospheric stilling; Daily stratification; Internal loading; Lake management; Water quality.