Submersed macrophyte restoration with artificial light-emitting diodes: A mesocosm experiment

Ye-Xin Yu; Yan Li; Hai-Jun Wang; Xiao-Dong Wu; Miao Zhang; Hong-Zhu Wang; David P Hamilton; Erik Jeppesen

doi:10.1016/j.ecoenv.2021.113044

Submersed macrophyte restoration with artificial light-emitting diodes: A mesocosm experiment

Ecotoxicol Environ Saf. 2021 Dec 1:228:113044. doi: 10.1016/j.ecoenv.2021.113044. Online ahead of print.

Authors

Ye-Xin Yu¹, Yan Li², Hai-Jun Wang³, Xiao-Dong Wu⁴, Miao Zhang⁵, Hong-Zhu Wang⁶, David P Hamilton⁷, Erik Jeppesen⁸

Affiliations

¹ State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; College of Fisheries, Huazhong Agricultural University, Wuhan, China. Electronic address: yuyx@ihb.ac.cn.
² State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China. Electronic address: liyan@ihb.ac.cn.
³ Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China. Electronic address: wanghj@ihb.ac.cn.
⁴ College of Urban and Environmental Sciences, Hubei Normal University, Huangshi, China. Electronic address: wuxd@hbnu.edu.cn.
⁵ State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China. Electronic address: zhangmiao@ihb.ac.cn.
⁶ State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China. Electronic address: wanghz@ihb.ac.cn.
⁷ Australian Rivers Institute, Griffith University, Nathan, Australia. Electronic address: david.p.hamilton@griffith.edu.au.
⁸ Department of Bioscience and WATEC, Aarhus University, Vejlsøvej, Silkeborg, Denmark; Limnology Laboratory, Department of Biological Sciences, Middle East Technical University, Ankara, Turkey; Sino-Danish Centre for Education and Research (SDC), University of Chinese Academy of Sciences, Beijing, China; Centre for Ecosystem Research and Implementation (EKOSAM), Middle East Technical University, Ankara, Turkey; Institute of Marine Sciences, Middle East Technical University, Mersin, Turkey. Electronic address: ej@bios.au.dk.

PMID: 34863077
DOI: 10.1016/j.ecoenv.2021.113044

Abstract

Urban lakes are important natural assets but are exposed to multiple stressors from human activities. Submersed macrophytes, a key plant group that helps to maintain clear-water conditions in lakes, tend to be scarce in urban lakes, particularly when they are eutrophic or hypertrophic, and their loss is linked, in part, to impaired underwater light climate. We tested if enhancing the underwater light conditions using light-emitting diodes (LEDs) could restore submersed macrophytes in urban lakes. Twelve mesocosms (1000 L each) were each planted with tape grass (Vallisneria natans) and monitored over three months (22 August-7 November), using a control and three artificial light intensity treatments (10, 50, and 100 µmol m^-2 s^-1). Compared with the control, the high light treatment (100 µmol m^-2 s^-1) had higher leaf number, maximum leaf length, and average leaf length (3.9, 5.8, and 2.8 times, respectively). Shoot number, leaf number, leaf dry mass, root dry mass, and photosynthetic photon flux density in the high-light treatment were significantly greater than the control, but root length and phytoplankton chlorophyll a were not related to plant growth variables and were low in all treatments. Periphyton chlorophyll a increased significantly with the plant growth variables (i.e., shoot number, leaf number, and maximum leaf length) and was high in the light treatments but did not hamper the growth of the macrophytes. These results indicate that LED light supplementation enables the growth of V. natans under eutrophic conditions, at least in the absence of fish as in our experiment, and that the method may have potential as a restoration method in urban lakes. Lake-scale studies are needed, however, to fully evaluate LED light supplementation under natural conditions where other stressors (e.g., fish grazing) may need to be controlled for successful restoration of urban lakes.

Keywords: Eutrophication; LED; Macrophyte restoration; Urban lakes.