title: Hydrological regulation drives regime shifts: evidence from paleolimnology and ecosystem modeling of a large shallow Chinese lake.
abstract: Quantitative evidence of sudden shifts in ecological structure and function in large shallow lakes is rare, even though they provide essential benefits to society. Such 'regime shifts' can be driven by human activities which degrade ecological stability including water level control (WLC) and nutrient loading. Interactions between WLC and nutrient loading on the long-term dynamics of shallow lake ecosystems are, however, often overlooked and largely underestimated, which has hampered the effectiveness of lake management. Here, we focus on a large shallow lake (Lake Chaohu) located in one of the most densely populated areas in China, the lower Yangtze River floodplain, which has undergone both WLC and increasing nutrient loading over the last several decades. We applied a novel methodology that combines consistent evidence from both paleolimnological records and ecosystem modeling to overcome the hurdle of data insufficiency and to unravel the drivers and underlying mechanisms in ecosystem dynamics. We identified the occurrence of two regime shifts: one in 1963, characterized by the abrupt disappearance of submerged vegetation, and another around 1980, with strong algal blooms being observed thereafter. Using model scenarios, we further disentangled the roles of WLC and nutrient loading, showing that the 1963 shift was predominantly triggered by WLC, whereas the shift ca. 1980 was attributed to aggravated nutrient loading. Our analysis also shows interactions between these two stressors. Compared to the dynamics driven by nutrient loading alone, WLC reduced the critical P loading and resulted in earlier disappearance of submerged vegetation and emergence of algal blooms by approximately 26 and 10 years, respectively. Overall, our study reveals the significant role of hydrological regulation in driving shallow lake ecosystem dynamics, and it highlights the urgency of using multi-objective management criteria that includes ecological sustainability perspectives when implementing hydrological regulation for aquatic ecosystems around the globe.
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.|Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.
authors.forename: Xiangzhen
authors.initials: X
authors.lastname: Kong
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Qishuang
authors.initials: Q
authors.lastname: He
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.|Institute of Water Sciences, Peking University, Beijing, 100871, China.
authors.forename: Fuliu
authors.initials: F
authors.lastname: Xu
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.|Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, Wageningen, 6700 AA, The Netherlands.
authors.forename: Annette B G
authors.initials: AB
authors.lastname: Janssen
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.|Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, Wageningen, 6700 AA, The Netherlands.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Kuiper
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.|Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, Wageningen, 6700 AA, The Netherlands.
authors.forename: Luuk P A
authors.initials: LP
authors.lastname: van Gerven
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Qin
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Yujiao
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Wenxiu
authors.initials: W
authors.lastname: Liu
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Zelin
authors.initials: Z
authors.lastname: Bai
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
authors.forename: Fanxiang
authors.initials: F
authors.lastname: Kong
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.|PBL Netherlands Environmental Assessment Agency, P.O. Box 303, Bilthoven, NL-3720 AH, The Netherlands.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Janse
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6700 AB, The Netherlands.|Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, Wageningen, 6700 AA, The Netherlands.
authors.forename: Wolf M
authors.initials: WM
authors.lastname: Mooij
mesh_terms: D002681:China; D017753:Ecosystem; D005068:Eutrophication; D006801:Humans; D062070:Hydrology; D060106:Lakes
keywords: Lake Chaohu; PCLake; nutrient loading; paleolimnology; regime shift; water level control