DOI: 10.5061/dryad.7m0cfxpsf
title: Long-term empirical evidence, early warning signals, and multiple drivers of regime shifts in a lake ecosystem

description: 1. Catastrophic regime shifts in various ecosystems are increasing with
 the intensification of anthropogenic pressures. Understanding and
 predicting critical transitions are thus a key challenge in ecology.
 Previous studies have mainly focused on single environmental drivers
 (e.g., eutrophication) and early warning signals (EWSs) prior to
 population collapse. However, how multiple environmental stressors
 interact to shape ecological behaviour and whether EWSs were detectable
 prior to the recovery process in lake ecosystems are largely unknown. 2.
 We present long-term empirical evidence of the critical transition and
 hysteresis with the combined pressures of climate warming, eutrophication
 and trophic cascade effects by fish stocking in a subtropical Chinese lake
 in the Yangtze floodplain. The catastrophic regime shifts are
 cross-validated by 64-year multi-trophic level monitoring data and
 paleo-diatom records. 3. We show that EWSs are detectable in both the
 collapse and recovery trajectories and that including body size
 information in composite EWSs requires shorter time series data and can
 improve the predictive ability of regime shifts. Although full recovery
 has not yet been observed, EWSs prior to recovery provide us with the
 opportunity to take measures for a clear-water regime. 4. Climate warming
 and top-down cascade effects have a negative influence on water clarity by
 altering lower trophic level abundance and body size, which in turn have a
 negative effect on macrophyte abundance. Furthermore, we identify a shift
 in the dominant driving forces from bottom-up to top-down after regime
 shifts, decoupling the relationships between nutrients and biological
 components and thus decreasing the efficiency of nutrient reduction. 5.
 Synthesis This study provides new insights into ecological hysteresis
 under multiple external stressors and improves our understanding of
 trait-based EWSs in both the collapse and recovery processes in natural
 freshwater ecosystems. For management practice, our work suggests that
 slowing down climate warming and weakening the fish predation pressure on
 food webs are necessary to increase the effectiveness of nutrient
 reduction in the restoration of lakes.
description: On July 8, 2010, a 50 cm sediment core was collected in Lake Donghu
 (30°33′02″ N, 114°21′40″ E) at a water depth of 2 m using a Kajak gravity
 corer with a 58 mm diameter. The sediment core was sliced at 0.5 cm
 intervals for dating and diatom analyses. The chronologies of the core
 were obtained by measuring <sup>210</sup>Pb and
 <sup>137</sup>Cs radionuclide activities in contiguous samples
 at the State Key Laboratory of Lake Science and Environment of the Chinese
 Academy of Sciences (CAS), Nanjing, China. A total of 98 sediment samples
 were prepared for diatom analysis using the standard method (Battarbee,
 Jones, & Flower, 2001). Diatom species were identified using oil
 immersion at 1000 magnification under an Olympus microscope (BX51). Diatom
 concentrations were estimated using DVB microspheres, which are expressed
 as relative percent abundances.
description: Paleo-Diatom: This file contains the diatom communities from
 dated sediment core. Fish_yield: This file contains the
 long-term changes of toal fish yield of Lake Donghu.
 Long-term_field_observation_phytoplankton: This file contains the
 long-term field observation data of phytoplankton community
 (1956-2019).