Synergistic impacts of nutrient enrichment and climate change on long‐term water quality and ecological dynamics in contrasting shallow‐lake zones

Abstract

Anthropogenic and climatic stressors on freshwater ecosystems are of global concern. However, the interactions and effects of multiple stressors (e.g., nutrient enrichment, climate warming, altered wind and precipitation) acting over different spatial and temporal scales are often complex and remain controversial. Here, we reconstructed one‐century dynamics of eutrophication and primary producer communities in algal‐dominated and macrophyte‐dominated zones of a large shallow lake (Taihu, China), by integrating sedimentary photosynthetic pigments and geochemical records with water monitoring and historical archives. We aimed to explore the long‐term underlying mechanisms of the responses of water quality and lake biota to multiple environmental perturbations. We found that water quality degradation and algal community modification showed similar trends but distinct timings and trajectories in contrasting ecological zones. Onset and intensity of eutrophication in north Meiliang Bay (since the 1950s) exceeded far beyond that of macrophyte‐dominated Eastern Taihu (~1990s). Anthropogenic nutrients overtook past climatic control on production and composition of phototrophic assemblages. More importantly, lake phytoplankton responded markedly to climate warming, decreasing wind speed, and extreme weathers after cultural eutrophication. Synergistic interactions of nutrients and climate on lake ecosystems became increasingly significant in promoting harmful algal blooms (HABs) dominated by Microcystis, close to the hyper‐eutrophic north lake zones. The asynchronous limnological and ecological responses also indicated the modulating roles of lake ecological regime and catchment hydrogeomorphic characteristic. Collectively, our findings suggest that mitigation of eutrophication and HABs calls for a triple management strategy integrating anthropogenic nutrients, climate change, and lake‐catchment setting.

Double‐edged effects of anthropogenic activities on lake ecological dynamics in northern China: Evidence from palaeolimnology and ecosystem modelling

“…On the other hand, reduced erosion could increase water transparency and enhance light penetration in the water column by decreasing inputs of suspended particulate matter (Lischke et al, 2014), which is in agreement with the remarkable increase in our pigment‐based UVR index after 2000 (Figure 3e). This result indicates better light conditions and increased underwater light penetration availability (Leavitt et al, 1997; Lin et al, 2021), which would provide a suitable abiotic environment for the photosynthesis of planktonic algae and an extensive habitat for benthic algae. Thus, all of these lines of evidence characterise long‐term decreases in the trophic state and an increase in the light availability of BLC Lake.…”

“…Competitive interactions among algal communities also modulate their composition and structure (Ewing et al, 2020). Percentage shifts in different pigment concentrations can reflect variations in the algal community structure (Lin et al, 2021; McGowan, 2013). The increased abundance of siliceous algae and cyanobacteria compared to green algae (chlorophytes) indicates a shift in the algal community towards the dominance of siliceous algae during the past 20 years (Figure 4g).…”

Lake ecosystems as proxies of change in a post-pandemic era

“…It has also been proven through global research reports that among the various impacts of climatic change, the relationships between the abiotic factors such as turbidity or total solids and the production characteristics of bacterial and viral populations are quite significant. Increases in the total solids concentrations through cultural eutrophication have a direct bearing on biotic survival in shallow and urban lake environments (Lin et al 2021 ).

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Anthropogenic forcing leads to an abrupt shift to phytoplankton dominance in a shallow eutrophic lake

“…In addition to anthropogenic stressors, interannual water-level fluctuations are driven by changes in climate variability throughout North America (Adrian et al, 2009;Havens & Jeppesen, 2018), particularly in arid regions where evaporation exceeds precipitation (Xiao et al, 2018). Furthermore, synergistic interactions between anthropogenic eutrophication, lake warming, and altered precipitation can stimulate excessive algal blooms during the summer months, leading to unprecedented changes in lake structure and function (Lin et al, 2021;Paerl & Huisman, 2008). Shallow lakes often exhibit two alternate states: a clear water state with abundant macrophytes, and a turbid, phytoplankton-rich state (Bayley et al, 2007;Scheffer et al, 1993).…”