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The combined impacts of anthropogenic activities and global climate changes threaten native fish communities. Such threats are particularly critical in biodiversity hot spot areas with many endemic species, as exemplified by the isolated Yun‐Gui Plateau, China. The risk of biotic homogenization is also expected to be high in such areas, but this risk and its underlying drivers remain poorly studied.Here, we established a database of fish distributions and used environmental filtering for spatial clusters (n = 3759) in river basins located at Yun‐Gui Plateau. This database was based on public data sources and a comprehensive review of relevant literature (n = 481) covering the period from 1950 to 2021. We divided the plateau into nine subbasins for spatial comparison and into two periods for temporal comparison—before and after the start of rapid economic growth development in 1978.We found: (a) a marginal increase in replacement (species exchange in different subbasins) and similarity index but a decrease in richness difference index, indicating homogenization and the loss of natural barriers across the entire plateau; (b) an increase in species richness accompanied by a discernible decline in phylogenetic diversity, also indicating homogenization; (c) the increase in species richness by species loss‐gain analyses was associated with climatic variables (temperature and precipitation), elevation and human activities in all subbasins.Temporal and spatial comparisons indicated that homogenization of fish assemblages in the Yun‐Gui Plateau was exacerbated by climatic and anthropogenic pressures.The observed homogenization of fish species is of great concern, and we call for systematic assessments and precautionary mitigation actions to maintain the uniqueness of biodiversity in the Yun‐Gui Plateau region. [ABSTRACT FROM AUTHOR]

Climate‐driven changes in temperature and high nutrient inputs from anthropogenic activities significantly impact the interactions between submerged macrophytes and phytoplankton, potentially causing regime shifts in shallow freshwater lakes. Cyanobacteria, in particular, are predicted to become dominant among the phytoplankton under climate change, contributing to the collapse of submerged macrophytes. This study aimed to explore how submerged macrophytes and phytoplankton respond to rising temperatures and nutrient addition, how the presence of submerged macrophytes influences the photosynthetic activity of cyanobacteria, and how submerged macrophytes adapt their morphology and physiology to cope with excess phytoplankton. We conducted a fully factorial experiment consisting of two temperature conditions (low and high temperature), two nutrient conditions (with and without nutrient addition) and two plant conditions (plant presence and absence). We analysed changes in phytoplankton biomass and diversity (taxonomic and functional) in response to rising temperatures and nutrient addition. The maximum photochemical efficiency of the photosystem II (Fv/Fm) and the maximum relative electron transport rates (rETRmax) of cyanobacteria were determined. We measured the response of macrophytes to environmental changes by measuring antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), as well as morphological indicators like plant height, weight, and the relative growth rate. In the absence of submerged macrophytes, rising temperatures led to higher total phytoplankton biomass and cyanobacteria dominance alongside reduced taxonomic and functional diversity. Conversely, when submerged macrophytes were present and no nutrients were added, rising temperatures did not lead to increased phytoplankton biomass. Macrophytes can suppress undesirable cyanobacterial proliferation by competing for nutrients and inhibiting Fv/Fm. Furthermore, under conditions of environmental stress, such as high chlorophyll a concentrations due to nutrient inputs, submerged macrophytes adapted by increasing height and the activity of antioxidant enzymes, such as SOD and CAT. Within the context of climate warming and increased nutrient inputs, phytoplankton growth, especially of cyanobacteria, may be favoured. However, our study demonstrated the critical role of submerged macrophytes in inhibiting phytoplankton, especially when nutrients were controlled. By using these physiological indicators to assess the life activity of organisms, our research provided new insights into macrophyte‐phytoplankton relationships during regime shifts in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Filter‐feeding silver carp (Hypophthalmichthys molitrix) has been extensively used to control algae blooms in Chinese lakes. However, the benefit of stocking silver carp to restore eutrophic lakes remains controversial and the reasons for the different responses observed are unclear.In this study, we conducted an outdoor experiment to assess the impact of the biomass level of four silver carp (c. 0, 25, 50, and 100 g/m3) on phytoplankton through direct grazing and fish‐mediated nutrient recycling, respectively. We used a nested design with nutrient‐permeable chambers with or without fish placed inside ponds. In this way, the phytoplankton incubated outside the chambers was affected by both consumer grazing and nutrient recycling, whereas the phytoplankton inside the fish‐free chambers was only affected by consumer‐mediated nutrient recycling.Outside the chambers, the concentrations of total nitrogen, dissolved total nitrogen, and total phosphorus did not differ significantly among the treatments, whereas the dissolved total phosphorus level was significantly higher in the fishless treatment. The concentration of chlorophyll a (Chl a), phytoplankton biomass and the ratio of nanophytoplankton Chl a to total phytoplankton Chl a in the fish‐present treatments were significantly higher than in the fishless treatment and the phytoplankton was dominated by small‐sized species. While the zooplankton biomass and zooplankton:phytoplankton biomass ratio were significantly lower in the fish‐present treatments, indicating a strong fish predation on zooplankton. As for the water inside the chambers, there was no significant difference among the four treatments for any of the measured variables except total phosphorus.Our results suggest that silver carp indirectly stimulated phytoplankton growth by reducing the zooplankton grazing rather than through nutrient recycling, and that fish grazing on phytoplankton could not compensate for the loss of grazing by zooplankton, leading to higher phytoplankton biomass when silver carp was present. The benefit of using filter‐feeding fish as a biomanipulation tool to create clear water is therefore questionable unless control of nanophytoplankton can be achieved. [ABSTRACT FROM AUTHOR]

Macrophyte composition and abundance affect the overall ecological structure and function of lakes, and information on the nature and timing of changes in macrophyte assemblages is therefore crucial for understanding their impact on the lake ecosystem.We examined plant macrofossils, diatoms, cladocerans, and physical and geochemical proxies in two sediment cores from Lake Liangzi, a large shallow lake located on the Yangtze floodplain in south‐east China, in order to assess recent and historical trajectories of ecological and environmental change. We also used archival records of environmental changes (i.e. hydrological, climatic, fishery, and social factors) in the lake and its catchment. Lake Liangzi is of particular interest as it, unlike most other lakes in the region, has maintained a macrophyte‐dominated state.The results revealed a shift in the lake during the past ca. 160 years from a clear water, low‐growing submerged macrophyte community (e.g. Najas minor, charophyte species), dominated by planktonic diatoms and planktonic cladocerans, towards a more pollutant‐resistant, tall‐growing macrophyte community (Potamogeton spp., Ceratophyllum demersum and Myriophyllum spicatum) and dominance by benthic and epiphytic diatoms and littoral cladocerans. However, a pronounced increase in the abundance of planktonic Bosmina spp. at the expense of true littoral cladoceran species and a decline in plant macrofossil assemblages in the surface samples suggest that the lake recently entered into a new unprecedented state.Redundancy analysis indicated major changes in hydrology and moderate inputs of anthropogenic pollutants as well as climate warming as the main drivers of ecological and environmental changes in the lake.Our study demonstrated that plant macrofossils from radionuclide‐dated short sediment cores provide reliable information on the nature and timing of changes in the macrophyte community in Lake Liangzi. Furthermore, our study provided information on the composition of the plant community before recent strong perturbations and also showed the trajectories and suggested the drivers of ecological and environmental change, thereby offering valuable information for lake managers in the Yangtze region and elsewhere.Our study identifies a relatively resistant community of submerged macrophytes, which may be an initial restoration target for managers when restoring the many lakes in the region where submerged vegetation coverage has declined during the last few decades. [ABSTRACT FROM AUTHOR]

Shallow lakes may play an important role for the nitrogen (N) balance in drainage basins by processing, transferring and retaining N inputs. An increase in the frequency of storm-induced short-term N pulses and increased water temperatures are both likely outcomes of climate change, potentially affecting the N processing in lakes., An experiment with a K15 NO3− pulse addition (increase in NO3− concentration from c. 0.1 to 2 mg/L) was carried out in 12 mesocosms with relatively low (applies to Danish lakes) total N ( TN) and total phosphorus ( TP) concentrations ( c. 0.3 mg N L−1 and 0.04 mg P L−1) to assess the effects of an N pulse on N processing and storage in shallow lake ecosystems. The mesocosms have a hydraulic retention time of approximately two and a half months, and at the time of the experiment, they had been adapted to contrasting temperatures for a period of 10 years: ambient, T3 (heating according to the Intergovernmental Panel on Climate Change 2007 A2 scenario, +3.7-4.5°C, depending on season) and T5 (heating with A2 + 50%, +4.9-6.6°C)., Macrophytes and filamentous algae retained up to 40% and 30% of the added 15N, respectively, reflecting their high biomass in the mesocosms. Macrophytes and filamentous algae constituted between 70% and 80% of the biomass of all primary producers during the experiment in the T3 and ambient treatments and between 20% and 40% in T5. By comparison, less than 1% of the added 15N diffused to the sediment and less than 5% was lost to the atmosphere as N2 gas. Snails represented the long-term storage of 15N, retaining up to 6% of the tracer and with detectable enrichment 100 days after tracer addition., We found no significant differences among the temperature treatments in the 15N turnover after pulse dosing. However, a larger percentage of 15N was stored in macrophytes in the ambient and T3 mesocosms, reflecting higher biomasses than in T5 where filamentous algae were more abundant. Macrophytes and filamentous algae rather than temperature were therefore key controllers of N processing during the summer N pulse in these shallow, relatively low TP lakes. [ABSTRACT FROM AUTHOR]