Contemporary evidence suggests that submerged macrophytes are experiencing a global decline due to the multiple compounding anthropogenic stressors impacting shallow lake ecosystems. Eutrophication and climate change are two main widespread, often co-occurring stressors, yet evidence concerning their interactive effects on aquatic plants remains partial and fragmented. Predicting the response of submerged aquatic vegetation to the combined effects of nutrient pollution and compound climate warming (mean + variability) is therefore crucial for the conservation and management of these valuable and vulnerable ecosystems. Here, we present the results of an outdoor mesocosm experiment examining the combined effects of nutrient enrichment (phosphorus addition) and warming (a 4 °C increase in mean temperature above present ambient conditions applied as either a constant increase or a variable increase ranging between 0 and 8 °C to mimic the effect of extreme events but keeping an equivalent total amount of warming) on Potamogeton crispus L. Warming accelerated the growth and senescence of P. crispus suggesting a more important role in maintaining the clear water state in winter-early spring but concomitant to possible earlier turbid states in summer. Warming also consistently advanced the flowering phenology but had no significant effect on flowering duration. There were no significant differences in the life cycle between the two warming treatments, while phosphorus addition also had little effect. However, under phosphorus enrichment, P. crispus increased sexual reproduction investment producing higher seed setting rate per infructescence. In contrast, warming, especially variable warming, may decrease sexual reproduction investment by reducing the number of infructescences. Seed and turion stoichiometry were altered by the combination of warming and phosphorus addition, but the changes were complex and difficult to interpret.

Globalization of fishery products is playing a significant role in shaping the harvesting and use of aquatic foods, but a vigorous debate has focused on whether the trade is a driver of the inequitable distribution of aquatic foods. Here, we develop species-level mass balance and trophic level identification datasets for 174 countries and territories to analyze global aquatic food consumption patterns, trade characteristics, and impacts from 1976 to 2019. We find that per capita consumption of aquatic foods has increased significantly at the global scale, but the human aquatic food trophic level (HATL), i.e., the average trophic level of aquatic food items in the human diet, is declining (from 3.42 to 3.18) because of the considerable increase in low-trophic level aquaculture species output relative to that of capture fisheries since 1976. Moreover, our study finds that trade has contributed to increasing the availability and trophic level of aquatic foods in >60% of the world’s countries. Trade has also reduced geographic differences in the HATL among countries over recent decades. We suggest that there are important opportunities to widen the current focus on productivity gains and economic outputs to a more equitable global distribution of aquatic foods.

Virus–host interactions are vital to microbiome ecology and evolution, yet their responses to environmental stressors under global change remain poorly understood. We perform a 10-month outdoor mesocosm experiment simulating multi-trophic freshwater shallow lake ecosystems. Using a fully factorial design comprising eight treatments with six replicates each, we assess the individual and combined effects of climate warming, nutrient loading, and pesticide loading on DNA viral communities and their interactions with microbial hosts. Metagenomic sequencing recovers 12,359 viral OTUs and 1628 unique prokaryotic metagenome-assembled genomes. Our analysis shows that combined nutrient and pesticide loading causes significant disruption by synergistically reducing viral alpha diversity while altering beta diversity and predator-prey linkages. Stressors lead to the simplification of virus-bacteria cross-kingdom networks, with nutrient-pesticide combinations exerting the strongest influence, although warming impacts diminish in the presence of pesticides. Stressor-driven changes also affect the abundance and composition of viral auxiliary metabolic genes, leading to complex shifts in virus-mediated metabolic pathways under multiple stress conditions. These findings underscore the importance of understanding the regulatory role of viruses on microbial communities to effectively address the challenges posed by global change.

Under the influence of human activities, eutrophication has become an increasingly serious global phenomenon, especially in shallow lakes. Many studies have shown that aquatic macrophytes play a significant role in controlling eutrophication, but only few of these studies are ecosystem based. In this paper, we applied a mass-balance ecosystem model to a shallow eutrophic lake (Lake Datong, China) as a case study with the aims of evaluating the status of ecosystem restoration via the recovery of aquatic vegetation and providing adaptive management suggestions. Results showed that the ecosystem was immature with weak energy flows and nutrient cycling largely due to the excessive submerged macrophytes and the lack of fish as consumer. In the early stages of restoration, the number of fish should be reduced, and aquatic vegetation needs to be recovered to mitigate eutrophication. When the aquatic vegetation community tends to be stable, herbivorous and omnivorous fish should be moderately stocked, and dead aquatic macrophytes should be harvested to maintain the healthy and sustainable development of the ecosystem. This study provided insights for the ecological restoration of shallow eutrophic lakes and revealed the urgent need for ecosystem-based restoration.

Multiple stressors such as climate change and eutrophication are responsible for the global decline in macrophytes in lakes. The loss of this key component can result in turbid conditions and a loss of important ecosystem functions and services, particularly in shallow lakes. Benthivorous fish, which can increase in abundance during eutrophication, can adversely affect macrophytes through physical disturbance, cascading effects on turbidity, suspended and attached algae (phytoplankton and periphyton) and direct consumption. However, whether warming amplifies their effects on macrophytes and can trigger regime shifts remains unexplored. Here, we tested the single and combined effects of warmer water (+4.5°C) and the widespread benthivorous juvenile common carp Cyprinus carpio on two different types of aquatic macrophytes in 24 mesocosms (2,500 L each). We monitored phytoplankton, periphyton, turbidity and the abundance of the submerged curly leafed pondweed Potamogeton crispus and the floating‐leaved water chestnut Trapa bispinosa during their growing season. These species dominated successively in spring and summer. Warming alone advanced the growing season of P. crispus by 17 days. Juvenile carp decreased the abundance of the more palatable P. crispus, but promoted the abundance of T. bispinosa, supporting an ecosystem shift to a dominance of floating‐leaved macrophytes. Fish also substantially increased water turbidity and the biomass of phytoplankton and periphyton. Warming amplified juvenile carp effects on turbidity and submerged macrophytes, but also decreased the abundance of floating‐leaved macrophytes leading to an overall macrophyte decline and increase in water turbidity. Synthesis and applications. Our study provides the first experimental evidence for a warming‐induced regime shift from clear‐water conditions dominated by submerged or floating/floating‐leaved macrophytes to a turbid state in shallow aquatic ecosystems. The regime shift was triggered by the impacts of warming on benthivorous fish (juvenile common carp) rather than on macrophytes. Lowering nutrient loading and other measures to reduce the abundance of benthivorous fish (e.g. fish removal and piscivorous fish restocking) thus may become increasingly important for the management of shallow lakes under global climate change.