Xiong Xiong

Lake-level rise driven by changing precipitation is increasing inundation in littoral wetlands, but responses of cbbL-harboring carbon-fixing microorganisms remain uncertain. A controlled soil-column experiment included four hydrological regimes: unflooded soil (CK), water level aligned with the soil surface (S0), and standing-water depths of 10 cm (S10) and 20 cm (S20). Amplicon sequencing of cbbL showed that the Shannon index was significantly higher in S20 than in CK (p = 0.0394), whereas Simpson, Chao1, and ACE did not differ significantly among treatments. Overall amplicon composition also lacked a significant treatment effect (PERMANOVA: R² = 0.344, p = 0.112). Pseudomonadota represented 96.9–97.7% of taxonomically assigned sequences and remained dominant across treatments, although several genera varied in relative sequence proportion. Exploratory LEfSe screening identified Rhodoblastus-, Hydrogenophaga-, and Azospirillum-related lineages as candidate indicators of CK, S10, and S20, respectively. Multivariate soil profiles did not differ significantly among treatments (PERMANOVA: R² = 0.374, p = 0.220). After collinearity filtering, EC had the highest normalized mean absolute out-of-fold SHAP contribution among EC, pH, and TC (43.8–59.1%). However, outer leave-one-out cross-validation produced negative predictive R² values (−0.43 to −0.11), indicating limited model generalizability. Overall, S20 was associated with higher Shannon diversity than CK, while Pseudomonadota remained dominant and several genera varied in relative sequence proportion. EC should therefore be regarded as an exploratory candidate correlate of cbbL alpha diversity rather than a validated environmental driver, and this association requires further evaluation under natural hydrological conditions.

Global lakes have experienced unprecedented salinity variation in recent decades, yet its ecological consequences in high-altitude ecosystems remain poorly resolved. Here, we quantified global patterns of salinity variation in alpine lakes and conducted extensive field surveys at 77 littoral sites across 40 lakes on the Qinghai-Tibet Plateau, which hosts nearly 40% of the world's alpine lakes and spans a broad salinity gradient (0.05-45‰). We integrated multidimensional diversity and assembly mechanism analyses to assess macroinvertebrate responses to salinity variation. Salinity emerged as the dominant measured correlate of macroinvertebrate communities across alpine lakes. Across taxonomic and functional dimensions, local diversity decreased monotonically with rising salinity. Community assembly shifted sharply along the gradient: deterministic filtering dominated high-salinity lakes (>7‰), mixed processes characterized moderate salinity (0.5-7‰), and low salinity (<0.5‰) exhibited a higher apparent stochastic component that may partly reflect unmeasured deterministic factors. At the taxon level, three contrasting adaptive strategies─strict halophiles, broadly euryhaline taxa, and low-optimum but wide-tolerance groups─revealed pronounced ecological divergence under saline stress. Simulated salinity variation further indicated asymmetric responses of regional biodiversity and functional distinctiveness, with salinization causing greater losses than freshening. Moderate-salinity lakes represented a critical mechanistic threshold, where the balance between deterministic and stochastic processes shifted and where regional diversity erosion accelerated. These findings suggest that salinity variation structures alpine lake macroinvertebrate communities across multiple biodiversity dimensions and assembly pathways, with important implications for conserving high-altitude ecosystems under ongoing global environmental change.

The mobilization of internal phosphorus (P) plays a crucial role in transitioning nutrient limitations within lake ecosystems. While previous research has extensively examined P release in littoral zones influenced by fluctuating water levels, there is a paucity of studies addressing the implications of sustained water level rise in this context, particularly as it pertains to nutrient limitations in benthic algae. To address this gap, we conducted an integrated study in Qinghai Lake. In the field sampling and microcosm experiment, we found that P concentrations are elevated in areas subjected to short-term inundation compared to those enduring prolonged inundation, primarily due to the dissolution of sedimentary P fractions. The results of nutrient diffusing substrata (NDS) bioassays indicated that benthic algae in Qinghai Lake displayed either P limitation or NP co-limitation. The transition from P limitation to NP co-limitation suggested that internal P release may serve to ameliorate nutrient limitations in benthic algae. This phenomenon could potentially contribute to the proliferation of Cladophora in the littoral zones of Qinghai Lake, thereby posing long-term implications for the lake’s aquatic ecosystem, particularly under conditions of sustained water level rise.

Plastic additives, represented by plasticizers, are important components of plastic pollution. Biofilms inevitably form on plastic surfaces when plastic enters the aqueous environment. However, little is known about the effect of biofilms on plastic surfaces on the release of additives therein. In this study, PVC plastics with different levels of di(2-ethylhexyl)phthalate (DEHP) content were investigated to study the effect of biofilm growth on DEHP release. The presence of biofilms promoted the migration of DEHP from PVC plastics to the external environment. Relative to biofilm-free controls, although the presence of surface biofilm resulted in 0.8 to 11.6 times lower DEHP concentrations in water, the concentrations of the degradation product, monoethylhexyl phthalate (MEHP) in water, were 2.3 to 57.3 times higher. When the total release amounts of DEHP in the biofilm and in the water were combined, they were increased by 0.6–73 times after biofilm growth. However, most of the released DEHP was adsorbed in the biofilms and was subsequently degraded. The results of this study suggest that the biofilm as a new interface between plastics and the surrounding environment can affect the transport and transformation of plastic additives in the environment through barrier, adsorption, and degradation. Future research endeavors should aim to explore the transport dynamics and fate of plastic additives under various biofilm compositions as well as evaluate the ecological risks associated with their enrichment by biofilms.