Invasive Spartina alterniflora accelerates the increase in microbial nitrogen fixation over nitrogen removal in coastal wetlands of China

Seaweed feed enhance the long-term recovery of bacterial community and carbon-nitrogen sequestration in eutrophic coastal wetland

Seaweed feed offers a promising approach to enhance sustainability in aquaculture. While much research has focused on its effects on aquatic organisms, the impact of seaweed feed residuals on sediment carbon sequestration and bacterial community dynamics remains underexplored. This study aimed to address this gap through a 96-day incubation experiment using sediment from the coastal wetlands of Zhuhai in southern China. We evaluated the effects of seaweed feed derived from the red seaweed Gracilaria lemaneiformis by analyzing temporal changes in sediment physicochemical properties and microbial community dynamics. Our findings reveal that seaweed feed significantly improved sediment organic carbon and nitrogen storage (p < 0.01), enhanced the recovery of dissolved oxygen levels (p < 0.001) and bacterial α-diversity (p < 0.01) compared to normal feed. Additionally, the variability in microbial community structure (p < 0.01) and functional potential (p < 0.05) due to seaweed feed was less pronounced than that caused by normal feed. This reduced variability may result from the role of seaweed feed in stabilizing microbial community assembly, which helps mitigate fluctuations in bacterial structure and function. Overall, this study offers valuable insights for managing aquaculture ponds and coastal wetlands, contributing to the understanding of seaweed carbon sequestration and highlighting the potential of seaweed feed as a significant carbon sink beyond traditional cultivation practices.

Deposition of sulfur by Spartina alterniflora promoted its ecological adaptability in cadmium-polluted coastal wetlands

Invasive Spartina alterniflora poses a significant threat to coastal wetland ecosystems. This study investigated the role of sulfur (S) in facilitating the invasion of S. alterniflora in cadmium (Cd)-contaminated coastal wetlands by greenhouse-control-experiment. Results demonstrate that increased S deposition significantly enhanced the formation of acid-volatile sulfur in sediments, thereby reducing the bioavailability of Cd to plants by 41%. Additionally, S supplementation improved plant nutrient uptake and stress tolerance by increasing the C/N ratio and the concentrations of essential mineral elements. These physiological and biochemical changes, including enhanced photosynthesis, increased carbohydrate storage, and improved antioxidant capacity, ultimately contributed to increased shoot and root biomass production by 15% and 31% respectively, and the competitive ability of S. alterniflora. The findings of this study highlight the critical role of S in promoting the invasion of S. alterniflora. Effective strategies can be developed to control the spread of S. alterniflora and protect coastal ecosystems.

Functional traits of exotic submerged macrophytes mediate diversity-invasibility relationship in freshwater communities under eutrophication

Plant diversity may respond differently in terms of whether it can drive plant invasions in freshwater ecosystem. Linkages and interactions between diversity and invasibility have not been clearly resolved, and it is unclear how nutrient enrichment (e.g., eutrophication) will affect this relationship. As a key predictor of plant growth, the ability of functional traits to mediate trade-offs in the diversity-invasibility relationship is unknown. Here, we conducted a series of experiments to determine the role of exotic plant functional traits in the diversity-invasibility relationship of submerged macrophyte communities under eutrophication. We selected common native and exotic submerged macrophytes in the subtropics to construct different diverse submerged macrophyte communities to simulate invasion. Meanwhile, to test the adaptability and importance of functional traits, we experimentally verified the differences in functional traits between exotic and native species. Our results showed a positive correlation between native plant diversity and community invasibility. Moreover, the invader's performance was predominantly determined by functional traits of exotic species, such as plant biomass and tissue nutrients, which were significantly altered by species diversity. Furthermore, our results suggested that functional traits contribute significantly more to the invasiveness of exotic submerged macrophytes than the other factors to which they are subjected. Plant functional traits can mediate the diversity-invasibility relationship because of the higher intrinsic dominance of exotic submerged macrophyte species. In summary, our study revealed diversity-invasibility relationship in submerged macrophyte communities and highlighted functional traits as key drivers of invasion of high-risk exotic submerged macrophyte species. Although previous studies have elucidated the importance of functional trait studies for plant invasions, our study provides the only current evidence demonstrating the important role of invaders' functional traits in mediating the diversity-invasibility relationship. This novel perspective offers valuable insights into the management and control of invasive aquatic plants.

The pivotal role of phosphorus level gradient in regulating nitrogen cycle in wetland ecosystems

Phosphorus (P) is one of key drivers in Earth's nitrogen (N) cycle, however, the global overview of the P-regulated microbial community structure and gene abundance carrying wetland N process remains to be investigated. The key environmental factors that influenced wetland N cycle were initially screened, verifying the central role P. More complex and stable community interaction can be established in rich (20 mg/kg < P ≤ 100 mg/kg) and surplus P groups (P > 100 mg/kg) compared to that in deficient P group (P ≤ 20 mg/kg), with enhanced participation of betaproteobacteria and actinobacteria (i.e., changed hub microorganisms). Accordingly, P-mediated variations in gene expression patterns can be expected. On the one hand, the gene responses to carbon (C), N, and P factors presented nearly synchronous variation, highlighting the potential C-N-P coupling cycle in wetland ecosystem. On the other hand, the gene sensitivity towards environmental factors was changed at different P levels. Overall, the P level gradient can influence N cycle in direct (i.e., influences on gene abundances) and indirect (i.e., influences on gene response to environmental factors) manners. These findings provide important insights for controlling the N cycle in wetland ecosystems, particularly in cases where P levels are limiting factors.