Constructed wetlands (CWs) are widely implemented as nature-based solutions for delivering essential ecosystem services such as water purification, carbon sequestration, and habitat provision. However, biodiversity monitoring within CWs remains limited and unevenly integrated into performance evaluations. This scoping review analyzed 76 peer-reviewed studies to assess current methods for biodiversity monitoring, explore linkages to ecosystem functions, and examine the diversity indices most frequently applied. Results revealed a predominant focus on microbial communities, primarily assessed through high-throughput sequencing and general ecological indices such as the Shannon–Wiener Diversity Index and Chao1 Richness Estimator, with limited taxonomic depth or functional specificity. Plant and animal biodiversity were addressed less frequently and were rarely linked to treatment outcomes or ecosystem services beyond regulation. Vertical subsurface flow systems were the most studied configuration, particularly in lab-scale studies, while free water surface systems exhibited greater microbial phylum richness. These findings highlight a critical need for CW-specific biodiversity monitoring frameworks that integrate microbial, plant, and faunal assessments using functionally relevant phylogenetic indices such as Rao’s Quadratic Entropy and Faith’s Phylogenetic Diversity. Emphasis on standardization, trait-based analyses, and mechanistic approaches is essential for enhancing ecological interpretation and ensuring biodiversity is recognized as a central component of CW design, performance, and resilience.

Mercury (Hg) contamination in soils poses significant environmental risks. In response, various nature-based solutions (NbSs) have been developed and studied in the past to treat mercury along with other heavy metals from both point and nonpoint sources. However, various land uses present uncertainties in mercury mobility and treatment efficiency, affecting the scalability of NbS systems. In this study, a systematic review of peer-reviewed articles addressing mercury pollution in NbS soils was conducted. Results revealed that lakeside environments and mining areas are key Hg accumulation zones due to hydrological connectivity and anthropogenic pressures. Constructed wetlands were the most studied NbSs, where those with Acorus calamus and Aquarius palifolius as the main vegetation achieved >90% Hg removal efficiencies. Although NbSs achieved high Hg removal, anaerobic conditions were found to promote MeHg formation, a critical drawback. Moreover, biochar demonstrated potential for immobilizing Hg and reducing bioavailability, though certain types increased MeHg formation under specific redox conditions. Overall, the study highlighted the need for site-specific design, long-term field evaluation, and multidisciplinary strategies to optimize NbS performance for mercury removal. Furthermore, future research on the scalability of mercury-treating NbSs across diverse land uses is recommended to address mercury risks and improve effectiveness.

Constructed wetlands (CWs) are nature-based solutions that integrate ecological processes for water purification, climate regulation, and biodiversity enhancement. However, biodiversity monitoring in CWs has often been underprioritized, limiting its recognition as a functional driver of ecosystem service performance. This study first developed the Biodiversity-based Ecosystem Service Index (BBESI), a hierarchical framework for evaluating biodiversity contributions to regulating services, and then systematically identified representative indicators from the literature to operationalize this framework. Following PRISMA 2020 guidelines, 39 studies spanning tropical, temperate, and arid climatic regions were reviewed across six ecosystem functions: pollutant removal, nutrient retention, biological uptake, carbon storage, greenhouse gas regulation, and microclimate control. Indicators were considered representative when they demonstrated clear functional relevance to CW ecosystem processes and were repeatedly supported across the reviewed studies. These included microbial diversity metrics, nutrient-cycling functional genes, plant–microbe functional complementarity, and vegetation structural attributes. Each indicator was mapped to the Essential Biodiversity Variables (EBV) framework, spanning Genetic Composition, Species Traits, Community Composition, Ecosystem Structure, and Ecosystem Function to provide a standardized basis for biodiversity assessment, using a rule-based assignment that prioritized the biological signal of each indicator rather than its functional category. Although all EBV classes were represented, this pattern reflects the available literature and is influenced by uneven reporting across microbial and plant indicators and across climatic regions, which limits broad generalization of indicator strength. The BBESI offers a transferable framework because its EBV-aligned structure and commonly measured indicators allow application across diverse CW designs and environmental contexts provided that multiple EBV co-signals are present rather than reliance on single-indicator measurements, with flexibility for future integration of various quantitative weighting approaches.

Various types of antibiotics used excessively in the livestock industry are often discharged into aquatic environments without being fully removed. The release of these antibiotics into natural systems causes a variety of issues, including water pollution and ecological toxicity. This study was conducted to elucidate the mechanisms that govern microbial growth by analyzing the behavior of antibiotics and the changes in microbial communities in a constructed wetland (CW) treating effluent from a livestock wastewater treatment plant (LWTP). The main groups of antibiotics detected in the wetland were sulfonamides and tetracyclines. While most antibiotics showed high removal efficiency in the CW, some were found to persist or accumulate in the wetland over a prolonged period. Distinct shifts in microbial community composition were observed between inflow and outflow samples, indicating that the CW functions as an ecological filter that selects for microbial taxa associated with antibiotic persistence and transformation. Bacillus belonging to the phylum Firmicutes was found to play a role in antibiotic removal as it produces various antibiotic-degrading enzymes. Moreover, the phyla Chloroflexi, Gemmatimonadetes, and Acidobacteria appeared to experience no growth inhibition due to antibiotics and were not directly involved in their degradation. The phylum Actinobacteria was found to possess selective degradation abilities. These findings provide insights for improving constructed wetland design by supporting microbial communities, such as Firmicutes (Bacillus) that are associated with enhanced antibiotic removal and compound-specific degradation.

Constructed wetlands depend strongly on filter-media characteristics to achieve effective pollutant removal and support associated geochemical functions. This study evaluated basalt, dolomite, steel slag, and recycled aggregate for nutrient removal, heavy metal attenuation, and aqueous total inorganic carbon (TIC) responses. Treatment performance was evaluated descriptively using observed pollutant-removal efficiencies and temporal changes in aqueous TIC concentrations. Steel slag exhibited the highest observed total nitrogen (TN) (32.3%) and total phosphorus (TP) (62.0%) removal efficiencies at 120 min. It also showed the highest observed Zn (97.1%) and Cu (66.4%) removal efficiencies among the tested media. Recycled aggregate exhibited a 90.0% increase in effluent TIC concentration between the first and fifth monitoring weeks, while steel slag showed a 63.5% increase. In contrast, basalt and dolomite exhibited decreases of 31.9% and 68.7%, respectively. Principal component analysis (PCA) characterized differences in pollutant-removal profiles among the four media, with the first two principal components explaining 70.9% of the total variance. The integrated descriptive assessment showed that steel slag had the highest numerical average overall pollutant-removal efficiency (62.3%) under the tested conditions, together with a positive temporal aqueous TIC response. These findings suggest that reactive and waste-derived filter media warrant further investigation for multifunctional constructed-wetland applications. However, observed changes in aqueous TIC may reflect mineral–water interactions and atmospheric CO₂ exchange and should not be interpreted as direct evidence of carbonate mineralization or permanent carbon sequestration.