Free water surface constructed wetlands (FWSCWs) provide multiple ecosystem services, including water quality improvement, yet their response to stormwater pulses under combined agricultural and urban pressures remains insufficiently characterised. The Tancat de la Pipa Constructed Wetland, located within the Albufera de València Natural Park (Spain), was monitored during 13 rainfall events in 2023–2025 to quantify pollutant concentrations in the storm-driven inflows reaching the Albufera Lagoon and assess treatment performance for conventional pollutants, trace metals and emerging contaminants. Rainfall events triggered pronounced but contrasting concentration increases at both inflows: NH₄+-N dominated the urban-influenced inflow response suggesting CSO contributions, while NO₃−-N, TN and PO₄3−-P responded most rapidly at the agricultural inflow, consistent with distinct catchment sources and drainage dynamics. Despite these pollutant surges, the wetland achieved EMC-based total removal efficiencies of 78% for TP, 67–74% for TN, 81% for NH₄+-N, 84–90% for NO₃−-N and 86–90% for TSS, with outlet concentrations statistically indistinguishable from long-term dry-weather values. Of the 22 trace metals monitored, 16 were consistently attenuated; high ecological risk (RQ > 10) was recorded for Al, Hg and Pb at both inlets, substantially reduced though not fully eliminated at the system outlets. Eight of the 21 screened emerging contaminants were detected, with variable removal efficiencies ranging from 4% to >82% across compound groups; mixture toxicity assessment revealed persistent moderate ecological risk at the final outlets. The results demonstrate that a large-scale FWSCW can effectively buffer the broad spectrum of pollutants mobilised by stormwater in a sensitive Mediterranean landscape.
With the increasing threats posed by global climate change, artificial coastal structures remain essential to mitigate coastal erosion and flood risks in many regions worldwide. However, these structures are often criticized for introducing non-native materials that disrupt habitats and support lower biodiversity than natural rocks. Over the past three decades, eco-engineering has emerged as a solution to mitigate these impacts while maintaining their protective function. This study analyzes field and laboratory tests in the literature to identify advances in ecological engineering and low-carbon materials for the design of ecologically enhanced coastal structures. Key interventions include increasing surface complexity and heterogeneity of artificial substrates, evaluating the suitability of substrate types for biodiversity enhancement, and developing sustainable bio-enhancing concrete blends. Research highlights that incorporating surface roughness at scales from millimeters to decimeters, coupled with appropriate material selection can significantly enhance biodiversity while maintaining engineering performance. Examples of cost-effective habitat enhancement solutions include the BIOBLOCK unit ($2500 per unit), drill-core pools (€60 per pool), and artificial rock pools (€38 per pool). Concrete, especially with low-binder cements like slag cements (CEM III/B), is a suitable alternative when natural rock is unavailable. In this paper, studies are selected based on their relevance to coastal engineering practices, highlighting areas where further research is needed and offering recommendations to overcome barriers to the effective implementation and broader adoption of more sustainable and multifunctional coastal defences. Challenges include strengthening the evidence on achievable enhancements, clarifying cost-benefit analyzes, and improving data presentation for decision-making.
Coastal deoxygenation is increasing globally, prompting growing interest in Engineered Oxygen Supply (EOS) as a remediation tool. While EOS can improve dissolved oxygen (DO), assessing whether this translates into broader ecological benefits remains challenging. Bacterial communities are potential indicators because they respond rapidly to environmental change and regulate key biogeochemical processes. We investigated pelagic bacterial community responses to EOS in Macquarie Harbour, Tasmania, a highly stratified estuary where sub-halocline waters typically remain above hypoxic thresholds, using a rhodamine water tracer release, and paired water quality and 16S rRNA gene metabarcoding, following six weeks of continuous oxygenation. Tracer observations demonstrated kilometre-scale transport of oxygenated waters beneath the halocline. Tidal currents repeatedly redistributed plume waters throughout the treatment basin, indicating widespread and cumulative exposure. Despite this, bacterial community composition remained primarily structured by temperature and nutrient gradients. No significant relationship between DO and community composition was detected within the plume layer, despite a strong DO gradient. Only a small number of taxa responded consistently to EOS, with most oxygen-associated taxa declining in relative abundance as DO increased. In contrast, several copiotrophic and metabolically flexible taxa, including Colwellia, Thioglobus, Arcobacteraceae, Nitrincolaceae and Rhodobacteraceae, were enriched within the EOS treatment basin relative to reference basins. These findings indicate that EOS can substantially alter oxygen exposure across a stratified estuary while producing only subtle changes in pelagic bacterial community composition. Observed responses appear more strongly associated with cumulative exposure than instantaneous plume conditions, highlighting the importance of exposure history when evaluating EOS outcomes.
Reestablishing nitrogen (N) cycling is critical for stabilizing ecosystems in semi-arid sandy lands, yet the microbial mechanisms driving functional reorganization during vegetation restoration remain unclear. This study investigated the coupling of soil physicochemical properties, microbial traits, and N-cycling genes across a five-stage restoration sequence in the Mu Us Sandy Land: bare sandy land (BSL), grassland (GL), shrubland (SL), grass-shrub mixed land (GSL), and forest land (FL). Restoration significantly ameliorated edaphic conditions, with soil organic carbon (SOC) increasing approximately 7-fold and pH declining from 8.57 to 6.79. Notably, the GSL stage emerged as a “biogeochemical hotspot”, exhibiting peak microbial biomass and hydrolytic enzyme activities (urease and sucrase) linked to resource heterogeneity. Metagenomic profiling revealed a functional shift in microbial strategies: genetic potential for N-fixation (nifH/K) and urea hydrolysis dominated in oligotrophic BSL, indicating a strong investment in N acquisition. In contrast, nitrification (amo) was most prominent in GL, while denitrification and anammox pathways intensified in shrub-grass mosaics (GSL). Structural Equation Modeling (SEM) and Mantel tests further demonstrated that SOC accumulation primarily drives these functional shifts by reshaping microbial biomass and community assembly. Collectively, these findings suggest that vegetation restoration transitions the soil N-cycle from an external-acquisition-dominated system to a tighter, internal-recycling regime, with mixed vegetation stages acting as critical functional transitions.
The inability to disentangle restoration pathway effects from age effects has long constrained mechanistic understanding of soil recovery in post-mining landscapes. To address this methodological challenge, we established a quasi-experimental design at a waste dump in the Hequ Open-pit Coal Mine, comparing four areas that share identical parent material but differ in restoration history: newly abandoned (A1), natural restoration (A2, 5 years), artificial reclamation (A3, 5 years, same origin as A2), and mature reclamation (A4, >10 years). We measured 23 physicochemical and biological indicators across three depths (0–30 cm) and applied ANOVA with Benjamini-Hochberg correction and principal component analysis (PCA). Results revealed that (1) all indicators except mean weight diameter (MWD) and geometric mean diameter (GMD) of water-stable aggregates differed significantly among plots (p < 0.001). In contrast, both aggregate metrics exhibited strong depth effects—a pattern consistent with the interpretation that structural recovery lags behind fertility recovery. (2) In A3, fertility indicators showed no significant vertical differences, indicating profile homogenization; deep-layer (20–30 cm) microbial biomass carbon was 117.36% higher than in A2, far exceeding the surface increase of 58.81%, thus revealing a distinct deep-layer activation effect. (3) PCA extracted two components explaining 88.13% of the variance: PC1 (78.30%) loaded heavily on fertility and basic physical properties; PC2 (9.82%) was defined by MWD, GMD, and silt content. Notably, this high cumulative variance reflects the full restoration gradient (<1 to >10 years)—a subset PCA of the two 5-year pathways (A2 and A3) explained substantially less variance, indicating that pathway effects alone account for a more modest proportion of soil variation. Nevertheless, the PC1 score gap between A3 and A2 (3.30) exceeded that between A1 and A2 (2.50), indicating substantial separation between the two 5-year pathways. (4) Four physical legacy types were identified based on aggregate size distribution and profile configuration. Collectively, these findings demonstrate that restoration pathways impose multidimensional, legacy-forming imprints on soil properties, offering a quantitative framework for site-specific soil quality assessment and adaptive remediation strategies. Moreover, our quasi-experimental design provides a methodological template for isolating pathway effects from age-related confounding—a persistent challenge in mine rehabilitation research—and the four legacy types offer a diagnostic tool for tailoring restoration interventions to site-specific soil conditions.
