Search Results (336)

Despite a growing interest in biochar for olive orchard fertility management, little is known about its effects on nitrogen (N) dynamics and greenhouse gas (GHG) emissions in Mediterranean soils, particularly when comparing neutral (pH 6.7) and alkaline (pH 8.2) soils using farmer-accessible flame-curtain pyrolysis biochar. In this 60-day soil mesocosm study, we hypothesized that biochar amendments in fertilized soils would enhance soil N availability and potentially reduce N₂O emissions, with effects modulated by soil pH. Treatments included: control, urea fertilizer, and urea plus biochar (5% w/w). Urea fertilization significantly increased soil ammonium (NH₄⁺) and total oxidized nitrogen (NO₃⁻ + NO₂⁻) in both soils, and co-application of biochar further increased these pools, particularly in the neutral soil (NH₄⁺: + 91% and + 62% in neutral and alkaline soil, respectively). Biochar addition consistently reduced cumulative carbon dioxide (CO₂) emissions in both soils, supporting its role in stabilizing soil organic carbon. However, impacts on nitrous oxide (N₂O) emissions were soil-pH-dependent: biochar slightly reduced N₂O emissions in neutral soil, though nearly doubled N₂O emissions in alkaline soil, highlighting that biochar’s efficacy for GHG mitigation is context-specific. These findings underscore biochar’s potential to improve soil N availability and reduce carbon losses but reveal clear limitations for N₂O mitigation in alkaline soils, necessitating site-specific application strategies that explicitly consider soil pH when targeting climate benefits in Mediterranean olive production. Full article

Bioturbating animals move around large amounts of sediment, changing its physicochemical properties and biogeochemical processes. The present study assessed the role of the ghost shrimp Lepidophthalmus louisianensis, a major coastal bioturbator in the Northern Gulf of Mexico, in the fate of crude oil after the 2010 Deepwater Horizon blowout. Experiments were conducted in greenhouse mesocosms, with or without ghost shrimp and with or without added oil, reflecting mild surface or subsurface oiling in a beach environment. To evaluate the hydrocarbon-degradation potential of the sediment microbial community, a respirometric radiotracer assay was conducted with ¹⁴C naphthalene as a model polycyclic aromatic hydrocarbon (PAH) compound. Oil augmentation led to a substantial increase in the PAH degradation potential of mesocosm sediments, which was further enhanced by the presence of the bioturbator. However, bioturbation alone, without previous oil exposure, did not enhance naphthalene degradation. 16S rRNA gene analyses showed that there were no significant changes in the microbial community composition associated with either bioturbation, oil augmentation, or both. This study demonstrated bioturbation- and oil-exposure-related enhancement in hydrocarbon degradation in mildly oiled sediment, and indicated that this may be due to an increased expression of PAH degrading activities in the preexisting community of hydrocarbon-degrading bacteria rather than resulting from a shift in the microbial community composition. Full article

Sorghum (Sorghum bicolor) is a key cereal for food and forage security in arid and semi-arid regions, where climate change is intensifying drought stress and threatening sustainable crop production. Intercropping cereals with legumes is widely promoted as a nature-based solution to improve resource-use efficiency, nitrogen (N) cycling, and drylands’ resilience. We evaluated the performance and interactions of a novel sorghum–legume combination by intercropping sorghum with the drought-tolerant legume serradella (Ornithopus sativus) in a 10-week mesocosm experiment. Cropping systems (sorghum monocrop, serradella monocrop, and strip intercropping) were subjected to moderate or severe water stress, with or without frequent cutting. We investigated how intercropping influenced individual crop growth, N accumulation, and survival, and whether benefits at the plant level translated to the system level. Under severe water stress, sorghum maintained higher biomass and survival than serradella. Intercropping did not increase aboveground biomass or N content at the mesocosm level. However, individual sorghum plants in intercrops accumulated up to 80% more biomass and 100% more aboveground N than in monocropping. In contrast, serradella experienced reduced growth, N accumulation, and survival in intercrops. Our results reveal trade-offs in this intercrop under dryland stress, where individual crop benefits do not translate into system-level gains. Although limited to early growth and controlled conditions, the results provide valuable insights for designing resilient sorghum–legume systems, including optimizing species density, intercrop configuration, and cutting regimes in drought-prone agroecosystems. Full article

Bioretention systems are increasingly implemented as green infrastructure for urban stormwater management. However, their long-term performance is jeopardized by the continuous accumulation of potentially toxic metals in substrates and vegetation, posing significant risks to ecosystem health and human safety. Despite their growing application, the mechanisms driving metal dynamics and plant responses within these systems remain poorly understood. This study conducts a comprehensive multi-factor investigation into the accumulation, mobility, and biological impacts of four representative potentially toxic metals (Cd, Cu, Zn, and Pb) in bioretention soils and vegetation. Through controlled mesocosm experiments, we quantified metal concentrations in soils and three plant species, analyzed alterations in the physical and chemical properties of soil, and assessed plant physiological stress responses. Metal concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS), and statistical analyses were conducted using one-way ANOVA (p < 0.05). Cadmium exhibited the highest enrichment, with plant uptake increasing by 330.0% to 563.2%, especially in Iris tectorum Maxim., which demonstrated superior phytoaccumulation potential. Conversely, Ophiopogon japonicus Ker Gawl. showed remarkable tolerance to metal-induced stress, maintaining stable levels of chlorophyll content, photosynthetic rate, peroxidase activity, and soluble sugar concentration. Notably, the incorporation of humic substances significantly enhanced metal immobilization in soil, while simultaneously reducing plant uptake and physiological stress, revealing a promising strategy for toxicity mitigation. By integrating the effects of plant species, substrate composition, and influent concentration, this study provides novel insights into the complex interactions governing pollutant fate in bioretention systems. The findings offer critical guidance for optimizing bioretention design and management to ensure sustained pollutant removal efficiency and ecological resilience in urban stormwater treatment. Full article

Numerous studies have confirmed that macrophytes contribute to improving water quality; however, it remains uncertain whether they can enhance lake carbon sequestration. We conducted a mesocosm experiment to compare six macrophyte species categorized into three life form groups: submerged, floating-leaved and emergent. The results showed that the concentrations of total phosphorus and total organic carbon in water were significantly lower in the submerged macrophyte group than in the other groups (p < 0.05). The sediment total phosphorus and sediment total carbon in the emergent macrophyte group were lower than those in the other groups. Plant tissue phosphorus in the submerged macrophyte group was significantly higher, while plant tissue carbon was significantly lower than in the other macrophyte groups (p < 0.05). Although the emergent macrophyte group released the highest CH₄ flux, it absorbed the most CO₂, resulting in a significantly lower CO₂-equivalent flux. Submerged macrophytes had a higher specific leaf area but a lower leaf area index and specific root length; floating-leaved macrophytes recorded a higher root mass ratio, total biomass, and relative growth ratio; meanwhile, emergent macrophytes had a lower root mass ratio. It is therefore recommended to configure macrophyte communities differentially based on specific restoration objectives. Full article

Freshwater bivalves influence ecosystem functioning by transferring pelagic material to the benthos through filtration and biodeposition, yet quantitative multiscale evidence remains scarce for South American lakes. We assessed the role of the native mussel Diplodon chilensis in Laguna Chica de San Pedro (southern Chile) by integrating laboratory measurements, seasonal in situ mesocosm experiments, and lake-scale estimates. Individual filtration rates were quantified under contrasting temperature and phytoplankton biomass conditions, while field experiments evaluated mussel effects on sediment biogeochemistry and zoobenthic assemblages. Filtration increased strongly with temperature, whereas food availability exerted a detectable effect only at lower temperatures. Live mussels consistently enhanced sediment organic matter and total nitrogen, while total phosphorus responses were weak and variable. Macroinvertebrate richness and abundance increased in association with mussel presence, whereas meiofaunal responses were weaker and inconsistent. When scaled to the lake level using bathymetric population distribution and seasonal deposition rates, D. chilensis accounted for substantial annual fluxes of organic matter and nitrogen to surface sediments, largely driven by shallow and intermediate depths. These results demonstrate that native freshwater mussels mediate a persistent downward component of benthic–pelagic coupling in clear-water temperate lakes of southern South America. Full article

Niclosamide has been the primary molluscicide for schistosomiasis control for over 50 years, but its chronic effects on inter-organ interactions in non-target mollusks remain poorly understood. Cipangopaludina cathayensis, a dominant species in East Asian schistosomiasis-endemic regions, was chronically exposed to environmentally relevant concentrations of niclosamide to assess its toxic effects. Digestive glands accumulated more niclosamide than the foot tissues. Prolonged exposure was associated with metabolic impairment of the digestive glands, characterized by tubular atrophy, inflammatory reactions, and depletion of nutrient components. Foot tissues exhibited epithelial lesions and muscle fiber atrophy. Alterations in foot structure were associated with changes in digestive gland nutrient status. Niclosamide exposure may weaken the metabolic coupling between these organs, thereby impairing locomotor function. At the population level, persistent niclosamide exposure may destabilize mollusk trophic-level populations, ultimately leading to ecological consequences. Our findings demonstrate the toxicological risks of niclosamide to freshwater mollusks. Full article

Spartina alterniflora, an invasive plant species in coastal regions of China, poses significant threats to local biodiversity and has become a pervasive weed in coastal wetlands and agricultural systems. With increasing nitrogen inputs in coastal areas, understanding the impact of nitrogen addition on plant–soil feedback dynamics in S. alterniflora is essential but remains poorly explored. This study aimed to investigate how nitrogen addition affects plant–soil feedback in S. alterniflora and its growth dynamics. We conducted a mesocosm experiment where nitrogen was added at different levels to assess its effects on the plant–soil feedback in S. alterniflora. The results showed that nitrogen addition significantly increased the aboveground biomass of S. alterniflora by approximately 38% to 88%, while decreasing its belowground biomass by about 22% to 41% Nitrogen addition weakened the negative plant–soil feedback, which typically limits the growth of S. alterniflora. This reduction in microbial resistance at higher nitrogen levels contributed to enhanced overall growth of the plant. These findings highlight the critical role of nitrogen inputs in facilitating the growth of invasive S. alterniflora and suggest that excessive nitrogen in coastal ecosystems could accelerate the spread of this invasive species. Future research should focus on exploring strategies to regulate nitrogen levels in coastal wetlands and agricultural systems to mitigate the ecological impact of invasive species. Full article

The widespread use of anticancer drugs (ACDs) in human therapies determines the occurrence of these potent cytotoxic chemicals into aquatic ecosystems. Nowadays, ACDs are ubiquitous contaminants in wastewater effluents and freshwater compartments, raising urgent questions about their environmental impact. Designed to disrupt cellular proliferation, these compounds are inherently bioactive and can exert toxic effects on non-target organisms even at trace concentrations. Conventional fate and toxicity tests provide important initial data but are limited in ecological realism, often focusing on single-specie and single-endpoint under controlled conditions and overlooking complex interactions, trophic dynamics, and long-term chronic exposures. Knowledge of all these aspects is needed for proper monitoring, assessment, and regulation of ACDs. Simulated ecosystem experiments, such as mesocosms, provide intermediate-scale, semi-controlled platforms for investigating real-world exposure scenarios, assessing ACD fate, and identifying both direct and indirect ecological effects. They offer distinct advantages for evaluating the chronic toxicity of persistent pollutants by enabling realistic long-term contamination simulations and supporting the simultaneous collection of comprehensive hazard and exposure endpoints. This perspective underscores the growing concern surrounding the contamination of ACDs, examines the limitations of traditional assessment approaches, and advocates for mesocosm-based studies as a critical bridge between laboratory research and ecosystem-level understanding. By integrating mesocosm experiments into environmental fate and risk evaluation, we can better predict the behavior and ecological consequences of anticancer pharmaceuticals, guiding strategies to mitigate their impact on aquatic life. Full article

The problem of steroid hormones in the aquatic environment remains a current global research topic. These substances have a strong impact on biological processes, contributing to reductions in the populations of numerous fish and amphibian species. The impact of steroid hormones, especially the third-generation progestogens, on aquatic invertebrates is poorly understood. We aimed to determine whether desogestrel, progestogen of low androgenic activity, affects the reproduction and growth of the following freshwater invertebrates: snails of the species Melanoides tuberculata and the planarian Dugesia sp. We also tried to estimate the threshold concentrations of this substance at which significant changes in both the behavior and reproductive activity of the studied organisms are observed. In the mesocosm experiment, we performed three treatments with the following different concentrations of desogestrel: control 0 ng/L, medium 10 ng/L, and high 100 ng/L. The high hormone concentration significantly reduced the reproduction of both snails and planarians, despite their different life history strategies, compared to the control. Both planarians and snails showed a significantly lower abundance in the high concentration compared to the 10 ng/L treatment, indicating a threshold concentration > 10 ng/L. The impacts of steroid hormone pollution on aquatic organisms and the need for further research are discussed. Full article

The detrimental effects of anthropogenic pollution are often magnified across ecosystems due to the interconnected nature of land, rivers, and oceans. Phytoremediation is an accessible technique that leverages the ability of plants to absorb and sequester pollutants and can potentially mitigate contaminants entering the ocean. It is a cost-effective and minimally invasive alternative to traditional water treatment methods. This study investigates the potential of the grapevine species Cissus verticillata (L.), a native plant from Puerto Rico, to be used in the phytoremediation of a creek in a highly urbanized site impacted by contaminated runoff due to heavy rainfall and sanitary waters. A mesocosm experiment was conducted using distilled water mixed with nutrients and known concentrations of cadmium (Cd) and lead (Pb) salts to assess whether C. verticillata could accumulate heavy metals in its tissues. Results showed that C. verticillata successfully absorbed heavy metals, with removal efficiencies of 80.13% (±0.16 SE) for Pb and 44% (±1 SE) for Cd. Results indicated a translocation factor <1 for both cadmium and lead, meaning C. verticillata is not a hyperaccumulator, but a metal stabilizer, as evident by the below detection limit (BDL) of the metals in Juan Mendez Creek. Despite evidence of new vegetative growth among individuals, no significant changes in total biomass or chlorophyll concentration were detected, indicating that C. verticillata maintained physiological stability under heavy metal exposure. Therefore, C. verticillata’s wide availability, adaptability to various environments, and climbing nature—which makes it less vulnerable to runoff and strong currents during rainy seasons—position it as a promising candidate for conservation initiatives and pollution management strategies. Full article

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis present serious ecological and public health concerns due to the production of brevetoxins (BTX). Clay flocculation and sedimentation of cells, particularly with polyaluminum chloride (PAC)-modified clays, is a promising HAB mitigation approach. This study evaluated the efficacy of Modified Clay-II (MCII), a PAC-modified kaolinite clay, in reducing K. brevis cell abundance in mesocosm experiments and examined the bioavailability of BTX potentially released from settled floc back into the water column and sediment over the first 72 h after treatment. Additionally, we quantified trace metals in benthic clams (Mercenaria mercenaria) exposed to the floc post-treatment to assess metal accumulation and potential toxicological effects from MCII application. MCII treatment (0.2 g/L) resulted in a 91% reduction in K. brevis cell density and a 50% decrease in waterborne brevetoxins after 5 h. Brevetoxins accumulated in sediment post-flocculation, with BTX-B5 emerging as the dominant congener. Clams exposed to MCII-treated floc showed comparable tissue BTX levels to controls and significantly elevated aluminum concentrations, though without mortality. The aluminum accumulations in this study do not raise concerns for the health of the clams or the humans who eat them, given other dietary exposures. These findings support the potential of MCII for HAB mitigation while underscoring the need for further evaluation of exposure risks to all benthic species. Full article

Salinization and eutrophication are increasingly severe pollution problems in wetlands. Myriophyllum spicatum is a cosmopolitan species widely used for pollution control, but its physiological responses under combined stressors remain largely unknown. Here, we used mesocosms to investigate the ecophysiological responses of M. spicatum to three ammonia nitrogen concentrations (0, 1.5, and 3 mg L⁻¹) and two salt concentrations (0 and 5 g L⁻¹). Shoot and stem biomass were significantly affected by both salinity and nitrogen, whereas leaf phosphorus and stem nitrogen responded only to salinity (two-way ANOVA, p < 0.05). A significant salinity–nitrogen interaction was observed for stem biomass (p < 0.05); specifically, low nitrogen alone caused no significant reduction, but under saline conditions it markedly exacerbated biomass suppression. A significant salt–nitrogen interaction was detected for stem biomass (p < 0.05), such that low nitrogen alone did not significantly reduce stem biomass but exacerbated its suppression under saline conditions. These indicate potential synergistic environmental effects and suggest that even low nutrient inputs may aggravate stress under salt exposure. Stem biomass was significantly negatively correlated with malondialdehyde content (Pearson analysis, p < 0.05). Salt–nitrogen co-stress significantly increased malondialdehyde content (Tukey HSD test), indicating enhanced lipid peroxidation and associated oxidative damage, which may represent a physiological mechanism underlying growth inhibition in M. spicatum. Our findings demonstrate the complex adaptive responses of M. spicatum and emphasize the need to consider salt–nutrient interactions in conservation and restoration practices. Full article

Submerged aquatic macrophytes play a key role in stream ecosystems, but their recovery in historically degraded Flemish streams is often limited. This study investigates whether sediment contamination constrains natural macrophyte germination and early seedling establishment. To address this knowledge gap, we combined a controlled mesocosm experiment with an analysis of long-term monitoring data from Flemish streams. The mesocosms showed that higher levels of sediment contamination reduced seedling emergence, indicating that sediment quality can directly inhibit germination and early establishment. In addition, historical monitoring data revealed only a weak association between sediment quality and macrophyte occurrence, pointing to the importance of interacting drivers such as hydrology, light availability, and habitat structure. Together, these findings highlight sediment contamination as a context-dependent but relevant barrier to macrophyte recruitment, underscoring the need to integrate sediment quality into broader restoration planning for streams in Flanders and abroad. Full article

The apodid sea cucumber Chiridota laevis has been a documented member of endobenthic marine communities in northern waters for over a century and the rare studies available on its biology identify it as distinctive species and promising model for research. The present study sought to elucidate fundamental aspects of its life history that remained unresolved. Adults were determined to be protandric, with individuals primarily demonstrating solely male or female gametes from winter (close to spawning) to the spring and summer months before undergoing a sex change in the fall months. Additionally, gametes of both sexes reached maturity synchronously in late winter (February to March). In mesocosms, free spawning occurred in February, as the temperature reached ~2.0 °C. The negatively buoyant eggs were encased in a sticky casing and fell to the sediment where they adhered to each other to form a mat on the muddy substratum. The realized fecundity was ~15,000 offspring. Development was lecithotrophic, demersal, and abbreviated, characterized by the absence of a pelagic larval stage. Embryos reached the gastrula stage after about 7 days post fertilization; the calcareous ring appeared at 6 weeks, and juveniles hatched from the sticky casing at 7 weeks, immediately becoming endobenthic. The size of late embryos and juveniles remained similar (~350 μm) until they began actively feeding at about 10 weeks of age. Feeding juveniles more than doubled in size in the first week (740 μm), reached 3.5 mm by year one, and measured up to 11 mm by year two. This growth rate suggests that it may take this species up to 7 years to reach adult size at ~24 mm contracted length. Full article