Large nutrient levels and herbivory stress, particularly when acting together, drive a variety of responses in seagrass communities that ultimately may weaken their carbon balance. An in situ three-months experiment was carried out in two contrasting seasons to address the effects of two levels of nutrient load and three levels of artificial clipping on Cymodocea nodosa plants. Nutrient enrichment shifted the community from autotrophic to heterotrophic and reduced DOC fluxes in winter, whereas enhanced community carbon metabolism and DOC fluxes in summer. Herbivory stress decreased the net primary production in both seasons, whereas net DOC release increased in winter but decreased in summer. A reduction of seagrass food-web structure was observed under both disturbances evidencing impacts on the seagrass ecosystems services by altering the carbon transfer process and the loss of superficial OC, which may finally weaken the blue carbon storage capacity of these communities.

The ecotoxicology of surfactants is attracting wide attention due to the rapidly expanding global application. As interspecific relationships play one of the central roles in structuring biological communities, it is necessary to take it into risk assessments on surfactants. With this aim, our study investigated the interference of three common surfactants on the inducible defense of a freshwater phytoplankton Scenedesmus obliquus. Nonlethal environmentally relevant concentrations (10 and 100 μg L⁻¹) of several surfactants were set up. Results showed that growth and photosynthetic efficiency of Scenedesmus were inhibited during first 96 h, but recovered in the later stage. Surfactants interfered inducible defense of Scenedesmus against Daphnia grazing, and the interference was related to chemical characteristics of surfactants. The anionic surfactant sodium dodecyl sulfate (SDS) enhanced the colony formation even without grazing cues, whereas fewer defensive colonies were formed under the effects of cationic surfactant benzalkonium bromide (BZK) and nonionic surfactant polyoxyethylene (40) nonylphenol ether (NPE). These findings highlighted the sensitivity of grazer-induced morphological defense of Scenedesmus to surfactants even at nonlethal concentrations, which potentially affects the energy and information flow between trophic levels. This study appeals for more attention to take interspecific relationships into consideration in assessing the potential ecological risk of pollutants.

Monitoring diverse components of aquatic ecosystems is vital for elucidation of diversity dynamics and processes, which alter freshwater ecosystems, but such studies are seldom conducted. Phytoplankton and zooplankton are integral components which play indispensable parts in the structure and ecological service function of water bodies. However, few studies were made on how zooplankton and phytoplankton community may respond simultaneously to change of circumstance and their mutual relationship. Therefore, we researched synchronously the phytoplankton communities as well as zooplankton communities based on monthly monitoring data from September 2011 to August 2012 in heavily polluted areas and researched their responses to variation in environmental parameters and their mutual relationship. As indicated by Time-lag analysis (TLA), the long-term dynamics of phytoplankton and zooplankton were undergoing directional variations, what's more, there exists significant seasonal variations of phytoplankton and zooplankton communities as indicated by Non-Metric Multidimensional scaling (NMDS) methods. Also, Redundancy Analysis (RDA) demonstrated that environmental indicators together accounted for 25.6% and 50.1% variance of phytoplankton and zooplankton, respectively, indicating that environmental variations affected significantly on the temporal dynamics of phytoplankton as well as zooplankton communities. What's more, variance partioning suggested that the major environmental factors influencing variation structures of zooplankton communities were water temperature, concentration of nitrogen, revealing the dominating driving mechanism which shaped the communities of zooplankton. It was also found that there was significant synchronization between zooplankton biomass and phytoplankton biomass (expressed as Chl-a concentration), which suggested that zooplankton respond to changes in dynamic structure of phytoplankton community and can initiate a decrease in phytoplankton biomass through grazing in a few months.

Excess exposure to fluoride causes substantive health burden in humans and livestock globally. However, few studies have assessed the distribution and controls of variability of ambient background concentrations of fluoride in soil. Ambient background concentrations of fluoride in soil were collated for Greater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia (n = 1005). Correlation analysis and machine learning techniques were used to identify environmental and anthropogenic influences of fluoride variability in soil. Sub-soils (>0.3 m deep), in some areas overlying siltstone and sandstone, and to a lesser extent, overlying basalt, were naturally enriched with fluoride at concentrations above ecological thresholds for grazing animals. Soil fluoride enrichment was predominantly influenced by parent material (mineralogy), precipitation (illuviation), leaching during palaeoclimates and marine inputs. Industrial air pollution did not significantly influence ambient background concentrations of fluoride at a regional scale. However, agricultural practices (potentially the use of phosphate fertilisers) were indicated to have resulted in added fluoride to surface soils overlying sediments. Geospatial variables alone were not sufficient to accurately model ambient background soil fluoride concentrations. A multiple regression model based on soil chemistry and parent material was shown to accurately predict ambient background fluoride concentrations in soils and support assessment of fluoride enrichment in the environment.

Magnetic particles (MP) emitted by an iron smelter were used to investigate the exposure of cows grazing on a grassland polluted by these MP and by large amounts of potentially toxic elements (PTE). The morphology as well as the chemical composition of the MP separated from cow dung were studied. Large amounts of typical MP were found (1.1 g kg−1 dry weight) in the cow dung sampled from the exposed site, whereas these particles were absent from the reference unpolluted site. The ingested MP were mainly technogenic magnetic particles (TMP) emitted by the smelter. Considering the MP concentration in the grazed grass on the exposed site, it was concluded that cows absorb the MP not only from the grass but also from the soil surface. The results of a mild acidic leaching of the MP suggested that the particles were possibly submitted to a superficial dissolution in the abomasum, pointing at a potential route of transfer of the PTE originating from the TMP and leading into food chains. TMP were only a small part of the anthropogenic contamination having affected the soil and the dung. However, due to their unequivocal signature, TMP are a powerful tracer of the distribution of PTE in the different compartments constituting the food chains and the ecosystems. Furthermore, the measurement of the particle sizes gave evidence that a noticeable proportion of the MP could enter the respiratory tract.

Although a great deal is known about the deposition of fluoride on vegetation, and the hazards associated with uptake by grazing herbivores, little is known about what happens to the concentration of fluoride in vegetation and soil at polluted sites once deposition ceases. The closure of Anglesey Aluminium Metals Ltd smelter, in September 2009, provided a unique opportunity to study fluoride loading once deposition stopped. Fluoride was monitored in plants and soil within 1 km of the former emission source. Fluoride concentrations in a range of plant material had decreased to background levels of 10 mg F kg−1 after 36 weeks. Concentrations of fluoride in mineral-rich soils decreased steadily demonstrating their limited potential to act as contaminating sources of fluoride for forage uptake. There were significant differences in the rate of decline of fluoride concentrations between plant species.

Grazed grassland systems are an important component of the global carbon cycle and also influence global climate change through their emissions of nitrous oxide and methane. However, there are huge uncertainties and challenges in the development and parameterisation of process-based models for grazed grassland systems because of the wide diversity of vegetation and impacts of grazing animals. A process-based biogeochemistry model, DeNitrification-DeComposition (DNDC), has been modified to describe N₂O emissions for the UK from regional conditions. This paper reports a new development of UK-DNDC in which the animal grazing practices were modified to track their contributions to the soil nitrogen (N) biogeochemistry. The new version of UK-DNDC was tested against datasets of N₂O fluxes measured at three contrasting field sites. The results showed that the responses of the model to changes in grazing parameters were generally in agreement with observations, showing that N₂O emissions increased as the grazing intensity increased.

Pasture management can be effective at sequestering soil organic C. We determined the depth distribution of particulate organic C (POC), non-particulate organic C (NPOC), particulate-to-total organic C (POC-to-TOC) ratio, and particulate organic C-to-N (POC-to-N) ratio under pastures near Watkinsville, GA, USA. POC was highly related with total organic C (TOC), but became an increasingly larger portion of TOC near the soil surface, where both pools were greatest. POC and NPOC were (i) greater under pasture than under conservation-tillage cropland, (ii) greater when pasture was grazed than when hayed, (iii) marginally greater with higher fertilization of pasture, (iv) greater with higher frequency of endophyte infection of tall fescue, and (v) greater under increasing stand age of grass. Soil under pasture comparisons that had greater TOC content had (i) larger improvements in POC than in NPOC and (ii) lower POC-to-N ratios, suggesting improvement in biochemical soil quality, as well as soil C sequestration.

Although livestock manure, such as from swine (Sus scrofa domestica), have high capacity to introduce endocrine-disrupting free estrogens into the environment, the frequency of estrogen detections from reconnaissance studies suggest that these compounds are ubiquitous in the environment, perhaps resulting from historic manure inputs (e.g. cattle grazing residues, undocumented historic manure applications) or uncontrolled natural sources. Compared to free estrogens, conjugates of estrogens are innocuous but have greater mobility in the environment. Estrogen conjugates can also hydrolyze to re-form the potent free estrogens. The objective of this study was to identify the transport of free and conjugated estrogens to subsurface tile drains and groundwater beneath fields treated with swine manure slurry. Three field treatments were established, two receiving swine lagoon manure slurry and one with none. Manure slurry was injected into soils at a shallow depth (∼8 cm) and water samples from tile drains and shallow wells were sampled periodically for three years. Glucuronide and sulfate conjugates of 17β-estradiol (E2) and estrone (E1) were the only estrogen compounds detected in the tile drains (total detects = 31; 5% detection frequency; conc. range = 3.9–23.1 ng L(−1)), indicating the important role conjugates played in the mobility of estrogens. Free estrogens and estrogen conjugates were more frequently detected in the wells compared to the tile drains (total detects = 70; 11% detection frequency; conc. range = 4.0–1.6 × 103 ng L(−1)). No correlations were found between estrogen compound detections and dissolved or colloidal organic carbon (OC) fractions or other water quality parameters. Estrogenic compounds were detected beneath both manure treated and non-treated plots; furthermore, the total potential estrogenic equivalents (i.e. estrogenicity of hydrolyzed conjugates + free estrogens) were similar between treated and non-treated plots.

Heavy metal(loid) rich ash (≤10,000 mg kg−1 total As, Cr, Cu and Zn) originating from the combustion of contaminated wood was subjected to several experimental procedures involving its incorporation into an upland pasture soil. Ash was added to soil that had been prior amended with local cattle manure, replicating practices employed at the farm scale. Metal(loid) concentrations were measured in soil pore water and ryegrass grown on soil/manure plus ash mixtures (0.1–3.0% vol. ash) in a pot experiment; toxicity evaluation was performed on the same pore water samples by means of a bacterial luminescence biosensor assay. Thereafter a sequential extraction procedure was carried out on selected soil, manure and ash mixtures to elucidate the geochemical association of ash derived metal(loid)s with soil constituents. Predictive modelling was applied to selected data from the pot experiment to determine the risk of transfer of As to meat and milk products in cattle grazing pasture amended with ash.The inclusion of manure to soils receiving ash reduced phyto-toxicity and increased ryegrass biomass yields, compared to soil with ash, but without manure. Elevated As and Cu concentrations in pore water and ryegrass tissue resulting from ash additions were reduced furthest by the inclusion of manure due to an increase in their geochemical association with organic matter. Zinc was the only measured metal(loid) to remain uniformly soluble and bioavailable regardless of the addition of ash and manure. Risk modelling on pot experimental data highlighted that an ash addition of >1% (vol.) to this pasture soil could result in As concentrations in milk and meat products exceeding acceptable limits.The results of this study therefore suggest that even singular low doses of ash applied to soil increase the risk of leaching of metal(loid)s and intensify the risk of As transfer in the food chain.