Wetlands in the Prairie Pothole Region (PPR) of North America support macroinvertebrate communities that are integral to local food webs and important to breeding waterfowl. Macroinvertebrates in PPR wetlands are primarily generalists and well adapted to within and among year changes in water permanence and salinity. The Williston Basin, a major source of U.S. energy production, underlies the southwest portion of the PPR. Development of oil and gas results in the coproduction of large volumes of highly saline, sodium chloride dominated water (brine) and the introduction of brine can alter wetland salinity. To assess potential effects of brine contamination on macroinvertebrate communities, 155 PPR wetlands spanning a range of hydroperiods and salinities were sampled between 2014 and 2016. Brine contamination was documented in 34 wetlands with contaminated wetlands having significantly higher chloride concentrations, specific conductance and percent dominant taxa, and significantly lower taxonomic richness, Shannon diversity, and Pielou evenness scores compared to uncontaminated wetlands. Non-metric multidimensional scaling found significant correlations between several water quality parameters and macroinvertebrate communities. Chloride concentration and specific conductance, which can be elevated in naturally saline wetlands, but are also associated with brine contamination, had the strongest correlations. Five wetland groups were identified from cluster analysis with many of the highly contaminated wetlands located in a single cluster. Low or moderately contaminated wetlands were distributed among the remaining clusters and had macroinvertebrate communities similar to uncontaminated wetlands. While aggregate changes in macroinvertebrate community structure were observed with brine contamination, systematic changes were not evident, likely due to the strong and potentially confounding influence of hydroperiod and natural salinity. Therefore, despite the observed negative response of macroinvertebrate communities to brine contamination, macroinvertebrate community structure alone is likely not the most sensitive indicator of brine contamination in PPR wetlands.

The present study aimed to investigate the metabolic response of edible amaranth cultivars to salt stress and the induced rhizosphere effects on Cd mobilization in soil. Two edible amaranth cultivars (Amaranthus mangostanus L.), Quanhong (low-Cd accumulator; LC) and Liuye (high-Cd accumulator; HC), were subject to salinity treatment in both soil and hydroponic cultures. The total amount of mobilized Cd in rhizosphere soil under salinity treatment increased by 2.78-fold in LC cultivar and 4.36-fold in HC cultivar compared with controls, with 51.2% in LC cultivar and 80.5% in HC cultivar being attributed to biological mobilization of salinity. Multivariate statistical analysis generated from metabolite profiles in both rhizosphere soil and root revealed clear discrimination between control and salt treated samples. Tricarboxylic acid cycle in root was up-regulated to cope with salinity treatment, which promoted release of organic acids from root. The increased accumulation of organic acids in rhizosphere under salt stress obviously promoted soil Cd mobility. These results suggested that salinity promoted release of organic acids from root and enhanced soil Cd mobilization and accumulation in edible amaranth cultivar in soil culture.

Sediment samples, including 40 surface samples and 12 sediment cores, were collected from 52 stations of the Yangtze River Estuary (YRE) in 2015 and 2016. The 95% linear prediction intervals (LPI) and principal components analysis (PCA), were conducted to evaluate the metal sources and grain-size effect (GSE). The in situ physico-chemical properties of pH, Eh, DO, salinity, temperature and turbidity were combined to elucidate the relationships between environmental factors and the fate of heavy metals in the river-estuary-shelf system. This study indicates a decreasing trend of metals in sediments from the estuary towards the adjacent shelf and the river channel and that Zn, Cu and Cr are mainly derived from natural processes throughout the catchment, whereas Pb appears to have anthropogenic inputs via atmospheric deposition. Furthermore, considering the best fit regression lines between the concentrations of Al and heavy metals as well as the deficiencies of the conventional Celements/CAl method, we introduce an approach (Al-SN: Al-scope normalization) that can eliminate the GSE on heavy metals and be applied to other estuaries. After Al-scope normalization, the relatively constant levels of Zn, Cu and Cr that remain in sediments from the river channel to the estuary and shelf confirmed that the variation of grain size in sediments almost entirely explained the distribution patterns of sediment toxicity in the YRE, while the enrichment of Pb in estuarine sediments could be attributed to its chemical species and physico-chemical properties. The results further suggest that the relationship between grain size and spatial behavior of sediment pollutants should be given priority over the contamination assessment and provenance discrimination in estuarine or similar environments with complex sediment compositions.

As a result of human activities, climate forecasts predict changes in the oceans pCO₂ and salinity levels with unknown impacts on marine organisms. As a consequence, an increasing number of studies have begun to address the individual influence of pCO₂ and salinity but much remains to be done to understand their combined effects on the physiology and ecology of marine species. Our study addressed this knowledge gap by measuring the influence of current and predicted levels of pCO₂ (380 and 1200 ppm, respectively) and salinity (20, 25 and 30 psμ) on the energetic physiology of juvenile mussels (Mytilus chilensis) from the south-eastern Pacific region. Our results indicate that a reduced salinity caused a significant reduction in clearance rate, absorption efficiency and scope for growth of this species. Meanwhile, an increase in pCO₂ levels caused a reduction in excretion rates and interacted significantly with salinity in the rate of oxygen uptake measured in the mussel. These results suggest that potential changes in salinity might have a direct role on the physiology of M. chilensis. The effect of pCO₂, although less prevalent among the variables measured here, did interact with salinity and is also likely to alter the physiology of this species. Given the ecological and economic importance of M. chilensis, we call for further studies exploring the influence of pCO₂ across a wider range of salinities.

Nitrite is a common pollutant in water and is highly toxic to aquatic animals. To reveal the mechanism of salinity in attenuating nitrite toxicity to fish, we measured the physiological responses of juvenile Takifugu obscurus exposed to nitrite concentrations (0, 10, 20, 50, and 100 mg/L) under different salinity levels (0, 10, and 20 ppt) for 96 h. Salinity increased the survival rates of juvenile T. obscurus exposed to nitrite. Changes in key hematological parameters, antioxidant system, malondialdehyde, Na⁺/K⁺–ATPase, and HSP70 indicated that nitrite induced considerable damage to juveniles; salinity mitigated the harmful effects. This finding reflects similar changing trends in both antioxidants and their gene expressions among different tissues. We applied an overall index, an integrated biomarker response (IBR), that increased under high−nitrite condition but recovered to the normal levels under salinity treatment. Analysis of the selected detection indices and IBR values showed that the overall mitigating effect of salinity on nitrite toxicity seems to be at sub-cellular level and associated with complicated physiological responses.

The distribution, feeding ecology and microplastic contamination were assessed in different ontogenetic phases of Haemulidae species inhabiting the Goiana Estuary, over a seasonal cycle. Pomadasys ramosus and Haemulopsis corvinaeformis are estuarine dependent species that use habitats with specific environmental conditions each season. Pomadasys ramosus was found in the upper and middle estuaries during the rainy season, when salinity showed the lowest values. Haemulopsis corvinaeformis was found in the lower estuary during the dry season, when salinity increased in the estuary. Juveniles of P. ramosus are zooplanktivores, feeding mainly on calanoid copepods. Sub-adults and adults are zoobenthivores, feeding on invertebrates associated to the bottom, mainly Polychaeta. Juveniles of H. corvinaeformis were not found in the main channel, but sub-adults and adults showed a zoobenthivore habit, feeding mainly on Anomalocardia flexuosa (Mollusca: Bivalvia). Dietary shifts along the life cycle and the spatio-temporal relationship between their distribution and the availability of microplastics along the estuary seem to have a strong influence in the ingestion of microfilaments. The highest average ingestion of microfilaments by P. ramosus coincided with the peak of ingestion of Polychaeta by sub-adults in the upper estuary during the late rainy season. For H. corvinaeformis the highest ingestion of microfilaments coincided with the peak of ingestion of A. flexuosa by adults in the lower estuary during the late dry season. Such contamination might be attributed to the time when these phases shifted to a more diverse diet and began to forage on benthic invertebrates. Research on microplastic contamination must consider species-specific behaviour, since the intake of microplastics is dependent on patterns of distribution and trophic guild within fish assemblages.

Differences in the distribution, partitioning, and bioaccumulation characteristics of arsenicals between freshwater and saltwater systems remain poorly understood. To determine the characteristics of distribution and behavior of arsenicals, multimedia environmental samples including water, suspended particles, zooplankton, sediments, and porewater were collected from inner (five sites, freshwater) and outer (five sites, saltwater) regions of the estuary dike of the Youngsan River Estuary in South Korea (Nov., 2012). Six organic and inorganic forms of As were separated and measured using HPLC–ICP/MS equipped with an anion exchange column. Concentrations of arsenicals in water samples of the inner region (mean = 1.5 μg As L−1) were significantly lower than in those of the outer region (mean = 5.2 μg As L−1). Conversely, concentrations of As in suspended particles in the inner region (mean = 14 μg As g−1) were much greater than in the outer region (mean = 5.7 μg As g−1). The field-based distribution coefficient (Kd) for As depended strongly on salinity; relatively greater Kd values were found in freshwater compared with saltwater. The AsV was found to be the major form of As in all water and particle samples in both inner and outer regions. The zooplankton species were significantly distinguishable between the inner and outer regions; cladocerans were the most dominant species in freshwater and cyclopoida were predominantly found in saltwater. The As concentrations in zooplankton were shown to be particle-concentration dependent, suggesting that dietary exposure plays a substantial role in the bioaccumulation of As. Inorganic arsenicals, such as AsV and AsIII were the most dominant forms found in zooplankton. Partitioning behavior of As between porewater and sediments was similar to that in water–particle distributions. The results of the present study enhance the understanding of As biogeochemistry in river and estuarine environments.

Salinity effects on the bioaccumulation and biokinetic processes of eight trace elements (Cu, Cr, Pb, Ni, Zn, Cd, Se, and As) in the black mussel Septifer virgatus were explored in the present study. A 6-week laboratory waterborne exposure first showed that salinity (15, 20, 25, and 30) had relatively weak or even no significant influence on trace element accumulation in the black mussels. Biokinetics including uptake and efflux was then quantified in the mussels at different salinities. Uptake rates of Ni and Zn were negatively correlated with the salinity, while the uptake of Cd was not significantly influenced by salinity. The efflux rates of Ni and Zn also exhibited an inverse relationship with salinity, whereas the case of Cd was on the contrary. Biokinetic modeling showed that the salinity effects on uptake and elimination of Ni and Zn counteracted with each other, thus weakening the combined effects on accumulation. Overall, the response of uptake to salinity could weakened, removed, or even overturned by elimination, depending on the relative magnitude of the change of the two processes. The combined effects of uptake and elimination further led to negative, no, or positive relationship between trace element accumulation and salinity.

Due to the severe degradation and environmental pollution of coastal wetlands by human activities, they have gradually become an important source of greenhouse gases (GHGs) emissions, so exploring the characteristics of their emission is important to reduce greenhouse gas emissions from coastal wetlands. In this study, the dynamics of methane (CH₄) and carbon dioxide (CO₂) emissions were investigated in five kinds of typical tidal flats from the Yellow River delta wetland during the years 2011–2013, and the influences of water level and salinity on their emissions were explored in laboratory experiments. The mean fluxes of CO₂ and CH₄ were −20.98 to 68.12 mg m⁻² h⁻¹ and −0.12 to 0.44 mg m⁻² h⁻¹ across all seasons in the five kinds of representative tidal flats. The highest and lowest mean fluxes of CO₂ were mainly observed during summer and winter, respectively, whereas the seasons with the highest and lowest mean fluxes of CH₄ varied according to the type of tidal flat. The results showed that the summer season and the mud flat environment had the largest contributions to greenhouse gas emissions. In laboratory experiments, the largest sequestration fluxes of CO₂ and CH₄ were observed with +4/+2 cm and −4 cm water levels, respectively, indicating that a moderately high water level was beneficial for CO₂ sequestration but led to the increase of CH₄ emission. In the study of salinity, we found that the largest sequestration fluxes of CO₂ and CH₄ were both detected at 24 g L⁻¹ salinity, indicating that high salinity level was advantageous for CO₂ and CH₄ sequestration in the five simulation devices. Furthermore, a carbon cycle pathway of coastal wetlands was proposed, which could have a vital significance for research into the global carbon cycle. We can reduce GHG emissions by protecting the coastal wetlands and lessening human activities.

Salts used for de-icing roads and sidewalks in northern climates can have a significant impact on water quality and vegetation. Sub-surface engineering systems, such as structural soil cells, can regulate water runoff and pollutants, and provide the necessary soil volume and irrigation to grow trees. However, the ability of such systems to manage de-icing salt contamination, and the impact of this contamination on the trees growing in them, have not been evaluated. We report on an field investigation of de-icing salt contamination in structural cells in two street-revitalization projects in Toronto, Canada, and the impact of this contamination on tree performance. We analyzed soil chemistry and collected tree attributes; these data were examined together to understand the effect of salinity on tree mortality rates and foliar condition. Data collected from continuous soil salinity loggers from April to June for one of the two sites were used to determine whether there was a long-term accumulation of salts in the soils. Results for both sites indicate that both sites displayed high salinity and alkalinity, with levels elevated beyond those suggested before those reported to cause negative tree effects. For one site, trees that were alive and trees that had a better foliar condition had significantly lower levels of soil salinity and alkalinity than other trees. High salinity and alkalinity in the soil were also associated with lower nutrient levels for both sites. Although tests for salinity accumulation in the soils of one site were negative, a longer monitoring of the soil conditions within the soil cells is warranted. Despite structural cells being increasingly utilized for their dual role in storm-water management and tree establishment, there may be a considerable trade-off between storm-water management and urban-forest function in northern climates where de-icing salt application continues to be commonplace.