An integrated constructed wetland to treat contaminants and nutrients from dairy farmyard dirty water

Water pollution by agriculture can include inappropriately managed dairy farmyard dirty water. In Ireland, dairy farmyard dirty water includes farmyard runoff, parlour washings, and silage/farmyard manure effluents. The objectives of this study were to determine (i) the quality and quantity of dirty water generated at a farm-scale and (ii) the seasonal effectiveness of a constructed wetland to treat farmyard dirty water. The wetland system was 4800 m² in area and treated dirty water from a 42-cow organic dairy unit with an open yard area of 2031 m². Monthly dirty water inflow rate to the wetland ranged between 3.6 and 18.5 m³ d⁻¹. Farmyard dirty water accounted for 27% of hydrological inputs to the wetland, whereas rainfall on wetland, along with wetland bank inflows accounted for 45 and 28%, respectively. Farmyard dirty water quality and quantity did not vary with season. Yearly mass loads discharged to the wetland were 47 ± 10 kg yr⁻¹ of soluble reactive phosphorus (SRP), 128 ± 35 kg yr⁻¹ of NH₄⁺, 5484 ± 1433 kg yr⁻¹ of organic material as measured by five-day biological oxygen demand (BOD₅), and 1570 ± 465 kg yr⁻¹ of total suspended solids (TSS). Phosphorus retention by the wetland varied with season (5–84%) with least amounts being retained during winter.     

Comparative study of ecological indices for assessing human-induced disturbance in coastal wetlands of the Laurentian Great Lakes

Several ecological indices have been developed to evaluate the wetland quality in the Laurentian Great Lakes. One index, the water quality index (WQI) can be widely applied to wetlands and produces accurate measurements of wetland condition. The WQI measures the degree of water quality degradation as a result of nutrient enrichment and road runoff. The wetland fish index (WFI), wetland zooplankton index (WZI), and the wetland macrophyte index (WMI), are all derived from the statistical relationships of biotic communities along a gradient of deteriorating water quality. Compared to the WQI, these indices are less labor-intensive, cost less, and have the potential to produce immediate results. We tested the relative sensitivity of each biotic index for 32 Great Lakes wetlands relative to the WQI and to each other. The WMI (r² = 0.84) and WFI (r² = 0.75) had significant positive relationships (P < 0.0001) with the WQI in a linear and polynomial fashion. Slopes of the WMI and WFI were similar when comparing the polynomial regressions (ANCOVA; P = 0.117) but intercepts were significantly different (P = 0.004). The WZI had a positive relationship with the WQI in degraded wetlands and a negative relationship in minimally impacted wetlands. The strengths and weaknesses of each index can be explained by the interactions among fish, zooplankton, aquatic plants and water chemistry. The distribution of different species indicative of low and high quality in each index provides insight into the relative wetland community composition in different parts of the Great Lakes and helps to explain the differences in index scores when different organisms are used. Our findings suggest that the WMI and WFI produce comparable results but the WZI should not be used in the minimally impacted wetlands without further study.     

Typha × glauca dominance and extended hydroperiod constrain restoration of wetland diversity

Urban wetlands typically have few plant species. In wetlands designed to improve water quality, nutrient-rich water and highly variable water levels often favor aggressive, flood-tolerant plants, such as Typha × glauca (hybrid cattail). At Des Plaines River Wetlands Demonstration Site (Lake Co., IL), we assessed T. × glauca dominance and plant community composition under varying hydroperiods in a complex of eight constructed wetlands. Plots flooded for more than 5 weeks during the growing season tended to be dominated by T. × glauca, while plots flooded fewer days did not. Plots with high cover of T. × glauca had low species richness (negative correlation, R² = 0.72, p < 0.001). However, overall species richness of the wetland complex was high (94 species), indicating that wetlands in urbanizing landscapes can support many plant species where T. × glauca is not dominant. T. × glauca-dominated areas resisted the establishment of a native plant community. Removing T. × glauca and introducing native species increased diversity initially, but did not prevent re-invasion. Although 12 of the 24 species we seeded became established in our cleared plots, T. × glauca rapidly re-invaded. In year 1, T. × glauca regained an average of 11 ramets m⁻², and its density doubled in year 2. The likelihood of planted species surviving decreased as duration of inundation increased, and in both seeded and planted plots, graminoids had greater survivorship through year 2 than forbs across a range of water levels. Within 4 years, however, T. × glauca was the most common plant, present in 92% of the cleared plots. Simply removing T. × glauca and adding propagules to an urban wetland is not sufficient to increase diversity.     

Assessing the importance of nursery areas of European hake (Merluccius merluccius) using a body condition index

In this study, we analysed the variability of reserve storage in juvenile European hake (Merluccius merluccius) off the western coasts of Italy (Central Mediterranean Sea). Reserve storage was measured by the hepatosomatic index (HSI), in relation to environmental and population covariates. HSI has been proved to be a consistent measure of energy storage in gadoids, thus reflecting quantity and quality of food availability for growth. Generalized Additive Models for Location, Scale and Shape (GAMLSS) were used to model the effect of depth, bottom temperature, bottom currents, fish density and fish body size on HSI of juvenile European hake. The results revealed that reserve storage in the liver appears to be maximized for juveniles living on the shelf break, between 120 and 170 m depth, with bottom temperature and current speed not exceeding 14 °C and 0.04 m s⁻¹ respectively. Furthermore, HSI significantly increased with fish density up to about 6000 individuals per km⁻² and decreased at higher densities indicating that reserve accumulation in the liver might be subject to density-dependent mechanisms (e.g. competition for food) as well. These findings suggest that the use of density as measure of nursery importance need to be further investigated. Finally, we found that HSI increased with fish size up to about 14 cm total length. Based on these results, HSI appears a reasonable index to indirectly measure the quality of habitats where juvenile European hake aggregate after their settlement on the bottom, and to potentially monitor habitat suitability as nursery across the spatial-temporal gradient.     

Diatoms are better indicators of urban stream conditions: A case study in Beijing,China

Urbanization dramatically affects hydrology, water quality and aquatic ecosystem composition. Here we characterized changes in diatom assemblages along an urban-to-rural gradient to assess impacts of urbanization on stream conditions in Beijing, China. Diatoms, water chemistry, and physical variables were measured at 22 urban (6 in upstream and 16 in downstream) and 7 rural reference stream sites during July and August of 2013. One-way ANOVA showed that water physical and chemical variables were significantly different (p < 0.05) between urban downstream and both reference and urban upstream sites, but not between reference and urban upstream sites (p > 0.05). Similarly, structural metrics, including species richness (S), Shannon diversity (H′), species evenness (J′) and Simpson diversity (D′), were significantly different (p < 0.05) between urban downstream and both reference and urban upstream sites, but not (p > 0.05) between reference and urban upstream sites. However, diatom assemblages were very different among all sites. Achnanthidium minutissima was a consistent dominant species in reference sites; Staurosira construens var. venter and Pseudostaurosira brevistriata were the dominant species in urban upstream sites; and Nitzschia palea was the dominant species in urban downstream sites. Clustering analyses based on the relative abundance of diatom species, showed all the samples fit into three groups: reference sites, urban upstream sites, and urban downstream sites. Canonical correspondence analysis (CCA) and Monte Carlo permutation tests showed that concentration of K⁺, EC, TN, Cl⁻ and pH were positively correlated with relative abundance of dominant diatom species in urban downstream samples; WT and F⁻ were correlated with reference and urban stream diatom composition. Our results demonstrate that the composition of diatom species was more sensitive to urbanization than the water physical and chemical parameters, and that diatom assemblage structure metrics more accurately assessed water quality. Some species, such as Amphora pediculus and Cocconeis placentula were among the dominant species in low nutrients stream sites; however, they were considered to be high nutrient indicators in some streams in USA. We suggest using caution in applying indicator indices based on species composition from other regions. It is necessary to build a complete set of diatom species data and their co-ordinate environment data for specific regions.     

Macrophyte decomposition in a surface-flow ammonia-dominated constructed wetland: Rates associated with environmental and biotic variables

Decomposition of senesced culm material of two bulrush species was studied in a surface-flow ammonia-dominated treatment wetland in southern California. Decomposition of the submerged culm material during summer months was relatively rapid (k = 0.037 day⁻¹), but slowed under extended submergence (up to 245 days) and during fall and spring sampling periods (k = 0.009–0.014 day⁻¹). Stepwise regression of seasonal data indicated that final water temperature and abundance of the culm-mining midge, Glyptotendipes, were significantly associated with culm decomposition. Glyptotendipes abundance, in turn, was correlated with water quality parameters such as conductivity and dissolved oxygen and ammonia concentrations. No differences were detected in decomposition rates between the bulrush species, Schoenoplectus californicus and Schoenoplectus acutus.     

Nitrogen transformations and balance in a constructed wetland for nutrient-polluted river water treatment using forage rice in Japan

A pilot-scale surface-flow wetland planted with a new rice variety (Oryza sativa ’Kusahonami’) developed for livestock feed was constructed for treating nutrient-polluted river water. To calculate the balance between nitrogen removal and rice plant uptake of nitrogen, nitrogen removal from river water and nitrogen interactions among plants, soil water, and soil were investigated for this constructed wetland over two growing seasons in 2004 and 2005. The constructed wetland removed 33% of the total nitrogen entering with the river water. Rice plants were found to constitute the major nitrogen storage, with plant uptake being the major removal mechanism. The total inorganic nitrogen concentration in the rhizosphere changed seasonally because of plant uptake. Most nitrogen taken up by rice plants was contained in the aboveground biomass, with the mean amount being 34.0 g N m⁻². However, the nitrogen balance calculation suggested that rice plants uptake some nitrogen from soil, decreasing the available nitrogen in the soil of the lined impermeable wetland.     

Comparison of the treatment performances of blast furnace slag-based and gravel-based vertical flow wetlands operated identically for domestic wastewater treatment in Turkey

In 2001, to foster the practical development of constructed wetlands (CWs) used for domestic wastewater treatment in Turkey, vertical subsurface flow constructed wetlands (30 m² of each) were implemented on the campus of the METU, Ankara, Turkey. The main objective of the research was to quantify the effect of different filter media on the treatment performance of vertical flow wetlands in the prevailing climate of Ankara. Thus, a gravel-filled wetland and a blast furnace granulated iron slag-filled wetland were operated identically with primarily treated domestic wastewater (3 m³ d⁻¹) at a hydraulic loading rate of 0.100 m d⁻¹, intermittently. Both of the wetland cells were planted with Phragmites australis. According to the first year results, average removal efficiencies for the slag and gravel wetland cells were as follows: total suspended solids (TSS) (63% and 59%), chemical oxygen demand (COD) (47% and 44%), NH₄⁺–N (88% and 53%), total nitrogen (TN) (44% and 39%), PO₄³⁻-P (44% and 1%) and total phosphorus (TP) (45% and 4%). The treatment performances of the slag-filled wetland were better than that of the gravel-filled wetland in terms of removal of phosphorus and production of nitrate. Since this study was a pioneer for implementation of subsurface constructed wetlands in Turkey using local sources, it has proved that this eco-technology could also be used effectively for water quality enhancement in Turkey.     

Side-by-side comparison of horizontal subsurface flow and free water surface flow constructed wetlands and artificial neural network (ANN) modelling approach

A horizontal subsurface flow (HSSF) and a free water surface flow (FWSF) constructed wetlands (4 m² of each) were set up on the campus of Harran University, Sanliurfa, Turkey. The main objective of the research was to compare the performance of two systems to decide the better one for future planning of wastewater treatment system on the campus. Both of the wetland systems were planted with Phragmites australis and Canna indica. During the observation period (10 months), environmental conditions such as pH, temperature and total chemical oxygen demand (COD), soluble COD, total biochemical oxygen demand (BOD), soluble BOD, total suspended solids (TSS), total phosphate (TP), total nitrogen (TN) removal efficiencies of the systems were determined. According to the results, average yearly removal efficiencies for the HSSF and the FWSF, respectively, were as follows: total COD (75.7% and 69.9%), soluble COD (85.4% and 84.3%), total BOD (79.6% and 87.6%), soluble BOD (87.7% and 95.3%), TN (33.2% and 39.4%), and TP (31.5% and 6.5%). Soluble COD and BOD removal efficiencies of both systems increased gradually since the start-up. After nine months of operation, above 90% removal of organic matters were observed. The treatment performances of the HSSF were better than that of the FWSF with regard to the removal of suspended solids and total COD at especially high temperatures. In FWSF systems, COD concentrations extremely exceeded the discharge limit values due to high concentrations of algae in spring months.The performance of the two systems was modelled using an artificial neural network-back-propagation algorithm. The ANN model was competent at providing reasonable match between the measured and the predicted concentrations of total COD (R = 0.90 for HSSF and R = 0.96 for FWSF), soluble COD (R = 0.90 for HSSF and R = 0.74 for FWSF) and total BOD (R = 0.94 for HSSF and R = 0.84 for FWSF) in the effluents of constructed wetlands.     

Response of epilithic diatom communities to environmental gradients along an Ecuadorian Andean River

Epilithic diatom communities are particularly suitable for the evaluation of freshwater quality. In Ecuador, however, no water quality index includes this biotic parameter. This work is the first attempt in the country to determine the composition of epilithic diatom communities associated with different degrees of eutrophication. This was accomplished by measuring physical, chemical and microbiological variables at five sampling sites along the Pita River, Ecuador, from August to December 2016. The results indicate a clear gradient of eutrophication from sampling sites P1 (good water) in the upper reaches to P5 (bad water) located in the lower reaches. Concerning diatom analyses, the results indicated a high diversity for tropical areas in terms of species richness, varying from S = 34 in headwaters to S = 42 downstream. Moreover, the results obtained suggest a lack of concordance with the trophic values given to some of the epilithic diatoms in the literature. There were also species that seem to be sensitive to downstream nutrient increases that were not considered as bioindicators in previous studies. We concluded that the trophic values of diatom species available in the scientific literature are not directly applicable to their sites in the Pita River. Hence, it is necessary to establish a trophic diatom index for the Andean region of Ecuador.     

Treatment of high-strength wastewater in tropical constructed wetlands planted with Sesbania sesban: Horizontal subsurface flow versus vertical downflow

Treatment of various types of wastewaters is an urgent problem in densely populated areas of many tropical countries. We studied the potential of using Sesbania sesban, an N₂-fixing shrub, in constructed wetland systems for the treatment of high-strength wastewater. A replicated horizontal subsurface flow system and a saturated vertical downflow system was established with planted and unplanted beds to assess the effects of system design and presence of plants on treatment performance. The systems were loaded with a mixture of domestic and pig farm wastewater at three hydraulic loading rates of 80, 160 and 320 mm d^?1. The S. sesban plants grew very well in the constructed wetland systems and produced 17.2–20.2 kg dry matter m^?2 year^?1 with a high nitrogen content. Mass removal rates and removal rate constants increased with loading rate, but at 320 mm d^?1 the effluent quality was unacceptable and hydraulic problems appeared. Mass removal rates and removal rate constants were much higher than reported in other studies probably because of the high-strength wastewater, the high loading rates and the tropical conditions. Planted systems removed pollutants much more efficiently than the unplanted controls. Direct plant uptake constituted only up to 8% of the total-N removal and 2% of the P removal at the lowest loading rate, and was quantitatively of low importance compared to other removal processes. The significant effects of plants were therefore related more to their indirect effects on the removal processes. This study for the first time documents that S. sesban can be used in constructed wetland systems for the treatment of polluted water while at the same time producing a valuable N rich biomass that can be used for animal fodder or soil amendment.     

Latitudinal changes in species diversity of permafrost wetland plant communities in Great Xing’an Mountain valleys of Northeast China

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude (P < 0.01), but decreased significantly in the shrub layer (P < 0.01). Species composition and the orders of dominant species in the plant communities by importance value changed along latitude. Latitudinal changes of α-diversity in permafrost wetland plant communities were different in the herb and shrub layers. With decreasing latitude, species richness and species diversity increased in the herb layer; but decreased in the shrub layer. The opposite patterns were found for species dominance. Species evenness in the shrub layer decreased with decreasing latitude. ?-diversity in the herb and shrub layers decreased first, and then increased, and finally decreased with increasing latitude. Species composition in the herb layer was similar among the plots at higher latitudes.     

A study of the microbial quality of grey water and an evaluation of treatment technologies for reuse

The reuse of grey water for non-potable water applications is a potential solution for water-deprived regions worldwide. Adequate treatment of grey water prior to reuse is important to reduce the risks of pathogen transmission and to improve the efficacy of subsequent disinfection. This study investigated the presence of common pathogens in grey water and compared the pathogen removal performance of leading contender treatment technologies. The opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus were detected in the grey water tested. Three configurations of constructed wetland, a membrane bioreactor (MBR), and a membrane chemical reactor (MCR) were evaluated for indicator bacteria (total coliforms, Escherichia coli, Enterococci, Clostridia, and heterotrophs) removal over a period of 2 years under conditions of low and high strength grey water influent. Total coliforms were found to be good indicators for P. aeruginosa, showing strong and significant Spearman's rank correlations in the influent grey water (r_s = 0.77, P = 0.005) and treated effluents (r_s = 0.81, P ≤ 0.001). The MBR provided the highest quality treated effluent and was the most robust treatment technology, remaining unaffected by an increase in influent grey water strength. Of the three constructed wetlands, the VFRB was the most reliable performer under low and high strength influent conditions, indicating aerobic unsaturated wetland to be the most suitable form of the technology for pathogen removal.     

Towards calcareous wetland creation in flooded abandoned aggregate quarries: A 3-year field mesocosm study

The purpose of this study was to demonstrate the feasibility of the rehabilitation of abandoned aggregate quarries to calcareous wetlands through a growth experiment at the quarry floor. We tested the effects of planting substrate (fine screenings, coarse rock, transplanted peatball, and topsoil addition to screenings) and springtime water depth (+15, 0, and ?15 cm relative to ground surface) on the growth of Carex aquatilis over 3 years. Survival rate of the transplanted material was 100%. Minimal growth was observed after the first growing season, but by the end of the third growing season the transplanted material had added on average 80, 4, and 3 shoots in the topsoil-amended, intact peatball, and coarse rock treatments, respectively, but lost on average 4 shoots in the fine screenings treatment. The addition of topsoil significantly increased final aboveground biomass (285 ± 49 g per plot) compared to the peatball (40 ± 16 g), rock (36 ± 11 g) and screenings (35 ± 21 g) treatments, which were not significantly different. The effect of water depth did not lead to overall significant differences, as Carex aquatilis ramets were capable of growing in springtime water levels from 15 cm above to 15 cm below ground surface. Our data demonstrate that some flooded abandoned aggregate quarry floors represent suitable sites for conversion to calcareous wetlands, even with a strategy of minimum maintenance, and that wetland species are capable of growth in these largely inorganic settings.     

Effects of plant diversity on microbial biomass and community metabolic profiles in a full-scale constructed wetland

There has been less understanding of relations of microbial community patterns with plant diversity in constructed wetlands. We conducted a single full-scale subsurface vertical flow constructed wetland (SVFCW, 1000 m²) study focusing on domestic wastewater processing. This study measured the size and structure of microbial community using fumigation extraction and BIOLOG Ecoplate? techniques, to examine the effects of macrophyte diversity on microbial communities that are critical in treatment efficiency of constructed wetlands. We also determined the relationship of plant diversity (species richness) with its biomass production under disturbance of the same wastewater supply. Linear regression analysis showed that plant biomass production strongly correlated with plant species richness (R = 0.407, P < 0.001). Increase in plant species richness increased microbial biomass carbon and nitrogen (R = 0.494, P < 0.001; R = 0.465, P < 0.001) and utilization of amino acids on Ecoplates (R = 0.235, P = 0.03), but limited the utilization of amine/amides (R = ?0.338, P = 0.013). Principal components analysis (PCA) showed that the diversity and community-level physiological profiles (CLPP) of microbial community at 168 h of incubation strongly depended on the presence or absence of plant species in the SVFCW system, but not on the species richness. This is the first step toward understanding relations of plant diversity with soil microbial community patterns in constructed wetlands, but the effect of species diversity on microbial community should be further studied.     

Performance of the Columbia,Missouri, treatment wetland

Constructed treatment wetlands have served the City of Columbia, MO, for fourteen years. Four free water surface wetland units in series, comprised of 23 cells, are an addition to the activated sludge wastewater treatment plant, for the purpose of added biochemical oxygen demand (BOD) and total suspended solids (TSS) control. The system operates year-round, and supplies water to the Eagle Bluffs Conservation Area for wetland maintenance. The cattail wetlands processed an average of 57,000 m³/d, at a water depth of 20 cm. The resulting detention time was approximately 2 days, and the hydraulic loading was 13 cm/d. Water temperatures were warm leaving the treatment plant and in the wetlands in winter, because of the short detention. The period of record average carbonaceous biochemical oxygen demand (CBOD) leaving the wetlands was 5.0 mg/L, and the TSS was 14.7 mg/L. Dissolved oxygen was depressed in summer, likely because of the high sediment demand. Nutrient concentrations were only minimally reduced, total nitrogen (TN) by 22% and total phosphorus (TP) by 6%. However, load reductions were maximal, 98 t/yr for nitrogen, and 3.6 t/yr for phosphorus. Fecal coliforms were reduced by 98%, and E. coli by 95%. First order rate coefficients were high for CBOD (64 m/yr), nitrate (61 m/yr) and organic nitrogen (42 m/yr), but relatively low for ammonia (8 m/yr) and phosphorus (5.7 m/yr). Nitrogen removal was strongly affected by vegetative uptake. Sediment accretion in the wetland inlets was substantial, at 1.6 cm/yr in the inlets to the upstream wetland units. Muskrats caused vegetation damage, and waterfowl use was high in winter, causing TSS excursions.     

Landscape hydrogeomorphic conditions determine structure and species composition of an ephemeral floodplain wetland

Wetlands are major sources of habitat heterogeneity, with certain environmental variables controlling wetland structure and composition. There is very little information on the heterogeneity of ephemeral floodplain wetland patch mosaics and how hydrogeomorphic circumstance affects composition and structure. Structure (wetland size) and composition (herbaceous species) are two attributes of an ephemeral wetland that are easily quantifiable using a moving window analysis. The moving window analysis is a statistical technique that identifies significant changes in parameters (i.e., structure and composition) along gradients. An analysis of changes in wetland structure and composition longitudinally identified two hydrogeomorphic types and laterally delineated wetland boundaries. The wide–flat type had a wide (131.2 ± 50.4 m) wetland patch and a mean lateral slope of 0.008 ± 0.003, in contrast the narrow–deep type had a significantly smaller (80 ± 40.2 m) and steeper (0.048 ± 0.06) wetland patch. Changes in hydrogeomorphology had distinct effects on the species composition of the wetland. Facultative wetland species such as Sporobolus pyrimidalis and Ischaemum afrum were associated with the wide–flat type, while, the narrow–deep type was characterized by more obligate, flood dependent species such as Phragmites australis, Mariscus congestus, and Eriochloa meyeriana. Internally, the structure and composition of ephemeral wetlands on the northern plains of Kruger National Park were spatially heterogeneous and correlated to hydrogeomorphic conditions, that are identifiable when examined at the wetland scale. Results add knowledge to wetlands as sources of landscape heterogeneity and highlight how environmental variation can result in increases in wetland heterogeneity.     

Toxicity evaluation of parboiled rice effluent using sperm quality of zebrafish as bioindicator

This study aimed to assess the acute toxicity of raw and treated wastewater generated by the rice parboiling industry using zebrafish (Danio rerio) sperm quality as a bioindicator. Toxicity bioassays were conducted comparing physicochemical parameters of sperm quality for zebrafish at sublethal conditions (n = 150 fish, 50 per treatment). Acute toxicity was detected in all sperm quality parameters assessed for both raw and treated wastewater, when contrasted to the control (p < 0.05). For zebrafish exposed to raw effluent, negative correlations with parameters of sperm quality were observed for the concentration of iron, phosphorus and total suspended solids (p < 0.05). Salinity, the biochemical oxygen demand and the concentration of total suspended solids were negatively correlated with parameters of sperm quality for zebrafish exposed to treated effluent (p < 0.05). In comparison with the levels observed for the raw effluent, most physicochemical parameters of the treated effluent were reduced to levels within the limits required by the environmental legislation. Despite the physical and chemical parameters measured in the treated wastewater meeting environmental legislation thresholds, acute toxicity persisted. These results show that the sperm quality can be used as a bioindicator for wastewater toxicity and release of wastewater to surface water could affect the fertility of fishes.     

Effects of plant diversity on biomass production and substrate nitrogen in a subsurface vertical flow constructed wetland

Most biodiversity experiments have been conducted in grassland ecosystems with nitrogen limitation, while little research has been conducted on relationships between plant biomass production, substrate nitrogen retention and plant diversity in wetlands with continuous nitrogen supply. We conducted a plant diversity experiment in a subsurface vertical flow constructed wetland for treating domestic wastewater in southeastern China. Plant aboveground biomass production ranged from 20 to 3121 g m^?2 yr^?1 across all plant communities. In general, plant biomass production was positively correlated with species richness (P = 0.001) and functional group richness (P = 0.001). Substrate nitrate concentration increased significantly with increasing plant species richness (P = 0.046), but not with functional group richness (P = 0.550). Furthermore, legumes did not affect biomass production (P = 0.255), retention of substrate nitrate (P = 0.280) and ammonium (P = 0.269). Compared to the most productive of the corresponding monocultures, transgressive overyielding of mixed plant communities did not occur in most polycultures. Because greater diversity of plant community led to higher biomass production and substrate nitrogen retention, thus we recommend that plant biodiversity should be incorporated in constructed wetlands to improve wastewater treatment efficiency.     

Soil bacterial community structure and physicochemical properties in mitigation wetlands created in the Piedmont region of Virginia (USA)

Wetland creation is a common practice for compensatory mitigation in the United States. Vegetation attributes have been used as a quick measure of mitigation success in most post-creation monitoring, while little attention has been paid to soils that provide the substrate for flora and fauna to establish and develop. Created wetland soils are often found not indicative of ‘hydric soil’ with a lack of development of physicochemical properties (i.e., bulk density, moisture content, and carbon and nitrogen contents) comparable to those in natural wetlands. Moreover, soil bacterial communities are rarely examined though they are integrally involved in biogeochemical functions that are critical for ecosystem development in created wetlands. We analyzed soil physicochemistry and profiled soil bacterial community structure using amplicon length heterogeneity polymerase chain reaction (LH-PCR) of 16S ribosomal DNA in three relatively young wetlands (<10 years old) created in the Piedmont region of Virginia. We examined the data by site and by specific conditions of each site (i.e., induced microtopography and hydrologic regime). Multidimensional scaling (MDS) and analysis of similarity (ANOSIM) showed clear clustering and significant differences both in soil physicochemistry (Global R = 0.70, p = 0.001) and in soil bacterial community profiles (Global R = 0. 77, p = 0.001) between sites. Soil physicochemistry (Global R = 1, p = 0.005) and bacterial community structure (Global R = 0.79, p = 0.005) of soils significantly differed by hydrologic regime within a wetland, but not by microtopography treatment. A significant association was found between physicochemistry and bacterial community structure in wetland soils, revealing a close link between two attributes (ρ = 0.39, p = 0.002). C/N (carbon to nitrogen) ratio was the best predictor of soil bacterial community patterns (ρ = 0.56, p = 0.001). The diversity of soil bacterial community (Shannon's H′) differed between sites with a slightly higher diversity observed in a relatively older created wetland, and seemed also fairly determined by hydrologic regime of a site, with a relatively dry site being more diverse.