Emissions of nitrous oxide (N sub(2)O) from wetland ecosystems are globally significant and have recently received increased attention. However, relatively few direct studies of these emissions in ...response to water depth-related changes in sediment ecosystems have been conducted, despite the likely role they play as hotspots of N sub(2)O production. We investigated depth-related differential responses of the dissolved inorganic nitrogen distribution in Phragmites australis (Cav.) Trin. ex Steud. rhizosphere versus non-rhizosphere sediments to determine if they accelerated N sub(2)O emissions and the release of inorganic nitrogen. Changes in static water depth and P. australis growth both had the potential to disrupt the distribution of porewater dissolved NH sub(4) super(+), NO sub(3) super(-), and NO sub(2) super(-) in profiles, and NO sub(3) super(-) had strong surface aggregation tendency and decreased significantly with depth. Conversely, the highest NO sub(2) super(-) contents were observed in deep water and the lowest in shallow water in the P. australis rhizosphere. When compared with NO sub(3) super(-), NH sub(4) super(+), and NO sub(2) super(-), fluxes from the rhizosphere were more sensitive to the effects of water depth, and both fluxes increased significantly at a depth of more than 1 m. Similarly, N sub(2)O emissions were obviously accelerated with increasing depth, although those from the rhizosphere were more readily controlled by P. australis. Pearson's correlation analysis showed that water depth was significantly related to N sub(2)O emission and NO sub(2) super(-) fluxes, and N sub(2)O emissions were also strongly dependent on NO sub(2) super(-) fluxes (r=0.491, p<0.05). The results presented herein provide new insights into inorganic nitrogen biogeochemical cycles in freshwater sediment ecosystems.
The prospective rise in atmospheric CO sub(2) and temperature may change the distribution and invasive potential of a species; and intraspecific invasive lineages may respond differently to climate ...change. In this study, we simulated a future climate scenario with simultaneously elevated atmospheric CO sub(2) and temperature, and investigated its interaction with soil salinity, to assess the effects of global change on the ecophysiology of two competing haplotypes of the wetland grass Phragmites australis, that are invasive in the coastal marshes of North America. The two haplotypes with the phenotypes 'EU-type' (Eurasian haplotype) and 'Delta-type' (Mediterranean haplotype), were grown at 0ppt and 20ppt soil salinity, and at ambient or elevated climatic conditions (700 ppm CO sub(2), +5 degree C) in a phytotron system. The aboveground growth of both phenotypes was highest at the elevated climatic conditions. Growth at 20ppt salinity resulted in declined aboveground growth, lower transpiration rates (E), stomata conductance (g sub(s)), specific leaf area, photosynthetic pigment concentrations, and a reduced photosynthetic performance. The negative effects of salinity were, however, significantly less severe at elevated CO sub(2) and temperature than at the ambient climatic conditions. The Delta-type P. australis had higher shoot elongation rates than the EU-type P. australis, particularly at high salinity. The Delta-type also had higher maximum light-saturated rates of photosynthesis (A sub(sat)), maximum carboxylation rates of Rubisco (V sub(cmax)), maximum electron transport rates (J sub(max)), triose phosphate utilization rates (T sub(p)), stomata conductance (g sub(s)), as well as higher Rubisco carboxylation-limited, RuBP regeneration-limited and T sub(p)-regeneration limited CO sub(2) assimilation rates than the EU-type under all growth conditions. Our results suggest that the EU-type will not become dominant over the Delta-type, since the Delta-type has superior ecophysiological traits. However, the projected rise in atmospheric CO sub(2) and temperature will alleviate the effects of salinity on both phenotypes and facilitate their expansion into more saline areas.
Pharmaceuticals are emerging contaminants in the environment and are a ubiquitous presence in rivers downstream of wastewater treatment plant outfalls. Questions remain about the persistence of ...pharmaceuticals in rivers, and the uptake and bioconcentration of pharmaceuticals by aquatic plants. Our study took place in the Yarrowee/Leigh/Barwon River system in southeastern Australia. We quantified the concentrations of five pharmaceuticals (carbamazepine, primidone, propranolol, tramadol, and venlafaxine) in surface water at five sites along a 144-km stretch of river, downstream of the presumed primary point source (a wastewater treatment plant outfall). We quantified pharmaceuticals in the leaves of two aquatic plant species (Phragmites australis and Vallisneria australis) sampled at each site, and calculated bioconcentration factors. All five pharmaceuticals were detected in surface waters, and the highest detected concentration exceeded 500 ng.L−1 (tramadol). Four of the pharmaceuticals (all except tramadol) were detected and quantified at all sites, including the furthest site from the outfall (144 km). Carbamazepine showed less attenuation with distance from the outfall than the other pharmaceuticals. Carbamazepine and venlafaxine were quantified in the leaves of both aquatic plant species (range: 10–31 ng.g−1), and there was evidence that bioconcentration factors increased with decreasing surface water concentrations. The study demonstrates the potential long-distance persistence of pharmaceuticals in river systems, and the bioconcentration of pharmaceuticals by aquatic plants in natural ecosystems. These phenomena deserve greater attention as aquatic plants are a potential point of transfer of pharmaceuticals from aquatic ecosystems to terrestrial food webs.
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•Carbamazepine, venlafaxine, and propranolol were quantified in a southeastern Australian river system 144 km from the presumed primary source.•Carbamazepine showed less attenuation along the length of the river system than other pharmaceuticals analysed.•Two aquatic plants speices bioaccumulated carbamazepine and venlafaxine from low-concentration surface water.
Introduced
Phragmites
(
Phragmites australis
ssp.
australis
) forms part of an invasion assemblage in North America that includes non-native insect herbivores and parasitoids, some of which are now ...found on both the introduced and native subspecies of
Phragmites
(
P. australis
ssp.
americanus
). This insect assemblage is key to understanding the impact of
P. australis
invasion and interpreting the efficacy of biological control used against introduced
P. australis
. Our study provides the first dedicated comparison of insect assemblages associated with native and introduced
P. australis
in Canada. From a 2016 to 2017 survey of 28 geographically paired sites across Ontario, Canada, fourteen insect taxa were recorded from both subspecies. Genotype had no effect on α-diversity but stem attack rates from at least one herbivore were higher on native populations than on paired introduced populations (+ 18.6%). We report the first record of
Chaetococcus phragmitis
(Homoptera: Pseudococcidae) and
Rhizedra lutosa
(Lepidoptera: Noctuidae) in Canada and of
R. lutosa
and
Lasioptera hungarica
(Diptera: Cecidomyiidae) on native
P. australis
in North America.
Studies of the North American native wetland plant Phragmites australis (Cav.) Trin. ex Steud. subsp. americanus Saltonst., P.M. Peterson & Soreng have been hindered by chlorosis - tissue yellowing ...due to reduced chlorophyll production - while grown in controlled conditions, resulting in reduced growth. This study tested the effects of reduced iron Fe(II) and magnesium Mg(II), both important nutrients for chlorophyll production, on photosynthetic performance and growth of North American Phragmites, a plant of interest for wetland restoration and management. Plants were exposed to five treatments in a 13-week greenhouse experiment. Four of the treatments consisted of a factorial arrangement of Fe(II) and Mg(II) treatments (0.0002M FeSO4, 0.0002M MgSO4, both, or none, in supplied water), supplemented with a slow-release fertilizer. A fifth treatment received no fertilizer, Fe(II), or Mg(II). Treatments that received added Fe(II) had significant increases in biomass, stem height, leaf and root production, chlorophyll B, and fluorescence parameters compared to non-Fe(II) treatments. Adding Mg(II) did not significantly improve plant health (growth, morphology, or resource capturing) compared to the fertilized control, and suppressed the stimulatory effect of Fe(II), possibly by interfering with root Fe(II) uptake. Under greenhouse conditions and normal fertilization practices, Fe(II) deficiency can sharply reduce growth and photosynthetic performance of Phragmites australis subsp. americanus. Supplementing plants with freshly prepared solutions of Fe(II) will alleviate limitation and facilitate experimental study and propagation under controlled conditions. The strong effect of iron limitation on native Phragmites suggests there could be a link between Fe(II) limitation and plant competitive interactions in some wetlands.
Invasive plants can influence ecosystem processes such as greenhouse gas (GHG) emissions from wetland systems directly through plant-mediated transfer of GHGs to the atmosphere or through indirect ...modification of the environment. However, patterns of plant invasion often co-vary with other environmental gradients, so attributing ecosystem effects to invasion can be difficult in observational studies. Here, we assessed the impact of Phragmites australis invasion into native shortgrass communities on methane (CH sub(4)) emissions by conducting field measurements of CH sub(4) emissions along transects of invasion by Phragmites in two neighboring brackish marsh sites and compared these findings to those from a field-based mesocosm experiment. We found remarkable differences in CH sub(4) emissions and the influence of Phragmites on CH sub(4) emissions between the two neighboring marsh sites. While Phragmites consistently increased CH sub(4) emissions dramatically by 10.4 plus or minus 3.7 mu mol m super(-2) min super(-1) (mean plus or minus SE) in our high-porewater CH sub(4) site, increases in CH sub(4) emissions were much smaller (1.4 plus or minus 0.5 mu mol m super(-2) min super(-1)) and rarely significant in our low-porewater CH sub(4) site. While CH sub(4) emissions in Phragmites-invaded zones of both marsh sites increased significantly, the presence of Phragmites did not alter emissions in a complementary mesocosm experiment. Seasonality and changes in temperature and light availability caused contrasting responses of CH sub(4) emissions from Phragmites- versus native zones. Our data suggest that Phragmites-mediated CH sub(4) emissions are particularly profound in soils with innately high rates of CH sub(4) production. We demonstrate that the effects of invasive species on ecosystem processes such as GHG emissions may be predictable qualitatively but highly variable quantitatively. Therefore, generalizations cannot be made with respect to invader-ecosystem processes, as interactions between the invader and local abiotic conditions that vary both spatially and temporally on the order of meters and hours, respectively, can have a stronger impact on GHG emissions than the invader itself.
Additional treatment of wastewater, such as constructed wetlands (CWs), is a possible solution to reduce the discharge of antibiotics and antibiotic resistance genes (ARGs) from households and ...industry to the environment. This study aims to investigate the occurrence and removal of antibiotics and ARGs by two full scale CWs operated at different hydraulic retention times (HRT), namely 1 day and 3 days. Both CWs were receiving the same wastewater treatment plant (WWTP) effluent. Temporally and spatially distributed sampling of water and sediment was conducted for one year and samples were analyzed for antibiotics and ARGs by using LC-MS/MS and qPCR. Results showed that both CWs removed antibiotics significantly with a comparable overall removal of 28%–100%, depending on the type of antibiotics. However, some of the antibiotics showed higher concentration after the CW treatment. Five antibiotics (tiamulin, tylosin, oxytetracycline, sulfamethoxazole and trimethoprim) were the most abundant (>1500 ng/l on average) in winter. Meanwhile, ermB was the most abundant (average of 5.0 log) in winter compared to summer (average of 3.5 log). Other ARGs did not show a significant increase or decrease between winter and summer. ARGs were removed from the wastewater by 0.8 to 1.5 log. The HRT did not influence the removal of either the antibiotics or the ARGs. A strong correlation was found between sul genes and intI1. The results also revealed a positive and a negative relationship from sampling point 1 to sampling point 5: a positive relation between abundance of antibiotics, ARGs, and of NO3–N, NH4–N, TP, COD and a negative relation between antibiotics, ARGs and temperature. This relationship showed the effect between antibiotics and ARGs concentrations with physicochemical parameters and nutrients. The ability of CWs to reduce the input of micropollutants into the environment makes CWs a potential post treatment to WWTP.
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•TIA, TYL, OTC, SMX and TRI were the most abundant antibiotics in winter.•ARGs except ermB did not show a significant increase or decrease between seasons.•Antibiotic removal for each CW ranges from 13% to 100%.•Log removal of ARGs in the water phase is low (0.8 to 1.5 log).•HRT does not influence the removal of either antibiotics or ARGs.
The present study investigated the levels of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn in the seagrasses Posidonia oceanica and Cymodocea nodosa, and in the wetland macrophytes Phragmites australis, ...Arundo donax, Typha domingensis, Apium nodiflorum, and Nasturtium officinale. Results showed that the bioaccumulation capacity from sediments, translocation, total levels in plant tissues, and bioindication of metals in sediments, are generally species-specific. In particular, the patterns of metals in the aquatic plants studied were overall independent of ecology (coasts vs wetlands), biomass, anatomy (rhizomatous vs non rhizomatous plants), and life form (hemicrytophytes vs hydrophytes). However, marine phanerogams and wetland macrophytes shared some characteristics such as high levels of heavy metals in their below-ground organs, similar capacity of element translocation in the rhizosphere, compartmentalization of metals in the different plant organs, and potential as bioindicators of Cu, Mn and Zn levels in the substratum. In particular, the present findings indicate that, despite ecological and morphological similarities, different plant species tend to respond differently to exposure to heavy metals. Furthermore, this seems to result from the species individual ability to accumulate and detoxify the various metals rather than being attributed to differences in their ecological and morpho-anatomical characteristics.
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•Plants respond differently to metal inputs, despite similar ecology and anatomy.•Bioaccumulation, internal translocation and bioindication are species-specific.•Total metal concentrations are generally species-specific.•Plants share high metal levels in roots and organ element compartmentalization.•P. australis was the best bioaccumulator and bioindicator species.
•The dominant species were almost missing in soil seed banks of farmed fields.•The structure and composition of soil seed banks changed after farming.•Restoration potential of plant communities ...differed due to salt tolerance.
Wetlands have degraded dramatically in recent decades due to wetland drainage, agricultural reclamation, and soil salinization in China. Soil seed banks, as a way of natural regeneration, can efficiently restore the aboveground vegetation if seeds can survive after farming. To explore the response of soil seed bank to farming and consequent environmental changes, we compared the structure and composition of soil seed banks between Carex-dominated and Phragmites-dominated natural wetlands and their adjacent farmed fields in the Songnen Plain, China. We found that the responses of soil seed banks to farming and saline-alkaline stress were different between the two community types. The seed density and species richness in Carex-dominated natural wetlands were significantly higher than nearby farmed fields, however, there was no significant difference between Phragmites-dominated natural wetlands and nearby farmed fields. Carex schmidtii and Phragmites australis, dominated in natural wetlands, were both missing after farming. At the same time, the invasive species Typha angustifolia dominated in the farmed fields. Redundancy analysis identified that soil salt content was one of the major factors which significantly affected seed bank composition. Saline-alkaline stress significantly restricted the seed germination in farmed Carex fields, however, it had no significant effect in farmed Phragmites fields. Our study indicated that the potential of vegetation restoration was restricted by seed limit and soil salinization, and it differed significantly between the original community types in the Songnen Plain. In addition to hydrological connection, special technologies (such as planting and seeding) and the improvement of soil conditions are also necessary for successful restoration in salt-affected wetlands.
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