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BACKGROUND Ecological treatments are effective for treating agricultural wastewater. In this study, wetland microcosms vegetated with Myriophyllum aquaticum were designed for nitrogen (N) removal from two strengths of swine wastewater, and 15N-labelled ammonium ( NH4+-N) was added to evaluate the dominant NH4+-N removal pathway. RESULTS The results showed that 98.8% of NH4+-N and 88.3% of TN ( TN: 248.6 mg L−1) were removed from low-strength swine wastewater ( SW1) after an incubation of 21 days, with corresponding values for high-strength swine wastewater ( SW2) being 99.2% of NH4+-N and 87.8% of TN ( TN: 494.9 mg L−1). Plant uptake and soil adsorption respectively accounted for 24.0% and 15.6% of the added 15N. Meanwhile, above-ground tissues of M. aquaticum had significantly higher biomass and TN content than below-ground ( P < 0.05). 15N mass balance analysis indicated that gas losses contributed 52.0% to the added 15N, but the N2O flux constituted only 7.5% of total gas losses. The dynamics of NO3−-N and N2O flux revealed that strong nitrification and denitrification occurred in M. aquaticum microcosms, which was a dominant N removal pathway. CONCLUSION These findings demonstrated that M. aquaticum could feasibly be used to construct wetlands for high N-loaded animal wastewater treatment. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The present study compares the practicability, reproducibility, power, and sensitivity of a Myriophyllum aquaticum growth inhibition test in a water-sediment system with the recently accepted Myriophyllum spicatum test in an equivalent testing system and the standard Lemna sp. test. Special consideration was given to endpoints based on M. aquaticum control plant growth and variability of relative growth rate and yield: shoot length, fresh weight, dry weight, and root weight. Sensitivity analysis was based on tests performed with 3,5-dichlorophenol, atrazine, isoproturon, trifluralin, 2,4-dichlorophenoloxyacetic acid, and dicamba. Growth rates for average M. aquaticum control plants were 0.119 d-1 and 0.112 d-1, with average estimated doubling time 6.33 d and 6.74 d for relative growth rate fresh weight and shoot length, respectively. Intrinsic variability of M. aquaticum endpoints was low: 12.9%, 12.5%, and 17.8% for relative growth rate shoot length, relative growth rate fresh weight and yield fresh weight, respectively. The power of the test was fairly high. When the most sensitive endpoints were used for comparison, the 2 Myriophyllum species were similarly sensitive, more sensitive (in the case of auxin simulators), or at least equally sensitive as Lemna minor to other tested herbicides. The M. aquaticum 10-d test with a 7-d exposure period in a water-sediment system has acceptable sensitivity and can provide repeatable, reliable, and reproducible results; therefore, it should not be disregarded as a good and representative additional test in environmental risk assessment. Environ Toxicol Chem 2015;34:2104-2115. © 2015 SETAC [ABSTRACT FROM AUTHOR]

A whole-sediment toxicity test with Myriophyllum aquaticum has been developed by the German Federal Institute of Hydrology and standardized within the International Organization for Standardization (ISO; ISO 16191). An international ring-test was performed to evaluate the precision of the test method. Four sediments (artificial, natural) were tested. Test duration was 10 d, and test endpoint was inhibition of growth rate ( r) based on fresh weight data. Eighteen of 21 laboratories met the validity criterion of r ≥ 0.09 d−1 in the control. Results from 4 tests that did not conform to test-performance criteria were excluded from statistical evaluation. The inter-laboratory variability of growth rates (20.6%-25.0%) and inhibition (26.6%-39.9%) was comparable with the variability of other standardized bioassays. The mean test-internal variability of the controls was low (7% [control], 9.7% [solvent control]), yielding a high discriminatory power of the given test design (median minimum detectable differences [MDD] 13% to 15%). To ensure these MDDs, an additional validity criterion of CV ≤ 15% of the growth rate in the controls was recommended. As a positive control, 90 mg 3,5-dichlorophenol/kg sediment dry mass was tested. The range of the expected growth inhibition was proposed to be 35 ± 15%. The ring test results demonstrated the reliability of the ISO 16191 toxicity test and its suitability as a tool to assess the toxicity of sediment and dredged material. Environ Toxicol Chem 2014;33:662-670. © 2013 SETAC [ABSTRACT FROM AUTHOR]

The assessment of the potentially harmful effects of metals on biota depends on the speciation and bioavailability of the metals. In the present study, the authors investigated Cu accumulation and toxicity in the aquatic plant Myriophyllum aquaticum after exposure to artificial sediments varying in peat or ferric hydroxide content and spiked with Cu (5-200 mg kg−1). Modeling of the kinetic diffusive gradient in thin film (DGT) measurements revealed fast and slow Cu resupply from the solid phase for sediment formulated with and without peat, respectively. Myriophyllum aquaticum proved to be sensitive to Cu, as the Cu accumulation and growth differed depending on the sediment composition and Cu concentration. Comparing the Cu accumulation in M. aquaticum with total dissolved concentration, free concentration, and concentration in solution derived from DGT measurements (CDGT), Cu concentrations revealed that CDGT concentrations were a better predictor of accumulation than the others. However, the relatively weak correlation observed ( r2 = 0.6) and the fact that plant uptake does not increase proportionally to DGT fluxes suggest that Cu uptake in plants was not diffusion limited. Thus, the free Cu concentrations near the root surface were sufficient to meet the plant's demand during the experiment. Furthermore, labile complexes that continuously resupply the Cu2+ pool may also contribute to the concentrations available for plant uptake. In the range of Cu concentrations investigated in the present study, saturation of uptake processes as well as toxicity are considered responsible for the poor DGT prediction of plant uptake. Environ Toxicol Chem 2014;33:278-285. © 2013 SETAC [ABSTRACT FROM AUTHOR]

A sediment contact test (SCT) battery consisting of five ecotoxicological test systems was applied to 21 native freshwater sediments characterized by a broad variety of geochemical properties and anthropogenic contamination. Higher plants ( Myriophyllum aquaticum), nematodes ( Caenorhabditis elegans), oligochaetes ( Lumbriculus variegatus), zebrafish embryos ( Danio rerio), and bacteria ( Arthrobacter globiformis), representing various trophic levels and exposure pathways, were used as test organisms. The test battery detected sediment toxicity caused by anthropogenic pollution, whereas the various tests provided site-specific, nonredundant information to the overall toxicity assessment. Based on the toxicity pattern derived from the test battery, the sediments were classified according to a newly proposed classification system for sediment toxicity assessment. The SCT-derived classification generally agreed well with the application of consensus-based sediment quality guidelines (SQGs), especially with regard to sediments with high toxic potential. For sediments with low to medium toxic potential, the SQGs often underestimated the toxicity that was detected by the SCTs, underpinning the need for toxicity tests in sediment quality assessment. Environ. Toxicol. Chem. 2013;32:144-155. © 2012 SETAC [ABSTRACT FROM AUTHOR]

The relative sensitivity and recovery potential of two aquatic macrophyte species, Lemna minor and Myriophyllum aquaticum, exposed to atrazine (concentration ranges 80-1,280 µg/L and 40-640 µg/L, respectively) were evaluated using slightly adapted standard protocol for Lemna spp.: relative growth rates (RGR) and yield of both plants were measured in 3-d-long intervals during the exposure and recovery phase. Myriophyllum aquaticum was also exposed to atrazine-spiked sediment (0.1-3.7 µg/g) in a water-free system. The results of M. aquaticum sediment contact tests showed that root- and shoot-based growth parameters are equally sensitive endpoints. In the water (sediment-free) test system, L. minor recovered after short (3 d) and longer exposure (7 d) to all atrazine concentrations after only a 5- to 6-d-long recovery phase. The recovery of M. aquaticum after short exposure was slower and less efficient: after 12 d of recovery phase the final biomass of plants exposed to 380 and 640 µg/L was below the initial values. The last interval RGR provides a good indication of plant recovery potential regardless of species growth strategy. If compared to L. minor, the difference in growth rate, sensitivity, lag phase, recovery potential from water-column substances, and also suitability for studies investigating the effect of sediment-bound pollutants advocates the use of M. aquaticum as an additional macrophyte species in risk assessment. Environ. Toxicol. Chem. 2012;31:417-426. © 2011 SETAC [ABSTRACT FROM AUTHOR]

1. By selective grazing, invasive grazers can alter macrophyte-herbivore relationships in shallow freshwater bodies. Evaluating the palatability of macrophytes and understanding the determinants of plant palatability can help predict grazing impact. In no-choice feeding assays, we tested the palatability of 21 species of freshwater macrophytes to the invasive freshwater apple snail Pomacea canaliculata. 2. Daily feeding rate varied greatly with plant species, ranging from 1.1 to 22% of snail body mass. We assessed six plant properties and examined their correlation with feeding rate. Total nitrogen content was positively related, and C:N ratio and dry matter content (DMC) negatively related, to snail feeding rate. There was no significant correlation between snail feeding rate and plant phenolic content, but the feeding rate on Myriophyllum aquaticum (the plant with the highest phenolic content) was very low. 3. We repeated the feeding assays for 15 species that were not palatable as fresh leaves with reconstituted plant tissues formed by mixing ground up dried leaves with agar. The feeding rate still differed greatly among macrophyte species. Phragmites australis and Vallisneria natans (two species with the highest DMC) were eaten much more as reconstituted plant than as fresh leaves, indicating that structure (i.e. DMC) may be important in their defence against snail herbivory. For two plants ( M. aquaticum and Alternanthera philoxeroides) that had moderate amounts of nitrogen/phosphorus but were consumed very little as fresh and reconstituted tissues, we incorporated their extracts into a palatable agar-based food. The extracts from both species greatly reduced snail feeding rate, indicating the presence of chemical defences in these two species. 4. These results indicated that feeding was affected by several plant traits. The snail favoured plants with a high nitrogen content and avoided plants with a high DMC. Only a few plants possessed chemical feeding deterrents that were effective against this snail. Given the invasive spread of P. canaliculata in Asia, ecologists and managers should consider plant palatability when selecting plants for use in wetland restoration and when predicting the impact of further invasion by this species. [ABSTRACT FROM AUTHOR]

Myriophyllum aquaticum is an aquatic plant of still or slow flowing waters. The species mostly occurs in its emerged growth form in dense stands, but submerged shoots can also be found. Due to its rapid growth, M. aquaticum is considered one of the most important aquatic weeds worldwide. In southern Europe, M. aquaticum occurs in irrigation and drainage systems, rice fields and lowland wetlands. In this study, root development and growth response of M. aquaticum to different water levels and nutrient availabilities were investigated in a rhizotron experiment under Central European climatic conditions. The species shows an ability to respond to drained soil conditions by a rapid root growth (up to >1 cm day−1), resulting in a deep root system under drained conditions. In waterlogged soil, the root system spreads more horizontally. Root density increased with increasing nutrient availability. Root:shoot ratio increased significantly with decreasing nutrient availability. In addition, total shoot length, shoot biomass, root biomass and total biomass differed significantly between different water levels and different nutrient availabilities. Relative growth rate increased with increasing water level and nutrient availability. Shoot porosity was higher in nutrient rich substrate than in nutrient low substrate. Root porosity increased with increasing water level. In conclusion, M. aquaticum shows a high tolerance to different water levels, which may be important for future habitat conditions in waterbodies and wetlands in Central Europe under the impact of global change with increased water level fluctuations. [ABSTRACT FROM AUTHOR]

The ecological assessment of a C12-15 AE-3S linear alkylethoxysulfate (AES) anionic surfactant to invertebrates, fish, periphyton, and an aquatic macrophyte was conducted in a 30-d outdoor stream mesocosm study with five replicated concentrations and controls. Alkylethoxysulfate structural integrity and exposure concentrations were maintained during the 30-d treatment period, with average measured concentrations of 0.7, 1.27, 2.2, 4.31, and 10.18 mg/L. No effects were observed on the aquatic macrophyte Myriophyllum aquaticum at the highest concentration tested. A sevenfold increase in periphyton biomass at 10.18 mg/L was observed relative to controls primarily because of increases in density of the filamentous alga Mougeotia sp. Densities of the invertebrates Annelida (Stylaria), Amphipoda, Copepoda, Trichoptera (Hydropsychidae), Cladocera, and Diptera (Chironomidae) significantly decreased in streams treated with AES at 10.18 mg/L. Densities of drifting invertebrates were not observed to be affected at any concentration tested. Reproduction of Pimephales promelas significantly decreased at 1.27 mg/L and growth of juvenile Lepomis macrochirus was significantly affected at 4.31 mg/L. Multivariate cluster analysis and nonmetric multidimensional scaling ordination showed distinct structural effects on the invertebrate communities in the streams treated with AES at 10.18 mg/ L compared to the control and streams treated at <10.18 mg/L through the 30-d treatment. Convergence of the communities treated at 10.18 mg/L toward control communities in the ordination suggests recovery in these communities after termination of surfactant treatment. The results from this study support an ecosystem value of >2.0 mg/L, and indicate that the conservative Dutch risk assessment for AESs has at least a fivefold margin of safety. [ABSTRACT FROM AUTHOR]