Effects of eutrophic water with ammonium chloride, urea, potassium dihydrogen phosphate and sodium-ß-glycerophosphate on Myriophyllum verticillatum and epiphytic bacteria.

With the rapid development of industry and agriculture, excessive nitrogen and phosphorus released into natural surface water have caused eutrophication. Applying submerged plants to manage eutrophic water has attracted widespread attention. However, there are limited studies on the effects of different nitrogen and phosphorus in the water environment on submerged plants and their epiphytic biofilm. Therefore, this paper investigated the effects of eutrophic water with ammonium chloride (IN), urea (ON), potassium dihydrogen phosphate (IP), and sodium-ß-glycerophosphate (OP) on Myriophyllum verticillatum and epiphytic biofilms. The results showed that Myriophyllum verticillatum exhibited a good purification effect on the eutrophic water with inorganic phosphorus, the removal rates of IP were 68.0%, and the plants grew best in this condition. The fresh weight of the IN group and ON group increased by 12.24% and 7.12%, and the shoot length of the IN group and the ON group increased by 17.71% and 8.33%; the fresh weight of the IP group and OP group increased by 19.19% and 10.83%, the shoot length of the IP group and the OP group increased by 21.09% and 18.23%. In addition, the enzyme activities of superoxide dismutase, catalase, nitrate reductase, and acid phosphatase in plant leaves were significantly changed in eutrophic water with different forms of nitrogen and phosphorus. Finally, the analysis of the epiphytic bacteria showed that different forms of nitrogen and phosphorus nutrients could significantly alter the abundance and structure of microorganisms and microbial metabolism also had significant changes. This study provides a new theoretical basis for evaluating the removal of different forms of nitrogen and phosphorus by Myriophyllum verticillatum, and it also provides new insights for the subsequent engineering of epiphytic microorganisms to improve the capability of submerged plants to treat eutrophic water.

Significance of manganese resistant bacillus cereus strain WSE01 as a bioinoculant for promotion of plant growth and manganese accumulation in Myriophyllum verticillatum.

Endophytic bacteria are generally helpful for plant growth and protection. Strain WSE01, which was identified as bacillus cereus, was isolated from the stem of Myriophyllum verticillatum and it displayed a high tolerance to Mn (1500 mg/L). The strain was found to be able to produce indole-3-acetic acid (IAA) and siderophores, fix the atmospheric nitrogen and dissolve potassium from insoluble K-bearing minerals. In hydroponic culture experiments, the inoculation of strain WSE01 significantly promoted the growth and increased the leaf enzyme activity in the inoculated plant M. verticillatum. Furthermore, the manganese content was increased by 36.4% in stems and by 54.7% in leaves of the inoculated plant under Mn stress at 400 mg/L, compared to the non-inoculated group. This study suggests that the strain WSE01 has the potential to be used as biocontrol and/or biofertilizing agents for application in macrophyte M. verticillatum and conduces to achieving more effective phytoremediation of metal-contaminated waters.

Bio-cord plays a similar role as submerged macrophytes in harboring bacterial assemblages in an eco-ditch.

Artificial carriers are widely used to enhance the formation of biofilm and improve pollutants' removal efficiency in agricultural wastewater treatment ditches (eco-ditches), yet comprehensive insight into their bacterial community is scarce. In this study, bacterial diversities in four different habitats-the water column, surface sediments, submerged macrophytes (Myriophyllum verticillatum L.), and the artificial carriers (bio-cord)-were compared in a Chinese eco-ditch. Comparable richness and evenness of bacterial communities were observed on M. verticillatum and bio-cord, both being higher than for free-living bacteria in the water column but lower than for bacteria in the surface sediment. The highest similarity of bacterial community composition and structure also occurred between M. verticillatum and the bio-cord, dominated by α- and γ-proteobacteria, Verrucomicrobia, and Bacteroidetes. Firmicutes and Planctomycetes, respectively, were the exclusive abundant phyla in M. verticillatum and the bio-cord, probably indicating the unique interaction between M. verticillatum and their epiphytic bacteria. Some abundant genera, such as Roseomonas, Pseudomonas, and Rhodopirellula, which were exclusively observed in M. verticillatum or the bio-cord, have been reported to have the same capacity to remove nitrogen and organic matter in wastewater treatment systems. In conclusion, in the studied eco-ditch, the bio-cord was found to play a similar role as submerged macrophytes in harboring bacterial assemblages, and we therefore propose that bio-cord may be a good alternative or supplement to enhance wastewater treatment in agricultural ditches.

Heavy Metal Uptakes by Myriophyllum verticillatum from Two Environmental Matrices: The Water and the Sediment.

To determine the preferred elements of the benthic plant Myriophyllum verticillatum, changes in the element concentrations in the plant were investigated in laboratory condition. The reactor was fed with synthetically contaminated water consisting of 2×10(-6) M of the heavy metals Fe, Cr, Zn, Ni, and Cu for 1060 hours. The elements that were preferentially taken up by the tested plant body were evaluated with respect to translocation factor, bio-concentration factor, and the amounts of partial elements and relative uptakes. Both the changing physical properties of the aqueous solution in the reactor during the experiment and the growth of the plant were tested using a two-sample t-test. The Zn and Cu levels in the combination of the leaves and stems were found to be significantly higher than the levels in the roots at the end of the trial. Based on the partial amount of each element, the affinity of the plant for different elements was found to follow the order of Ca>Fe>Mn. Scanning electron microscope (SEM) analyses of the plant bodies indicated that these elements were located both inside the organs and on the surface of the tissues alone or with microorganisms such as diatoms.

COMPARISON OF METHODS TO DETECT ALLELOPATHIC EFFECTS OF SUBMERGED MACROPHYTES ON GREEN ALGAE(1).

Detecting allelopathic inhibition of phytoplankton by submerged macrophytes in an ecologically meaningful way is not easy. Multiple-approach investigations from a laboratory scale to the ecosystem level have been recommended to overcome the shortcomings of individual methods. Whether results of different methods are qualitatively or quantitatively comparable has not yet been tested. Here, we compare the sensitivity of the green algae Desmodesmus subspicatus (Chodat) E. Hegewald et Ant. Schmidt and Stigeoclonium helveticum Vischer to the allelopathic effect of the submerged macrophyte Myriophyllum verticillatum L. The following three approaches were used: (i) coincubation of algae in dialysis membrane tubes in a lake inside and outside a M. verticillatum stand, (ii) coincubation of algae in dialysis membrane tubes in aquaria with and without M. verticillatum, and (iii) single additions of tannic acid (TA), an allelopathically active polyphenol present in this macrophyte, to the algae cultures. For each method, fluorescence-based (chl a, PSII activity) and particle-based (cell count, biovolume) parameters were compared after 48 h of incubation. Results revealed quantitative and qualitative differences between methods. Algae incubated in dialysis membrane tubes in aquaria showed a strong decrease in all parameters under the influence of macrophytes. In situ measurements were influenced by adverse growth conditions for the test algae and only detected significant reductions for biovolume. Single additions of TA induced a strong reduction of fluorescence-based parameters similar to aquarium results, but an increase in the cell count. Even the qualitative transfer of laboratory results to field conditions thus requires caution and a proper selection of parameters.