Potential of Lemnoideae Species for Phytoremediation of Fresh Water with Elevated Manganese Concentration

Abstract

Background. Wastewater treatment using physical, chemical, and biological methods is primary solution for the reduction of water pollution that reaching the critical thresholds. The members of subfamily Lemnoideae, commonly called duckweed, are considered the most efficient aquatic plants for wastewater remediation. Although properties of duckweed to survive in water with high concentration of heavy metal ions such as chromium, cobalt, lead, nickel and cuprum are well documented, the growth of duckweed in water with high concentrations of manganese and the efficiency of retention of manganese from water by these species has not been estimated. Objective. Four duckweed species (Spirodela polyrhiza, Landoltia punctata, Lemna aequinoctialis, and L. turionifera) were used for establishment of influence Mn on their vitality and growth and for studying their potential for phytoremediation of fresh water with elevated manganese concentration. Methods. Duckweed collected in Eastern China was introduced in tissue culture in vitro by surface sterilization. The identification of the collected duckweed species was determined by DNA barcoding using primers specific for chloroplast intergenic spacers atpF-atpH (ATP) and psbK-psbL (PSB). The experiments for establishment of influence Mn on duckweed growth carried out in aseptic condition. To determinate concentration of Mn, the samples of different water type (Hongze Lake, ponds around Hongze Lake, Huaian local municipal sewage plant and industrial sewage plant) were analyzed by the Inductively Coupled Plasma Optical Emission Spectrometry. Results. The most sensitive duckweed to Mn was S. polyzhiza, the first characteristic symptoms of toxicity like brown spots have appeared when concentration of Mn was 40 mg/L, the concentration 200 mg/L Mn resulted in chlorosis and death of fronds. L. aequinoctialis and L. turionifera had similar effects in SH medium supplemented with 650 mg/L and 975 mg/L Mn, respectively. L. punctata was the most tolerant duckweed to Mn plants continued to grow even at concentration 975 mg/L. Response of duckweed on Mn was dependent on availability of nitrogen in nutrient medium. Using four duckweed species for treatment of water containing 4.12 mg/L Mn allowed to reduce concentration until safe level of standard (0.1 mg/L Mn). Conclusions. All investigated duckweed species (S. polyrhiza, L. punctata, L. aequinoctialis, and L. turionifera) were characterized by a high level of resistance to manganese, especially L. punctata. Response of duckweed on Mn was dependent on availability of nitrogen in nutrient medium. The tested species of subfamily Lemnoideae were high effective for phytoremediation of water with elevated manganese concentration.

Species- and Metal-Specific Responses of the Ionome of Three Duckweed Species under Chromate and Nickel Treatments

“…B, Cu, Fe, and Zn typically showed one order of magnitude higher range of BCF (~800–5700) compared to K, Na, Ca, and Mg, while the highest BCF in all the tested species was calculated for Mn (BCF = ~7500–15000, Figure 4 ). Duckweeds have long been known to efficiently accumulate various trace elements [ 2 , 50 ], and particularly high bioaccumulation capability was reported, amongst others, for B, Cu, Zn, and Mn [ 8 , 11 , 15 , 41 , 51 , 52 , 53 ]. Our data are in line with those observations and indicate that in the applied Steinberg medium, Mn was by far the most efficiently incorporated essential metal ( Figure 4 and Table S4 ), explaining its rapid decline in the medium.…”

“…Therefore, selection and matching of the most suitable species for any given application can be crucial. For example, pertaining to metal accumulation, the high affinity of a particular species to a particular trace element can be either advantageous in remediating polluted waters, e.g., [ 15 ], or a disadvantage if duckweed is produced for use in feed or food, e.g., [ 16 ]. Further, a high metal bioaccumulation rate may not involve high tolerance to the same element that potentially limit the usefulness of certain species in some applications.…”

Ammonium Uptake, Mediated by Ammonium Transporters, Mitigates Manganese Toxicity in Duckweed, Spirodela polyrhiza

“…Our previous study demonstrated that the extend on Mn toxicity in four aquatic species of duckweed (Lemnaceae) depends on the source and concentration of nitrogen in the cultivation medium [ 43 ]. In particular, in great duckweed, Spirodela polyrhiza , the first characteristic symptoms of Mn stress appeared in form of characteristic brown spots when concentration of Mn was 40 mg/L (0.73 mM); however, the symptoms were largely reduced by the presence of ammonium in the medium in addition to nitrate.…”

“…Similar to rice growing on paddy fields [ 5 , 7 ], aquatic duckweeds have clear bias for ammonium as a source of nitrogen when given a choice between ammonium and nitrate [ 42 ]. In our previous study [ 43 ], we have demonstrated that great duckweed, Spirodela polyrhiza , is sensible to Mn toxicity and manifests characteristic symptoms of Mn stress when concentrations of Mn exceed 40 mg/L (0.73 mM).…”

Duckweeds for Phytoremediation of Polluted Water

“…An environmentally friendly and economical treatment technology for the remediation of wastewater polluted with heavy metals is needed [ 114 ]. Duckweeds are relatively tolerant to heavy metals and able to take up many heavy metal ions, including those of cadmium, chromium, copper, iron, mercury, manganese, nickel, palladium, lead, and zinc [ 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 ]. Therefore, duckweed also has potential uses for monitoring and remediating heavy metals [ 125 ].…”