Free-floating Aquatic Macrophytes Research Articles

Tolerance of free-floating aquatic macrophytes to sugarcane vinasse and its implications for phytoremediation strategies

Abstract Sugarcane vinasse is a byproduct of the ethanol industry that has been associated with environmental impacts, including ecotoxicity. However, several nature-based alternatives have been studied to attenuate environmental pollution, including phytoremediation. In such a scenario, this research aimed to evaluate the phytotoxicity of vinasse to aquatic plants, assessing the tolerance of three free-floating aquatic macrophytes, namely Eichhornia crassipes, Pistia stratiotes, and Salvinia auriculata. Five vinasse proportions (up to 20%) were considered to assess the short-term growth of aquatic plants. P. stratiotes and S. auriculata were more sensitive to vinasse than E. crassipes, which showed resistance at 10 and 20%. Lower dilutions were non-toxic and even stimulated the growth of macrophytes, which might contribute to the uptake of nutrients and potentially toxic elements. The selection of tolerant species contributes to the application of phytotechnologies, and the studied plants might have potential for the phytoremediation of vinasse.

Artificial floating islands as a tool for the water quality improvement of fishponds

In this study, the ecotechnology artificial floating islands (AFIs), colonized by Eichhornia crassipes, have been tested as a tool for water quality improvement of fishponds. The experiment was carried out in semi-intensive production during the grow-out period of Nile tilapia, comprising one production cycle. It was completely randomized with two treatments (with and without AFIs) and three replications. Temperature, dissolved oxygen, conductivity, pH, turbidity, total dissolved solids (TDS), transparency (Secchi) and concentrations of chlorophyll a (CL a), total nitrogen (TN), total ammonia nitrogen (TAN), total phosphorus (TP) and orthophosphate (PO43--P) were analyzed fortnightly in the fishponds. Two groups ordered based on environmental characteristics were formed by applying the Principal Component Analysis (70.68% of explicability). The fishponds with AFIs were assigned to higher values of Secchi and lower values of pH, turbidity, TDS and concentrations of nutrients. On the other hand, the fishponds without AFIs were assigned to the highest values of these variables, except for Secchi. In 30 days, the AFIs showed the lowest concentrations of TP and PO43--P, and for CL a, TN and TAN, the differences were recorded after 90 days. The use of AFIs has demonstrated potential to conserve water quality in fishponds, notably for biologically assimilable elements (PO43--P  and TAN) and for those directly related to eutrophication (P and N). Artificial floating islands should be encouraged for small and medium-sized farmers as tool to improve water quality in fishponds. However, new AFIs coverage rates must be evaluated, as well as the control of hydraulic retention rates.
 Keywords: aquaculture, ecotechnology, free-floating aquatic macrophytes.

Estimation of Total Carbohydrate content by Phenol Sulphuric acid Method from Eichhornia crassipes (Mart.) Solms

Eichhornia crassipes is free-floating aquatic macrophytes. For performing normal body function carbohydrate is an essential source for living organisms. Low carbohydrate intake results in muscle breakdown, ketosis, and dehydration. Daily 50-100gms of carbohydrate is recommended. In this study, the total carbohydrate content was detected in the aqueous extract by using phenol- sulphuric acid method. This was a rapid colorimetric method that determines the total carbohydrate present in the sample. The role of sulphuric acid is to convert polysaccharides, oligosaccharides, and disaccharides into monosaccharides. The result showed that the carbohydrate content was 30.50% in the sample solution. So the weed can be utilized as the source of carbohydrate.

Uptake and elimination kinetics of perfluoroalkyl substances in submerged and free-floating aquatic macrophytes: Results of mesocosm experiments with Echinodorus horemanii and Eichhornia crassipes

Studies investigating the bioaccumulation behavior of perfluoroalkyl substances (PFASs) in aquatic macrophytes are limited. The present study involved controlled mesocosm experiments to assess uptake and elimination rate constants (ku,ke), bioconcentration factors (BCFs) and translocation factors (TFs) of several perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs) in two aquatic plant species, including one submerged species (Echinodorus horemanii) and one free-floating species (Eichhornia crassipes). The results indicated all PFASs were readily accumulated in these aquatic macrophytes. ku and BCFs increased with increasing perfluoroalkyl chain length. For PFCAs and PFSAs with identical perfluoroalkyl chain length, the corresponding PFSA exhibited higher bioaccumulation potential. On a whole-plant basis, the bioaccumulation potential of PFASs in submerged and free-floating macrophytes were comparable, indicating sorption to plant biomass is similar in the different species. Conversely, when considering accumulation in foliage, BCFs in the free-floating macrophyte were substantially lower compared to submerged species, especially for longer-chain PFASs. Compounds with shorter perfluoroalkyl chain length (PFBS, PFPeA and PFHxA) exhibited preferential translocation to leaf tissue (TFs >1). BCFs exhibited a sigmoidal relationship with pefluoroalkyl chain length, membrane-water distribution coefficients (Dmw), protein-water distribution coefficients (Dpw) and organic-water partition coefficients (Koc). For these trends, maximum BCF values were exhibited by long-chain PFCAs, with a log Dmw, log Dpw and log Koc of 6.47, 5.72 and 5.04, respectively. These findings are useful for future design and implementation of phytoremediation systems, as well for future develop of mechanistic models for predicting the environmental fate and distribution of these contaminants of concern.

The Morphophysiological Responses of Free-Floating Aquatic Macrophytes to a Supra-optimal Supply of Manganese

Among the many anthropogenic abiotic stresses, manganese (Mn) toxicity has been recognized for its impact on aquatic ecosystems as well as on the biological components of these ecosystems, including aquatic plants. The objective of this study was to determine the Mn accumulation ability of aquatic macrophytes (Azolla caroliniana, Salvinia minima and Spirodela polyrhiza) and evaluate the morphophysiological responses of the species that gather the highest amount of Mn when exposed to a supra-optimal supply of manganese. The experiments were conducted in the laboratory, and the effects of Mn were evaluated based on plant growth; the concentration of total chlorophyll, carotenoids, and anthocyanins; the enzymatic activity of catalase and peroxidase; and leaf anatomy. All of the studied species accumulated Mn in their tissues. Moreover, it was observed that this accumulation was dependent on the concentration of the metal in solution. S. polyrhiza showed higher concentrations of Mn in its tissues (17.062 mg g−1 dry weight (DW)), followed by S. minima (4.283 mg g−1 DW) and A. caroliniana (1.341 mg g−1 DW). Despite the Mn accumulation in all species, S. polyrhiza was the only one selected for further analyses because of its greater ability to accumulate Mn. The high Mn concentration found in tissues of S. polyrhiza suggests that this species has the potential to sequester and accumulate this metal. However, a sensitive response in the plants exposed to higher Mn concentrations (0.4 mM) was observed. The phytotoxicity effects of this accumulation were responsible for a decrease in the plant growth, a reduction in the pigment content (total chlorophyll, carotenoids, and anthocyanins), a low activity of catalase, and the disarrangement of the leaf aerenchyma.

Growth of free-floating aquatic macrophytes in different concentrations of nutrients

The objective of the study was to evaluate the effect of different concentrations of nitrogen and phosphorus on the growth of the free-floating aquatic macrophytes Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta. The plants were cultured in 2,000-l outdoor concrete tanks. Triplicate tanks, with a continuous flow of effluent from culture ponds containing Nile tilapia, were used for each plant type (n = 3). The plant material was collected monthly from 0.25 m2 floating quadrats, at the two ends of the tanks (higher nutrient concentrations near the inflow and lower nutrient concentrations near the outflow). In low nutrient concentrations, the maximum relative growth rates (RGRs) for E. crassipes (0.016/day) and P. stratiotes (0.016/day) were significantly lower (P ≤ 0.05) than for S. molesta (0.029/day). There were no significant differences between the RGRs of S. molesta in the different nutrient concentrations. Eichhornia crassipes and P. stratiotes had their growth limited by nitrogen and phosphorus concentrations. The increase in plant density during the experiment probably also affected the growth of these species. In this context, E. crassipes and P. stratiotes can cause problems in nutrient-rich waterbodies, but under these experimental conditions their growth was limited by nitrogen and/or phosphorus concentrations. The growth of S. molesta was not influenced by the different nutrient concentrations.

Valor nutritivo de macrófitas aquáticas flutuantes (Eichhornia crassipes, Pistia stratiotes e Salvinia molesta) utilizadas no tratamento de efluentes de aqüicultura

The aim of this study was to evaluate the nutritive value of free-floating aquatic macrophytes, Eichhornia crassipes (Mart.) Solms (Pontederiaceae), Pistia stratiotes (L.) (Araceae) and Salvinia molesta (Mitchell) (Salviniaceae) used in a Nile tilapia ( Oreochromis niloticus ) waste treatment, and these species biomass potential uses. The vegetal biomass samples were collected from 0.25 m ² floating squares and divided in aerial and submerse parts, to determine the concentrations of cell wall fraction, soluble carbohydrates, polyphenols, lipids, crude protein and total phosphorus. The higher nutritive value was observed in E. crassipes and S. molesta aerial parts, and in P. stratiotes total biomass, due to their lower cell wall fraction mean rates (60.7; 64.2 and 56.9 % dry mass, respectively) and to the higher rates of: crude protein (10.1; 9.1 and 8.8 % dry mass, respectively), soluble carbohydrates (26.6; 18.7 and 12.4 mg.g -1 dry mass, respectively) and lipids (7.6; 4.5 and 4.4% dry mass, respectively). It may be concluded that P. stratiotes total biomass, and E. crassipes and S. molesta aerial biomass have nutritive values with potential use for ruminant feeding or as ration ingredients.

Competitive interactions between Salvinia auriculata Aubl., Limnobium laevigatum (Humb. and Bonpl. ex Willd.) Heine, and other free-floating aquatic macrophytes under varying nutrient availability

Competitive interrelationships between Salvinia auriculata Aubl. and Limnobium laevigatum (Humb. and Bonpl. ex Willd.) Heine, in combination with additional Brazilian free-floating aquatic macrophyte species, were studied using the De Wit replacement series method, under conditions of varying nutrient availability. The relative competitive success, measured as biomass production, relative yield total, and aggressivity, of the two target species with each other, with Pistia stratiotes, and (individually) with either Salvinia minima or Lemna minor, was determined in a series of five glasshouse experiments. The competitiveness of three free-floating species relative to S. auriculata was ranked as L. minor > P. stratiotes = L. laevigatum; and relative to L. laevigatum as P. stratiotes > S. auriculata > S. minima. The findings support observations in the literature on the co-existence of these species in Brazilian waterbodies.

Accumulation of metals in macrophytes from water reservoirs of a power supply plant, Rio de Janeiro State, Brazil

Aquatic macrophytes are well known accumulators for heavy metals, the reason why they are used as bioindicators for water quality and in phytoremediaton strategies. This study reports on the elemental concentrations in four free-floating aquatic macrophytes (S. auriculata; P. stratiotes; E. crassipes and E. azurea) growing in two water reservoirs (Santana e Vigario, Rio de Janeiro State, Brazil) of an electric power plant that receive input from the polluted Paraiba do Sul River. Filtered water samples and water suspended solids from these environments were also analysed. Inductively coupled plasma mass spectrometry was used as the principal method, allowing the determination of up to 41 elements, including the rare-earth elements (REEs) and other trace metals not assayed before in these macrophytes. The results show that all elements studied are accumulated by the macrophytes with concentration ratios (CR = [plant]: [water]) varying from about 1,000 to 200,000, based on the dry weight of the plant species. With a few exceptions, highest accumulations were observed in E. crassipes in which CRs increase in the sequence: Cu < Mo < Cr < Pb < Tl < Fe < La < Zn < Ce< Mn. Surprisingly high CRs (e.g. Ce: 74,000) and corresponding mass concentrations were observed for the rare-earth elements (e.g. ∑REE: 112 mg kg−1), also measured in the water suspended particle fraction. The results show that this fraction acts as an effective sink for trace metals in the aquatic system studied and seems to play also an important role in the transfer of metals from water to the plant species.

Competition for space between Eichhornia crassipes (Mart.) Solms and Pistia stratiotes L. cultured in nutrient-enriched water

The interrelationships between two free-floating aquatic macrophytes, Eichhornia crassipes (Mart.) Solms and Pistia stratiotes L, were investigated using a reciprocal replacement series for the intermixed combinations. The carrying capacity for each species was investigated in monoculture. The plants were cultured in outdoor tanks in Gainesville, Florida, where nutrient-enriched water was replenished at weekly intervals. E. crassipes showed dominance over P. stratiotes when the species were grown together. Interaction between the two species for growth space became apparent within the first month of the experimental period. The luxuriant growth and high plasticity of E. crassipes plants enabled them to grow above the P. stratiotes plants, thus shading and stressing them. Higher concentrations of nitrogen (N) (by about two-fold) were accumulated in the shoots of E. crassipes than in its roots, whereas N accumulation in the roots and shoots of P. stratiotes was similar. The N content of E. crassipes shoots increased throughout the experimental period ∼ six-fold, while the N content of roots increased two-fold. Phosphorus accumulation was equally distributed between the roots and shoots of both species.