Typha Domingensis Research Articles

Review of Effective Vegetation Mapping Using the UAV (Unmanned Aerial Vehicle) Method

We tried more precise mapping of vegetation using UAV (unmanned aerial vehicle), as a new method of creating vegetation maps, and we objected to be clearly the efficient mapping of vegetation using the UAV method by comparing vegetation maps created by analysing aerial photographs taken by a UAV and an aircraft (manned flight). The aerial photography using UAV was conducted in the Niida River estuary (the secondary river flowing into Minamisoma City in Fukushima Prefecture, Japan). The photography period was in August 2013. We analysed the aerial photographs using ArcGis 9 (Esri Japan Corporation, Tokyo, Japan). The aerial photographs of the main plant communities (Phragmites australis, Typha domingensis, and Miscanthus sacchariflorus) taken by the UAV could clearly discriminate each plant community at the 1/50 scale. Moreover, it could clearly discriminate the shape of a plant at the 1/10 scale. We compared the vegetation maps by analysing the aerial photos taken by a UAV (2013 shooting) and an aircraft (2011 shooting). As a result, the vegetation map created by the UAV method could clearly discriminate community distributions. We conclude that vegetation surveys using UAV are possible and are capable of a highly precise community division in places where field reconnaissance is difficult. The UAV method is effective and will contribute to the improvement of research methods in the future; this method may reduce research costs associated with a reduction in field survey days and man-power.

Processes Governing the Retention of Phosphorus and Nitrogen in Nyashishi Wetland

One of the important functions of the wetland is the retention of catchment nutrients and improving lacustrine water quality. This study analyzed how much nutrients were retained in the Nyashishi wetland, southern part of Lake Victoria, and went further to analyze the processes which were responsible in the reduction of nutrients. Three major processes were analysed in this study, namely nutrients uptake by three macrophyte species (Eichhornia crassipes, Cyperus papyrus and Typha domingensis) dominating the Nyashishi wetland, nitrification and denitrification processes. The study demonstrated high nutrients retention especially phosphorus nutrients of which up to 98% were retained. In some occasions, particularly for nitrogen nutrients, there was 0% retention especially during wet season. In some other instances, the inflow exceeded the outflow meaning that, more nutrients were generated by the wetland itself. Among the three processes analyzed, nutrients uptaken by macrophytes were more efficient in reducing nutrients in wetland water. Biological nitrification and denitrification which are believed to be the major pathway for ammonia removal in both natural and constructed wetlands were less important in this study. Among the macrophyte species, Eichhornia crassipes demonstrated higher uptake rate than the other two species possibly due to its high turnover rate. This ability can be exploited in removing excess nutrients from runoff by frequent harvesting of the mature plants.

Phytoremediation of water contaminated with mercury using Typha domingensis in constructed wetland

The presence of mercury in aquatic environments is a matter of concern by part of the scientific community and public health organizations worldwide due to its persistence and toxicity. The phytoremediation consists in a group of technologies based on the use of natural occurrence or genetically modified plants, in order to reduce, remove, break or immobilize pollutants and working as an alternative to replace conventional effluent treatment methods due to its sustainability – low cost of maintenance and energy. The current study provides information about a pilot scale experiment designed to evaluate the potential of the aquatic macrophyte Typha domingensis in a constructed wetland with subsurface flow for phytoremediation of water contaminated with mercury. The efficiency in the reduction of the heavy metal concentration in wetlands, and the relative metal sorption by the T. domingensis, varied according to the exposure time. The continued rate of the system was 7 times higher than the control line, demonstrating a better performance and reducing 99.6±0.4% of the mercury presents in the water contaminated. When compared to other species, the results showed that the T. domingensis demonstrated a higher mercury accumulation (273.3515±0.7234mgkg−1) when the transfer coefficient was 7750.9864±569.5468Lkg−1. The results in this present study shows the great potential of the aquatic macrophyte T. domingensis in constructed wetlands for phytoremediation of water contaminated with mercury.

Influence of Inundation Depth on Typha domingensis and its Implication for Phosphorus Removal in the Everglades Stormwater Treatment Area

The influence of inundation depth on phytomass, shoot density, photosynthesis, elongation, and nutrients of Typha domingensis in Stormwater Treatment Area-1East (STA-1East) was examined and results were evaluated relative to phosphorus (P) treatment from 2006 to 2011. Biomass and nutrient concentrations of T. domingensis were not related to inundation depth. Necromass and belowground/leaf biomass ratio increased with increasing inundation depth from 30 to 80 cm. Shoot density, photosynthesis, and elongation decreased with inundation depth. The contents of necromass nutrients and phytomass nitrogen increased with inundation depth. Annual total P (TP) concentration increase (−) or decrease (+) from inflow to outflow was −21 %, −3 %, +8 %, −54 %, +41 %, and +29 % in 2006–2011, respectively. Decreases in soluble reactive P (SRP), total dissolved P (TDP), dissolved organic P (DOP), and/or particulate P (PP) from inflow to outflow were low or did not occur annually. Prolonged inundation damaged T. domingensis community and thus adversely impacted the capacity of the system to treat P. Inundation depths in the STAs can be categorized into optimal, subtle stress, and lethal stress zones. This study stressed the importance in maintaining vegetation within an optimal zone of inundation for a sustainable system.

Propriedades físicas e químicas de substratos produzidos utilizando macrófitas aquáticas

Aquatic macrophytes are widely used as bioindicators of water quality because their proliferation usually occurs in eutrophic water sources and has hit several parts of Brazil and the world, restricted the multiple uses of aquatic ecosystems. However, this group of plants is able to retain considerable amounts of nutrients, presenting high productivity and high growth rate, thus, a good source of biomass for use in the production of substrates. In order to evaluate the potential of aquatic macrophytes water hyacinth ( Eichhornia crassipes Solms.), water lettuce ( Pistia stratiotes L.) and cattail ( Typha domingensis Pers.) in the production of substrates was performed in this work, the physical and chemical characterization and evaluation of the degree of humification. The treatments were arranged in a 3 × 4 factorial, completely randomized design with three replications. All substrates produced with 100% macrophyte density present within the limits of 400 kg m-3, considered ideal. The composite substrates with water hyacinth and water lettuce are with the electrical conductivity of 0,79 a 2,49 dS m-1 within recommended. organic compounds produced are considered mature and have high levels of nitrogen phosphorus and potassium; The substrate produced with 70% water lettuce +30 % dung and 70% composed of cattail manure +20% +10% topsoil and 70 +30% cattail manure have C/N ratio within the considered ideal; the humification ratio and humification index, except for the four treatments (70 % water lettuce manure +30%), 5 (100% water hyacinth) and 8 (70% water hyacinth manure +30%) are within the considered ideal, the percentage of humic acids and polymerization rate, except for treatments 1 (100% water lettuce) and 12 (100% cattail), are shown below the ideal.

Long-term vegetation changes in a tropical coastal lagoon system after interventions in the hydrological conditions

Over a period of 44 years, we observed the vegetation changes in the western part of the lagoon system of the Ciénaga Grande de Santa Marta, which is situated on the Caribbean coast of Colombia and is separated from the sea by a sandy barrier. Since the construction of the Barranquilla-Ciénaga Road between 1956 and 1960, the lagoon system has been exposed to different interventions in its hydrological make-up, as well as changes to the vegetation. During the time of our investigations, four periods with different plant cover were distinguished. In 1965, the road was bordered by dense mangrove forests. The low surface water salinity and the presence of freshwater plants indicated the influence of the Magdalena River. At the beginning of the seventies, the second period was marked by a decrease in the freshwater in-flow from the river, which led to an increase in salinity and a gradual decay of vegetation. In 1988, the areas formerly covered by mangroves had converted into salt flats. The third period began with the reconstruction of several channels (1995–1998) which renewed the freshwater in-flow from the river to the lagoons. The subsequent vegetation development was characterized by the establishment of Typha domingensis Pers. In 1999, a year with an unusually high amount of rainfall, this species covered most of the former mangrove area in the western part of the lagoon system. The very low surface water salinity favored its spread. The last period began in 2001/2002, when growth conditions for T. domingensis became unfavorable due to an increase in salinity. Instead, conditions for mangrove regeneration improved. This process was slower than expected and is still ongoing. The striking vegetation changes indicate the sensitivity of the coastal lagoon system to hydrological variability.

Removal of Phenolic Compounds from Aqueous Solution by Using Agricultural Waste (Al-Khriet)

Adsorption techniques are widely used to remove organics pollutants from waste water particularly, when using low cost adsorbent available in Iraq. Al-Khriet powder which was found in legs of Typha Domingensis is used as bio sorbent for removing phenolic compounds from aqueous solution. The influence of adsorbent dosage and contact time on removal percentage and adsorb ate amount of phenol and 4- nitro phenol onto Al-Khriet were studied. The highest adsorption capacity was for 4-nitrophenol 91.5% than for phenol 82% with 50 mg/L concentration, 0.5 gm. dosage of adsorbent and pH 6 under a batch condition. The experimental data were tested using different isotherm models. The results show that Freundlich model resulted in the best fit also the kinetic study make it clear that the adsorption process proceeded according to the pseudo second order model.

Potential Macrophytes for Nitrogen Removal from Domestic Wastewater in Horizontal Subsurface Flow Constructed Wetlands in Tanzania

The role of six indigenous macrophytes (Cypreus grandis, C. dubis, Kyllinga erectus, Phragmites mauritianus, Typha domingensis and T. capensis) was investigated for nitrogen removal in horizontal subsurface flow constructed wet- lands at the University of Dar es Salaam in Tanzania receiving waste stabilization ponds effluent. Seven horizontal sub- surface flow constructed wetlands were fed with the same source of domestic wastewater, where six of them were planted with a monoculture macrophytic species while the seventh was not planted and it acted as a control cell. On alternatedays' basis for twenty eight weeks both the influent and effluent water samples from each cell were collected and sent to the laboratory for ammonia-N, nitrate-N and Total Kjeldahl-N analysis. Nitrogen bioaccumulation and plant biomasses were analyzed during the transplanting time, after ten weeks and after flowering. Temperature, pH and plant heights were de- termined in situ. Results show that overall nitrogen removal was through denitrification where K.erectus performed better (75.59%) than the rest.Since P.mauritianus(74.37% )established well and had the longest growing period after harvest useso therefore it was selected as the best macrophyte. More research needs to be done prior to making a final decision on the use of any of these macrophytes for nitrogen removal depending on the weather and soils of the specific area.

The role played by aquatic macrophytes regarding CO2 balance in a tropical coastal lagoon (Cabiúnas Lagoon, Macaé, RJ)

AIM: Carbon dioxide (CO2) is an important atmospheric trace gas that is involved in both the biological carbon cycle and global warming. Inland waters - mainly lakes - contribute to C cycling and have been considered a large source of atmospheric CO2. However, scientific studies usually neglect lake morphometry and the presence of aquatic macrophytes in littoral zones, which have a great potential for CO2 absorption and for C storage. This study aimed to evaluate the importance of the littoral region on the CO2 balance in the Cabiunas Lagoon, while also considering the contribution of the limnetic region and of Typha domingensis and Eichhornia azurea, prominent species in the area. METHODS: CO2 flux was estimated by a linear integration of CO2 concentrations measured in the internal atmospheric of a single-component static closed chambers at the studied sites. The distribution of macrophyte stands throughout lagoon surface was taken into account to evaluate the effects of macrophytes on CO2 supersaturation. Other factors were also measured throughout the sampling process to evaluate their relationship with CO2 flux data by means of Akaike model selection criterion. The area covered by aquatic macrophytes at the Cabiunas lagoon was estimated by profiles and transects. RESULTS AND DISCUSSION: CO2 flux through the water surface ranged from - 7.39 to 17.56 mgCO2m - 2h - 1. An emission pattern predominated, suggesting that water columns are CO2 supersaturated at all sampling sites. Rates were similar among all the sampling sites, suggesting that aquatic macrophytes do not influence CO2 saturation in the water column at Cabiunas lagoon. On the other hand, CO2 fluxes from macrophyte tissues showed a clear assimilation pattern. Influxes were higher in T. domingensis ( - 229.1 ± 320.9 mg CO2.m - 2.h - 1) than in E. azurea stands ( - 43.8 ± 39.5 mg CO2.m - 2.h - 1). Once these macrophytes covered a considerable area of the lagoon and CO2 absorption strongly overwhelmed the emission processes, then we were able to extrapolate data from the total estimated area of the evaluated sites (75% of the Cabiunas lagoon), which resulted in a net influx of 46.6 mg CO2.m - 2.h - 1. The strong Typha domingensis contribution to CO2 absorption and other C cycling processes indicate that it is one of the most important species to Carbon cycling in the studied ecosystem. Thus, it is worth considering C cycling in lake littoral zones as a key process when estimating C balance in shallow aquatic ecosystems.

Microbial effects in leaf breakdown in tropical reservoirs of different trophic status

AbstractThe objective of our study was to compare leaf breakdown rates (k) and the influence of microorganisms and aquatic invertebrates on mass loss of Eichhornia crassipes (Mart.) Solms and Typha domingensis Pers in 2 reservoirs (eutrophic and oligotrophic). We hypothesized that k would be higher in eutrophic than in oligotrophic conditions because of increased microbial activity in eutrophic conditions. We collected green leaves, which we air-dried, weighed, placed in litter bags, and incubated in each reservoir. We calculated k (negative exponential model) for each species in each reservoir. We characterized initial leaf chemistry, estimated total microbial biomass (as adenosine triphosphate [ATP]) and fungal biomass (as ergosterol), and evaluated invertebrate community composition and structure. Both species decomposed faster in the eutrophic reservoir. During leaf breakdown, bacteria were more important in the eutrophic reservoir, whereas fungi were more important in the oligotrophic reservoir. Inve...

Dynamics of dissolved organic carbon from aerobic and anaerobic decomposition of Typha domingensis Pers. and Eleocharis interstincta (Vahl) Roem. & Schult. in a tropical coastal lagoon

AIM: The aim of this study was to evaluate the initial stage of decomposition of two aquatic macrophytes (Typha domingensis and Eleocharis interstincta) under aerobic and anaerobic conditions; METHODS: The samples of aquatic macrophytes and water were collected in Cabiúnas lagoon, Rio de Janeiro, Brazil. In the experiment 1 mineralization chambers were prepared with fresh plant fragments and water from the lagoon in aerobic and anaerobic conditions. DOC and CO2 formation and O2 consumption were measured during 30 days. In the experiment 2 mineralization chambers were prepared with aquatic macrophytes leachate and glucose for each experimental condition. CO2 formation and O2 consumption were measured during 1 day; RESULTS: In experiment 1 DOC concentrations in T. domingensis decomposition were higher. Despite this, CO2 formation was more efficient in E. interstincta decomposition. The oxygen consumption increased in the beginning of decomposition and tended to stabilize towards the end. The O/C values increased in the beginning of decomposition and decreased thereafter. In experiment 2, aerobic decomposition presented higher CO2 formation. E. interstincta leachate presented higher CO2 concentration than T. domingensis; CONCLUSION: Our results showed that aerobic decomposition in the initial stages is higher only in T. domingensis mineralization. Oxygen consumption varies according to the alterations in the chemical composition of the detritus. The formation of CO2 from T. domingensis and E. interstincta decomposition in the water column is irrelevant in Cabiúnas Lagoon. The low DOC release from fresh aquatic macrophytes detritus indicates that particulate organic matter mineralization is the main route of T. domingensis and E. interstincta decomposition.

Comparative performance of trace element bioaccumulation and biomonitoring in the plant species Typha domingensis, Phragmites australis and Arundo donax

Toxic levels of trace elements in the environment have been reported worldwide over the last few decades, and their increasing concentrations are of the utmost concern because of the adverse effects on human life and ecosystems. Several plant species are able to accumulate trace elements, and may be used for monitoring and remediation of polluted sites. This study compared the capacity of trace element bioaccumulation in three wetland plants distributed worldwide: Typha domingensis, Phragmites australis and Arundo donax. The aims were to identify which species show better potential for removal and monitoring of these elements: Al, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn. Results showed that all species may be used as biomonitors of trace element contamination in sediment, but only P. australis and A. donax showed also a correlation with water. Overall, T. domingensis and P. australis showed a greater capacity of bioaccumulation as well as a greater efficiency of element removal than A. donax. In particular, T. domingensis and P. australis may be used for Hg phytostabilization, the former acted also as a hyperaccumulator for Hg phytoextraction and as a promising species for As phytostabilization. In contaminated wetlands, the presence of T. domingensis and P. australis may increase the general retention of trace elements, thus, their introduction is recommended for possible actions of phytoremediation and biomonitoring.

Accumulation of heavy metals by naturally colonising Typha domingensis (Poales: Typhaceae) in waste-rock dump leachate storage ponds in a gold–copper mine in the central tablelands of New South Wales, Australia

Naturally colonised populations of Typha domingensis in mine waste-rock dump leachate ponds (northern leachate pond [NLP] and southern leachate pond [SLP] and a nearby reference site (Cadiangullong Creek [CAC] were analysed for accumulation of Cu, Mn, and Zn in the winter of 2010 and early autumn of 2011. Concentrations in sediment, leachate and creek water at NLP, SLP, and CAC were also analysed for Cu, Mn, and Zn. Linear regression of Cu, Mn, and Zn concentrations in the leachate at each site revealed a significant reduction in these metals at NLP only in early autumn as leachate travelled away from the toe of the waste-rock dump and through the naturally colonised populations of T. domingensis. This study indicates that this species is a suitable candidate for the process of phytoimmobilisation of the tested metals.

Emergent plants used in free water surface constructed wetlands: A review

Constructed wetlands with free water surface (FWS CWs) have been used for many purposes worldwide. Emergent macrophytes play important roles in FWS CWs; they reduce wind speed and thus support sedimentation and prevent re-suspension, provide substrate for periphyton and bacteria, take up nutrients and in carbon-limited systems provide carbon for denitrification during biomass decomposition. It has been reported that treatment performance of planted FWS CWs is superior to unvegetated lagoons. However, treatment performance of FWS CWs could be affected by plant species used. The literature survey of 643 FWS CWs from 43 countries recorded 150 plant species and revealed that the most commonly used macrophyte genera were Typha, Scirpus (Schoenoplectus), Phragmites, Juncus and Eleocharis. In terms of species, most frequently used species were Typha latifolia, Phragmites australis, Typha angustifolia, Juncus effusus, Scirpus lacustris, Scirpus californicus and Phalaris arundinacea. In terms of continents, P. australis is the most frequent species in Europe and Asia, T. latifolia in North America, Cyperus papyrus in Africa, P. australis and Typha domingensis in Central/South Americas and Scirpus validus (S. tabernaemontani) in Oceania.

Fitoremediasi Logam Berat Kadmium (Cd)

Phytoremediation consists in treating environmental pollutions through the use of plants and their associated microbes. Phytoremediation can be used for pollutant stabilization, extraction, degradation or volatilization. Cadmium is one of the most toxic trace metallic elements for living organisms and its accumulation in the environment is recognized as a worldwide concern. Plants suitable for efficient pollutant extraction from the soil should combine different characteristics like fast growth, high biomass, high tolerance and high accumulation capacities in harvestable parts. Several studies haveshown that plants can accumulate Cd in the body such as Eichornia crassipes, Brassica napus, Avicenna marina, Lycopersicon esculentum, Wolffia globosa, Phytolacca Americana, Solanum nigrum, Typha domingensis, Sedum plumbizincicola, Thlaspi caerulescens, Helianthus annuus,Lolium perenne, Tagetes erecta, Chara australis, Jatropha curcas, Sedum alfredii, Atriplex halimus,Phragmites cummunis, Nitella opaca, Phragmites australis, Typha angustifolia, Cyperus esculentus, Chara aculeolata, Ricinus communis, Hibiscus cannabinus, Zea mays, Arabidopsis halleri, Arundo donax, and Vetiveria zizanioides.Keywords: Cadmium, Phytoremediation, Plant

Organ-Disparate Allocation of Plasticity in Phosphorus Response as an Underlying Mechanism for the Sawgrass-To-Cattail Habitat Shift in Florida Everglades Wetlands

Premise of research. Formerly sparsely distributed southern cattail (Typha domingensis) is now rapidly replacing the historically predominant sawgrass (Cladium jamaicense) in Florida Everglades wetlands. Previous studies have attributed anthropogenic phosphorus (P) enrichment as a causal factor. We investigated various traits of known importance to P acquisition and use in cattail and sawgrass, in order to determine the underlying mechanisms driving the sawgrass-cattail habitat shift.Methodology. An integration of morphological, physiological, biochemical, and molecular approaches were used to examine growth, root structure, photosynthesis, enzyme activities, and gene expression in plants grown under different P conditions.Pivotal results. Cattail and sawgrass exhibited distinct patterns of P responses between roots and shoots. While cattail displayed plasticity in shoots and inflexibility in roots, sawgrass demonstrated the opposite pattern, exhibiting a remarkable capacity for modulating its root system...

Nitrogen and phosphorus resorption efficiency, and N : P ratios in natural populations of Typha domingensis Pers. in a coastal tropical lagoon

AIM: We studied nitrogen (N) and phosphorus (P) resorption patterns in Typha domingensis Pers. in a tropical coastal lagoon during different seasons of throughout one year. METHODS: Resorption of N and P is uttered as resorption efficiency (NRE and PRE, respectively), which may be used as an indicator of a nutrient limitation. Higher resorption efficiency values might indicate limitation of a certain element for the growth of aquatic macrophytes. RESULTS: N was inferred to be less limiting than P for the growth of T. domingensis in Campelo Lagoon, since N content varied less than P content and resorption efficiency of N was lower than that of P and, concomitantly, low resorption efficiency of this element. However, T. domingensis of Campelo Lagoon frequently utilized P that was already present in its tissues, contributing to the longer residence time of this element in system. Green leaves of T. domingensis showed N : P ratio, ranging 49-96, corroborating the inference of P limitation. CONCLUSIONS: N : P ratio and resorption efficiency indicate P limitation by T. domingensis in Campelo Lagoon.

Spatial variability of macrozoobenthic community and trophic structure of a subtropical lagoon on southeastern Brazil's Atlantic coast

The objective of this study was to investigate the macrobenthic community of two compartments of the Maricá-Guarapina lagoon system, along the coast of Rio de Janeiro, Brazil, in relation to its abiotic sediment factors. An additional discrimination between sites was made, wherever the macrophyte Typha domingensis was found. This vegetation supposedly represents a potentially important food source for consumers. Furthermore, the trophic pathways were analyzed functionally by means of stable isotope analysis to assess the role of organic matter sources for consumers in the study area. In conclusion, the results showed differences between abiotic features in the compartments of the lagoon system, which, although they have affected the different species' distribution, have led to a homogeneous low-diversity system. Macrozoobenthic species tend to change with increasing distance from the sea, with a slightly different distribution in the two compartments. The macrophyte T. domingensis did not exercise any great influence on the biotic distribution and was not the main food source for consumers in the lagoon system, where, instead, sedimentary organic matter and macrophyte detritus also seem to play an important role in the trophic web.

Modeling water management scenarios for the Cienega de Santa Clara, an anthropogenic coastal desert wetland system, based on inflow volumes and salinities

The Cienega de Santa Clara in the Colorado River Delta, Mexico is a self-designed wetland system fed since 1977 by brackish groundwater diverted from the U.S. to Mexico. The vegetated upper portion of the Cienega provides habitat for endangered Yuma-Clappers rails and other marsh birds and fulfills other ecological functions. Outflow water pools in the Santa Clara Slough south of the Cienega and provides habitat for migratory shorebirds. Conditions in the Cienega and Santa Clara Slough could be altered by operation of the Yuma Desalting Plant (YDP), which will divert water from the Cienega and replace it with brine water resulting from the desalting process. Our objective was to integrate water budget components into models predicting the extent of the dominant vegetation (southern cattail, Typha domingensis Pers.) in the marsh and the area of the outflow pool below the marsh in response to different operating scenarios for the YDP. The models are intended to serve as tools for resource managers charged with maintaining this wetland complex. Unlike many wetland water budget models, this one explicitly takes into account salinity as a factor in the water budget. We modeled inflow rates ranging from 1 to 6m3s−1 and inflow salinities ranging from 0 to 6gL−1 Total Dissolved Solids. The model indicates that if the inflow rate is reduced below the current 4–5m3s−1 the vegetated area of the Cienega would decrease in proportion, as would the area of the outflow pool in the Santa Clara Slough. Increases in salinity will also reduce the vegetated area due to the low salt tolerance of T. domingensis. In winter about 90% of inflow water exits the Cienega into the Santa Clara Slough due to low evapotranspiration, and on an annual basis 70% of inflows exit into the Santa Clara Slough. These flushing flows maintain the salt balance in the Cienega. The Santa Clara Slough is periodically flushed by spring tides, making this a sustainable, open wetland system in its present state.

Sustainability of a constructed wetland faced with a depredation event

A free water surface constructed wetland (CW) designed for effluent treatment was dominated by the emergent macrophyte Typha domingensis reaching a cover of roughly 80% for 5 years. Highly efficient metal and nutrient removal was reported during this period. In June 2009, a population of approximately 30 capybaras (Hydrochoerus hydrochaeris) caused the complete depredation of the aerial parts of macrophytes. However, plant roots and rhizomes were not damaged. After depredation stopped, T. domingensis showed a luxuriant growth, reaching a cover of 60% in 30 days. The objective of this work was to evaluate the sustainability of the CW subjected to an extreme event. Removal efficiency of the system was compared during normal operation, during the depredation event and over the subsequent recovery period. The CW efficiently retained contaminants during all the periods studied. However, the best efficiencies were registered during the normal operation period. There were no significant differences between the performances of the CW over the last two periods, except for BOD. The mean removal percentages during normal operation/depredation event/recovery period, were: 84.9/73.2/74.7% Cr; 66.7/48.0/51.2% Ni; 97.2/91.0/89.4% Fe; 50.0/46.8/49.5% Zn; 81.0/84.0/80.4% NO3-; 98.4/93.4/84.1% NO2-; 73.9/28.2/53.2% BOD and 75.4/40.9/44.6% COD. SRP and TP presented low removal efficiencies. Despite the anoxic conditions, contaminants were not released from sediment, accumulating in fractions that proved to be stable faced with changes in the operating conditions of the CW. T. domingensis showed an excellent growth response, consequently the period without aerial parts lasted a few months and the CW could recover its normal operation. Plants continued retaining contaminants in their roots and the sediment increased its retention capacity, balancing the operating capacity of the system. This was probably due to the fact that the CW had reached its maturity, with a complete root-rhizome development. These results demonstrated that faced with an incidental problem, this mature CW was capable of maintaining its efficiency and recovering its vegetation, demonstrating the robustness of these treatment systems.