Aquatic Plant Ceratophyllum Demersum Research Articles

The production bioethanol from Ceratophyllum demersum L . in Iraq

Biofuels have attracted a lot of attention due to the growing demand for energy resources and concerns about greenhouse gas emissions. Unlike other green energy resources, biofuels like bioethanol, can provide liquid fuels that is essential for transportation. Second-generation bioethanol can be produced from lignocellulosic biomass through acid hydrolysis and fermentation. Lignocellulosic biomass is widely available and does not affect on the nutritional needs of agricultural crops. In this study, the aquatic plant Ceratophyllum demersum was used. Ceratophyllum demersum is a type of invasive aquatic plant that can live in fresh and brackish waters, and it is abundant in most regions of southern Iraq. The bioethanol with the highest concentration was identified by high-performance liquid chromatography (HPLC). The results showed that 14% of bioethanol was produced in the absence of acid hydrolysis, while the concentration of it increased to 25% with the presence of acid hydrolysis. Acid hydrolysis aims to increase the breaking bonds of lignin and hemicellulose, increase the porosity of the material, and damage the crystalline structure of cellulose, and thus facilitates its conversion to glucose and increases the percentage of ethanol production.

Ecotoxicological assessment of copper and zinc in a common aquatic plant Ceratophyllum demersum: Physiological effects and biomarker responses

Utilizing and discharging chemical products containing trace metals lead to widespread contamination in the aquatic environment. Although copper (Cu) and zinc (Zn) are essential plant micronutrients, excessive concentrations may induce stress and mortality. This study investigated the physiological responses of a common aquatic plant, Ceratophyllum demersum, exposed to Cu (0, 2, 5, 10, and 50 μM) or Zn (0, 50, 100, 500, and 1000 μM) for 3 days. Both Cu and Zn were accumulated in plant tissues. Cu exposure led to severe phytotoxicity effects, manifested as a rapid decrease in photosynthetic efficiency (Fv/Fm and ՓPSII), a significant reduction in pigments and an increase in oxidative stress markers. In contrast, minor effects were observed in Zn-treated plants. In addition, Cu exposure suppressed the expression of D1, rubisco large subunit, and alpha-tubulin proteins but did not affect the PSI-B core subunit of PSI. Our study suggested that Cu is a potent phytotoxin by disturbing the principal reactions of photosynthesis and inducing oxidative stress and protein degradation. The overall health status of C. demersum was assessed by adopting the biomarker response index (BRI) approach. The effects of Cu were categorized as moderate in 2 μM and severe in 5, 10, and 50 μM whereas the effects of Zn were categorized as slight in 50 μM, negligible in 100 μM and major in 500 and 1000 μM. BRI effectively substantiates data interpretation of complex plant responses to trace metals and should be further adapted into biomonitoring suites in aquatic systems.

CHANGES IN BLOOD PARAMETERS OF GRASS CARP CTENOPHARYNGODON IDELLA (VALENCIENNES, 1844) FINGERLINGS UNDER THE EFFECT OF CHLOROFETE

The present study has carried out to clarify the changes of blood parameters of grass carp Ctenopharyngodon idella (Valenciennes, 1844), responding to chlorofete effect under laboratory conditions, in the presence and absence of aquatic plant Ceratophyllum demersum (L.). Three concentrations used during chronic exposure time extended to (15days). Blood tests of (R. B. Cs., Hb, P.C.V.) were studied for fish exposed to concentration investigated. The hematological parameters decreased with the increasing of pesticide concentrations. Moreover, values of indices (M.C.V.) showed significant increase with the increasing of pesticide concentration, particularly at highest concentration used (3.8) mg/l during (5, 6 and 9) days with absence aquatic plant. However, apparent increasing of (M.C.H.) were observed at especially at concentration of (3.8) mg/l during (6 and 9) days of exposure time. Significant increasing were recoded in (M.C.V.) values for treatment aquatic plant during (7 and 10) days at concentration (3.8) mg\l and during (10) days for (M.C.H.). The present study showed nonsignificant reduction in (M.C.H.C.) values for both treatments with and without aquatic plant.

​Application of Aquatic Plant Ceratophyllum demersum (L.) in Phytoremediation of Wastewater

Background: Phytoremediation, plant usage for remediating natural resources, is being sought as a modern method to clean up polluted lands and streams, including water from ground. Bioremediation assisted by plant, also known as phytoremediation and includes the involvement of microbes associated with certain root systems to remediate soils comprising elevated organic compound concentrations. These strategies could provide cheaper methods for remediating polluted lands and streams with radionuclides, chemicals and different types of organics, with less secondary contaminants and less environmental effect than traditional methods of remediation can produce. All plants consume essential nutrients from their soil and water conditions like metals. Methods: The domestic wastewater quality was determined by analyzing physico-chemical parameters like pH, TDS, TS and electrical conductivity, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, calcium, potassium, magnesium, sulphate, phosphate, nitrogen, iron and manganese and contaminant removal indices were determined during the year 2018-19. Result: The present study was conducted to check the phytoremediation capability of aquatic plant Ceratophyllum demersum (L.). Wastewater was characterized using standard methods and pollutant concentrations were measured in sample of wastewater initially and after phytoremediation. The result of present study revealed maximum increase in value of DO (127.89%) while the other parameters viz. pH (7.24%), TDS (46.77%), TS (51.00%), BOD (60.79%), COD (58.88%), EC (49.89%), Ca (45.41%), K (46.58%), Mg (43.57%), S (45.21%), P (43.73%), N (42.80%), Fe (46.30%) and Mn (47.06%) recorded a decrease in 60 days at 40% value due to absorption of nutrients during phytoremediation.

Predicting the habitat suitability of Schistosoma intermediate host Bulinus truncatus, its predatory aquatic insect Odonata nymph, and the associated aquatic plant Ceratophyllum demersum using MaxEnt.

Schistosomiasis is one of the most important parasitic diseases in tropical and subtropical areas. Its prevalence is associated with the distribution of freshwater snails, which are their intermediate hosts. Thus, control of freshwater snails is the solution to reduce the transmission of this disease. This will be achieved by understanding the relationship between the snails and their habitats including natural enemies and associated aquatic plants as well as the factors affecting their distribution. In this study, Maximum Entropy model (MaxEnt) was used for mapping and predicting the possible geographic distribution of Bulinus truncatus snail (the intermediate host of Schistosoma haematobium), Odonata nymph (predatory aquatic insect), and Ceratophyllum demersum (the associated aquatic plant) in Egypt based on topographic and climatic factors. The models of the investigated species were evaluated using the area under receiver operating characteristic curve. The results showed that the potential risk areas were along the banks of the Nile River and its irrigation canals. In addition, the MaxEnt models revealed some similarities in the distribution pattern of the vector, the predator, and the aquatic plant. It is obvious that the predictive distribution range of B. truncatus was affected by altitude, precipitation seasonality, isothermality, and mean temperature of warmest quarter. The presence of B. truncatus decreases with the increase of altitude and precipitation seasonality values. It could be concluded that the MaxEnt model could help introducing a predictive risk map for Schistosoma haematobium prevalence and performing better management strategies for schistosomiasis.

Enhanced nitrate reduction in water by a combined bio-electrochemical system of microbial fuel cells and submerged aquatic plant Ceratophyllum demersum

High nitrate (NO3−) loading in water bodies is a crucial factor inducing the eutrophication of lakes. We tried to enhance NO3− reduction in overlying water by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plant Ceratophyllum demersum. A comparative study was conducted by setting four treatments: open-circuit SMFC (Control), closed-circuit SMFC (SMFC-c), open-circuit SMFC with C. demersum (Plant), and closed-circuit SMFC with C. demersum (P-SMFC-c). The electrochemical parameters were documented to illustrate the bio-electrochemical characteristics of SMFC-c and P-SMFC-c. Removal pathways of NO3− in different treatments were studied by adding quantitative 15NO3− to water column. The results showed that the cathodic reaction in SMFC-c was mainly catalyzed by aerobic organisms attached on the cathode, including algae, Pseudomonas, Bacillus, and Albidiferax. The oxygen secreted by plants significantly improved the power generation of SMFC-c. Both electrogenesis and plants enhanced the complete removal of NO3− from the sediment–water system. The complete removal rates of added 15N increased by 17.6% and 10.2% for SMFC-c and plant, respectively, when compared with control at the end of experiment. The electrochemical/heterotrophic and aerobic denitrification on cathodes mainly drove the higher reduction of NO3− in SMFC-c and plant, respectively. The coexistence of electrogenesis and plants further increased the complete removal of NO3− with a rate of 23.1%. The heterotrophic and aerobic denitrifications were simultaneously promoted with a highest abundance of Flavobacterium, Bacillus, Geobacter, Pseudomonas, Rhodobacter, and Arenimonas on the cathode.

Studies on phytoremediation of municipal waste water with reference to aquatic plant Ceratophyllum demersum

C. demersum is a cosmopolitan submerged aquatic varieties that has presumably as of now attacked a large portion of its potential intriguing extent. It has the upsides of being a perpetual surviving great overwinter in more profound water and by becoming both by asexual reproduction of broken or finish stems and by sexual reproduction of a lot of seeds. It has a wide biological resistance and becomes moderately quick. Unsettling influence of the water body brings about increments in development through changes in supplement accessibility yet in addition in quicker dispersal around water bodies permitting more noteworthy rivalry with less overwhelming species.

Meiobenthic Invertebrates Community Associated with Aquatic plant Ceratophyllum demersum Salamiyat irrigation canal / north Baghdad

The aim of the present study is to study the meiobenthic invertebrate's community associated with the aquatic plant Ceratophyllum demersum in Al-Salamiyat irrigation canal / north Baghdad, with the chemical and physical parameters of the canal water, during the study period from September 2015 to May 2016. Two sites were chosen for sample collection, the first site (S1) at the beginning of the canal near it's connection with Tigris river, and the second site (S2) after 10 km from the first site. The chemico-physical analysis results revealed that the water temperature ranged from 10-30oC, and pH values ranged between 6.9-7.8, and the dissolved oxygen concentration and the BOD values from 7.2-9.2 mg/l, and 1.2-5.4 mg/l, respectively. The salinity values were ranged between 0.45 and 0.86 ‰, and the total suspended solids were changed 357-674mg/l. A total of 9089 individuals of meiobethic invertebrates were sorted out from C. demersum during the study perid , representing 34 species including Hydra oligactis (Hydrozoa , Cnidaria); two species of Turbellaria ( Platyhelminthes); five species of Nematoda; seven species of Rotifera; 14 species of aquatic Oligochaeta (Annelida); four Crustacea, and one species of chironomid larva species, in addition to recording one individual of Tardigrada from (S2). The highest total number of meiobenthic invertebrates of 5600 individuals were recorded at (S2), while at (S1) less number of (3489) individuals were reported. Four species were recognized as a new records for Iraqi fauna, including Hydra oligactis (Hydrozoa:Cnidaria); Macrostomum tuba (Platyhelminthes: Turbellaria(, Dero cooperi (Annelida:Oligochaeta,) and Stenocypris hislopi )Crustacea: Otracoda(.

Meiobenthic Invertebrates Community Associated with Aquatic plant Ceratophyllum demersum Salamiyat irrigation canal / north Baghdad

The aim of the present study is to study the meiobenthic invertebrate's community associated with the aquatic plant Ceratophyllum demersum in Al-Salamiyat irrigation canal / north Baghdad, with the chemical and physical parameters of the canal water, during the study period from September 2015 to May 2016. Two sites were chosen for sample collection, the first site (S1) at the beginning of the canal near it's connection with Tigris river, and the second site (S2) after 10 km from the first site. The chemico-physical analysis results revealed that the water temperature ranged from 10-30oC, and pH values ranged between 6.9-7.8, and the dissolved oxygen concentration and the BOD values from 7.2-9.2 mg/l, and 1.2-5.4 mg/l, respectively. The salinity values were ranged between 0.45 and 0.86 ‰, and the total suspended solids were changed 357-674mg/l. A total of 9089 individuals of meiobethic invertebrates were sorted out from C. demersum during the study perid , representing 34 species including Hydra oligactis (Hydrozoa , Cnidaria); two species of Turbellaria ( Platyhelminthes); five species of Nematoda; seven species of Rotifera; 14 species of aquatic Oligochaeta (Annelida); four Crustacea, and one species of chironomid larva species, in addition to recording one individual of Tardigrada from (S2). The highest total number of meiobenthic invertebrates of 5600 individuals were recorded at (S2), while at (S1) less number of (3489) individuals were reported. Four species were recognized as a new records for Iraqi fauna, including Hydra oligactis (Hydrozoa:Cnidaria); Macrostomum tuba (Platyhelminthes: Turbellaria(, Dero cooperi (Annelida:Oligochaeta,) and Stenocypris hislopi )Crustacea: Otracoda(.

Removal of aluminum by aquatic plants Ceratophyllum demersum and Chara fragilis from water of experimental ecosystems

Changes in the concentration of the aluminum ions in water of experimental systems (microcosms) have been studied. The Al ion concentration was measured by the fluorescent method. As macrophytes for microcosm incubation served hornwort Ceratophyllum demersum and stonewort Chara fragilis, with the latter hydrobiont used for the first time in similar experiments. It has been convincingly proven that, in the microcosms with the aquatic plants tested, the Al ion concentration decreased much faster than in the macrophyte-free control microcosms. The data obtained suggest that Ceratophyllum demersum and Chara fragilis are promising candidates for phytoremediation applications.

Effects of lead toxicity on the total chlorophyll content and growth changes of the aquatic plant Ceratophyllum demersum L.

This paper reports results of a laboratory-scale experiment conducted to determine the effects of different initial concentrations of a toxic heavy trace metal (lead) on the total chlorophyll (a + b) content of aquatic plant tissues Ceratophyllum demersum L., and also to monitor the visible growth changes during the experiment under different lead concentrations (2, 4 and 6 mg/L), as well as in control plants (without any addition of lead nitrate solution). Lead concentrations in water and plant samples were determined using AAS, where the total chlorophyll content in plant leaf tissues was measured every 15 days during the experimental period using a UV/VIS Spectrophotometer, Model 160A, Shimadzu, with wavelengths of 665 and 649 nm. The results showed that the content of total chlorophyll decreased noticeably, with increasing initial concentrations of lead throughout the exposure time. Decreases in total chlorophyll content in the tissues of C. demersum over the period of the experiment were accompanied by different morphological changes in the plants, depending on the initial lead concentration and exposure duration. These changes in morphology and growth affected the number and length of branches, the number of leaves and the number of leaflets.

Analysis of sublethal arsenic toxicity to Ceratophyllum demersum: subcellular distribution of arsenic and inhibition of chlorophyll biosynthesis.

Arsenic (As) pollution is a serious concern worldwide. Recent studies under environmentally relevant conditions revealed that, in the aquatic plant Ceratophyllum demersum, pigments are the first observable target of toxicity, prior to any effect on photosynthetic parameters or to oxidative stress. Lethal toxicity was initiated by a change of As species and their distribution pattern in various tissues. Here, the localization of As was investigated at the subcellular level through X-ray fluorescence using a submicron beam and a Maia detector. Further, it was possible to obtain useful tissue structural information from the ratio of the tomogram of photon flux behind the sample to the tomogram of Compton scattering. The micro-X-ray fluorescence tomograms showed that As predominantly accumulated in the nucleus of the epidermal cells in young mature leaves exposed to sublethal 1 µM As. This suggests that As may exert toxic effects in the nucleus, for example, by interfering with nucleic acid synthesis by replacing phosphorous with As. At higher cellular concentrations, As was mainly stored in the vacuole, particularly in mature leaves. An analysis of precursors of chlorophyll and degradation metabolites revealed that the observed decrease in chlorophyll concentration was associated with hindered biosynthesis, and was not due to degradation. Coproporphyrinogen III could not be detected after exposure to only 0.5 µM As. Levels of subsequent precursors, for example, protoporphyrin IX, Mg-protoporphyrin, Mg-protoporphyrin methyl ester, and divinyl protochlorophyllide, were significantly decreased at this concentration as well, indicating that the pathway was blocked upstream of tetrapyrrole synthesis.

Deficiency and toxicity of nanomolar copper in low irradiance—A physiological and metalloproteomic study in the aquatic plant Ceratophyllum demersum

Essential trace elements (Cu2+, Zn2+, etc) lead to toxic effects above a certain threshold, which is a major environmental problem in many areas of the world. Here, environmentally relevant sub-micromolar concentrations of Cu2+ and simulations of natural light and temperature cycles were applied to the aquatic macrophyte Ceratophyllum demersum a s a model for plant shoots. In this low irradiance study resembling non‐summer conditions, growth was optimal in the range 7.5–35nM Cu, while PSII activity (Fv/Fm) was maximal around 7.5nM Cu. Damage to the light harvesting complex of photosystem II (LHCII) was the first target of Cu toxicity (>50nM Cu) where Cu replaced Mg in the LHCII-trimers. This was associated with a subsequent decrease of Chl a as well as heat dissipation (NPQ). The growth rate was decreased from the first week of Cu deficiency. Plastocyanin malfunction due to the lack of Cu that is needed for its active centre was the likely cause of diminished electron flow through PSII (ΦPSII). The pigment decrease added to the damage in the photosynthetic light reactions. These mechanisms ultimately resulted in decrease of starch and oxygen production.

Uptake of the cyanobacterial neurotoxin, anatoxin-a, and alterations in oxidative stress in the submerged aquatic plant Ceratophyllum demersum

The prevalence of cyanobacterial blooms in fresh water bodies worldwide has become a serious environmental problem. The blooms can increase the occurrence of cyanobacterial neurotoxin, anatoxin-a, and this toxin can interact with aquatic plants and other pivotal components of aquatic ecosystems. Despite this, several questions regarding the uptake of the toxin by aquatic plants and its association with toxic effects still remain. This study investigated the uptake of anatoxin-a in relation to alterations in oxidative stress, estimated by changes in lipid peroxidation and tocopherol contents (alpha-, beta-, gamma-, and delta-tocopherol), in the submerged aquatic plant, Ceratophylum demersum, at environmentally relevant concentrations. Exposure to five different concentrations of anatoxin-a (0.005, 0.05, 0.5, 5 and 50μgl−1) for 24h increased concentrations in C. demersum in a dose-dependent manner. All four forms of tocopherols were elevated at low concentrations of anatoxin-a (0.005. 0.05. 0.5 and 5μgl−1). However, a decline in the four tocopherol forms along with a high level of lipid peroxidation was observed at 50μgl−1 exposure dose. During 336-h exposure to 15μgl−1 anatoxin-a, rapid toxin uptake during the first 24h and subsequent steady accumulation of the toxin were observed. The four tocopherol forms increased in response to anatoxin-a uptake, attaining their maximum levels together with a significant increase of lipid peroxidation after 12 or 24h. After 24-h exposure, the four tocopherol forms decreased gradually without recovery. The results clearly indicate that anatoxin-a uptake can cause a disturbance of the oxidative stress in the aquatic plant, and depending on the concentration and exposure duration, oxidative damage occurs.

Speciation and distribution of arsenic in the nonhyperaccumulator macrophyte Ceratophyllum demersum.

Although arsenic (As) is a common pollutant worldwide, many questions about As metabolism in nonhyperaccumulator plants remain. Concentration- and tissue-dependent speciation and distribution of As was analyzed in the aquatic plant Ceratophyllum demersum to understand As metabolism in nonhyperaccumulator plants. Speciation was analyzed chromatographically (high-performance liquid chromatography-[inductively coupled plasma-mass spectrometry]-[electrospray ionization-mass spectrometry]) in whole-plant extracts and by tissue-resolution confocal x-ray absorption near-edge spectroscopy in intact shock-frozen hydrated leaves, which were also used for analyzing cellular element distribution through x-ray fluorescence. Chromatography revealed up to 20 As-containing species binding more than 60% of accumulated As. Of these, eight were identified as thiol-bound (phytochelatins [PCs], glutathione, and cysteine) species, including three newly identified complexes: Cys-As(III)-PC2, Cys-As-(GS)2, and GS-As(III)-desgly-PC2. Confocal x-ray absorption near-edge spectroscopy showed arsenate, arsenite, As-(GS)3, and As-PCs with varying ratios in various tissues. The epidermis of mature leaves contained the highest proportion of thiol (mostly PC)-bound As, while in younger leaves, a lower proportion of As was thiol bound. At higher As concentrations, the percentage of unbound arsenite increased in the vein and mesophyll of young mature leaves. At the same time, x-ray fluorescence showed an increase of total As in the vein and mesophyll but not in the epidermis of young mature leaves, while this was reversed for zinc distribution. Thus, As toxicity was correlated with a change in As distribution pattern and As species rather than a general increase in many tissues.

Assessment of heavy metal accumulation in Anzali wetland, Iran, using a submerged aquatic plant, Ceratophyllum demersum

The objective of this study in 2009 was to examine whether levels of cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb) and chromium (Cr) were higher in the leaves than in the stems of a submerged aquatic plant Ceratophyllum demersum in Anzali wetland. Cadmium, Pb and Cr concentrations were highest in the leaves. The mean concentrations of Cd and Cr in the leaves at all the sampling sites ranged between 0.94–1.26 μg g−1 and 1.03–2.71 μg g−1, respectively. Lead also had its highest concentrations in the leaves. The mean concentration of Pb in the leaves at all sampling sites ranged between 7.49–11.88 μg g−1. Copper and Zn concentrations were highest in the stems. The mean concentrations of Cu and Zn in the stems at all sampling sites ranged between 10.79–17.91 μg g−1 and 19.89–40.01 μg g−1, respectively. Cadmium and Pb concentrations were higher in the leaves than in the stems, while Zn concentration was higher in the stems than in the leaves. Accumulation of Cu and Cr in the organs of C. demersum was in descending order of leaf ∼ stem, since there was no significant difference between their mean concentrations in the leaves and stems.

Investigation of the influence of <i>Ceratophyllum demersum</i> to refine diluted compost latex

Water pollution has always been a major problem in the environment. Polluted water is harming for human health and need to clean water from pollution factors. One of the economic and rapid methods forelements removal is displacement metals by biosorption. The purpose of this study was refining diluted compost latex by Ceratophyllum demersum that was diluted 200 times with distilled water. Diluted compost latex (DCL)accompany with aquatic plant Ceratophyllum demersum was located in bottles which were 6 liter in four replication. The experimental performed at the open air of Khorasgan (Isfahan, Iran) University area for 18 dayswithout aeration. Result of Chemical oxygen demand (COD) indicates that the COD was decreased from 728 mg/L to 189.5 mg/L. Also, this investigation was demonstrated that the amount of ammonium in diluted compost latex was decreased from 60 meq/L to 13.33 meq/L. The amount of nitrate in diluted compost latex has decreased from 90 meq/L to 26.66 meq/L, and the amount of Phosphorous was declined from 1.2 meq/L to 0.21 meq/L. EC of diluted compost latex was reduced from 1.02 ds/m to 0.74 ds/m. All of the consequences which were mentioned indicated that this aquatic plant (Ceratophyllum demersum) is one of the best natural ways to refine Polluted water.

Accumulation and Elimination of Chromium by Freshwater Species Exposed to Spiked Sediments

The bioaccumulation and elimination capacity of chromium were examined in four freshwater species: the submersed aquatic plant Ceratophyllum demersum (Ceratophyllaceae), the oligochaete Limnodrilus udekemianus (Tubificidae), the crab Zilchiopsis collastinensis (Decapoda), and the fish Cnesterodon decemmaculatus (Poeciliidae). All of the species were exposed simultaneously to sediments spiked with Cr (K(2)Cr(2)O(7)) at different concentrations for 28 days, followed by 7 days without Cr to evaluate the concentration of residual Cr. We found that Cr accumulated in the tissues of all four species. The highest bioconcentration factor obtained for each species is as follows: C. demersum, 718.66 (+/-272.91); L. udekemianus, 172.55 (+/-80.8), Z. collastinensis, 67.72 (+/-35.4); C. decemmaculatus, 23.11 (+/-12.82), all at 28 days of exposure.

Isotherm Models for Predicting the Dye Adsorption Potential of Coon Tail(Ceratophyllum Demersum)and Water Milfoil(Myriophyllum Spicatum)

The dye adsorption potential and characteristics of the submerged aquatic plants Ceratophyllum demersum and Myriophyllum spicatum were investigated using an azo dye (Basic Blue 41 – BB41). Adsorption equilibria were attained after 160 min at various initial BB41 concentrations (in the range 5–80 mg/l). Attempts were made to fit the equilibrium data obtained using the Langmuir, Freundlich, Redlich–Peterson, Temkin and Dubinin–Radushkevich adsorption isotherm models. The data obtained from the C. demersum and M. spicatum studies were fitted exactly by the Redlich–Peterson and Temkin adsorption isotherms models with correlation coefficient (r) values of 0.999 and 0.981, respectively. The fits of the Langmuir and Freundlich adsorption isotherm models were also acceptable. Evaluation of the experimental data using the Langmuir equation revealed that the maximum adsorption capacities of C. demersum and M. spicatum were 50.0 mg/g and 64.9 mg/g, respectively.

Dissolved natural organic matter (NOM) impacts photosynthetic oxygen production and electron transport in coontail Ceratophyllum demersum

Dissolved natural organic matter (NOM) is dead organic matter exceeding, in freshwater systems, the concentration of organic carbon in all living organisms by far. 80–90% (w/w) of the NOM is made up of humic substances (HS). Although NOM possesses several functional groups, a potential effect on aquatic organisms has not been studied. In this study, direct effects of NOM from various origins on physiological and biochemical functions in the aquatic plant Ceratophyllum demersum are presented. Environmentally relevant concentrations of NOM cause inhibitory effects on the photosynthetic oxygen production of C. demersum. Various NOM sources and the synthetic humic substance HS1500 inhibit the photosynthetic oxygen production of the plant as observed with 1-amino-anthraquinone, a known inhibitor of plant photosynthesis. 1-Aminoanthraquinone may serve as an analogue for the quinoid structures in NOM and HS. Most likely, the effects of NOM may be related to quinoid structures and work downstream of photosynthesis at photosystem (PS) II.