Ludwigia Octovalvis Research Articles

Screening for Resistant and Tolerable Plants (Ludwigia Octovalvis and Phragmites Karka) in Crude Oil Sludge for Phytoremediation of Hydrocarbons

Screening for Resistant and Tolerable Plants (Ludwigia Octovalvis and Phragmites Karka) in Crude Oil Sludge for Phytoremediation of Hydrocarbons

The Role of Leaf Volatiles of Ludwigia octovalvis (Jacq.) Raven in the Attraction of Altica cyanea (Weber) (Coleoptera: Chrysomelidae).

Larvae and adults of Altica cyanea (Weber) (Coleoptera: Chrysomelidae) feed on the rice-field weed Ludwigia octovalvis (Jacq.) Raven (Onagraceae), commonly known as willow primrose, which is considered a biocontrol agent of the weed. Volatile organic compounds from undamaged plants, plants after 4, 12, and 36h of continuous feeding by A. cyanea larvae or adult females and after mechanical damaging were identified by GC-MS and GC-FID analyses. Twenty nine compounds were identified from undamaged plants. 2Z-Penten-1-ol, geraniol, and 1-tridecanol were present in all plants damaged by larvae. In contrast, feeding by adults caused the release of 2Z-penten-1-ol only after 12 and 36h; whereas geraniol and 1-tridecanol appeared only after 36h. Farnesyl acetone was detected after 12 and 36h of feeding by larvae and after 36h of feeding by adults. Farnesene was detected after 36h of feeding by larvae and adults. Linalool was unique after 36h of feeding by larvae. In Y-shaped glass tube olfactometer bioassays, A. cyanea females were attracted to volatiles after 36h of feeding by larvae or adults compared to volatiles released by undamaged plants. The insects were attracted to five synthetic compounds: 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol. Synthetic blends were more attractive than individual compounds. Compared to undamaged plants, volatiles released by plants, damaged by conspecific individuals, were more attractive to A. cyanea females, due to elevated emissions of 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol.

Effects of soil saturation and salinity on seed germination in seven freshwater marsh species from the tropical coast of the Gulf of Mexico

The Gulf of Mexico will be strongly impacted by climate change. Most climate change scenarios predict increases in sea level, which will affect coastal wetland systems. Our aim is to understand how salinity and flooding affect germination in tropical freshwater marsh species. The germination of seven species occurring in coastal freshwater marshes in central Veracruz on the Gulf of Mexico was evaluated. The purpose of this study was to determine in the laboratory the rate and percentage of seed germination at different levels of salinity and flooding for the species: Typha domingensis, Sagittaria lancifolia, Ludwigia octovalvis, Pontederia sagittata, Boehmeria cylindrica, Cyperus digitatus and Fuirena simplex. Germination tests were conducted in Petri dishes. The treatment consisted of two factors: saturation and salinity. The first factor presented two levels (moist and saturated), and the second factor four levels (freshwater, 5, 10 and 15 ppt). The controlled conditions in the germination chamber were light for 14h at 25°C and dark for 10h at 20°C. The results showed that the species germinated faster and had higher germination percentages in the freshwater treatment compared to the more saline conditions. The three most salt-tolerant species were T. domingensis, L. octovalvis and C. digitatus. Additionally, germination was higher under saturated conditions for all species except for B. cylindrica. Based on our results, we conclude that changes in hydroperiod, but mainly an increase in saline conditions, can significantly affect the germination process of coastal freshwater marsh species under wetland salt intrusion.

Long-chain alkanes and fatty acids from Ludwigia octovalvis weed leaf surface waxes as short-range attractant and ovipositional stimulant to Altica cyanea (Weber) (Coleoptera: Chrysomelidae).

The importance of leaf surface wax compounds from the rice-field weed Ludwigia octovalvis (Jacq.) Raven (Onagraceae) was determined in the flea beetle Altica cyanea (Weber) (Coleoptera: Chrysomelidae). Extraction, thin layer chromatography and GC-MS and GC-FID analyses of surface waxes of young, mature and senescent leaves revealed 20, 19 and 19 n-alkanes between n-C15 and n-C35, respectively; whereas 14, 14 and 12 free fatty acids between C12:0 and C22:0 fatty acids were identified in young, mature and senescent leaves, respectively. Tricosane was predominant n-alkane in young and mature leaves, whilst eicosane predominated in senescent leaves. Heneicosanoic acid, palmitic acid and docosanoic acid were the most abundant free fatty acids in young, mature and senescent leaves, respectively. A. cyanea females showed attraction to 0.25 mature leaf equivalent surface waxes compared with young or senescent leaves in a short glass Y-tube olfactometer bioassay. The insects were attracted to a synthetic blend of 0.90, 1.86, 1.83, 1.95, 0.50 and 0.18 µg ml-1 petroleum ether of hexadecane, octadecane, eicosane, tricosane, palmitic acid and alpha-linolenic acid, respectively, comparable with the proportions as present in 0.25 mature leaf equivalent surface waxes. A. cyanea also laid eggs on a filter paper moistened with 0.25 mature leaf equivalent surface waxes or a synthetic blend of 0.90, 1.86, 1.83, 1.95, 0.50 and 0.18 µg ml-1 petroleum ether of hexadecane, octadecane, eicosane, tricosane, palmitic acid and alpha-linolenic acid, respectively. This finding could provide a basis for monitoring of the potential biocontrol agent in the field.

Screening and Identification of Plants at a Petroleum Contaminated Site in Malaysia For Phytoremediation

There is lack of sufficient data that describe which plants can be used in phytoremediation for petroleum and heavy metal contaminated sites, especially in the tropical climate region. The aim of the study was to identify native plants growing on a petroleum contaminated site in Malacca, Malaysia, which have a phytoremediation potential on petroleum. The second aim was to identify native plants at the same contaminated site for phytoremediation of heavy metal contaminants or hyper accumulation plants. In the initial screening of contaminated sites, some of the native plants were found to have the capability to grow in very high concentration of total petroleum hydrocarbon (TPH). This indicates that some of these plants have high potential to act as a phytoremediator. Paspalum vaginatum Sw, Paspalum scrobiculatum L. varbispicatum Hack, Eragrostis atrovirens (Desf.) Trin. exSteud, Cayratia trifolia (L.) Domin, Chloris barbata (L.) Sw, Pycreus polystachyos (Rottb.) Beauv and Ischaemum timorense Kunth were found to be potential phytoremediatory of TPH in contaminated soil. These plants were chosen based on thier high rate of survival in contaminated sites and in terms of uptake or in degrading contaminants. The Biological Accumulation Coefficient (BAC) has been used as a guideline to choose potential plants for heavy metal phytoremediation. In the study, the plants were screened based on BAC values for arsenic (As) and lead (Pb). The selected plants, Melochia corchorifolia L., Ludwigia octovalvis (Jacq.) P. H. Raven, P. vaginatum, Cyperus sphacelatus Rottb., are potential as phytoremediators while L. octovalvis and Melastoma malabathricum L. are potential Pb phytoremediators.

English

Leaves of nine species of Ludwigia were collected from Southwestern Nigeria and the crude proteins were extracted and analysed by electrophoretic fractionation. The results shows that Ludwigia octovalvis var linearis, Ludwigia octovalvis var brevisepala, Ludwigia hyssopifolia and Ludwigia abyssinica are more closely related based on the position of protein bands. Also, Ludwigia decurrens A and Ludwigia adscendens subsp. diffusa are more closely related based on the number of band and the position of band. The band at 2.1 is taxonomic for all the species of Ludwigia studied. Similarly, the band at 1.0 delimits L. leptocarpa from the other species. Protein abundance sequence of the samples is in the order L. hyssopifolia ˃ L. octovalvis var linearis ˃ L. abyssinica ˃ L. octovalvis var brevisepala ˃ L. erecta ˃ L. decurrens B ˃ L. leptocarpa ˃ L. decurrens A ˃ L. adscendens subsp. diffusa. The occurrence of a new band in Ludwigia decurrence B separates it from Ludwigia decurrence A, a new hypothetical name is suggested for the delimitation of the two species. The protein bands are taxonomically distinct as no two species have the same band distribution; diagnostic bands which could be employed for the identification of each species are also reported.   Key words: Ludwigia, protein bands distribution, taxonomic implication, Nigeria.

Phytoremediation of contaminated soils containing gasoline using Ludwigia octovalvis (Jacq.) in greenhouse pots.

Greenhouse experiments were carried out to determine the phytotoxic effects on the plant Ludwigia octovalvis in order to assess its applicability for phytoremediation gasoline-contaminated soils. Using plants to degrade hydrocarbons is a challenging task. In this study, different spiked concentrations of hydrocarbons in soil (1, 2, and 3g/kg) were tested. The results showed that the mean efficiency of total petroleum hydrocarbon (TPH) removal over a 72-day culture period was rather high. The maximum removal of 79.8% occurred for the 2g/kg concentration, while the removal rate by the corresponding unplanted controls was only (48.6%). The impact of gasoline on plants included visual symptoms of stress, yellowing, growth reduction, and perturbations in the developmental parameters. The dry weight and wet weight of the plant slightly increased upon exposure to gasoline until day 42. Scanning electron microscopy (SEM) indicated change to the root and stem structure in plant tissue due to the direct attachment with gasoline contaminated compared to the control sample. The population of living microorganisms in the contaminated soil was found to be able to adapt to different gasoline concentrations. The results showed that L. octovalvis and rhizobacteria in gasoline-contaminated soil have the potential to degrade organic pollutants.

Banco de sementes do solo em áreas de cultivo de subsistência na Floresta Ombrófila Aberta com Babaçu (Orbygnia phalerata Mart.) no Maranhão

Os objetivos desta pesquisa foram identificar e avaliar a estrutura das comunidades e a diversidade das espécies herbáceas invasoras presentes no banco de sementes do solo, em áreas de cultivo de subsistência nos Municípios de Bacabal, Lago Verde, São Luís Gonzaga e Vitorino Freire, localizados em trechos da Floresta Ombrófila Aberta com Babaçu, no Maranhão. Em cada município foram alocadas 15 parcelas de 50 m2, de onde foram retiradas 90 amostras de solo com um gabarito de metal vazado de 25 x 16 x 3 cm e colocadas em bandejas em casa telada. Foi avaliado o número de espécies e de indivíduos, bem como os valores relativos da densidade, frequência, abundância e o valor de importância de cada espécie. Os dados foram submetidos às Análises de Variância e de Coordenadas Principais. A diversidade foi calculada por meio do Índice de Diversidade de Shannon. O banco de sementes apresentou a maior riqueza florística em Bacabal, com 50 espécies de 34 gêneros e 17 famílias, bem como o maior número de indivíduos, 11.541. A maior similaridade florística foi observada entre Lago Verde e Vitorino Freire. As espécies predominantes, baseado no valor de importância, foram: Ludwigia octovalvis (VI = 34,8%) em Bacabal; Scleria lithosperma (VI = 37,0%), em Lago Verde; e Boerhavia erecta (VI = 40,4%), em São Luís Gonzaga; e (VI = 57,0%), em Vitorino Freire. A maior diversidade foi observada em Bacabal, com H’ = 2,66 nats ind-1. Os resultados podem ser aplicados na previsão de infestações de plantas invasoras nos municípios da região.

Identifying the problem weeds of rice‐based systems along the inland‐valley catena in the southern Guinea Savanna, Africa

While weeds generally are considered as the most important overarching production constraints in inland‐valley cropping systems in West Africa, little is known about species' associations with environmental and crop management factors. Weed species' associations with seasonal and environmental factors, such as their position on the catena, soils and cropping systems, were studied during two seasons (dry and wet) in 45 arable fields of three inland valleys in south‐western Benin, Africa. The three most dominant weed species were Dactyloctenium aegyptium, Commelina benghalensis and Digitaria horizontalis on the inland‐valley crests (uplands), Ludwigia hyssopifolia, Corchorus aestuans and Ludwigia octovalvis on the sloping hydromorphic fringes and Leersia hexandra, Ipomoea aquatica and Fimbristylis ferruginea in the valley bottoms (lowlands). Echinochloa colona, Cleome viscosa and Talinum triangulare were the three most dominant species in the dry‐season crops (maize or vegetables) and Leer. hexandra, I. aquatica and Sphenoclea zeylanica were the three most dominant species in the wet‐season crop (rice). Ageratum conyzoides, Synedrella nodiflora and D. horizontalis were observed throughout the catena. Problem weeds in inland‐valley agro‐ecosystems are those that combine a high frequency with a high submergence tolerance and ecological plasticity, C4 grasses, perennial C3 species with persistent root structures and broad‐leaved species with high propagation rates. Weed management strategies that are aimed at increasing the resilience of rice‐based cropping systems in the inland valleys of the southern Guinea Savanna of Africa should address the categories of problem species that were identified in this study. This can be done best by following an integrated approach, including the use of more weed‐competitive cultivars and rotation crops.

Phytotoxicity and Uptake of Arsenic by Ludwigia octovalvis in a Pilot Reed Bed System

Arsenic (As) is in the first rank of dangerous and toxic chemicals. A phytotoxicity bioassay was used to select plant species for phytoremediation that were able to remove As from a contaminated site. Ludwigia octovalvis (Jacq.) P.H. Raven has been described as a plant that can survive on a contaminated site in Malaysia. In this study, the phytotoxicity and uptake of As by L. octovalvis were examined at various As concentrations of 5, 22, and 39 mg/kg in a pilot reed bed system. The total extractable As and bioavailable As concentrations were determined using the wet digestion method and a solution of ethylene diamine tetraacetic acid disodium (Na2-EDTA) respectively. Results showed symptoms of phytotoxicity at all As concentrations after 42 days of exposure as the ratio of plant numbers to total mass of As was low. An increase in As-induced symptoms of phytotoxicity occurred with increasing As concentration in the spiked sand and with days of exposure. The concentration of the bioavailable As in the spiked sand decreased, and percentages removed were 76.5%, 72.0%, and 62.9% for initial As concentrations of 5, 22, and 39 mg/kg respectively. Maximum As uptake in stems reached approximately 1092.6±106.7 mg/kg on day 14 at an As concentration of 39 mg/kg, while the maximum As uptake in roots and leaves on day 28 was 794.5±110.4 and 883.9±110.97 mg/kg respectively. An increase in As uptake by whole L. octovalvis plants occurred with increasing As concentration in the spiked sand, giving evidence that As can induce toxic effects on L. octovalvis when it is taken up and accumulated in its tissues.

The anti-aging effects of Ludwigia octovalvis on Drosophila melanogaster and SAMP8 mice

We investigated the anti-aging effects of Ludwigia octovalvis (Jacq.) P. H. Raven (Onagraceae), an extract of which is widely consumed as a healthful drink in a number of countries. Using the fruit fly, Drosophila melanogaster, as a model organism, we demonstrated that L. octovalvis extract (LOE) significantly extended fly lifespan on a high, but not a low, calorie diet, indicating that LOE may regulate lifespan through a dietary restriction (DR)-related pathway. LOE also attenuated age-related cognitive decline in both flies and in the senescence-accelerated-prone 8 (SAMP8) mouse, without causing any discernable negative trade-offs, including water intake, food intake, fecundity, or spontaneous motor activity. LOE contained high levels of polyphenols and flavonoids, which possess strong DPPH radical scavenging activity, and was shown to attenuate paraquat-induced oxidative damage and lethality in flies. Gas chromatography-mass spectrometry (GC-MS) analyses identified 17 known molecules, of which β-sitosterol and squalene were the two most abundant. We further demonstrated that β-sitosterol was capable of extending lifespan, likely through activating AMP-activated protein kinase (AMPK) in the fat body of adult flies. Taken together, our data suggest that LOE is a potent anti-aging intervention with potential for treating age-related disorders.

Floristic diversity of the soil weed seed bank in a rice-growing area of Brazil: in situ and ex situ evaluation

The objective of this study was to compare the ex situ and in situ floristic diversity of the soil weed seed bank of a rice field in northeastern Brazil. In a rice field in the county of Bacabal, located in the state of Maranhao, thirty 25-m2 plots were laid out. From 15 plots, soil samples (6/plot; n = 90) were taken with a soil probe (25 × 16 × 3 cm) and placed in aluminum trays in the greenhouse. From the remaining 15 plots, weed samples (6/plot; n = 90) were taken with the same soil probe. The number of seeds was estimated by germination. We evaluated the numbers of species and individuals, as well as the density, frequency, abundance and importance value (IV) for each species. Diversity was computed by the Shannon index (H'). We recorded 13,892 individuals (among 20 families, 40 genera and 60 species), of which 11,530 (among 50 species) germinated ex situ and 2,362 (among 34 species) germinated in situ. The family Cyperaceae had the highest number of species (16), followed by Poaceae (10). The dominant species, in situ and ex situ, were Schoenoplectus juncoides (IV=47.4%) and Ludwigia octovalvis (IV=34.8%), respectively. Floristic diversity was higher ex situ (H'=2.66). The information obtained here could help determine the infestation potential of these species, which could lead to improved management strategies.

Effect of applying rhizobacteria and fertilizer on the growth of Ludwigia octovalvis for arsenic uptake and accumulation in phytoremediation

The aim of this study was to investigate the effect of applying a six-rhizobacterial consortium and nitrogen phosphate potassium (NPK) fertilizer in inorganic arsenic (arsenate) phytoremediation using Ludwigia octovalvis (Jacq.) Raven plants. The experiment included control L. octovalvis plants and three phytoremediation treatments with L. octovalvis plants, namely an arsenic (As) concentration of 39mgkg−1 only, the addition of a six-rhizobacterial consortium at 2% (v/v) with an As concentration of 39mgkg−1 and the addition NPK fertilizer at 0.02% (w/w) with an As concentration of 39mgkg−1. In the As phytoremediation treatment with the presence of As only, plants showed signs of phytotoxicity such as wilting and senescent leaves. L. octovalvis grew well until the end of exposure (Day 42) in the phytoremediation treatment with 2% rhizobacteria consortium or with 0.02% NPK fertilizer addition. The As phytoremediation treatment with 2% rhizobacteria showed the highest removal percentages of bioavailable As (89%), total extractable As (78%) and As in the leachate of the reed beds (98%) resulting in lower As uptake by L. octovalvis than in the other two phytoremediation treatments. This indicates that the bioremediation process played a role in the treatment with 2% rhizobacteria. The fresh weight of L. octovalvis biomass in treatment with 0.02% NPK fertilizer increased by almost five-fold compared with the As only treatment. The effectiveness of phytoremediation in terms of As uptake at Day 42 reached 49.8% in the phytoremediation treatment with 0.02% NPK fertilizer addition. It was the highest than in the other two phytoremediation treatments. In conclusion, NPK fertilizer addition gave the best results in As uptake using L. octovalvis plants in terms of the effectiveness of phytoremediation.

Arsenic Toxicity on Ludwigia octovalvis in Spiked Sand

Wilting, especially of the leaves, was observed as an initial symptom of arsenate [As(V)] to Ludwigia octovalvis (Jacq.) P. H. Raven. The plants tolerated As(V) levels of 39 mg kg⁻¹ for as long as 35 days of exposure. After 91 days, the maximum concentration of As uptake in the plant occurred at As(V) concentration of 65 mg kg⁻¹ while As concentration in the stems, roots and leaves were 6139.9 ± 829.5, 1284.5 ± 242.9 and 1126.1 ± 117.2 mg kg⁻¹, respectively. In conclusion, As(V) could cause toxic effects in L. octovalvis and the plants could uptake and accumulate As in plant tissues.

Effect of tillage systems and herbicides on weed emergence, weed growth, and grain yield in dry-seeded rice systems

Farmers in many Asian countries are moving from puddled-transplanted rice to dry-seeded rice systems. Dry-seeded rice can be sown after land preparation or under zero-till conditions. Weeds, however, are the major constraint to the production of dry-seeded rice. A study was conducted during the wet season of 2011 and dry season of 2012 at the farm of the International Rice Research Institute to evaluate the effect of tillage systems (zero-till and conventional tillage) and herbicides on weed emergence, weed growth, and grain yield in dry-seeded rice systems. In the zero-till system, the densities of Digitaria ciliaris, Eleusine indica, Eclipta prostrata, and Ludwigia octovalvis increased many-fold from the first season to the second. The efficacy of herbicides (oxadiazon followed by fenoxaprop+ethoxysulfuron and oxadiazon followed by penoxsulam+cyhalofop) was lower in the zero-till system than in the conventional tillage system. Grain yield in the herbicide-treated and weed-free plots was similar between the tillage systems and this response was consistent during both the seasons. However, grain yield in the zero-till-control (one hand-weeded) plots was lower (0.9–1.5tha−1) than in the conventional tillage-control plots. The information gained from this study suggests that yields in zero-till systems similar to those in conventional-tilled systems can be achieved if weeds are effectively controlled. In the absence of effective weed control, zero-till systems may result in poor grain yield.

Sludge removal from primary wastewater stabilization ponds with excessive accumulation: a sustainable method for developing regions

Wastewater stabilization ponds have long been considered a sustainable treatment option for developing regions. Sludge buildup in primary ponds is also a sustainability issue since ponds must be desludged every 2–15 years depending on their design and solids loading. Pond systems in developing regions are often designed without a desludging plan and operated without the amortized desludging cost included in the operation and maintenance budget. This paper presents a method where sludge drying within a pond is effected by rooted plants; after drying, the sludge is removed with a mid-sized excavator. The method was tested in the desludging of a primary pond in Tela, Honduras, where sludge 4 m deep was dried to a solid (TS ≈ 18%) to a depth >1 m using the wetland plant Ludwigia octovalvis. The data suggest that both evapotranspiration and drainage through the root system contributed to dewatering. The total cost in 2011 US dollars was $13,716 or $4.47 m3 removed, which was paid from the municipality's general fund without external aid. The method presented is sustainable, and serves as a model for desludging operations where excessive sludge accumulation has occurred – a likely scenario in many primary ponds in developing regions.

Arsenic Range Finding Phytotoxicity Test Against Ludwigia octovalvis as First Step in Phytoremediation

Arsenic Range Finding Phytotoxicity Test Against Ludwigia octovalvis as First Step in Phytoremediation

Isolation and screening of arsenic resistant rhizobacteria of Ludwigia octovalvis

Ludwigia octovalvis was characterized for its potential in arsenic phytoremediation. Epiphyte rhizobacteria from the roots of L. octovalvis were isolated in five different arsenic concentrations (4, 20, 40, 60 and 80 mg kg -1 ) and control after single exposure for 35 days. Results show that 109 colonies were isolated which were further grouped into 29 groups of isolated rhizobacteria. After preliminary screening, 17 rhizobacterial isolates were considered to be resistant to arsenic (arsenate or As[V]) and after secondary screening, 12 rhizobacterial isolates showed potential resistance to arsenic. Identification was conducted using biolog GEN III microbial identification system. One of the arsenate potentially resistant rhizobacterial was identified as Arthrobacter globiformis . The k (growth rate constant) value of A. globiformis was 0.112 h -1 with g (generation time) value of 8.943 h and i (specific growth rate) value of 0.077 h -1 . Minimal inhibitory concentration (MIC) value of A. globiformis on arsenate exposure was 500 mg L -1 and has the potential to promote arsenic phytoremediation at contaminated site. Key words : Phytoremediation, arsenic, isolation, screening, identification, minimal inhibitory concentration (MIC).

Phosphorus, nitrogen, and carbon contents of macrophytes in lakes lateral to a tropical river (Paranapanema River, São Paulo, Brazil)

AIM: The aim of this paper was to determine the phosphorus, nitrogen, and carbon contents of aquatic macrophyte species during two periods of the year in the land-water transition zone of three lakes lateral to the Paranapanema River (São Paulo); METHODS: Plants, water, and sediment were collected during two distinct periods (August 1998 and February 1999) in three transects perpendicular to littoral zones of the sampled sites. For the determination of the phosphorus, nitrogen and carbon contents of aquatic macrophyte species, aerial and submerged plant structures (leaves, roots, and stems) were used; RESULTS: In Camargo Lake, which has a poor connection with the river during the dry period (August 1998), the highest nitrogen content was obtained for Salvinia auriculata Aublet, while the highest phosphorus contest was observed for Eichhornia azurea (Swartz) Kunth. During the rainy season (February 1999), Echinochloa polystachya (H.B.K.) Hitch was the species with the highest phosphorus, nitrogen, and carbon contents. In Coqueiral Lake (a lake with great connectivity to the river), the highest phosphorus and nitrogen concentrations during the dry period were observed for Cyperus esculentus L. Similar carbon contents were found for both C. esculentus and Eichhornia azurea. During the rainy season, the species with the highest phosphorus and nitrogen concentrations were E. polystachya, Ludwigia octovalvis (Jacq.) P.H.Raven, and Polygonum spectabile Mart. Considering the plants recorded during the dry period in Cavalos Lake, which is isolated from the river, Myriophyllum aquaticum (Vellozo) Verdcourt was the species with the highest phosphorus and nitrogen concentrations. During the rainy period, C. esculentus and E. azurea had the highest nitrogen concentration. All the aquatic macrophyte species presented similar carbon contents. The highest phosphorus concentration was that of C. esculentus; CONCLUSIONS: The bottom of Camargo and Coqueiral Lakes (both with permanent connection with the river) and some sites of Cavalos (an isolated lake) can be considered similar. They were characterized by sediment with more phosphorus, organic matter, silt, and clay than other sites, which can affect the macro-nutrient content of macrophytes. In the isolated lake, the degradation of submerged plants at the land-water interface contributed to the nutrient pool of aquatic macrophytes after rainfall.

Phosphorus, nitrogen, and carbon contents of macrophytes in lakes lateral to a tropical river (Paranapanema River, São Paulo, Brazil)

AIM: The aim of this paper was to determine the phosphorus, nitrogen, and carbon contents of aquatic macrophyte species during two periods of the year in the land-water transition zone of three lakes lateral to the Paranapanema River (Sao Paulo); METHODS: Plants, water, and sediment were collected during two distinct periods (August 1998 and February 1999) in three transects perpendicular to littoral zones of the sampled sites. For the determination of the phosphorus, nitrogen and carbon contents of aquatic macrophyte species, aerial and submerged plant structures (leaves, roots, and stems) were used; RESULTS: In Camargo Lake, which has a poor connection with the river during the dry period (August 1998), the highest nitrogen content was obtained for Salvinia auriculata Aublet, while the highest phosphorus contest was observed for Eichhornia azurea (Swartz) Kunth. During the rainy season (February 1999), Echinochloa polystachya (H.B.K.) Hitch was the species with the highest phosphorus, nitrogen, and carbon contents. In Coqueiral Lake (a lake with great connectivity to the river), the highest phosphorus and nitrogen concentrations during the dry period were observed for Cyperus esculentus L. Similar carbon contents were found for both C. esculentus and Eichhornia azurea. During the rainy season, the species with the highest phosphorus and nitrogen concentrations were E. polystachya, Ludwigia octovalvis (Jacq.) P.H.Raven, and Polygonum spectabile Mart. Considering the plants recorded during the dry period in Cavalos Lake, which is isolated from the river, Myriophyllum aquaticum (Vellozo) Verdcourt was the species with the highest phosphorus and nitrogen concentrations. During the rainy period, C. esculentus and E. azurea had the highest nitrogen concentration. All the aquatic macrophyte species presented similar carbon contents. The highest phosphorus concentration was that of C. esculentus; CONCLUSIONS: The bottom of Camargo and Coqueiral Lakes (both with permanent connection with the river) and some sites of Cavalos (an isolated lake) can be considered similar. They were characterized by sediment with more phosphorus, organic matter, silt, and clay than other sites, which can affect the macro-nutrient content of macrophytes. In the isolated lake, the degradation of submerged plants at the land-water interface contributed to the nutrient pool of aquatic macrophytes after rainfall.