Biomass Of Aquatic Macrophytes Research Articles

Aquatic Macrophyte Biomass Periodically Harvested Form Shipping Routes and Drainage Systems in a Selected Region of Poland as a Substrate for Biogas Production

One of the identified obstacles to the development of biogas plants is the limited sources of organic substrates. Hydrophytes varying in morphology, chemical composition, and origin proved to be viable alternatives. This study’s aim was to determine the feasibility of deploying biomass from the cleansing of water reservoirs for anaerobic digestion. A mass and energy balance was estimated for Warmia–Mazury Province (Poland), the so-called Thousand Lake District. The effectiveness of anaerobic digestion was determined in anaerobic batch respirometric reactors. The biomass of hydrophytes harvested from this area approximated 38,070 Mg FM/year. The biogas yield from emergent plants approximated 350 m3/MgVS, and the average CH4 content of biogas reached 55%, whereas the respective values obtained from submerged biomass reached 270 m3/MgVS and 58% CH4. The total CH4 volume achievable from the facility fed with waste biomass of this type allows producing ca. 1,654,560 m3CH4/year, which enables reaching 866 kW theoretical thermal power and 636 kWe net electrical power with the facility. The contribution of biomass from mowing in this energy effect was about 84%, whereas that of the submerged vegetation obtained by hacking the bottom was 16%.

Microalgae biofilm formation and antioxidant responses to stress induce by Lemna minor L., Chlorella vulgaris, and Aphanizomenon flos-aquae

The study shows how microalgae biofilm formation and antioxidant responses to the production of reactive oxygen species (ROS) is alter by the presences of Lemna minor L., Chlorella vulgaris, and Aphanizomenon flos-aquae. The study involves the cultivation of the biofilm of Chlorella vulgaris and Aphanizomenon flos-aquae in three bioreactors. The condition of growth for the biofilm formation was varied across the three bioreactors to enable the dominance Chlorella vulgaris and Aphanizomenon flos-aquae in one of the bioreactors. Lemna minor L. was also introduce into one of the bioreactors to determine its effect on the biofilm formation. The result obtained shows that C. vulgaris and A. flos-aquae dominate the biofilm, resulting in a high level of H2O2 and O2- (H2O2 was 0.122 ± 0.052 and 0.183 ± 0.108 mmol/L in C. vulgaris and A. flos-aquae, respectively, and O2- was 0.261 ± 0.039 and 0.251 ± 0.148 mmol/L in C. vulgaris and A. flos-aquae, respectively). The study also revealed that the presence of L. minor L. tend to reduce the oxidative stress to the biofilm leading to low production of ROS (H2O2 was 0.086 ± 0.027 and 0.089 ± 0.045 mmol/L in C. vulgaris and A. flos-aquae respectively, and O2- was 0.185 ± 0.044 and 0.161 ± 0.065 mmol/L in C. vulgaris and A. flos-aquae respectively). The variation in the ability of the biofilm of C. vulgaris and A. flos-aquae to respond via chlorophyll, carotenoid, flavonoid, anthocyanin, superoxide dismutase, peroxidase, catalase, glutathione reductase activities, antioxidant reducing power, phosphomolybdate activity, DPPH reduction activity, H2O2 scavenging activity, lipid content and organic carbon also supports the fact that the presence of biomass of microalgae and aquatic macrophytes tend to affect the process of microalgae biofilm formation and the ability of the biofilm to produce antioxidant. This high nutrient utilization leads to the production of biomass which can be used for biofuel production and other biotechnological products.

Interactions between a planktivorous fish and planktonic microcrustaceans mediated by the biomass of aquatic macrophytes

AbstractHabitat complexity is recognized to mediate predator–prey relationships by offering refuge or not. We investigated the availability of planktonic microcrustaceans and the diet of a planktivorous fish (Hyphessobrycon eques) at different levels (low, intermediate and high) of aquatic macrophyte biomass. Sampling was carried out in a river with low flow speed, located in a Neotropical floodplain. We collected fish and microcrustaceans in macrophyte stands with variations in biomass. There were no differences in microcrustacean density in the water among the levels of macrophyte biomass, but microcrustacean richness and diet composition of H. eques differed. Microcrustacean richness and trophic niche breadth of the planktivorous fish were higher in high biomass stands. There was high consumption of a small cladoceran species in low macrophyte biomass, which was replaced by larger species, such as copepods, in intermediate and high biomass. Thus, the selection of some species was different among the biomass levels. These results suggest that plant biomass plays an important role in the interaction between fish and microcrustaceans, and prey characteristics such as size, escape ability and energy value make them more or less subject to predation by fish according to habitat structuring.

Habitat complexity and individual variation in diet and morphology of a fish species associated with macrophytes

AbstractPopulations of generalist fish can be composed of individuals specialised to a small subset of food resources, a process known as individual specialisation. In this study, we hypothesised that variation in the diet and morphology of individuals is related to habitat complexity and that greater levels of individual specialisation are found at intermediate levels of macrophyte biomass. Fish and aquatic plants were sampled in 15 multispecific macrophyte stands with different biomasses in the Baía River (Upper Paraná River floodplain). We assessed habitat complexity using the biomass of aquatic macrophytes (three levels of classification: low, intermediate and high). The diet of Moenkhausia forestii was evaluated with the volumetric method. To assess individual diet specialisation, we used the IS (specialisation index) and NODF (nestedness based on overlap and decreasing fill) index and for individual morphological specialisation we used ecomorphological metrics. We tested for a correlation between diet and morphology with a Mantel test. Contrary to our hypothesis, IS and NODF values indicated greater individual specialisation in the diet of M. forestii from low macrophyte biomass. However, the greatest individual morphological specialisation was found in macrophyte stands with intermediate biomasses. The Mantel test showed that there was no significant correlation between diet and morphology. Thus, individual specialisation of M. forestii diet may be related to an increase in competition (likely intraspecific) in stands with low macrophyte biomass, while morphological specialisation is probably related to greater resources availability and accessibility within stands of intermediate macrophyte biomass.

Assessing the safe operating space of aquatic macrophyte biomass to control the terrestrialization of a grass-type shallow lake in China

As an important type of aquatic ecosystem, lake ecosystems play an irreplaceable role in providing water resources, controlling floods, regulating the regional climate, and maintaining the regional ecological balance. However, multiple lake ecosystems have been threatened by the expansion of aquatic macrophytes and the resulting bioaccumulation, which accelerates the process of lake terrestrialization. Therefore, it is necessary to identify the safe operating space of macrophyte biomass in order to control the terrestrialization of shallow lakes. In this study, we investigated the biomasses of dominant species and community types at different growth stages in different terrestrialized zones for a typical shallow lake in North China. Then, we developed a suitable method for estimating the safe operating space for the aquatic macrophyte biomass in different terrestrialization stages. Our results showed that the aquatic macrophyte biomass generally increased with the increasing terrestrialization stage. In addition, the biomass in September was lower than that in May. On the community scale, the biomass of Phragmites australis, Phragmites australis – Ceratophyllum demersum, and Nelumbo nucifera - Ceratophyllum demersum - Typha orientalis communities was significantly higher than that of Potamogeton pectinatus and Potamogeton pectinatus - Nelumbo nucifera communities. Terrestrialization exhibited lower impacts on plant biomass in May, whereas a greater impact of terrestrialization was observed in September. Generally, single-species communities had higher plant biomass than mixed communities. The target management years for different terrestrialized zones were established to calculate the safe operating space of macrophyte biomass. The current biomass values were much higher than those calculated for the safe operating space, especially in September and for the P. australis and P. australis - C. demersum communities, indicating that there is high pressure to manage these communities. The approach proposed in the study provides a scientific reference for macrophyte management to control the terrestrialization status of grass-type shallow lakes.

Seasonal macrophyte growth constrains extent, but improves quality, of cold‐water habitat in a spring‐fed river

AbstractRooted aquatic macrophytes affect abiotic conditions in low‐gradient rivers by altering channel hydraulics, consuming biologically available nutrients, controlling sediment transport and deposition, and shading the water surface. Due to seasonal macrophyte growth and senescence, the magnitude of these effects may vary temporally. Seasonal changes in aquatic macrophyte biomass, channel roughness and flow velocity, were quantified and trends were related to spatiotemporal patterns in water temperature in a low‐gradient, spring‐fed river downstream from high‐volume, constant‐temperature groundwater springs. Between spring and summer, a nearly threefold increase in macrophyte biomass was positively correlated with channel roughness and inversely related to flow velocity. On average, flow velocity declined by 34% during the study period, and channel roughness increased 63% (from 0.064 to 0.104). During the spring and fall period, the location of a minimum water temperature variability “node” migrated upstream more than 4 km, whereas daily maximum water temperature cooled by 2–3°C. Water temperature modelling shows that the longitudinal extent of cold‐water habitat was shortened due to increased channel roughness independent of seasonal surface water diversions. These results suggest that macrophyte growth mediates spatiotemporal patterns of water temperature, constraining available cold‐water habitat while simultaneously improving its quality. Understanding complex spatial and temporal dynamics between macrophyte growth and water temperature is critical to developing regulatory standards reflective of naturally occurring variability and has important implications for the management and conservation of cold‐water biota.

Seasonal variation of aquatic macrophytes and its relationship with environmental factors in Baiyangdian Lake, China

The relationships of aquatic macrophytes and 14 environmental factors of the Baiyangdian Lake in spring, summer and autumn were investigated by Pearson correlation analysis and redundancy analysis (RDA) method. The pollutant concentrations in water and sediment were at high level and changed obviously with season. TOC, NO2-N and NH4-N exhibited a strong correlation with other environmental factors in water. TC, TOC and TN had a strong correlation with other environmental factor in sediments. The total biomass of aquatic macrophytes reached its maximum value of 2411.6 g/m2 in spring and the total species number achieved its maximum in summer. Potamogeton pectinatus was the most dominant species in three seasons. From RDA analysis, the top three water chemical factors that influence aquatic macrophytes were Chla, NO3-N and TN (contributions of 14.6%, 13.8% and 10.5%, respectively). The top three environmental factors in sediment were TOC, IP and NH4-N (contributions of 35.6%, 25.7% and 20.7%, respectively). The aquatic macrophytes also had distinct major environmental factors. The diversity indexes of the aquatic macrophytes had less than 0.5 fluctuations. This work might provide more insights into the control and remediation of lake pollution in North China.

Response of benthic algae to environmental conditions in an urban lake recovered from eutrophication, China

Benthic algae communities dominate the primary production in littoral zone of shallow lake. To understand the long-term effect of alteration in the composition of benthic algae community assemblage in such as a lake in China, we analyzed the benthic algae developments and indicators in the Donghu Lake in Wuhan, central China in 2004 and 2014. We compared the benthic algae biomass, compositions, and species richness of aquatic macrophytes and the changes of primary physicochemical parameters. The results show that in the 10-year period, chl a and conductivity declined significantly but nutrient level of the whole lake remained largely stable. The benthic algae biomass doubled and the relative proportion of green algae increased, whereas the benthic diatom ratio decreased. The benthic diatom assemblages and taxa differed in a number of ways, showing more epiphytic diatom species, and the relative abundance and species richness changed markedly. The number of aquatic macrophyte species increased from 3 in 2004 to 15 in 2014, presenting a remarkable recovery from previous eutrophication conditions. The changes of water level, chl a, and conductivity played a crucial role in governing aquatic macrophytes re-colonization in the littoral zones in the period. The ecological characteristics of littoral benthic diatoms reflect habitat coupling as indicated by redundancy analysis. Therefore, the close link between benthic algae and macrophyte recovery demonstrates that the benthic algae metrics are much more useful than nutrient levels to quantify the process of restoration in the lake.

Comparação da retenção de cádmio e chumbo nos tecidos vegetais das macrófitas aquáticas aguapé (Eichhornia sp.) e taboa (Typha sp.) por biossorção e fitorremediação

Tecnologias alternativas como a biossorção e a fitorremediação são eficazes para remoção de metais da água. A fim de comparar essas duas tecnologias, em escala laboratorial, o presente trabalho teve como objetivo avaliar a retenção mássica dos metais tóxicos Cd e Pb nos tecidos vegetais de duas espécies de macrófitas aquáticas, o Aguapé (Eichhornia sp.) e a Taboa (Typha sp.). Na biossorção a biomassa seca das macrófitas aquáticas Eichhornia sp. e Typha sp. permaneceram em contato com soluções contaminadas com Cd (4 mg L-1) e Pb (4 mg L-1) isolados em intervalos de tempo distintos, até 24 horas. As amostras foram coletadas, filtradas e analisadas por ICP OES. No ensaio de fitorremediação as plantas mães permaneceram em processo de aclimatação em solução nutritiva. Após a aclimatação plantas filhas foram coletadas e acondicionadas em frascos de polietileno com soluções nutritivas contaminadas com as mesmas concentrações de Cd e Pb isoladamente. Ao longo do período de ensaio, alíquotas da solução foram coletadas, filtradas e analisadas no ICP OES. Para verificação da concentração de metais acumulados nos tecidos vegetais, após 21 dias de contato com as soluções contaminadas, as plantas foram retiradas dos frascos, lavadas e secas para realização da digestão Nitro-Perclórica seguida da análise no ICP OES. Para ambos os tratamentos, os ensaios foram em triplicatas e para a análise estatística utilizou-se o ANOVA e o Teste-t, com nível de significância de 5%. Os metais retidos nos tecidos vegetais (q) do Aguapé apresentaram os valores máximos de 18,8 mg g-1 (Cd) e de 8,6 mg g-1 (Pb) e a Taboa de 15,0 mg g-1 (Cd) e 4,6 mg g-1 (Pb) na biossorção. Na fitorremediação a concentração de metais nos tecidos vegetais do Aguapé foi de 3,2 mg g-1 (Cd) e 4,28 mg g-1 (Pb) e de 5,0 mg g-1 (Cd) e 2,3 mg g-1 (Pb) na Taboa. Aparentemente, as biomassas secas apresentam um melhor desempenho na remoção de Cd e Pb.

Response of aquatic macrophyte biomass to limnological changes under water level fluctuation in tropical reservoirs.

We evaluated the response of the biomass of aquatic macrophytes under limnological changes after water level fluctuation (WLF) of two tropical reservoirs (R1 and R2), located in northeastern Brazil. Initially we tested the hypothesis that post-WLF limnological conditions and biomass of macrophytes increase or decrease, depending on the variable or species. We monitored a 4 × 50 m permanent plot, in four expeditions per period (pre- or post-WLF), assessing species biomass and 10 limnological variables. We utilized 0.25 × 0.25 m quadrats for biomass. Once the effect of WLF in limnological variables and species biomass was confirmed, we utilized Canonical Correspondence Analysis to understand the relationship between limnological variables and species biomass. The abundant and/or dominant species in pre-WLF of R1 ( Pistia stratiotes, Eichhornia crassipes and Salvinia auriculata) and R2 (Paspalidium geminatum and S. auriculata) reduced their biomass post-WLF and were correlated with temperature, total phosphorous and nitrate. The reduced biomass of P. stratiotes, E. crassipes and S. auriculata in post-WLF widened resource availability, allowing coexistence of species. Therefore, we suggest that the change of limnological conditions in post-WLF in artificial lakes acts only as a moderator factor of the interspecific interaction (especially coexistence), without direct relation between these conditions and species biomass.

Simulated bioavailability of phosphorus from aquatic macrophytes and phytoplankton by aqueous suspension and incubation with alkaline phosphatase

Bioavailability of phosphorus (P) in biomass of aquatic macrophytes and phytoplankton and its possible relationship with eutrophication were explored by evaluation of forms and quantities of P in aqueous extracts of dried macrophytes. Specifically, effects of hydrolysis of organically-bound P by the enzyme alkaline phosphatase were studied by use of solution 31P-nuclear magnetic resonance (NMR) spectroscopy. Laboratory suspensions and incubations with enzymes were used to simulate natural releases of P from plant debris. Three aquatic macrophytes and three phytoplankters were collected from Tai Lake, China, for use in this simulation study. The trend of hydrolysis of organic P (Po) by alkaline phosphatase was similar for aquatic macrophytes and phytoplankton. Most monoester P (15.3% of total dissolved P) and pyrophosphate (1.8%) and polyphosphate (0.4%) and DNA (3.2%) were transformed into orthophosphate (14.3%). The major forms of monoester P were glycerophosphate (8.8%), nucleotide (2.5%), phytate (0.4%) and other monoesters P (3.6%). Proportions of Po including condensed P hydrolyzed in phytoplankton and aquatic macrophytes were different, with the percentage of 22.6% and 6.0%, respectively. Proportion of Po hydrolyzed in debris from phytoplankton was approximately four times greater than that of Po from aquatic macrophytes, and could be approximately twenty-five times greater than that of Po in sediments. Thus, release and hydrolysis of Po, derived from phytoplankton debris would be an important and fast way to provide bioavailable P to support cyanobacterial blooming in eutrophic lakes.

Richness and distribution of aquatic macrophytes in a subtropical reservoir in São Paulo, Brazil

Abstract Aims: to evaluate the richness, biomass and distribution of aquatic macrophytes in a subtropical reservoir in the dry and rainy seasons. Methods this study was carried out in the Itupararanga Reservoir, an important water source in São Paulo State, undergoing a continuous process of eutrophication. Samples of macrophytes were collected at 12 sampling sites in the summer and at 9 sampling sites in the winter in the Itupararanga Reservoir using the quadrat method (0.25 m2). In the laboratory, the plants were washed to remove the coarse material and then were dried (60 °C) for biomass determination (gDW. m-2). All the species in the sampling sites in both periods were identified using the specific literature. In each sampling site, the water temperature, pH, electrical conductivity and dissolved oxygen were measured using a probe. The temporal and spatial differences were analyzed using t-test and a Cluster Analysis was performed. Results The checklist showed sixteen species, 75% of them were emergent. From the 16 species, 15 were present in the summer and 10 in the winter. Eichhornia crassipes, Polygonum sp., and Urochloa sp. were the frequent taxa and had the highest biomass in both periods. The winter showed the highest biomass mainly due to the growth of free-floating species. The headwaters of the reservoir, the most eutrophic region, showed that the highest macrophyte richness and the sampling sites of this area were clustered in both the summer and winter. Conclusions There was no significant spatial variation among the measured variables. E. crassipes, Salvinia sp. and Urochloa sp. showed a significant variation of biomass between two periods. Urochloa sp. is a nuisance species occurring in up to 60% of the sampling sites having implications for the whole catchment. Continuous macrophyte monitoring is important due to the increasing trophic status of this ecosystem.

Seasonal Variation on Physiochemical Parameters and Macrophytes Production of Rupa Lake, Kaski, Nepal

The Rupa lake is the third largest and heavily tampered lake of Pokhara Valley. Physiochemical parameters like, water temperature, pH, dissolved oxygen (DO), total nitrogen (TN) and PO4-P and biomass of aquatic macrophytes were analyzed during pre and post-monsoon. Biomass ranged from 27.25g/m2–389.25g/m2 throughout the experimental period and the highest biomass was observed during post-monsoon period. Regarding the growth form, the highest biomass was represented by emergents (251.16 ± 95.16g/m2) and lowest biomass by submerged species (48.39 ± 7.27g/m2). The lake can be categorized as eutrophic.J. Nat. Hist. Mus. Vol. 26, 2012: 80-87

Planktonic or non-planktonic food in young-of-the-year European perch Perca fluviatilis in ponds.

Higher biomass especially of some aquatic macrophyte species offered a higher density of phytophilous zoobenthos, but did not increase the proportion of non-planktonic to planktonic prey in young-of-the-year perch Perca fluviatilis. Both abundance and biomass of non-planktonic prey dominated over planktonic prey in the pond with lower biomass of aquatic macrophytes and lower food. Survival of P. fluviatilis was lower (20%) in the pond with lower food than in the other pond (34%), however, specific growth rate (1.3% day(-1) ) and final Fulton's condition factor of P. fluviatilis were similar in both ponds.

Can organic rice crops help conserve aquatic plants in southern Brazil wetlands?

AbstractQuestionsAre organic rice crops better than convention crops for aquatic plant conservation? We tested three hypotheses: (1) richness, diversity and biomass of aquatic macrophytes are higher in organic rice fields than in conventional ones; (2) aquatic macrophyte species composition in organic rice fields is more similar to that of natural wetlands than to conventional rice fields; and (3) aquatic macrophyte richness, diversity, biomass and species composition in natural wetlands will differ from those of organic and conventional rice fields.LocationCoastal plain of southern Brazil.MethodsWe sampled macrophytes at four conventional crops, four organic crops and four natural intermittent wetlands. We sampled at six different times at each site throughout the rice cultivation cycle.ResultsA total of 55 species was recorded in natural wetlands and 36 species in rice fields, with 23 found in conventional crops and 27 found in organic crops. The richness, biomass and species composition of macrophytes was similar in the two rice production systems and lower than that of natural wetlands over the cultivation cycle studied. Species composition of natural wetlands differed from that of rice crops mainly through the presence of hydrophytes and rushes.ConclusionsSome macrophyte species used rice crops as a complementary habitat, but diversity was lower and composition was different from that of natural wetlands. Both conventional and organic systems negatively impacted macrophyte biodiversity. However, the similar richness and biomass of plants in organic and conventional crops indicated that natural techniques with less impact could be efficient in reducing undesirable plant diversity in agricultural systems.

Ecological effects of common carp (Cyprinus carpio) in a semi-arid floodplain wetland

Common carp, Cyprinus carpio, is a highly invasive fish species across freshwater systems of south-eastern Australia, and especially in semi-arid floodplain wetlands. However, multi-component, large-scale experimental studies on carp effects on such ecosystems are scarce. This is in spite of demands to prioritise management and control of carp for the rehabilitation of habitats across the Murray–Darling Basin. A 2-year, large-scale field experiment in a terminal wetland of the lower River Murray (South Australia) evaluated the effects of free-ranging carp on water transparency, aquatic macrophytes (biomass and cover), zooplankton density, benthic invertebrates (density, richness and diversity) as well as native fish. Within 1 year since artificial inundation, transparency sharply decreased and this was accompanied by a decrease in aquatic macrophyte biomass and cover, a fluctuation in zooplankton density, and a decrease in benthic invertebrate richness and diversity. Also, the decreases in transparency and benthic invertebrate richness were significantly related to carp biomass, which averaged 68.0 kg ha–1 and induced a shift from clear- to turbid-water state. Following a flood event, increased connectivity caused carp to further access the newly inundated areas.

Aquatic Macrophytes Within a Mesohaline Bay, Sanctuary for Manatees (Trichehus manatus), on the Caribbean Coast of Mexico

Bahia de Chetumal, on the Caribbean coast of the Yucatan Peninsula, is a large mesohaline bay that receives significant runoff of fresh water and supports salt-tolerant macrophytes and seagrasses. This bay is important for the endangered Antillean manatees (Trichechus manatus) in Mexico, and the maintenance of submerged populations of macrophytes is a priority in the conservation plans for manatees because these plants play an important role in the habitat of the manatee. We surveyed the cover and biomass of aquatic macrophytes in the northern section of Bahía de Chetumal from November 1998–April 2000 and found them restricted to a small proportion of the area with Halodule wrightii and Ruppia maritima being the most frequent species. Less common species were Najas marina, Thalassia testudinum, and the algae Batophora oerstedii and Chara chara. Cover (<50%), biomass (38.6–83.0 g of dry weight m−2 and 22.4–32.4 g dry weight m−2 in denser stands of H. wrightii and R. maritima, respectively), and leaf length (maximum length near 4 cm) were lower than that reported for nearby coastal areas. Above-ground:below-ground biomass ratio was <1 in H. wrightii and R. maritima. The community of submerged aquatic macrophytes of the northern Bahía de Chetumal differs from other such communities in the region, and this might be caused by turbidity, low salinity, and herbivory by manatees. Given the low cover and density of submerged aquatic macrophytes, they should be conserved and monitored continuously to aid in the long-term conservation of manatees.La bahía de Chetumal, en la costa caribe de la península de Yucatán, es una extensa bahía mesohalina que recibe escurrimientos significativos de agua dulce y que alberga a macrofitas tolerantes a la salinidad y a pastos marinos. Esta bahía es un área importante para el manatí antillano (Trichechus manatus) en México, una especie en peligro de extinción. El mantenimiento de las poblaciones de macrofitas sumergidas es prioritario en los planes de conservación del manatí porque estas plantas juegan un papel importante en su hábitat. Muestreamos la cobertura y biomasa de macrofitas acuáticas en la sección norte de la bahía de Chetumal desde noviembre de 1998 hasta abril de 2000. Encontramos que éstas fueron restringidas a una porción reducida del área y que Halodule wrightii y Ruppia maritima fueron las dos especies más frecuentes. Las especies menos comunes fueron Najas marina, Thalassia testudinum y las algas Batophora oerstedii y Chara chara. La cobertura (<50%), biomasa (38.6–83.0 g de peso seco m−2 y 22.4–32.4 g de peso seco m−2 en las parcelas más densas de H. wrightii y R. marítima, respectivamente), y el largo de la hoja (cerca de 4 cm de longitud máxima) fueron menores que los reportados para zonas costeras cercanas. La proporción de biomasa arriba:debajo la tierra fue <1 en H. wrightii and R. maritima. La comunidad de macrofitas acuáticas sumergidas en el norte de la bahía de Chetumal es diferente de otras comunidades parecidas de la región, y eso puede deberse a la turbidez, baja salinidad y la herbivoría por manatíes. Dados la baja cobertura y densidad de estas macrofitas acuáticas sumergidas, estas se deben de conservar y monitorear constantemente para ayudar en la conservación a largo plazo de los manatíes.

Seasonal variation in Importance Value Index (IVI), Diversity Indices and Biomass of aquatic macrophytes at Biratnagar and adjoining areas, eastern Nepal

Aquatic macrophytes of three freshwater bodies of Biratnagar and adjoining areas in eastern Nepal namely, Betana-a natural oxbow pond, Bhattapokhari-an aged derelict depression, and Singhia river were analysed for their importance value index (IVI), diversity indices and biomass seasonally from January 2008 to December 2009. Singhia river had high species richness-d (2.08-3.84) and Shannon Wienner index-H' (2.16-2.68). Betana pond and Bhattapokhari had low diversity indices; however, nutrient rich Bhattapokhari had highest primary productivity (2675.5 g/m2/yr) in comparison to Betana pond (303.7 g/m2/yr) and Singhia river (479.09 g/m2/yr). Seasonally vittates dominated Betana pond had IVI range between 6.3 and 258.8 and biomass range between 168.1±7.3 and 265.8±38.7 g/m2); pleustophytes dominated Bhattapokhari had IVI range between 41.6 and 192.8 and biomass range between 925.5±353.2 and 2020.02±213.1 g/m2), and hyperhydate dominated Singhia river had IVI ranged between 2.5 and 160.9 and biomass ranged between 120.7±55.8 and 283.5±28.3 g/m2.DOI: http://dx.doi.org/10.3126/njbs.v1i0.7462 Nepalese Journal of Biosciences 1: 1-7 (2011)

Submerged macrophyte biomass distribution in the shallow saline lake Fuente de Piedra (Spain) as function of environmental variables

Aquatic macrophyte biomass, diaspore bank distribution and their relationship to spatial variability of depth, nutrients (nitrite, nitrate, ammonium and soluble reactive phosphorus) as well as sediment granulometry in an athalassohaline lake have been studied during one wet hydrological year. The results indicate that species growing in the lake show different spatial distribution patterns throughout the lake. Indirect gradient analysis (canonical analysis) results showed a first axis defined as a function of Ulva flexuosa Wulfen biomass which is, in turn, positively correlated with interstitial ammonium and Soluble Reactive Phosphorus (SRP). The second axis was mainly established due to Lamprothamnium papulosum (Wallr.) J. Groves biomass which correlated positively to depth and negatively to interstitial ammonium and SRP. These results revealed a NESW eutrophic gradient allowing the U. Flexuosa biomass proliferation. This phenomenon could increase the shadow effect over the rest of the macrophytes inhabiting this shallow lake. Moreover, the eutrophic harmful effect on the macrophyte physiology and over the diaspore bank could have important consequences in the survival of such important populations. The results reported in this study show the need for studies as the base to select sampling points for monitoring this wetland.

Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.