Concentrations of Trace Metals in Dominant Aquatic Plants of the Lake Provala (Vojvodina, Yugoslavia)

The trace metal (Fe, Mn, Zn, Cu, Ni, Pb, Cd, Sr, and Cr) contents in the most common submerged and floating aquatic plants Ceratophyllum demersum L., Myriophyllum spicatum L., and Nymphoides flava Hill. of Provala Lake were evaluated. Considerable higher contents of iron, manganese, zinc, nickel, lead and strontium were found in submerged species than in the floating ones. The presence of cadmium and lead in plant tissues points to a certain degree of lake water pollution.     

Nymphoides peltata (Gmel.) Kuntze, Myriophyllum spicatum L. and Ceratophyllum demersum L. biomass dynamics in Lake Provala (the Vojvodina Province, Serbia)

Sixty-five plant species have been found in Lake Provala (the Vojvodina Province, Serbia) and its riparian zone. Among them, three hydrophytes were dominant: Nymphoides peltata, Myriophyllum spicatum and Ceratophyllum demersum. As interactions between different ecological factors, especially light, temperature and nutrient level, are of prime importance for productivity of macrophytes, we analyzed the main physical and chemical indicators of water quality in the studied location. In the vegetation period of the year 2000, the dominant hydrophytes were analyzed for biomass production dynamics in the studied aquatic ecosystem, including fresh weight (FW), dry weight (DW) and ash free dry weight (AFDW). The studied plant species achieved maximum biomass production in June, with statistical differences among the species at the significance level of α = 0.05.     

Functioning and dynamics of wetland vegetation of Lake Victoria: an overview

The aquatic macrophytic vegetation constituting the wetlands situated along the coast of Lake Victoria provides valuable services to both local and regional communities as well as an important ecological function through the transition between terrestrial and aquatic ecosystems. The wetland vegetation is typically rooted in the substrate on the landward side of the lake, but forms a floating mat towards the middle of the wetland and at the wetland/lake interface. Cyperus papyrus and Miscanthidium violaceum vegetation typically dominate the permanently inundated wetland areas along most of the shores of Lake Victoria. Due to the prevailing climatic and hydrological catchment conditions, these macrophytic plants (papyrus in particular) tend to exhibit high net productivity and nutrient uptake which strongly influences both wetland status and lake water quality. In addition, these wetlands provide important economic livelihoods for the local populations. The integrity and physical structure of these wetlands strongly influences their associated mass transport mechanisms (water, nutrients and carbon) and ecosystem processes. Wetland degradation in Africa is an increasing problem, as these ecosystems are relied upon to attenuate industrial, urban and agricultural pollution and supply numerous services and resources. In an integrated project focused on the wetlands of Lake Victoria, the ecological and economic aspects of littoral wetlands were examined and new instruments developed for their sustainable management.     

Echosounding observations of coverage,height, PVI,and biomass of submerged macrophytes in the southern basin of Lake Biwa,Japan

We have developed a procedure to process echosounding data to map the distribution of submerged aquatic macrophytes in the southern basin of Lake Biwa, a water body that has a surface area of 52 km² and a mean depth of 4 m. Echosounding observations were made along 27 transect lines spaced at 500-m intervals on August 4 and September 2 and 30, 2003. Quantitative vegetation data including percent coverage, mean vegetation height, and percent vegetation infestation were directly determined using image data from the echosounder recorded digitally on videotape. Based on the image data from an echosounder, a regression model was developed for estimating biomass of submerged macrophytes. The regression model using the total echo strength as the explanatory variable could reliably estimate macrophyte biomass up to 300 g m⁻². Distribution maps of macrophyte height and biomass suggest that the recent summer decline of submerged macrophytes started earlier in shallow areas (<3 m of depth) than deep areas (>4 m) in the southern basin of Lake Biwa.     

Primary production of epipsammic algal communities in Lake Balaton (Hungary)

Benthic algal communities can play an important role in matter and energy flux of shallow lakes. Their contribution to total primary production of lakes has been largely unexplored. The aim of this study was to estimate the primary production of the epipsammic algal communities at different water depths in Lake Balaton (Hungary) with photosynthetic measurements performed in laboratory. The photosynthesis of the benthic algae of different origin was studied at nine different irradiance levels, in three replicates. The maximum photosynthetic rate (P _max) was always higher in samples from the shallow parts than those from the deeper regions of the lake. Along the west–east longitudinal axis of the lake P _max decreased in the southern part and increased in the middle of the lake as a consequence of differences in the chlorophyll-a concentrations. Knowing P _max, I _k, global radiation and extinction coefficient, the primary production (mg C m⁻² day⁻¹) of the epipsammic algal community was calculated at different water depths. In the shallow regions at 0.5 and 1 m water depth 75–95% and 60–85% of the production was attributable to the epipsammon. The percentage contribution of epipsammon was at 2 m water depth 20–65%. In the deeper pelagic region (>3 m) more than 85% of the primary production originated from the phytoplankton.     

Seasonal and interannual variability in the taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake,Oregon

Taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon, were examined during time periods between 1984 and 2000. The objectives of the study were (1) to investigate spatial and temporal patterns in species composition, chlorophyll concentration, and primary productivity relative to seasonal patterns of water circulation; (2) to explore relationships between water column chemistry and the taxonomic composition of the phytoplankton; and (3) to determine effects of primary and secondary consumers on the phytoplankton assemblage. An analysis of 690 samples obtained on 50 sampling dates from 14 depths in the water column found a total of 163 phytoplankton taxa, 134 of which were identified to genus and 101 were identified to the species or variety level of classification. Dominant species by density or biovolume included Nitzschia gracilis, Stephanodiscus hantzschii, Ankistrodesmus spiralis, Mougeotia parvula, Dinobryon sertularia, Tribonema affine, Aphanocapsa delicatissima, Synechocystis sp., Gymnodinium inversum, and Peridinium inconspicuum. When the lake was thermally stratified in late summer, some of these species exhibited a stratified vertical distribution in the water column. A cluster analysis of these data also revealed a vertical stratification of the flora from the middle of the summer through the early fall. Multivariate test statistics indicated that there was a significant relationship between the species composition of the phytoplankton and a corresponding set of chemical variables measured for samples from the water column. In this case, concentrations of total phosphorus, ammonia, total Kjeldahl nitrogen, and alkalinity were associated with interannual changes in the flora; whereas pH and concentrations of dissolved oxygen, orthophosphate, nitrate, and silicon were more closely related to spatial variation and thermal stratification. The maximum chlorophyll concentration when the lake was thermally stratified in August and September was usually between depths of 100 m and 120 m. In comparison, the depth of maximum primary production ranged from 60 m to 80 m at this time of year. Regression analysis detected a weak negative relationship between chlorophyll concentration and Secchi disk depth, a measure of lake transparency. However, interannual changes in chlorophyll concentration and the species composition of the phytoplankton could not be explained by the removal of the septic field near Rim Village or by patterns of upwelling from the deep lake. An alternative trophic hypothesis proposes that the productivity of Crater Lake is controlled primarily by long-term patterns of climatic change that regulate the supply of allochthonous nutrients.     

Aquatic macrophyte composition in relation to environmental factors of irrigation ponds around Lake Shinji,Shimane, Japan

A comparative study of aquatic vegetation of 149 irrigation ponds in the surrounding area of Lake Shinji, Shimane Prefecture, Japan, was done to document the present status of aquatic flora and water chemistry. In addition, influence of 17 environmental factors on the between-pond variation in aquatic macrophyte composition was assessed by using detrended correspondence analysis (DCA). A total of 38 taxa were recorded, and the most frequent taxon was Trapa spp. (>50%). Number of taxa per pond ranged from 1 to 14 and mean number was 4.1. Floristic composition was primarily related to variation of the factors such as conductivity, Mg, Ca, Na, alkalinity, altitude, pH and depth. In contrast, no significant correlations were found with total P, PO₄-P, transparency, COD, ignition loss of bottom soil, Mn and Fe. Of the 33 significant species associations between 19 species with more than 5% frequency occurrence, 28 were positive and the remaining 5 were negative. All of these negative associations involved Trapa spp., and not only water chemistry but some other factors like competition and bottom soil preference were assumed to influence species associations.Abbreviations (DCA) Detrended Correspondence Analysis     

Primary production of Lake Peipsi-Pihkva

Primary production (PP) in Lake Peipsi-Pihkva, the tripartite border waterbody between Estonia and Russia, was first measured in 1965–1966. Since 1970 there exists a continuous timeseries of monthly PP measurements from May to October. Detailed investigations of the seasonal and daily dynamics as well as the vertical distribution of PP were carried out in 1985–1987. The long-term average values of integral PP (PP_int) in Lakes Peipsi and Pihkva were equal (0.8 g C m^–2 d^–1), although the values per cubic metre (PP_max) differed more than twofold and characterized L. Pihkva as a eutrophic lake and L. Peipsi as a transition type between meso- and eutrophic lakes. The years from 1973 to 1980, 1987 and 1991 were of low productivity, while in 1971, 1983, 1988 and 1990 PP peaks occurred in both lakes. In the seasonal pattern PP_int had peaks in May and July. In June, after the spring bloom, PP as well as the chlorophyll a (Chl) and ATP content were low. The high Chl peak in autumn was probably built up by the degradation products of chlorophyll, as neither PP nor ATP increased. Seasonal changes in integral PP in L. Peipsi could be well described (R ² = 0.91) by an empirical model relating PP_int to PP_max, Secchi depth (S) and total solar radiation (Q). In mixed conditions prevailing in both lakes, PP was inhibited in the surface layer and its maximum was located at a depth of 0.25...0.5 S. The threshold total solar radiation level for the onset of inhibition was between 1200 and 2000 kJ m^–2 h^–1 in May and July, and decreased to < 500 kJ m^–2 h^–1 in October. As a rule, inhibition started in the morning at a higher irradiance than necessary for keeping it up during evening hours. When compared with PP_max, photosynthesis in the surface layer at noon was suppressed by 56% in May, by 45% in July and by 40% in October.     

Decomposition of dominant submerged macrophytes: implications for nutrient release in Myall Lake, NSW, Australia

Breakdown and nutrient dynamics of submerged macrophytes were studied in Myall Lake, Australia. Mass loss of Myriophyllum sulsagineum was the lowest (64.90%) among the studied macrophytes during the 322 days followed by charophytes (60.79%), whereas Najas marina and Vallisneria gigantea lost 91.15 and 86.02% of their respective initial mass during that time. The overall exponential breakdown rates of Najas marina and Vallisneria gigantea were similar, with k-values of 0.24 and 0.23 day⁻¹, respectively. These rates were significantly higher than the break down rates of charophytes (0.007 day⁻¹) and M. sulsagineum (0.008 day⁻¹). During growth phase, water column depicted lower nutrient concentrations while during decay period, significant increase in water column nutrients resulted. Release of nutrients from decomposing macrophytes and incorporation of these nutrients into sedimentary phase as well as uptake of nutrients by the growing macrophytes, can present a considerable cycling pathway of nutrients in Myall lake system. The results of this study suggest that different submerged macrophytes may differ appreciably in quality and may exhibit different decomposition rates, patterns and nutrient dynamics in aquatic ecosystems in general, and Myall lakes in particular.     

Long-term production dynamics of aquatic vegetation in the Arakhlei Lake (Eastern Transbaikalia)

Long-term data on aquatic vegetation production in the mesotrophic Arakhlei Lake was comparatively analyzed. The results demonstrated that the production dynamics of aquatic vegetation communities depend on the water-level conditions of the lake. The data on the succession of dominant vegetation communities are given: Chara sp. and Ceratophyllum demersum → C. demersum and Lemna trisulca. At the same time, the increased proportion of C. demersum and L. trisulca pointed to an increased anthropogenic stress on the lake.     

Myriophyllum quitense Kunth (Haloragaceae) in Bolivia: A terrestrial growth-form with bisexual flowers

A terrestrial growth-form of Myriophyllum quitense growing in a lake bed in the interandean valley region of Bolivia represents the first report of a terrestrial growth-form for this species. While typically M. quitense possesses leaves and flowers in whorls of (3–) 4, this population is noteworthy for possessing 2–5% of individuals with both leaves and flowers in whorls of five, and for the presence of bisexual flowers. Observations regarding the distribution, habitat preferences and intraspecific variation of M. quitense in Bolivia are also given.     

Submerged vascular plants and water chemistry in the coastal marsh Albufera de Mallorca (Balearic Islands)

Ten species of aquatic macrophytes have been analyzed for seven environmental variables by means of a significance test. A synthetic view has been obtained through a cluster analysis for species and a principal component analysis for 17 variables which form the multidimensional space where we project the species habitats. Myriophyllum spicatum L., Najas marina L., Potamogeton crispus L., Potamogeton pectinatus L. and Zannichellia pedunculata Reichenb. are widely distributed in the Albufera. Ceratophyllum submersum L. and Ruppia maritima L. var. brevirostris Ag. are considered stenoic. The tolerance of Ceratophyllum submersum to salts is significantly low and that of Ruppia cirrhosa (Petagna) Grande and Ruppia maritima var. brevirostris significantly high. Ceratophyllum submersum has a significantly negative distribution with regard to chlorophyll a and phosphate concentrations. Ceratophyllum demersum L. and C. submersum primarily occur in nitrate-rich waters whereas Ruppia cirrhosa primarily occurs in low nitrate waters.     

Long-term Changes in Littoral Habitats and Communities in Lake Mikolajskie (Poland)

Lake Mikolajskie is seriously affected by Mikolajki town and tourism. The amount of sewage entering the littoral zone is increasing as also is the area of the artificially transformed shore. During the past 20 years the area occupied by macrophytes has decreased markedly. The decline of Phragmites australis, changes in species composition, and reductions in biomass and in the depth-range colonized by submerged plants have been observed. Simultaneously the biomass of algae has increased markedly. Animals characteristic of polluted sites have become more abundant. Changes in animal numbers result to a great extent from changes in the availability of natural substrates. Zonation of the occurrence of organisms has been observed for years on sites directly affected by sewage—quantitatively and qualitatively poor communities are found at sewage discharge points and the richer ones at a greater distance in the zone fertilized by diluted sewage.     

Decomposition of macrophyte litter in a subtropical constructed wetland in south Florida (USA)

The South Florida Water Management District has constructed large treatment wetlands (stormwater treatment areas (STAs)) to reduce total phosphorus concentrations in agricultural runoff before this water enters the Everglades. An important component of nutrient removal and storage in these systems is incorporation of nutrients into aquatic macrophytes and burial of this biomass in the sediments. However, decomposition of plant biomass before burial returns nutrients to the water column and may reduce STA treatment efficiency. As part of research on biogeochemical control of STA performance, we conducted a summer (July–September) and a long-term (12-month) experiment (February–February) that measured decomposition rates and release of chemical constituents from dominant aquatic macrophytes in a constructed wetland located in south Florida. The rank order of mean decomposition rates was Najas/Ceratophyllum (0.0568 d⁻¹) > Pistia (0.0508 d⁻¹) > Eichhornia (0.0191 d⁻¹) > submerged Typha (0.0059 d⁻¹) > aerial Typha (0.0008 d⁻¹). Summer decomposition rates were generally higher than rates from the long-term experiment, which suggested a temperature effect. Decomposition rates were negatively correlated with litter C:N and C:P molar ratios and cellulose and lignin content and positively correlated with N and P content. There was no significant difference in decomposition rates among sampling stations despite the fact that there was a decreasing gradient in water column inorganic phosphorus and nitrogen concentrations at these sites. Relatively little of the initial P mass remained in the litter of all species, except Typha, by the end of both experiments. First-order decomposition models derived using nonlinear regression generally had explanatory power, i.e. accounted for variance, comparable to more complex decreasing-coefficient models. Decomposition rates for the species examined in this study were within the range of published values when comparisons were made either by species or by plant group.     

Model-based predictions of anaerobic digestion of agricultural substrates for biogas production

A modified Anaerobic Digestion Model No. 1 (ADM1), calibrated on a laboratory digester with a feeding mix of 30% weight of cow manure and 70% weight of corn silage, was implemented, showing its performances of simulation as a decision-making and planning-supporting tool for the anaerobic digestion of agricultural substrates. The virtual fermenter obtained was used to conduct simulations with different feeding compositions and loading rates of cow manure, corn silage, grass silage and rape oil. All simulations were started at the same initial state which was represented by a steady state with an organic loading rate of 2.5 kg ODM/(). The effects of the different feeding combinations on biogas composition and biogas yield were predicted reasonably, and partly verified with the available literature data. Results demonstrated that the simulations could be helpful for taking decisions on agricultural biogas plant operation or experimental set-ups, if used advisedly.     

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.     

Aquatic macrophytes of Lake Bled: changes in species composition,distribution and production

The macrophytes of Lake Bled were studied from 1987 to 1990. Three main factors influenced the decline of the aquatic vegetation in the lake during that period: (1) reduced light in the littoral zone due to an increase in phytoplankton (2) grazing by herbivorous fish and waterfowl, and (3) direct human impact.     

Nitrogen and phosphorus dynamics and retention in ecotones of Lake Titicaca,Bolivia/Peru

We are studying present conditions and consequences of material movement from land to water in the Lake Titicaca basin, and how fluxes are affected by human activities. The principal objective of this research is to describe and explain the variability in the Andean Altiplano of (a) water, nutrient and sediment fluxes from land and (b) composition, nutrient limitation and other important features of nearshore lake communities, and compare the effects of different agricultural practices (especially traditional and modern) on these factors. We are focusing on a comparison of the impacts of two forms of agriculture in this region: ancient raised fields currently under rehabilitation, and flat pastures and fields, which are more common. Results of the first year of study indicate there is substantial variability in nitrogen and phosphorus dynamics in relation to ecotone complexity (simple vs. intermediate vs. complex). Raised field sites have the beneficial effect of reducing high available nutrient concentrations (nitrate and soluble reactive phosphorus) and sediment load (measured as turbidity) as the water passes through them enroute to the lake. Aquatic vegetation (algae and macrophytes) reflect well ambient total nitrogen and phosphorus concentrations. Experimental nutrient limitation bioassays indicate that nitrogen is the most important limiting nutrient, though there is important spatial variability within the landscape, and phosphorus as well as nitrogen can be limiting.     

Aboveground decomposition dynamics in riparian depression and slope wetlands of central Pennsylvania

We examined two types of groundwater-fed wetlands (riparian depressions and slopes) classified using the hydrogeomorphic (HGM) system. These wetland types had previously been shown to differ hydrologically. Our first objective was to determine if HGM was a useful structuring variable when examining aboveground decomposition dynamics (rate of mass loss and rate of nitrogen loss). Our second objective was to determine what soil variables were related to any differences in aboveground decomposition dynamics we might find regardless of HGM subclass. We used the litterbag field bioassay technique, and employed a standard litter type (Phalaris arundinacea) across all wetlands. Our results indicated that HGM would not readily serve as an adequate structuring variable for aboveground decomposition in riparian depressions and slope wetlands of central Pennsylvania. Discriminant analysis and classification and regression tree (CART) modeling found soil cation exchange capacity, soil pH, soil organic matter, and soil % nitrogen to be potentially important soil variables related to mass loss, and soil % nitrogen and soil pH to be potentially important variables related to nitrogen loss rate.