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Vegetative reproduction promotes human-mediated dispersal of aquatic invasive plants as fragments "hitchhike" between water bodies on boats and trailers. However, desiccation of plant fragments may also reduce fitness, decreasing the likelihood of fragment survival as transport distances increase. Current inter-lake invasive species spread models do not directly consider fitness loss due to desiccation and mechanical damage of the transport pathway. Here, we estimate survival as a function of desiccation exposure for Eurasian watermilfoil (Myriophyllum spicatum). Following desiccation treatments, we monitored survival and root formation of individual fragments and assessed the differences between treatments. Highest survival rates occurred for short (< one hour) air exposures and coiled fragments with root production for the coiled treatment occurring in less than two weeks, irrespective of fragment length. In contrast, fragments that experienced desiccation for more than 24 hours had little risk of surviving. Our results emphasize the threat posed by same-day overland movements of boats from invaded to uninvaded waterways, and provide managers with a surveillance radius to inform delimitation surveys arising from the discovery of a new invasion. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

The distribution of egg strands of perch Perca fluviatilis and factors affecting this distribution, in terms of spawning sites and spawning depths used, was studied in spring 2010 in Chabařovice Lake, Czech Republic, using areas with an artificial spawning substrate (A.S.S.) and control areas outside the A.S.S. Perch significantly preferred a calm shore instead of a windward shore for spawning. The depths at which perch egg strands were found increased significantly during the spawning period in both A.S.S. areas and in areas outside the A.S.S. (on average from 4.9 m at the beginning to 12.3 m at the end of the spawning period). With increasing depth of deposition the size of the egg strands decreased significantly. The mean depth of egg strands on individual dates corresponded to the position of 10-12°C water layers. From the third week onward, however, egg strands were deposited in much deeper and colder water. A strong relationship was found between the depth at which egg strands were deposited and the duration of the daylight period, indicating that, at the end of the spawning season, perch do not react to the actual temperature of the water column but that they follow their inner clock, assuming that "normally" the shallower depth layers are too warm for successful embryo development. Factors influencing the depth distribution of egg strands were identified as waves, temperature and duration of the daylight period. Factors influencing the selection of spawning sites were identified as wind inducing current, internal seiches and temperature instability of the water column. The first perch larvae were present in the open water of Chabařovice Lake before mid-May, and the latest larvae not earlier than the beginning of July, since warming of the water in deeper layers was very slow. It appears that with prolonged spawning and hatching periods and with spawning occurring at various depths and temperatures, perch have evolved a powerful mechanism to protect their population against the vagaries of the weather and temporary bad biological conditions in the lake. [ABSTRACT FROM AUTHOR]

Abstract: Proliferation of exotic submerged aquatic vegetation (SAV) has the potential to alter trophic interactions among native fauna. The invasion of Myriophyllum spicatum (Eurasian watermilfoil) into brackish and freshwater wetlands on the Gulf Coast of the United States has decreased the abundance of native plant species such as Ruppia maritima (widgeongrass). Macroinvertebrates use SAV to meet nutritional requirements and seek refuge from predators. Shifts in SAV dominance can alter patterns of SAV use by associated fauna, but the dynamics of these alterations following Myriophyllum displacement of Ruppia are not well understood. In our study, we examined the trophic implications of shifts between native (Ruppia) and exotic (Myriophyllum) SAV in a brackish wetland in Port Arthur, Texas, USA. This study addressed the following questions: 1) Do aquatic invertebrates directly consume Myriophyllum, and 2) do predator–prey interactions differ in native and exotic SAV canopies? We collected Ruppia, Myriophyllum, Palaemonetes spp. (grass shrimp), and juvenile Callinectes sapidus (blue crabs) from the field and ran a series of three mesocosm experiments in the laboratory. In a “no-choice” grazing experiment, Palaemonetes consumed 13% of the Ruppia biomass but had no impact on Myriophyllum biomass. In a second study, when given a choice of plant canopies, Palaemonetes selected Ruppia over Myriophyllum 60% of the time when Callinectes was absent, but selected Myriophyllum more frequently in the presence of Callinectes. The selection of Myriophyllum was likely due to its refuge value; a third mesocosm experiment resulted in 60% Palaemonetes mortality due to Callinectes predation in Ruppia canopies but only 20% mortality in Myriophyllum canopies. Myriophyllum has a more structurally complex canopy that probably provides better protection from predation. Our studies suggest that native and exotic plants provide substantially different values as food sources and as refuges from predators for lower trophic levels. [Copyright &y& Elsevier]

Abstract: The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20μgSeL−1 and 10mgSeL−1). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10mgSeL−1, averaged 212±12μgSeg−1 DM in M. spicatum (grown from 8–13d), and 492±85μgSeg−1 DM in C. demersum (grown for 31d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP–MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels. [Copyright &y& Elsevier]

Temperature, acidity, light conditions, total dissolved salts, conductivity, dissolved oxygen, submerged macrophytes and shade and sun path directions were measured at 23 sites along the River Nile banks with Acacia nilotica growing at water's edge around the First Cataract Conservation Islands. Ceratophyllum demersum and Potamogeton crispus were common in the shaded and unshaded zones, Myriophyllum spicatum and Vallisneria spiralis were found only in the unshaded zone and Azolla filiculoides only in the shaded zone. Banks of the sites surveyed were oriented to five directions (NW, SE, NE, SW, N). There is a significant difference in both the type and density of submerged plants growing under the shade of riparian trees (Acacia nilotica) as compared to unshaded areas. Water column irradiance is the most influential variable dictating the distribution of submerged plants. The area of the shade provided by riparian trees was affected by environmental and/or plant variables. Environmental variables comprised the daily course of the exposition to sun; and plant variables included the area of the tree crown, the height of the tree and geographical position of the tree in relation to sun exposition. Trees on the west bank of the islands at the SW-NE direction have the highest shading effect. The management of tree vegetation might control incoming solar radiation affecting submerged macrophytes. [ABSTRACT FROM AUTHOR]

Abiotic heterogeneity of the littoral zone of Lake Balaton influences both horizontal and vertical distribution of macrophytes, but biotic differences could shape the nature of a community. Vertical and temporal (small timescale) biomass distributions of Potamogeton perfoliatus and Myriophyllum spicatum were analysed in relation to their photosynthetic capacities to understand their coexistence, general presence over the northern shore of the lake seasonal shift of dominance within the community.Our results indicated the adaptation of these macrophytes to the rapidly changing and mostly low irradiance of the Lake Balaton originated from its high turbidity: both P. perfoliatus and M. spicatum had high photosynthetic activity (20 to 50 mg O2.g drw−1.h−1), low dark respiration (around 12–14% of maximal photosynthetic capacity) and high shade tolerance (Ic of plants were 29±18 and 26±18 μmol.m−2.s−1, respectively). The majority of photosynthetic parameters had no (or little) seasonal changes. On the other hand, in Lake Balaton P. perfoliatus and M. spicatum differed in vertical distribution of biomass: Myriophyllum concentrated its biomass in the upper, well-lit region of the water more strongly than the Potamogeton.Results suggest that the autogenic shift of dominance from Potamogeton to Myriophyllum in Lake Balaton can't be explained only by seasonal patterns of photophysiological changes, but supported by constitutive differences in plants architecture could led to the described phenomena. [ABSTRACT FROM PUBLISHER]

Abstract: The uptake kinetics of phosphate (Pi) by Myriophyllum spicatum was determined from adsorption and absorption under light and dark conditions. Pi uptake was light dependent and showed saturation following the Michaelis–Menten relation (in light: V =16.91×[Pi](1.335+[Pi]), R 2 =0.90, p <0.001; in the dark: V =5.13×[Pi](0.351+[Pi]), R 2 =0.77, p <0.001). Around 77% of the loss of Pi in the water column was absorbed into the tissue of M. spicatum, and only 23% was adsorbed on the surface of the plant shoots. Our study shows that M. spicatum shoots have a much higher affinity (in light: 3.9μmolg−1 dwh−1 μM−1; in the dark: 3.7μmolg−1 dwh−1 μM−1) and V max (maximum uptake rate, shoot light) for Pi uptake than many other aquatic macrophytes (in light: 0.002–0.23μmolg−1 dwh−1 μM−1; in the dark: 0.002–0.19μmolg−1 dwh−1 μM−1), which may provide a competitive advantage over other macrophytes across a wide range of Pi concentrations. [Copyright &y& Elsevier]

Invasive species are one of the widespread stressors of aquatic ecosystems. Several studies document food web effects of invasive fish, but little information is available on the effects of invasive macrophytes. We studied differences in food chain length as well as trophic position and trophic diversity of fish and odonates in lakes dominated by native plants or invasive Eurasian watermilfoil. Trophic position and food chain length were determined using baseline-adjusted δN isotope signatures. Trophic diversity, or isotope niche width, was estimated from convex hull area analysis. Results show that trophic position of secondary consumers was not affected by the invasive macrophyte, whereas trophic diversity was greater in watermilfoil-dominated lakes. The direction of isotopic niche expansion was different in fish and odonates, suggesting potential decoupling in predator-prey interactions. This study shows that dominant non-native macrophytes may cause significant changes in food web structure of invaded ecosystems. Trophic diversity may be a more sensitive indicator of environmental stress than trophic position and has the potential to be used for assessment of invasive species impacts and restoration success. [ABSTRACT FROM AUTHOR]

As a contribution to the continuing discussion of the ecological differentiation and stable coexistence of species, we investigated the extent to which the two sister species, Macroplea mutica and M. appendiculata, use the host plants Myriophyllum spicatum and Potamogeton sp. Specimens from four populations differing in host plant experience were used for behavioural observations. Both species did not feed on Myriophyllum but on Potamogeton. Beetles kept on Myriophyllum or without plant lost weight, while those on Potamogeton maintained or increased their weight. Only M. appendiculata laid eggs on this plant, as well as on Potamogeton, where M. mutica exclusively oviposited. In choice experiments, all larvae preferred the roots of Potamogeton over Myriophyllum for attachment (also the M. mutica larvae that had been collected from Myriophyllum). The data are discussed in the light of the unusual occasional occurrence of M. mutica on Myriophyllum and the speciation in the genus Macroplea. [ABSTRACT FROM AUTHOR]

The effects of non-native invasive species are costly and environmentally damaging, and resources to slow their spread and reduce their effects are scarce. Models that accurately predict where new invasions will occur could guide the efficient allocation of resources to slow colonization. We assessed the accuracy of a model that predicts the probability of colonization of lakes in Wisconsin by Eurasian watermilfoil (Myriophyllum spicatum ). We based this predictive model on 9 years (1990-1999) of sequence data of milfoil colonization of lakes larger than 25 ha (n = 1803). We used milfoil colonization sequence data from 2000 to 2006 to test whether the model accurately predicted the number of lakes that actually were colonized from among the 200 lakes identified as being most likely to be colonized. We found that a lake's predicted probability of colonization was not correlated with whether a lake actually was colonized. Given the low predictability of colonization of specific lakes, we compared the efficacy of preventing milfoil from leaving occupied sites, which does not require predicting colonization probability, with protecting vacant sites from being colonized, which does require predicting colonization probability. Preventing organisms from leaving colonized sites reduced the likelihood of spread more than protecting vacant sites. Although we focused on the spread of a single species in a particular region, our results show the shortcomings of gravity models in predicting the spread of numerous non-native species to a variety of locations via a wide range of vectors. [ABSTRACT FROM AUTHOR]

Size-related asexual reproduction of submersed macrophytes is still poorly understood. Here, we investigate how size-related auto-fragmentation in Myriophyllum spicatum L. responds to sediment nutrients and plant density. An experiment was carried out with sediments containing two different nutrient levels and with two levels of plant density. The results show that sediment nutrients and plant density brought about a strong dependency of auto-fragment production and the amount of total non-structural carbohydrate (TNC) storage in auto-fragments on individual plant size (total plant biomass). However, these two factors acted differently on size dependency. Sediment nutrients positively affected auto-fragment production and the amount of TNC in auto-fragments of M. spicatum. High concentrations of sediment nutrients significantly increased these two traits in absolute value and the value relative to plant size. Although the auto-fragment biomass and the amount of TNC in auto-fragments did not differ between density treatments when plant size was considered, the absolute values of these two traits were much larger in the low plant density treatment than in the high plant density treatment, which suggested an indirect negative effect of plant density on the auto-fragmentation of M. spicatum. In addition, higher percentages of large auto-fragments (>100 mg) were produced by plants that grew in nutrient poor sediment and low plant density environment than plants in nutrient rich sediment and high plant density environment. These results do not solely highlight a size-dependent effect, but also a size-independent effect of auto-fragment production and the amount of TNC in auto-fragments of M. spicatum. Furthermore, such size-independent effects can be explained by the significant biomass partitioning differences and the similar TNC-concentrations in auto-fragments under different environmental conditions. [ABSTRACT FROM AUTHOR]

Invasive species are one of the major threats to ecosystems. One of these “invaders”, Eurasian watermilfoil, can crowd out important native aquatic plants, decrease habitat and diversity of native species in a lake, and interfere with water-based recreation. This study uses a hedonic property-value method to estimate the effect of Eurasian watermilfoil on lakefront property values at selected Vermont lakes. Results indicate that as the primary component of total aquatic macrophyte growth in a lake Eurasian watermilfoil significantly and substantially affects lakefront property values. As Eurasian watermilfoil infests a lake, adding to the total macrophyte growth, property values can diminish by <1% to 16% for incremental increases in the infestation level. Hence, policies that successfully prevent infestations have significant economic benefits to owners of lakefront properties and local communities. [Copyright &y& Elsevier]

The influence of elevated temperature was studied on the respiratory potential of a microplankton community, two macrophytes species ( Myriophyllum spicatum and Chara aspera), and sediments, all from an oligotrophic lake, in order to estimate their susceptibility to temperature change. Samples collected in winter, spring, summer and autumn were incubated at three different temperatures. The respiratory potential, measured as electron transport system (ETS) activity at a standard temperature of 20 °C was, in average, greater at higher incubation temperatures for 117% in microplankton and for 30% in sediments, indicating that elevated temperature influenced the respiratory capacity of the microbial communities for mineralization of organic matter through respiration. The large increases of respiratory potential in winter microplankton community (for 184% at the highest incubation temperature compared to the temperatures of the multiyear period) and spring microplankton community (190%), and in spring sediment (64%) reveal that those communities are most susceptible to elevated temperatures during the coldest period of a year and at the beginning of lake warming. The respiratory activity of Myriophyllum spicatum was independent of incubation temperature, indicating its wide physiological tolerance. The lower respiratory potential at higher temperatures in Chara aspera optimized the use of energy in plants. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Habitat structure influences organism communities by mediating interactions between individuals and species, affecting abundance and species richness. We examined whether variations in the morphology of soft-bottom plants affect their function as habitat and whether complex structured plants support higher macroinvertebrate abundance and species richness. Three Baltic Sea plant species were studied, together with artificial plants resembling each species. In a field collection, we found higher invertebrate abundance on the morphologically more complex plants Myriophyllum spicatum and Chara baltica than on the structurally simpler plant Potamogeton perfoliatus. In a colonization experiment, we found the highest invertebrate abundance on artificial M. spicatum but found no difference between natural plants. Invertebrate taxon richness displayed no consistent relationship with plant structural complexity. The results imply that plant morphology influences small-scale invertebrate distribution, partly supporting the hypothesis that structurally complex plants harbour higher invertebrate abundance. [ABSTRACT FROM AUTHOR]

The value of Myriophyllum spicatum and Najas marina as indicators for contamination by certain trace elements was studied in two artificial lakes (Velenjsko jezero and Družmirsko jezero, Slovenia). The lakes lie in the vicinity of the Šoštanj Thermal Power Plant and are the result of mining activity. The concentrations of heavy metals (Cd, Cu, Pb, Zn, Cr) and As were determined in sediment, water samples, and shoots of macrophytes. The sediment of Družmirskojezero contained significantly higher concentrations of trace elements Cu, Pb, and Cr than that of Velenjsko jezero. The concentrations of trace elements in shoots of M spicaturn were higher than those in shoots of N. marina in indicating their concentrations in lake sediments. While the concentration of Pb was significantly higher in the tissues of both species from Družmirsko jezero, the difference in Cr sediment loading between the two lakes was indicated only in shoots of M spicatum. The concentrations of Cu in shoots of the two species did not reflect the differences in the concentration of Cu in the lake sediments. [ABSTRACT FROM AUTHOR]

Abstract: Batch experiments were conducted to assess the effects of Cu(II) and Zn(II) on the biosorption of Pb(II) ions by fresh tissues of Myriophyllum spicatum. The biosorption of Pb(II) was examined for single, binary and ternary solutions at different initial concentrations and different pH values. The experimental results showed that the biosorption capacity increased with increasing pH from 2.0 to 6.0. Both Cu(II) and Zn(II) ions were found to have an adverse effect on the biosorption of Pb(II). The biosorption equilibrium data for single-metal solution were fitted to three isotherm models: Langmuir, Freundlich and Sips, and the Sips isotherm model gave the best fit for the experimental data. The maximum biosorption of Pb(II) in Pb–Cu binary system decreased with increasing concentration of copper ions, and the biosorption equilibrium data for the binary metal solution fitted the Langmuir competitive model well. Comparison between biosorption of Pb(II) and Cu(II) by M. spicatum in the binary solution could lead to the conclusion that the biosorbent (M. spicatum) has no preference of Pb(II) over Cu(II). Fourier transform infrared (FT-IR) spectroscopy was used to characterize the interaction between M. spicatum and Pb(II) ions. The results revealed that the carboxyl, hydroxyl and carbonyl groups are the main binding sites for Pb(II). [Copyright &y& Elsevier]

Abstract: For revealing the mechanism of allelopathic influence on phytoplankton by aquatic macrophytes, the growth and photosynthetic activities of cyanobacteria Microcystis aeruginosa and the chlorophyte Selenastrum capricornutum were investigated when they coexisted with submerged macrophyte Myriophyllum spicatum and were exposed to allelopathic polyphenols: pyrogallic acid (PA), gallic acid (GA), ellagic acid (EA) and (+)-catechin (CA). According to the results of coexistence assays, the non-photochemical quenching (NPQ) and effective quantum efficiency (YII) of M. aeruginosa were affected earlier and more rapidly than the cell density. However, the influence of M. spicatum on S. capricornutum was not found. When the Toxicity Index (TI) was applied to evaluate the combined effects of binary and multiple mixtures of polyphenols, it was found that the four tested polyphenols with the proportion identified in the M. spicatum-cultured solution were observed to present synergistic effect (0.36–0.49) according to the cell density, NPQ and YII of M. aeruginosa. With the combined effects of polyphenols on S. capricornutum, only additive action (0.52–1.62) was found. On the other hand, PA (2.97mgL−1), GA (2.65mgL−1) caused significant reductions of photosystem II (PSII) and whole electron transport chain activities of M. aeruginosa by 71.43 and 18.37%, 70.95 and 40.77% (P <0.05), respectively, after 24-h exposure, but no inhibition effect was found in S. capricornutum. The dark respiration and photosystem I (PSI) activities of M. aeruginosa were significantly increased by exposure to PA and GA (P <0.05). Nevertheless, EA and CA had no influence on the electron transport activities of the tested organisms. These results indicate that the reduction in photosynthetic activity of M. aeruginosa and the synergistic effect of allelochemicals may be two important causes for the inhibition of undesired phytoplankton by submersed macrophytes in natural aquatic ecosystems, and PSII in cyanobacteria is considered to be one of the target sites attacked by allelopathic polyphenols. [Copyright &y& Elsevier]

Abstract: Preference for 14N over 15N was assessed for Myriophyllum spicatum L. by exposing shoots to the same initial concentration of N, but different isotopic compositions (100% 14N, 50% 14N and 50% 15N, and 100% 15N) for 6 weeks. Regardless of treatment, all available inorganic N was taken up by M. spicatum at similar rates. Significant differences in tissue isotopic composition were evident across treatments in 2 weeks, and persisted for the remainder of the experiment. At 6 weeks, atom (at) % 15N was twice as high in the 100% 15N treatment as in the 50% 15N treatment, and the at% of the 14N treatment (0% 15N) remained unchanged. This observed absence of preference for 14N in M. spicatum suggests that this species can be useful in determining N sources to freshwater systems, which often differ in 15N/14N ratio. [Copyright &y& Elsevier]

With multiple invasions, the potential arises for interactions between invasives inhibiting or promoting spread. Our goal was to investigate the interaction between two invasives, Eurasian watermilfoil (Myriophyllum spicatum) and rusty crayfish (Orconectes rusticus), which co-occur in several lakes in western Quebec, Canada, and to determine their overlap with littoral fish communities. Crayfish potentially aid milfoil dispersal by fragmentation or, alternatively, inhibit its proliferation through destruction and direct consumption. With a mesocosm experiment, we quantified milfoil fragment production versus biomass reduction by crayfish. More fragments were produced at medium to high crayfish densities, with a significant reduction of milfoil only at the highest densities, demonstrating the potential for both positive and negative interactions. Second, we determined the habitat preferences of each species by conducting a survey in the same lake. There was little overlap in the species’ distributions, with each preferring different habitat features, indicating either a low probability of interaction or that interaction occurred historically, resulting in a contemporary exclusion pattern. While our experiment showed a potential for significant interaction, the low natural co-occurrence of these species suggests that they do not currently influence each other or that they previously excluded each other. L’interaction entre de multiples espèces envahissantes peut inhiber ou favoriser leur dispersion. L’objectif de notre étude était de déterminer l’interaction entre deux espèces envahissantes, le myriophylle à épis (Myriophyllum spicatum) et l’écrevisse à taches rouges (Orconectes rusticus), introduites dans plusieurs lacs de l’ouest du Québec, Canada, et de déterminer leur chevauchement avec les poissons littoraux. Les écrevisses peuvent favoriser la dispersion du myriophylle par fragmentation, mais aussi diminuer sa prolifération par leur consommation et leur destruction. Une expérience en mésocosmes fut réalisée pour quantifier la production de fragments et la réduction de la biomasse des myriophylles par les écrevisses. Plus de fragments furent produits à des densités d’écrevisses moyennes et élevées alors que seules des densités élevées réduisirent significativement la biomasse, démontrant un potentiel d’interactions positives comme négatives. Ensuite, leurs habitats préférentiels furent déterminés par un échantillonnage dans le même lac. Il y avait peu de chevauchement dans leurs répartitions, chacune préférant différentes caractéristiques de l’habitat, ce qui indique une faible probabilité d’interaction ou alors une interaction historique ayant mené à l’exclusion actuelle. Alors que les expériences indiquent la possibilité d’une interaction significative entre ces deux espèces envahissantes, le faible chevauchement et les densités dans le milieu naturel suggèrent qu’elles ne s’influencent pas pour l’instant ou qu’elles se sont exclues l’une l’autre dans le passé. [ABSTRACT FROM AUTHOR]

1. The control of invasive species has become a widespread management practice, yet information on the community effects of such efforts is very limited, there is no unified framework for monitoring their success and no guidelines exist to help minimize potential adverse impacts. 2. This study was conducted to determine how long-term efforts to control a widespread invasive macrophyte, Eurasian watermilfoil, affect native macrophytes, fish and macroinvertebrates. In addition, we examined how members of the aquatic fauna respond to changes in invasive macrophyte abundance and habitat complexity to understand the mechanisms underlying any potential community response. 3. Selective control of the invasive macrophyte had minor effects on habitat complexity due to timely recolonization by native macrophytes and it did not affect littoral fish richness and abundance. Macroinvertebrate communities were highly variable and some of that variation could be attributed to characteristics of the macrophyte community. Fish and macroinvertebrates were more affected by habitat complexity than by other attributes of the macrophyte assemblage. 4. Synthesis and applications. Management plans to control invasive species need to prioritize selective removal and timely restoration of the native assemblage. In this study, the invasive macrophyte was used by aquatic fauna, which emphasizes the need for immediate restoration of the native macrophyte community to mitigate for the lost habitat after invasive plant control efforts. As both fish and macroinvertebrates were more affected by complexity than other attributes of the macrophyte assemblage, re-establishment of habitat complexity appears to be a promising restoration strategy. On a more general note, we highlight the importance of assessing community response to the habitat provided by the invader and invader’s function in the community when evaluating strategies to control invasive species. [ABSTRACT FROM AUTHOR]

Abstract: Our investigation on macrophytes in Lake Qattieneh, a large, shallow reservoir in western Syria, is a first assessment of ecological status of this lake. We studied spatial distribution patterns of aquatic macrophyte vegetation and heavy metal concentrations to determine if they can be used as indicators of point sources of pollution. Industrial and municipal point sources at the lake shore increase nutrient load and contamination by heavy metals. Water analyses revealed high concentrations of some heavy metals at some littoral sites: Ni 88.7μgL−1, Cr 49.99μgL−1, Co 14.38μgL−1, and Cu 11.65μgL−1. Despite hypertrophic conditions and high heavy metal contamination, we recorded several submerged macrophyte species with heterogeneous spatial distribution patterns. Whereas Potamogeton pectinatus L. dominates in the eastern part of the lake, near industrial point sources, both Myriophyllum spicatum L. and Potamogeton lucens L. form extended patches in the western part of the lake. The shallow, littoral areas near villages are dominated by Ranunculus trichophyllus Chaix in Villars and Ceratophyllum demersum L. The west–east gradient in nutrient and heavy metal concentrations in waters and sediments are reflected by the spatial distribution of submersed species. While the heavy metal concentrations of the water body vary considerably in different seasons, the contents in submersed macrophytes integrate seasonal variations of longer time periods. Spatial distribution and tissue accumulation of littoral macrophyte species reflect the environmental conditions at respective sites such as heavy metal contents in water and sediment. [Copyright &y& Elsevier]

This study evaluates the effects of the triazine herbicide simazine in an outdoor pond microcosm test system that contained two submerged rooted species (Myriophyllum spicatum and Elodea canadensis) and two emergent rooted species (Persicaria amphibia and Glyceria maxima) over a period of 84 days. Simazine was applied to the microcosms at nominal concentrations of 0.05, 0.5 and 5 mg/L. General biological endpoints and physiological endpoints were used to evaluate herbicide toxicity on macrophytes and the algae developing naturally in the system. Concentration-related responses of macrophytes and algae were obtained for the endpoints selected, resulting in a no observed ecologically adverse effect concentration (NOEAEC) at simazine concentrations of 0.05 mg active ingredient/L after 84 days. E. canadensis was the most negatively affected species based on length increase, which was consistently a very sensitive parameter for all macrophytes. The experimental design presented might constitute a suitable alternative to conventional laboratory single-species testing. [Copyright &y& Elsevier]

Abstract: The effects of temperature, water level and burial depth on seed germination of two submerged species, Myriophyllum spicatum and Potamogeton malaianus, were investigated under controlled laboratory conditions. There was no significant difference in final germination of M. spicatum among water level treatments, but P. malaianus germinations at 1cm and 12cm water levels were better than at 0cm water level at temperatures of 20°C and 30°C. Little to no germination was observed for either species at the temperature of 10°C. At 15°C, however, germination increased significantly to 66.3–70.6% for M. spicatum and to 29.4–48.1% for P. malaianus under all three water level treatments. Increased temperature from 15°C to 30°C had no significant effect on the final germination of M. spicatum except at the 1cm water level, but enhanced significantly the germination of P. malaianus. Analysis of the mean time to germination revealed that M. spicatum was a faster germinator relative to P. malaianus. The two species’ germination differed markedly in response to burial depth. Germination percentage of M. spicatum was 71.3% at 0cm burial depth, but decreased to 5.0% and to 2.5% at depths of 1cm and 2cm, respectively; whereas germination percentages of P. malaianus were 40.0%, 23.8%, 12.5%, 7.5% and 1.3% at depths of 0cm, 1cm, 2cm, 3cm and 5cm, respectively. We concluded that the two species respond differently to germination strategies. The findings provided further insight into how germination strategy contributes to the seed bank formation and species invasion. [Copyright &y& Elsevier]

The submersed macrophytes Elodea canadensis, Myriophyllum spicatum and Potamogeton lucens were constantly exposed over a five-week period to environmentally relevant concentrations of atrazine, isoproturon, diuron, and their mixture in outdoor mesocosms. Effects were evaluated investigating photosynthetic efficiency (PE) of the three macrophytes and growth of M. spicatum and E. canadensis. Adverse effects on PE were observed on days 2 and 5 after application. M. spicatum was found to be the more sensitive macrophyte. E. canadensis and P. lucens were less sensitive to atrazine, diuron and the mixture and insensitive to isoproturon. PE of M. spicatum was similarly affected by the single herbicides and the mixture demonstrating concentration addition. Growth of E. canadensis and M. spicatum was not reduced indicating that herbicide exposure did not impair plant development. Although PE measurements turned out to be a sensitive method to monitor PSII herbicides, plant growth remains the more relevant ecological endpoint in risk assessment. [Copyright &y& Elsevier]

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte–epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C·m–2·h–1. Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C·m–2·h–1 (standard deviation (SD), ±0.65) or 56 µg C·g dry weight–1·h–1 (SD, ±8), which we suggest can be used for extrapolations at the lake scale. [ABSTRACT FROM AUTHOR]

The distribution of egg strands of perch Perca fluviatilis was studied in relation to water depth and spawning substrate during late April and early May 2007 in Chabařovice Lake, Czech Republic, using SCUBA divers and parallel transects. The depth distribution of egg strands differed significantly between the two sampling dates, being much deeper in early May compared to late April. Perch used at least seven different spawning substrates of which the most important were curly pondweed Potamogeton crispus, worm weed Artemisia sp. and common reed Phragmites communis. However, while living submerged vegetation, although more abundant, was generally avoided, dead submerged vegetation was strongly preferred. It appears that dead vegetation is an ideal spawning substrate for perch since placement of the egg strands over those hard, complex three-dimensional structures ensures that the eggs remain well oxygenated 24 hours a day. Factors with significant influence on the distribution of egg strands were as follows (in order of decreasing influence): depth of deposition, type of spawning substrate, date of spawning and temperature at the depth of deposition. [ABSTRACT FROM AUTHOR]

Abstract: Sediment may play an important role during the submerged macrophyte decline in the eutrophication progress. In order to investigate the response in root morphology and nutrient contents of submerged macrophytes Myriophyllum spicatum to sediment, five sediment types were treated and used (five types of sediment were used in the experiment: treatment 1 was nature sediment+sand, a 50:50 (v/v) mixture, treatment 2 was the studied sediment only, treatment 3 was sediment+nitrogen (N, NH4Cl 400mgkg−1), treatment 4 was sediment+phosphorus (P, NaH2PO4 300mgkg−1); treatment 5 was sediment+phosphorus (P, NaH2PO4 600mgkg−1)). The results show that the root N content was only significantly affected by adding N in sediments and P was elevated by adding N and P. The root mass and its percentage increased at first, the peak values were reached at 35d, and then decreased. The root growth was restrained by adding sand and N in sediments, root senescence process was delayed at the later experimental time by adding P in sediments. The increase of root volume showed a similar trend to that of root growth, except for plant with P addition where root volume remained high after 35d. The root volume decreased while the main root number increased significantly by adding sand in sediments. The mean root length and main root diameter were reduced by adding P in sediments. The compatible sediment nutrient condition is necessary to restore submerged macrophytes in a degraded shallow lake ecosystem, and the effect of sediment on the root morphology and nutrient content is one of the important aspects restricting the restoration of submerged macrophytes. [Copyright &y& Elsevier]

This study uses hedonic analysis to estimate the effects of a common aquatic invasive species—Eurasian watermilfoil (milfoil)—on property values across an extensive system of over 170 lakes in the northern forest region of Wisconsin. Since milfoil is inadvertently spread by recreational boaters, and since boaters are more likely to visit attractive lakes, variables indicating the presence of milfoil are endogenous in a hedonic model. Using an identification strategy based on a spatial difference-in-differences specification, results indicate that lakes invaded with milfoil experienced an average 13% decrease in land values after invasion. [ABSTRACT FROM AUTHOR]

Many freshwater lakes have been invaded by non-native aquatic plants. Although managing the invasions is necessary to restore native macrophytes, little is known about the effects of invasive macrophyte eradication on fish foraging. This study was designed to determine whether fish feeding was affected by large-scale changes in plant composition after selective control of invasive Eurasian watermilfoil, Myriophyllum spicatum, and whether feeding was correlated with habitat complexity or abundance of invasive plants on a smaller scale. Popnets were used to collect plants, invertebrates and fishes in the littoral zone of four Minnesota lakes twice a year for 4 years. The degree of stomach fullness in fishes was not correlated with the proportion of invasive plants or habitat complexity. Bluegills, the most abundant fish species, exhibited high selectivity for Diptera and their preferences varied little in different plant habitats. Changes in niche width of bluegills were not consistent with invasive plant control. Overall, invasive macrophyte control with timely restoration of the native plant community did not affect the characteristics of fish feeding we investigated. This study also contributes to our understanding of fish–macroinvertebrate interactions as a function of habitat complexity. [ABSTRACT FROM AUTHOR]

The article discusses research conducted on the ways in which microcystins impact aquatic plants and how certain plants develop a tolerance to these impacts. Microcystins of different concentrations were applied to evaluate the toxic effects in Lemna minor and Myriophyllum spicatum. The growth of these plants, chlorophyll a content, and superoxide dismutase (SOD) activity were all evaluated. It was discovered that Myriophyllum spicatum displays greater tolerance to a wide range of microcystins than does Lemna minor. Catalase within these species was also discussed.

Abstract: Recent studies in Conesus Lake, New York, documented significant decreases in the biomass of Eurasian watermilfoil (Myriophyllum spicatum) near the mouths of streams draining sub-watersheds where reductions in nutrient loading occurred as a result of the implementation of agricultural Best Management Practices (BMPs). In situ experiments were conducted to further investigate the relationship between stream loading, foliar uptake, and growth of Eurasian watermilfoil. In two of three experiments, plants cropped to a height of approximately 50 cm had the lowest growth (g/m2) downstream from a sub-watershed where major BMPs had been implemented (80% and 0%). In sub-watersheds where minimal or no BMPs were introduced, plants showed significantly higher growth as biomass increased (216% and 22%). In a second set of experiments, shoots of Eurasian watermilfoil plants were incubated for 24 h in ambient lake water and in lake water with enriched concentrations of nitrate and soluble reactive phosphorus comparable to rain event stream effluent concentrations and then allowed to grow in situ for a 2-week experimental period. For all experiments combined, the shoot biomass increased significantly in the enhanced nutrient treatments when compared to the ambient treatment at the Sand Point macrophyte bed (reduced loading) but not at the Eagle Point macrophyte bed (high loading). Overall, the results indicate that foliar uptake of nutrients in stream effluent can contribute to the growth of Eurasian watermilfoil and reinforce the hypothesis that reductions in stream loading through agricultural BMPs can help reduce macrophyte growth in the lake littoral. [Copyright &y& Elsevier]

Abstract: Long-term studies of macrophyte beds growing near streams in Conesus Lake, New York, have revealed a high biomass and continuing dominance of the invasive rooted species Eurasian watermilfoil (Myriophyllum spicatum). We tested whether agricultural best management practices (BMPs) designed to reduce tributary nutrient and soil loss from the watershed could reduce populations of Eurasian watermilfoil downstream in the lake littoral. Six macrophyte beds were monitored during a 3-year baseline period (2001–2003) prior to the implementation of BMPs and for a 4-year experimental period after a variety of agricultural BMPs were implemented in three sub-watersheds. For three macrophyte beds downstream from sub-watersheds managed as part of our project, quadrat biomass decreased by 30–50% and was statistically lower than Pre-BMP baseline values in 7 of 11 experimental sample years. Biomass loss primarily in the form of the dominant Eurasian watermilfoil ranged from 6.2 to 10 t wet weight for each bed. The declines in biomass coincided with significant annual and January–August decreases in the concentrations and fluxes of dissolved nutrients, total phosphorus, and total suspended solids in nearby streams. For three macrophyte beds downstream from watersheds in which landowners applied less extensive or no new agricultural management, biomass was statistically indistinguishable from Pre-BMP baseline values in all 12 experimental sample years. Milfoil remained the overwhelmingly dominant species at all sites during the entire study period. These results provide impetus for the use of watershed nutrient management to control the nuisance growth of Eurasian watermilfoil on a local scale in the lake littoral. [Copyright &y& Elsevier]

Abstract: Plant growth, biomass allocation and autofragmentation were investigated in response to root and shoot competition in the submersed macrophyte Myriophyllum spicatum L. growing in two sediment environments. Biomass accumulation and allocation were significantly affected by sediment fertility, with a higher total biomass observed in fertile sediment (average: 4.69g per plant vs. 1.12g per plant in infertile sediment). Root-to-shoot ratios were 0.34 and 0.06 in the infertile and fertile sediments, respectively, reflecting the high investment placed on roots under infertile conditions. In the presence of root, shoot, and full competition, whole plant biomass decreased by 18%, 12% and 24% in the infertile sediments, and 23%, 25% and 33% in the fertile sediments, respectively. Root weight ratios (RWRs) increased with root competition by 38% (P <0.001) and 12% (P =0.002), while leaf weight ratios (LWRs) decreased with shoot competition by 6% (P =0.042) and 5% (P =0.001) in the infertile and fertile sediments, respectively. A total of 406 autofragments were harvested in the fertile sediments, but none were obtained from the infertile sediments. In the control, autofragment number and biomass was 166% and 175% higher compared to the competition treatment. Root and shoot competition resulted in a 21% (P =0.043) and 18% (P =0.098) decrease in the autofragment biomass, respectively. These results indicated that M. spicatum responds to different sediment fertility by changing its allocation patterns. Moreover, both root and shoot competition influenced plant growth and autofragmentation, while sediment nutrient availability played an important role in M. spicatum autofragmentation. [Copyright &y& Elsevier]

1. Invertebrates and aquatic plants often play a key role in biogeochemical processes occurring at the water–sediment interface of aquatic ecosystems. However, few studies have investigated the respective influences of plants and bioturbating animals on ecological processes (nutrient fluxes, benthic oxygen uptake, microbial activities) occurring in freshwater sediments. 2. We developed a laboratory experiment in aquaria to quantify the effects of (i) one invertebrate acting as a bioturbator ( Tubifex tubifex); (ii) one submersed plant with a high sediment-oxygenating potential ( Myriophyllum spicatum) and (iii) one submersed plant with a low sediment-oxygenating potential ( Elodea canadensis). 3. The tubificid worms significantly increased the fluxes of nitrogen at the water–sediment interface (influx of nitrate, efflux of ammonium), whereas the two plant species did not have significant influences on these nitrogen fluxes. The differences in nitrogen fluxes between tubificid worms and plants were probably due to the bioirrigation process caused by T. tubifex, which increased water exchanges at the water–sediment interface. Tubifex tubifex and M. spicatum produced comparable reductions of nutrient concentrations in pore water and comparable stimulations of benthic oxygen uptake and microbial communities (percentages of active eubacteria and hydrolytic activity) whereas E. canadensis had a very weak influence on these variables. These differences between the two plants were due to their contrasting abilities to increase oxygen in sediments by radial oxygen losses (release of oxygen from roots). 4. Our study suggests that the bioirrigation process and radial oxygen loss are major functional traits affecting biogeochemical functioning at the water–sediment interface of wetlands. [ABSTRACT FROM AUTHOR]

The triazine herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-trazine) was selected as a chemical stressor in an investigation of how toxicological responses of individually grown macrophytes reflect those of plants grown in more natural model populations and two-species communities. Phytotoxicity of the compound to Myriophyllum spicatum L. and Elodea canadensis Michx. was assessed under semi-natural field conditions using 12000l outdoor microcosms. Exposure concentrations of 25, 50, 100, 250μgl−1 plus controls (n =3) were evaluated, selected to fall within a range of concentrations known to produce a toxic response in the tested macrophytes, and effective concentrations required to cause a decrease in biomass endpoints by 10%, 25%, and 50% were estimated. The sensitivities of aquatic plants to atrazine did not differ substantially between planting systems, and few interactions between the effects of the planting method and atrazine effects on macrophyte biomass were detected using a two-way ANOVA. A lack of significant differences in biomass and relative growth rate measures between plants grown under the various test systems also indicated that interactions between and among species did not influence growth of plants in the model population and communities. Under these test conditions, the use of the “cone-tainer” method provided estimates of toxicity consistent with those from plants grown in assemblages, and potential interactions between plants were not found to modify the response of macrophytes to atrazine. [Copyright &y& Elsevier]

Abstract: We examined the ability of lake and landscape features to predict a variety of macrophyte cover metrics using 54 north temperate lakes. We quantified submersed cover, emergent cover, floating leaf cover, Eurasian watermilfoil cover and total macrophyte cover. Measured lake features included lake physio-chemical and morphometric variables and landscape features included hydrologic, catchment and land use/cover variables. Univariate regression analyses demonstrated that these macrophyte cover metrics are predicted by a wide range of predictor variables, most commonly by: Secchi disk depth, maximum or mean depth, catchment morphometry, road density and the proportion of urban or agricultural land use/cover in the riparian zone or catchment (r 2 =0.06–0.46). Using a combination of lake and landscape features in multiple regressions, we were able to explain 29–55% of the variation in macrophyte cover metrics. Total macrophyte cover and submersed cover were related to Secchi disk depth and mean depth, whereas the remaining metrics were best predicted by including at least one land use/cover variable (road density, proportion local catchment agriculture land use/cover, proportion cumulative catchment urban land use/cover, or proportion riparian agriculture land use/cover). The two main conclusions from our research are: (1) that different macrophyte growth forms and species are predicted by a different suite of variables and thus should be examined separately, and (2) that anthropogenic landscape features may override patterns in natural landscape or local features and are important in predicting present-day macrophytes in lakes. [Copyright &y& Elsevier]

A point-intercept survey was implemented in August 2000 to determine the distribution and richness of aquatic plant species present in Waneta Lake and Lamoka Lake, NY. Myriophyllum spicatum (Eurasian watermilfoil) was the most commonly observed species in Waneta Lake (25% of entire lake, 78% of littoral zone) and Lamoka Lake (43% of entire lake, 77% of littoral zone). Eurasian watermilfoil biomass (24.3 g DW/m²) was also significantly greater (p ≤ 0.001) in Waneta Lake than native plant biomass. Our data suggests that Eurasian watermilfoil is invading the native plant communities of Waneta Lake and Lamoka Lake, thereby displacing native plants and limiting their growth to the shallow waters of the littoral zone. [ABSTRACT FROM AUTHOR]

Abstract: Larvae of the freshwater moth Acentria ephemerella (Pyralidae, Lepidoptera) can fully develop on Myriophyllum spicatum, a submerged macrophyte containing 7–10% of its dry mass as tannins. We investigated the physicochemical gut parameters of larvae fed with M. spicatum or Potamogeton perfoliatus, a food plant lacking tannins, and the chemical fate of ingested polyphenols. Microelectrode studies revealed that larval midguts were slightly alkaline (pH 8) and had a positive redox potential. Whole guts were oxygen sinks owing to the oxygen demand of the gut contents. Oxygen penetrated the midgut up to 100μm, but the centres of the foregut and midgut were always anoxic. The physicochemical parameters of the guts did not change with the food plant. The major tannin from M. spicatum, tellimagrandin II, was significantly depleted in the midgut and was not detected in faeces. In vitro studies indicated that tellimagrandin II is rapidly depleted mainly through oxidation, and hydrolysis might also occur. Our findings for A. ephemerella are compared with those for terrestrial Lepidoptera, and possible mechanisms for adaptations to tannin-rich food plants are discussed. [Copyright &y& Elsevier]

Abstract: Myriophyllum spicatum L. is a nonindigenous invasive plant in North America that can displace the closely related native Myriophyllum sibiricum Komarov. We analyzed the chemical composition (including: C, N, P, polyphenols, lignin, nonpolar extractables, and sugars) of M. spicatum and M. sibiricum and determined how the chemistry of the two species varied by plant part with growing environment (lake versus tank), irradiance (full sun versus 50% shading), and season (July through September). M. spicatum had higher concentrations of carbon, polyphenols and lignin (C: 47%; polyphenols: 5.5%; lignin: 18%) than M. sibiricum (C: 42%; polyphenols: 3.7%; lignin: 9%) while M. sibiricum had a higher concentration of ash under all conditions (12% versus 8% for M. spicatum). Apical meristems of both species had the highest concentration of carbon, polyphenols, and tellimagrandin II, followed by leaves and stems. Tellimagrandin II was present in apical meristems of both M. spicatum (24.6mgg−1 dm) and M. sibiricum (11.1mgg−1 dm). Variation in irradiance from 490 (shade) to 940 (sun) μmol of photons m−2 s−1 had no effect on C, N, and polyphenol concentrations, suggesting that light levels above 490μmol of photons m−2 s−1 do not alter chemical composition. The higher concentration of polyphenols and lignin in M. spicatum relative to M. sibiricum may provide advantages that facilitate invasion and displacement of native plants. [Copyright &y& Elsevier]

Abstract: Ecological optima and ranges of submerged macrophytes are, amongst other factors, assumed to be influenced by ecoregion and flow velocity. In order to test the influence of ecoregion within Europe, species indicator values of three European macrophyte river trophic indices were compared to each other. Species indicator values of the United Kingdom (UK), French and German bioindication methods are significantly correlated with each other. The most obvious difference between the three indicator systems is the number of included indicator taxa. Two species exhibit major differences in indicator values: Callitriche hamulata has a broader ecological amplitude in Germany and France than in the UK, where it is restricted to oligotrophic rivers, while Ranunculus fluitans has a broad ecological amplitude in the UK, whereas the species is restricted to eutrophic rivers in Germany and France. In order to test if current velocity has an influence on macrophyte trophic indicator qualities, species indicator values of a river (Trophic Index of Macrophytes, TIM) and a lake macrophyte trophic index (Macrophyte Index, MI), both of them applicable in Bavaria, Germany, were compared to each other. Species indicator values are significantly correlated. The most important difference is that different species are included in lake and river indicator lists. Only approximately 60% of the total species are used in both TIM and MI. Three species exhibit a major difference in ecological optima between rivers and lakes: Ranunculus circinatus has a broader ecological amplitude in rivers whereas the species is restricted to eutrophic lakes, Myriophyllum spicatum and Nuphar lutea show the opposite reaction. [Copyright &y& Elsevier]

Abstract: The submerged aquatic plant Myriophyllum spicatum L. (Eurasian water milfoil) has been suggested as an efficient plant species for the treatment of metal-contaminated industrial wastewater. The process of metal removal by plants involves a combination of rapid sorption on the surface and slow accumulation and translocation in the biomass. This study focussed on the sorption/desorption characteristics of the surface of M. spicatum for Co, Cu, Ni and Zn. Batch sorption tests with mixed metal solutions covering a range of 0, 1, 5, 10, 50 and 100mgl−1 of each metal, were performed. For Co, Ni and Zn, the sorption process was well described by the Langmuir model, whereas sorption of Cu was better described by the Freundlich model. The biomass showed the highest affinity for Cu and Zn. Langmuir sorption maxima of Co, Ni and Zn were 2.3, 3.0 and 6.8mgg−1 DM, respectively. At the highest initial concentration of 100mgl−1, a maximum of 29mgg−1 DM of Cu was sorbed onto the surface of the biomass. Desorption by 0.1M HCl did not fully recover the metals sorbed onto the surface and there was evidence of leaching from within the biomass. Recovery of heavy metals and regeneration of the biomass by washing with 0.1M HCl was therefore not suggested as a viable strategy. [Copyright &y& Elsevier]

Limnomysis benedeni (Czerniavsky, 1882) (Mysidacea) was recorded for the first time in Croatia in the summer of 2004. Five specimens were found in samples from macrophyte stands of Myriophyllum spicatum (L.) and Ceratophyllum demersum (L.) with associated invertebrates, in Lake Sakadaš in the Kopački rit floodplain. From environmental monitoring data of Kopački rit, no important effect from the presence of this species has been recorded yet. However, according to its biological attributes, especially a short life span and generation time, protection of its juveniles, non-specific food preference, and suspension feeding, L. benedeni is characterized as a successful Ponto-Caspian invader, so monitoring of this species in Croatian inland waters is important. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the dependence of macrophyte parameters (distribution depth, width of the reed belt, density and length of shoots) on a number of abiotic factors (wind patterns, nutrient loading, slope of the littoral, granulometric sediment composition) in a large, shallow, and eutrophic Lake Võrtsjärv (270km2, average depth 2.8m) in Estonia in 1997. The macrophytes colonized 19% of the lake area, whilst 95% was potentially suitable by depth. The most affected were the floating-leaved plants that colonized the smallest percentage (6%) of areas suitable for them with regard to depth. Factor analysis revealed a strong polarisation of the lake''s vegetation both in west–east and north–south direction caused by (1) dominating westerly and south-westerly winds, (2) the shape of the lake narrowing down from north to south, and (3) concentration of bigger inflows at the west and south shores of the lake. The eutrophication process caused the disappearance of several species, on one hand, and the extension of the distribution areas of other species, on the other hand. Myriophyllum spicatum L. has become the dominating species among the submerged plants, replacing the earlier dominant, Potamogeton perfoliatus L. [Copyright &y& Elsevier]

Changes in antioxidant activity, total phenolic and abscisic acid (ABA) constituents of Myriophyllum spicatum L. and Myriophyllum triphyllum Orchard, cadmium (Cd) aqueous macrophytes, were investigated exposed to 0, 2, 4, 6, 8, 16 mg l-1 Cd concentrations. M. triphyllum exhibited strong antioxidant activity but not M. spicatum before and after exposure. Free radical scavenging activity of M. triphyllum was significantly affected from the Cd concentrations and a significant increase was observed at 6 mgl-1 Cd concentration. Total phenolic constituent and ABA concentration of M. triphyllum is higher than that of M. spicatum with or without heavy metal exposure (P < 0.05). While total phenolic constituents of both species were not significantly affected from Cd concentrations except for 6 mglc Cd concentration ABA contents did. ABA content of M. triphyllum increased from 1.81 ± 0.10 µg g-1 (control) to 5.13 ± 0.15 µg g-1 at 16 mg l-1 Cd concentration and increase was from 0.59 ± 0.08 µg g-1 (control) to 2.05 ± 0.10 µg g-1 for M. spicatum at the same Cd concentration. Both species accumulated ABA indicating submerge plants can also accumulate ABA and its concentration increase with increasing Cd concentration. Such studies as this one may be important for evaluation of the metabolic variations of toxic metal tolerant macrophytes that grown in polluted aqueous ecosystem. [ABSTRACT FROM AUTHOR]

Abstract: The distribution and abundance of macrophytes, land-use beyond the riparian zone, characteristics of the riparian zone and selected channel properties have been studied in 9 streams flowing through an agricultural landscape in the north-eastern part of Slovenia. The streams studied supported a rich macrophyte community. Altogether, 53 plant taxa were observed on 93km of the streams. Canonical correspondence analysis indicated that 10 out of the 11 parameters examined significantly influenced macrophyte distribution. Of these, substrate characteristics and riparian vegetation type were the most influential. Species composition analysis revealed that the majority of species indicated moderate nutrient load while, in the more strongly modified reaches, species indicating eutrophic conditions, i.e. Myriophyllum spicatum and different species of genus Potamogeton, were more abundant. [Copyright &y& Elsevier]

This paper describes the spectral light reflectance characteristics of Eurasian watermilfoil (Myriophyllum spicatum L.) and the application of aerial colour-infrared (CIR) photography and videography for distinguishing infestations of this invasive, exotic, submersed aquatic weed in Texas waterways. Airborne videography was integrated with global positioning system (GPS) and geographic information system (GIS) technologies for mapping the distribution of Eurasian watermilfoil. Field reflectance measurements showed that Eurasian watermilfoil could be spectrally distinguished from other associated plant species in either the visible green, visible red or near-infrared regions of the electromagnetic spectrum. Eurasian watermilfoil submerged at depths greater than 5 cm below the water surface had similar visible reflectance to water. Surfaced Eurasian watermilfoil could be distinguished on CIR aerial photography and videography where it had a greyish-pink or faint pink image response. Integration of the GPS with the video imagery permitted latitude-longitude coordinates of Eurasian watermilfoil infestations to be recorded on each image. A stretch of the Rio Grande River in southwest Texas was flown with the photographic and video systems to detect Eurasian watermilfoil infestations. The GPS coordinates on the CIR video scenes depicting Eurasian watermilfoil infestations were entered into a GIS to map the distribution of this invasive weed in the Rio Grande. [ABSTRACT FROM AUTHOR]

Abstract: In regions with thousands of lakes, large scale regional macrophyte surveys are rarely done due to logistical difficulties and high costs. We examined whether remote sensing can be used for regional monitoring of macrophytes in inland lakes using a field study of 13 lakes in Michigan, USA (nine model development lakes and four model testing lakes). Our objectives were: (1) to determine if different levels of macrophyte cover, different growth forms or specific species could be detected using the Landsat-5 TM sensor, and (2) to determine if we could improve predictions of macrophyte abundance and distribution in lakes by including sediment type or measures of water clarity (Secchi disk transparency, chlorophyll a, phytoplankton biovolume, or water color) in our models. Using binomial and multinomial logistic regression models, we found statistically significant relationships between most macrophyte measures and Landsat-5 TM values in the nine model development lakes (percent concordant values: 58–97%). Additionally, we found significant correlations between three lake characteristics and the TM values within lake pelagic zones, despite the inability of these variables to improve model predictions. However, model validation using four lakes was generally low, suggesting caution in applying these models to other lakes. Although the initial model development results suggest that remote sensing is a potentially promising tool for regionally assessing macrophytes, more research is necessary to refine the models in order for them to be applied to unsampled lakes. [Copyright &y& Elsevier]

The distributions of three submersed macrophytes Najas marina, Myriophyllum spicatum and Zostera noltii were surveyed in the inner coastal lagoons of the German Baltic Sea. Growth and photosynthetic performances of these species were investigated in crossed laboratory experiments (salinity × irradiance). Z. noltii showed the potential to grow in mesohaline lagoons, while N. marina seemed to be restricted to oligohaline areas. The potential distribution area of M. spicatum overlapped with those of the other two species. The laboratory results for N. marina and M. spicatum correspond with the recent distribution of the two species in the investigation area. However, neither historical nor recent distribution records of Z. noltii match the potential of this species to grow at 3 and 8 psu. Potential depth limits were calculated for the three species at their collection sites. Accordingly, N. marina had the potential to grow at 0.9–1.1 m depth in the Saaler Bodden, M. spicatum at 1.1–2.1 m depth in the Großer Jasmunder Bodden and Z. noltii down to 2.5–5.1 m depth in the Salzhaff. N. marina grows maximally at 1.0 m in the Saaler Bodden, M. spicatum at 2.0 m in the Großer Jasmunder Bodden and Z. noltii at 3.0 m in the Salzhaff. Thus, recent and modelled historical values of all three species do not differ, and recent distribution limits do not indicate an eutrophication-induced decrease in depth distributions of these species at their respective collection sites. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to investigate the effects of competition on growth and performance of Nymphoides peltata (Gmel.) O. Kuntze in microcosm. Part of the research on growth and biomass allocation of N. peltata in response to competition had been reported early (Wu, Z. & D. Yu, 2004, Hydrobiologia 527: 241–250). This paper focuses on the morphological variations of N. peltata under competitive pressure. First, competition between N. peltata and Zizania latifolia (Griseb.) Turcz. ex Stapf. was assigned with the densities of N. peltata to Z. latifolia ratios of 4:0, 4:2, 4:4 and 4:8. Water surface coverage, surface area per leaf blade and number of leaves per plant of N. peltata all declined significantly with increasing density of competitor. Similar results were also found for petiole length and density of branching. However, the variations of planting density did not significantly affect the number of ramets per plant and the stolon length of N. peltata. Second, competitions between N. peltata and emerged Z. latifolia, floating-leaved Trapa bispinosa Roxb. and submerged Myriophyllum spicatum L. were also studied simultaneously. The results showed that significant difference was only found for the water surface coverage of N. peltata. No other significant differences were found for the number of ramets per plant, number of leaves per plant, density of branching, surface area per leaf blade, petiole length, and stolon length of N. peltata. Our studies indicate that N. peltata presents morphological variations when it is growing with Z. latifolia, such that the growth of above-ground parts decrease (i.e., leaf number, petiole length, branching density) and the growth of below-ground parts remains stable (i.e., stolons length). However, N. peltata does not show apparent differences in morphology when it is growing with T. bispinosa or M. spicatum. Accordingly, we conclude that the growth of N. peltata may be apparently inhibited by the presence of Z. latifolia, while T. bispinosa and M. spicatum may have little impact on the growth and performance of N. peltata. [ABSTRACT FROM AUTHOR]