The hypothesis tested in this study is that changes in benthic ecosystem components interrelationships may mirror the degree of environmental stress in the Mediterranean coastal lagoons. Multivariate matrices deriving from four benthic components (macrophytes, zoobenthos, epibenthic decapods and demersal fish) from four lagoonal stations along a well-defined disturbance gradient were compared by means of second-stage non-metric multidimensional scaling (MDS). The resulting inter-matrix distances were used as a proxy for the identification of the degree of disturbance. The approach followed is novel in that it uses information from higher levels of the biological organization by taking into account more than a single benthic component, thus representing broad categories of functional groups. The second-stage MDS plots depict differences between inter-component distances in the sampling stations according to the degree of disturbance they experience and the BIOENV analysis demonstrates that certain components are correlated with the environmental variables at a higher degree in the most disturbed stations.

Although habitats of hard emergent macrophyte beds, including reed beds (Phragmites australis), are very common in the littoral zones of stagnant waters in central Europe, research investigating their macroinvertebrate communities is still lacking. In this study, the spatial distribution of macroinvertebrates was studied within large reed beds in the littoral zone of a lowland fishpond (Nesyt, SE Moravia, Czech Republic). Using a hand net, horizontal line transects in the reed bed leading from the marginal area with the open water towards the shore were sampled. The results of NMDS ordination and PERMANOVA test proved that the taxonomic composition of the macroinvertebrate assemblage changed significantly along the investigated horizontal transect from the open water towards the shore, together with gradual changes in some environmental factors. The taxa diversity was found to be the highest in the areas closest to the shore. In the reed bed areas near open water, corixids, aquatic insects larvae, leeches, water mites, some naidids and tubificids, which represented free-swimming invertebrates with tracheal gill breathing, ectoparasites, gatherers/collectors and taxa preferring pelal and inorganic substrates, were more abundant compared with the interiors of reed beds. On the other side, in the shallow dense interior of reed beds close to the shore, gastropods, water slaters, some naidids and enchytraeids, aquatic beetles and dipteran larvae were characteristic taxa, which belonged especially to grazers and scrapers, shredders and invertebrates preferring phytal and POM (particulate organic matter) microhabitats. Different predators were recorded in areas near open water and near the shore. This invertebrate spatial distribution probably reflects changes in microhabitat and environmental conditions along the investigated horizontal transect. The results of this study proved that extensive reed beds serve as refuges for many groups of aquatic macroinvertebrates within lowland fishpond ecosystems.

A survey of the 1:100,000 topographic maps of Papua New Guinea revealed that there are about 5383 freshwater lakes in the country. They range in size up to 647 km2 but the majority are less than 10 ha. They are found at all altitudes to over 4000 m but most are situated below 40 m in the floodplains of the Fly, Sepik and Aramia rivers. The majority of lakes are undoubtedly shallow but depths range up to 360 m. The lakes were formed in at least 20 different ways but the majority by fluviatile action. The few data on chemical and physical conditions suggest that most lakes are chemically poor with low light penetration and low pH values. With the possible exception of the macrophytes the fauna and flora of the lakes are virtually unstudied, particuarly from a quantitative aspect. Most lakes are probably polymictic.

A set of 21 ponds was sampled three times for odonate larvae during spring 2002. At the same time 17 environmental variableswere recorded including area, wet phase duration, total nitrogen, total phosphorus, aquatic macrophytes and land use. Atotalof 16 odonate species belonging to Lestidae, Coenagrionidae, Aeshnidae and Libellulidae were recorded, and the total numberof species per pond varied from zero to six. The relationships between species richness, assemblages and environmental variableswere studied by simple and multiple correlation and by Canonical Correspondence Analysis (CCA). The results showed thatpermanent ponds were larger, deeper, had more macrophyte species, had more extensive macrophytes cover and lower concentrationsof nitrogen and phosphorus than temporary ponds. Multiple regression analysis showed that the number of odonate specieswas positively affected firstly by the number of macrophyte species, and then by pond depth. However, pond depth appearedto be interchangeable with several others variables, such as pond area and water duration and negatively correlated withnitrogen concentration, variables which are all linked with the permanent or temporary status of the ponds. CCA analysis indicatedthat odonate species presence was linked with a few environmental variables, showing a tendency of Odonata to avoidponds with higher nitrogen concentrations, with the exception of Lestes barbarus, a species typical of temporary water in centralItaly. At the same time, the majority of species were linked with longer water phase duration and with greater macrophytespecies richness. Acomparison with previous studies, and in particular with those carried out in central Italy, confirmed the positiveinfluence of macrophytes, water duration, and also the negative effect of nutrient load. However, several other variables,in particular land use, shade, presence of fish, which were influential in other studies, were not significant in this study.

The programme LIFE Nature "Conservation and restoration of habitats of the Rhine fringe" (2002-2005) focussed on the assessment of the conservation status of terrestrial and aquatic habitats. Along the Rhine fringe, the degree of connection between waterbodies and the river main channel determined the water flow (surface or phreatic waters, flow velocity) and induced flood disturbances (hydromorphological quality, scouring effect). A new typology based on metrics characterizing the conservation status, was proposed for the upper Rhine floodplain. Seven physical and biological metrics were selected: specific richness, presence or absence of rare, polluto-tolerant and exotic species, species abundance, degree of connection, and trophy level defined by the macrophyte community. Aquatic macrophytes surveys were conducted at 315 sites along the Rhine French fringe. Multiple correspondence analysis and discriminant analysis were used to define metrics scores in a preliminary network of 129 macrophytes surveys stands. Metrics were combined to give a measure of the conservation status of the 315 sites. Five classes of the conservation status have been defined from degraded to excellent status. The mapping of the conservation status was realized to answer the question addressed by the program “Life Nature”. We discuss on the choice of the metrics and their justification in the definition of the conservation status. The method was tested in the fluvial hydrosystem of Ill river, the main tributary of the Rhine river in the Alsace floodplain, and compared to the French trophic index based on macrophytes, IBMR.

Large rivers have played a prominent role in biogeographic theory for their potential to act as barriers for the dispersal of terrestrial organisms,and therefore be involved in the generation of species diversity (Brown & Lomolino 1998). In this paper, we document the potential role of macrophyte rafts as a mechanism by which Amazonian rivers could act as dispersal agents rather than barriers, transferring organisms across banks and possibly across very large distances. These vectors could therefore act against speciation and towards homogenization of the local biota.

Dans la région méditerranéenne, une composante importante des habitats aquatiques est constituée par les zones humides stagnantestemporaires. Ces milieux ont des usages multiples (chasse, agriculture, protection des oiseaux), mais sont en contre partieliés à une nuisance forte : le développement de moustiques, du genre Aedes, en particulier.L'objet de cet article est la mise en évidence d'une relation existant entre les caractéristiques des habitats (aux échelles macroet micro-géographique) et la distribution spatiale des pontes d'Aedes caspius.Les groupements végétaux, par l'intermédiaire des espèces discriminantes, permettent de localiser avec précision les différentsniveaux de fertilité des aires de pontes des Aèdes caspius. Les variables explicatives humidité, texture, oxydes ferriques sont traduites d'une manière pertinente par la végétation, cette dernière pouvant être appréhendée de manière opérationnelle par l'utilisation des niveaux écologiques "outils techniques et opérationnels" de l'Entente Interdépartementale pour la Démoustication du littoral Méditerranéen (EIDM).

New legislation has encouraged regulatory biologists in the UK to examine the impacts of eutrophication in rivers for the first time. The principal tools for this have been new indices based on macrophyte and diatom communities. The use of such indices is placed within an appropriate theoretical framework. The importance of recognizing the upper limit of sensitivity of such indices, as well as factors such as organic pollution, which can confuse interpretation, is discussed. Despite their limitations, community-based indices are valuable tools for reconnaissance studies and, in the long-term, as indicators of the extent to which nutrient reductions have led to an ecological response. Some general guidelines for monitoring eutrophication in rivers are proposed.

The temperature dependence of UV effects was studied for Arctic and temperate isolates of the red macrophytes Palmaria palmata, Coccotylus truncatus and Phycodrys rubens. The effects of daily repeated artificial ultraviolet B and A radiation (UVBR: 280–320 nm, UVAR: 320–400 nm) treatments were examined for all isolates at 6, 12 and 18 °C by measuring growth, optimal quantum yield of PSII (Fv/Fm) and cyclobutane–pyrimidine dimer (CPD) accumulation. Furthermore, possible ecotypic differences in UV sensitivity between Arctic and temperate isolates were evaluated. Large species-specific differences in UV sensitivity were observed for all parameters: the lower subtidal species C. truncatus and P. rubens were highly sensitive to the UV treatments, whereas P. palmata, which predominantly occurs in the upper subtidal zone, was not affected by these treatments. Only minor differences were found between Arctic and temperate isolates, suggesting that no differences in UV sensitivity have evolved in these species. Relative growth rates were temperature-dependent, whereas species-specific UV effects on growth rates were relatively independent of temperature. In contrast, the species-specific decrease in Fv/Fm and its subsequent recovery were temperature-dependent in all species. UV effects on Fv/Fm were lower at 12 and 18 °C compared with 6 °C. In addition, UV effects on Fv/Fm decreased in the course of the experiment at all temperatures, indicating acclimation to the UV treatments. CPDs accumulated during the experiment in both isolates of P. rubens, whereas CPD concentrations remained low for the other two species. CPD accumulation appeared to be independent of temperature. The results suggest that summer temperatures occurring in temperate regions facilitate repair of UV-induced damage and acclimation to UV radiation in these algae compared with Arctic temperatures. Because the differences in UV effects on Fv/Fm, growth and CPD accumulation were relatively small over a broad range of temperatures, it was concluded that the influence of temperature on UV effects is small in these species.

Split-beam hydroacoustic techniques have been used to enumerate adult Atlantic salmon (Salmo salar) passage on the River Wye since 1994. Aggregations of aquatic macrophytes, principally Ranunculus fluitans, are seasonally present at the monitoring site. At high densities, these macrophytes return target strength (TS) values similar to those of adult salmon. Target direction-of-movement information readily resolves upstream-migrant salmon from static- or downstream-traveling macrophytes. However, Atlantic salmon are iteroparous, and downstream-migrant kelts must be factored into the acoustic estimates. Net upstream target movement and/or TS were not reliable indicators of salmon passage at the River Wye site when aquatic macrophyte aggregations were present. In 1995, a subset of data (n = 71) was selected from the ongoing monitoring program to determine the feasibility of resolving salmon from macrophytes using acoustic parameters other than target direction-of-movement or mean TS. Individual targets were visually identified as either salmon or macrophytes based on concurrent video records. Distributions of available acoustic parameters were statistically compared between the two target-types using a two-tailed t-test assuming equal variance (P = 0.05). Available acoustic parameters included echo position, pulse width (at –6, –12, and –18 dB power points), amplitude, beam pattern factor and target strength. Pulse width standard deviation (PWSD) measurements were determined to be the most effective individual parameters for discriminating macrophytes from salmon. Based on PWSD at the –6 dB echo power points, 77% of all macrophyte targets were removed from the mixed data set. Multiple selection criteria increased total target discrimination. Applying a combination of –6 and –12 dB PWSD, and Y–axis target slope criteria rejected 94% of all macrophytes, retaining all salmon targets.

Les proliférations de macrophytes atteignent désormais les eaux courantes et entraînent de nombreuses nuisances. La compréhension de ce phénomène nécessite une étude approfondie des peuplements végétaux en place et des paramètres d'environnement qui les conditionnent, afin de déterminer les phytocénoses de référence et leurs séquences de dégradation. Lors de cette étude, vingt et un cours d'eau, situés en tête de bassin versant et représentatifs de la diversité géologique de la Lorraine, ont été prospectés. Le choix des stations d'étude a été réalisé en fonction d'un découpage abiotique, définissant des zones de cours d'eau homogènes au niveau de la géologie, la pente et la largeur. La pertinence de l'utilisation de la géologie (classes de perméabilité) comme premier critère hiérarchique de classification des cours d'eau est confirmée par les résultats de cette étude. Les analyses chimiques et les relevés morphométriques effectués sur chaque station d'étude ont conduit à individualiser quatre grands types de cours d'eau (sur granites, sur grès, sur calcaires et sur marnes), dont la végétation aquatique a été inventoriée. Des successions végétales typiques en fonction de la position amont-aval ont été observées. Les notions de milieux naturellement fragiles et d'espèces « à risque de prolifération » ont été affinées. Cette étude constitue la base d'une typologie des cours d'eau par la végétation aquatique.

Species composition, distribution and biomass of benthic macrophyte communities have been studied in a high mountain, oligotrophic, softwater lake from the Central Pyrenees. Isoetids (Isoetes lacustris L., Isoetes setacea Lam., Subularia aquatica L. and Eleocharis acicularis (L.) Roemer & Schultes) are the dominant macrophytes in areas over 2-3 meters in depth. Natopotamids (Sparganium angustifolium Michx.) are restricted to shallow waters. Algae (Nitella gracilis (Smith) Agardh) only predominate in deep waters. Three main communities have been distinguished : the Sparganium angustifolium community (160 g dwt m-2), the Isoetes lacustris community (120-460 g dwt m-2) and the Nitella gracilis community (11 g dwt m-2). Biomass differences between shallow and deep water Isoetes populations have been attributed to ice-scour stress. Neither irradiance nor slope can explain the lower boundaries observed in the distribution of vascular plants ; sediment features may be responsible for them. Mean lake macrophyte biomass amounts to 140 g dwt m-2 (20 g C -2), a very high value if compared with boreal lakes with similar limnological characteristics.