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Historical information on marine organisms needs to be incorporated to develop effective management plans and conservation targets. In the Mediterranean Sea most species of brown seaweeds of the order Fucales are threatened or endangered and need protection. Here we merge data on historical and current records to create the first reference dataset on past and present distributions of Fucales from shallow and sheltered shores of Catalonia (NW Mediterranean Sea). Most Cystoseira sensu lato populations were found in the northern shores, where the most suitable environments exist. Carpodesmia mediterranea and Cystoseira compressa are far more abundant in exposed than in shallow, sheltered shores. Populations of most of the taxa (i.e. Carpodesmia crinita, Treptacantha elegans, T. sauvageauana, T. barbata f. aurantia) have suffered an important regression and two taxa have apparently become locally extinct (Cystoseira foeniculacea, Treptacantha barbata f. barbata). Carpodesmia caespitosa is still widespread in sheltered environments from the northern shores and a previously unreported taxon has been found (T. ballesterosii var. tenuior). Our regional-scale study makes available a solid, comprehensive baseline for future monitoring and application of conservation measures for the several threatened species of Fucales.

Identifying scales at which most of the spatial heterogeneity occurs is important to understand how ecological communities are structured. Rocky shore communities are distributed vertically as a response to environmental variables and mainly water availability gradients. There has been much debate about the relative importance of vertical and horizontal variation gradients in littoral community structure and richness. In this study we assessed if horizontal variability is responsible for changes in community structure at a regional scale (hundreds of Km) by restraining vertical variability. We studied ten different rocky shore communities from the upper mediolittoral to the upper infralittoral levels with different geographical distribution patterns. We aimed at assessing if structure and species richness are affected by their geographical position of each community. The results proved that horizontal variation in species composition and richness was community-dependent and there was no common pattern at a regional scale. Communities with a wide geographic distribution typically showed some variation, which was related to changes in the environmental factors across the geographical gradient. This study sheds light on the existence of latitudinal variability in species composition and richness at a regional scale in rocky shores. It also strongly supports the validity of littoral communities and habitats from conservation panels as consistent ecosystem subdivisions and reliable working units.

Identifying scales at which most of the spatial heterogeneity occurs is important to understand how ecological communities are structured. Rocky shore communities are distributed vertically as a response to environmental variables and mainly water availability gradients. There has been much debate about the relative importance of vertical and horizontal variation gradients in littoral community structure and richness. In this study we assessed if horizontal variability is responsible for changes in community structure at a regional scale (hundreds of Km) by restraining vertical variability. We studied ten different rocky shore communities from the upper mediolittoral to the upper infralittoral levels with different geographical distribution patterns. We aimed at assessing if structure and species richness are affected by their geographical position of each community. The results proved that horizontal variation in species composition and richness was community-dependent and there was no common pattern at a regional scale. Communities with a wide geographic distribution typically showed some variation, which was related to changes in the environmental factors across the geographical gradient. This study sheds light on the existence of latitudinal variability in species composition and richness at a regional scale in rocky shores. It also strongly supports the validity of littoral communities and habitats from conservation panels as consistent ecosystem subdivisions and reliable working units.

Species distribution models (SDMs) have been used to predict potential distributions of habitats and to model the effects of environmental changes. Despite their usefulness, currently there is no standardized sampling strategy that provides suitable and sufficiently representative predictive models for littoral marine benthic habitats. Here we aim to establish the best performing and most cost-effective sample design to predict the distribution of littoral habitats in unexplored areas. We also study how environmental variability, sample size, and habitat prevalence may influence the accuracy and performance of spatial predictions. For first time, a large database of littoral habitats (16,098 points over 562,895 km of coastline) is used to build up, evaluate, and validate logistic predictive models according to a variety of sampling strategies. A regularly interspaced strategy with a sample of 20% of the coastline provided the best compromise between usefulness (in terms of sampling cost and effort) and accuracy. However, model performance was strongly depen upon habitat characteristics. The proposed sampling strategy may help to predict the presence or absence of target species or habitats thus improving extensive cartographies, detect high biodiversity areas, and, lastly, develop (the best) environmental management plans, especially in littoral environments.

Species distribution models (SDMs) have been used to predict potential distributions of habitats and to model the effects of environmental changes. Despite their usefulness, currently there is no standardized sampling strategy that provides suitable and sufficiently representative predictive models for littoral marine benthic habitats. Here we aim to establish the best performing and most cost-effective sample design to predict the distribution of littoral habitats in unexplored areas. We also study how environmental variability, sample size, and habitat prevalence may influence the accuracy and performance of spatial predictions. For first time, a large database of littoral habitats (16,098 points over 562,895 km of coastline) is used to build up, evaluate, and validate logistic predictive models according to a variety of sampling strategies. A regularly interspaced strategy with a sample of 20% of the coastline provided the best compromise between usefulness (in terms of sampling cost and effort) and accuracy. However, model performance was strongly depen upon habitat characteristics. The proposed sampling strategy may help to predict the presence or absence of target species or habitats thus improving extensive cartographies, detect high biodiversity areas, and, lastly, develop (the best) environmental management plans, especially in littoral environments.

We studied the habitat structure (macrofaunal assemblages and bottom types) and zonation patterns of 29 unvegetated shoreline strands along the 900-km coast of Catalonia (NW Mediterranean Sea). Organisms were sampled with grabs, pitfall traps, sticky traps, clam nets and spades to ensure capture of the different proportions of macrofaunal assemblages from the supra-, medio- and infralittoral levels. We collected 211 taxa: 194 animals and 17 algae. The most abundant and dominant organisms collected with van Veen grabs were Nematoda, Oligochaeta and Collembola at the supralittoral level; the polychaetes Saccocirrus spp. and Pisione remota, the amphipod Corophium orientale, Nematoda, and Turbellaria at the mediolittoral level; and Nematoda at the upper infralittoral level. SIMPER analysis revealed great dissimilarity between the organisms inhabiting the supralittoral and the other littoral levels. Regarding the epifauna, the sticky traps used at the supralittoral level mainly collected Collembola, which were nearly absent in pitfall traps. The qualitative study performed with a clam net and a small spade revealed that Nematoda, Saccocirrus spp., Turbellaria, Nemertea and the polychaete P. remota were the most abundant animals at both the medio- and the infralittoral levels and no differences were found between these levels. Different qualitative sampling methodologies showed that in fine sediments the bivalves Donax trunculus and D. semistriatus determined more than 97% of dissimilarity from coarse-sand sites. Richness increased in protected sandy and cobble shores. Littoral level and bottom-type features were only to a certain extent valid indicators of specific biotic components for a specific habitat., Se ha estudiado la estructura de los hábitats (comunidades de macrofauna y tipos de sedimento) y los patrones de zonación de 29 playas desprovistas de vegetación a lo largo de los 900 km de la costa de Cataluña (Mediterráneo noroccidental). El muestreo de los organismos se realizó mediante dragas, trampas de caída, trampas adhesivas, redes de marisqueo y palas para asegurar una captura exhaustiva de los organismos presentes en las comunidades de macrofauna de los niveles supralitoral, mediolitoral e infralitoral. Se colectaron 211 taxones: 194 animales y 17 algas. Los organismos más abundantes y dominantes recolectados con dragas van Veen fueron: Nematodos, Oligoquetos y Colémbolos en el nivel supralitoral; los poliquetos Saccocirrus spp. y Pisione remota, el anfípodo Corophium orientale, Nematodos y Turbelarios en el nivel mediolitoral; y Nematodos en la parte menos profunda del nivel infralitoral. Los análisis SIMPER detectaron grandes diferencias entre los organismos del nivel supralitoral y los de los otros niveles. Respecto a la epifauna, las trampas adhesivas usadas en el nivel supralitoral capturaron principalmente Colémbolos, los cuales estaban ausentes en las trampas de caida. El estudio cualitativo realizado con una red de marisqueo y una pala pequeña reveló que Nematodos, los poliquetos Saccocirrus spp. y Pisione remota, Turbelarios y Nemertinos eran los animales más abundantes tanto en el nivel mediolitoral como en el nivel infralitoral y que no había diferencias entre ambos niveles. Diferentes métodos cualitativos de muestreo revelaron que en los sedimentos finos los bivalvos Donax trunculus y D. semistriatus determinaban más del 97% de la disimilitud con los sedimentos gruesos. La riqueza en especies aumentaba en playas mixtas de arenas y cantos. El nivel y el tipo de sedimento fueron solo hasta cierto punto indicadores válidos de la composición de especies para cada hábitat concreto.

[EN]Here we compare the applicability, the information provided and the cost-benefit of three sampling methods usually used in the study of rocky benthic assemblages. For comparative purposes, sampling was performed seasonally and along a depth gradient (0-50 m) in the Cabrera Archipelago (western Mediterranean). The destructive scraping (collection) method was the least cost-effective but provided the best qualitative and quantitative information. The in situ visual method was the most time-effective but provided low levels of taxonomic resolution and its accuracy decreased with depth due to the increasing difficulty of recognizing species in situ due to nitrogen narcosis, reduced light and cold. The photoquadrat method showed intermediate values of cost-effectiveness and information but was not suitable for multilayered assemblages, as it only accounted for the overstory. A canonical correspondence analysis showed that depth was highlighted as the main environmental gradient (16.0% of variance) by the three methods. However, differences due to the sampling method (7.9% of variance) were greater than differences due to temporal variability (5.8% of variance), suggesting that the three methods are valid but their selection has to be carefully assessed in relation to the targeted assemblages and the specific goals of each study.[ES]Este trabajo compara la aplicabilidad, la calidad de la información, los costes y los beneficios de tres métodos de muestreo usados habitualmente en el estudio de comunidades en el bentos rocoso mediterráneo. Para fines comparativos, el muestreo se realizó estacionalmente y a lo largo de un gradiente de profundidad (0-50 m) en el Archipiélago de Cabrera (Mediterráneo Occidental). El método destructivo de raspado (recolección) tuvo altos costes, pero proporcionó la información de mejor calidad, tanto a nivel cualitativo como cuantitativo. El método visual in situ fue el más eficiente en cuanto a la obtención de información, pero proporcionó

1. Variability in C and N stable isotopes has been acknowledged to hinder their use as tracers of food sources in the study of trophic interactions in ecosystems. This is particularly so whenever benthic primary production is substantial (variability in d13C) and the ecosystem under study is affected by human impacts (variability in d15N) in aquatic ecosystems. 2. In this study, we aim to better understand the large and often unexplained variability in the natural abundance of d13C and d15N signatures of aquatic plants by analyzing the isotopic composition of plants from 81 lentic systems from NE Spain in relation to extrinsic (alkalinity, pH, nutrient concentrations, water body typology and basin land use) and intrinsic (functional group, carbon assimilation metabolism, elemental composition) predictors. 3. We have encountered significant plasticity in isotopic signatures of aquatic plants associated with the variation in local conditions at the regional scale. The d13C signature varied from 43.1& to 7.5& (35.7& range) and drivers were both intrinsic and extrinsic. The functional group was the most important factor as it is influenced by different carbon sources. Aquatic plants with leaves in contact with the atmosphere (helophytes, free floating and floating attached; 34.8& to 14.6&) responded in a similar way as terrestrial plants. This contrasted with the enriched mean values of rooted submerged plants ( 16.7& to 10.5&) that were more enriched than the described terrestrial C3 range ( 34& to 22&) and completely overlapped the terrestrial C4 range ( 20& to 8&). Concentration of DIC and pH also emerged as important extrinsic factors driving d13C variability. 4. The d15N signature ranged from 5.2& to 20.1& (25.2& range) and the variability was mostly associated with extrinsic factors such as water body type and basin land use, as they influence both the d15N signature and concentration of the dissolved inorganic nitrogen in the aquatic ecosystems. 5. Only one multi

Recovery of the submersed vegetation is a target for the management of soft-water shallow lakes if they are to meet water quality and biodiversity standards. Knowledge of patterns of macrophyte space occupation and time to recovery is poor and mostly restricted to free floating species or riparian vegetation. Here we use pre- and post-impact monitoring data over 20 years showing the evolution of submersed aquatic vegetation of lake Baciver (Pyrenees), and develop models to infer space occupation and time to recovery. We use pre-impact macrophyte distribution in relation to bathymetry-derived data to fit logistic models to further simulate lake equilibrium scenarios. Depth and slope were found to be the best predictors, and models suggested that an assemblage dominated by Sparganium angustifolium was, at time of this study, over 95% of its potential distribution area. A dense, newly grown monospecific Isoetes lacustris population occupied\10% of its potential area and model projections suggest that it will take decades to recover. An I. lacustris residual population remains below the estimated depth threshold for survival and is bound to disappear. The lake appears to evolve towards a new steady-state where the current lake hypsography promotes the expansion of algae (Nitella sp.) over angiosperms.

Gender biases in science have received increasing attention in recent years. Underrepresentation at the highest academic levels and bias in publication are some of the factors affecting women in science. In this study, we assessed the situation of women in Limnology, a specific field of natural sciences, within the geographic context of the Iberian Peninsula. We used a multi-faceted approach to diagnose the situation, and we propose guidelines to reduce gender gaps in Limnology. The database of members of the Iberian Limological Association (AIL) was used to analyse the. variability between genders at different professional stages. Data was also compiled on plenary speakers who attended conferences organized by different associations (AIL, SEFS and ASLO) to assess women's visibility. A published data set was used to identify leadership patterns in publications with respect to gender. Finally, a survey of AIL members was conducted to understand their perception of the barriers in science that result in differences between the genders. This study recognized differences at the recruitment level (more tenured positions are held by men), visibility at conferences (fewer women are invited as plenary speakers) and publication as team leaders (men have more publications as first and last authors). Survey participants recognised the scarcity of grants/funding, difficulties in balancing life and career, and the scarcity of job opportunities as the three main barriers in science, regardless of gender. Yet, women identified family-related barriers such as having children and gender biases more frequently. Overall, our study indicates that there is a general gender bias in the field of Limnology in the Iberian Peninsula; however, it is slightly lower than the reported levels in Europe and for other disciplines in Spain. Finally, we provide a list of recommendations to balance the current biases based on suggestions made by the participants of a round table held at the XVII Congr

The boundary between land and sea, i.e. the littoral zone, is home to a large number of habitats whose distribution is primarily driven by the distance to the sea level but also by other environmental factors such as littoral's geomorphological features, wave exposure, water temperature or orientation. Here we explore the relative importance of those major environmental factors that drive the presence of littoral rocky habitats along 1100 Km of Catalonia's shoreline (Spain, NW Mediterranean) by using Geographic Information Systems and Generalized Linear Models. The distribution of mediolittoral and upper infralittoral habitats responded to different environmental factors. Mediolittoral habitats showed regional differences drawn by sea-water temperature and substrate type. Wave exposure (hydrodynamism), slope and geological features were only relevant to those mediolittoral habitats with specific environmental needs. We did not find any regional pattern of distribution in upper infralittoral habitats, and selected factors only played a moderate role in habitat distribution at the local scale. This study shows for the first time that environmental factors determining habitat distribution differ within the mediolittoral and the upper infralittoral zones and provides the basis for further development of models oriented at predicting the distribution of littoral marine habitats.

Root functional diversity of submerged vegetation exerts a major effect on nitrogen (N) cycling in lake sediments. This fact, however, is neglected in current N-balance models because the links between the engineering role of plants and in situ microbial N cycling are poorly understood. We hypothesized that macrophyte species with high root oxygen loss (ROL) capacity promote the highest denitrification because of a higher abundance of ammonia oxidizers and tighter coupling between nitrifiers and denitrifier communities. We sampled five small ultraoligotrophic shallow lakes with abundant macrophyte cover including sediments dominated either by Isoetes spp. (high ROL), mixed communities of natopotamids (low ROL), and unvegetated sandy sediments. At each site, we quantified denitrification (DNT) rates and proxies for the abundance of denitrifiers (nirS and nirK genes), and both ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) and the diversity of nirS-harboring bacteria. Vegetated sediments showed significantly higher abundances of N-cycling genes than bare sediments. Plant communities dominated by Isoetes generated sediments with higher redox and NO2 3 concentrations and significantly higher DNT rates than natopotamidsdominated landscapes. Accordingly, increasing DNT rates were observed along the gradient from low ROL plants-bare sediments-high ROL plants. Significantly higher abundance of the archaeal amoA gene was recorded in sediments colonized by high ROL plants unveiling a key biogeochemical role for AOA in coupling macrophyte landscape and ecosystem denitrification.

Distribution of aquatic macrophytes in lakes is related to geographical, morphological, catchment and water chemistry variables as well as human impacts, which modify the original environment. Here, we aim at building statistical models to establish the ecological niches of 11 aquatic macrophytes (10 different phanerogams and the genus Nitella) from oligotrophic soft-water lakes and infer their ecological requirements and environmental constraints at the southernmost limit of their distribution. Macrophyte occurrence and environmental variables were obtained from 86 non-exploited oligotrophic soft-water lakes from the Pyrenees (Southern Europe; 42°50´N, 1°00´E); macrophytes inhabited 55 of these lakes. Optimum ranges and macrophyte occurrence were predicted in relation to 18 geographical, morphological, catchment and water chemistry variables using univariate and multivariate logistic models. Lakes at low altitude, in vegetated catchments and with low water concentration of NO3 – and SO4 –2, were the most suitable to host macrophytes. In general, individual species of aquatic macrophytes showed clear patterns of segregation along conductivity and pH gradients, although the specific combination of variables selected in the best models explaining their occurrence differed among species. Based on the species response to pH and conductivity, we found Isoetes lacustris have its optimum in waters with low conductivity and pH (i.e., negative monotonic response). In contrast, Callitriche palustris, Ranunculus aquatilis, Subularia aquatica, Nitella spp., and Myriophyllum alterniflorum showed an optimum at intermediate values (i.e. unimodal response), whereas Potamogeton berchtoldii, Potamogeton alpinus, and Ranunculus trichophyllus as species had their optimum at relatively high water pH and conductivity (i.e. positive monotonic response). This pattern has been observed in other regions for the same species, although with different optima and tolerance ranges. The parsimonio

Studies aimed at describing habitats and mapping their distributions are pivotal to implementing management plans and to effectively guide conservation measures. We developed a novel approach of data collection and entry (CAT-LIT) to establish a detailed cartography of the littoral habitats found along the Catalan coast (Spain). Field data were recorded using coded, two-digit hierarchical lists (e.g. Aa, Ab, etc.) of horizons found at each point along the coast, called catenas. The horizons were either dominated by species (on the rocky bottoms) or sediment types (on the beaches) and corresponded to LPRE, EUNIS and CORINE habitats. Catenas were transferred into a database and calculations about the extent of bottom types, habitats, and catenas themselves along the coast were carried out with GIS tools. In addition, habitat link richness was calculated and represented using network analysis programs. The application of CAT-LIT to the Catalan coast showed that the habitats dominated by the lichen Verrucaria amphibia and the flattened barnacle Euraphia depressa and those dominated by the barnacle Chthamalus spp. were almost ubiquitous. Those dominated by the red alga Corallina elongata, the mussel Mytilus galloprovincialis and the red alga Rissoella verruculosa were also common. Because of the frequency of their connections, those habitats formed a huge hub of links in the networks. By using catenas, the habitats can be viewed using GIS based programs keeping the catena as the main informational and ecological unit. The catenas allow maximum compactness when vertically distributed habitats are to be shown on a 2D map. The complete cartography and dataset on the spatial distribution of the littoral habitats from Catalonia is valuable for coastal management and conservation to study changes in the habitat distribution and relate such changes to anthropogenic pressures. Furthermore, the CAT-LIT can be easily adapted to shores of other seas and oceans to obtain accurate ca

Vertical variation in the distribution of rocky shore assemblages is greater than horizontal variation, as shown by univariate and multivariate analysis performed with data obtained along 1000 km of shoreline and covering from the upper supralittoral to the upper infralittoral zone (−1 m). Consequently, vertical littoral zonation is a consistent pattern at a regional scale within the same biogeographical zone. While their distribution varies at the same shore height, marine species and assemblages from rocky shores show a specific vertical sequence known as zonation. A key question in ecology is how consistent is zonation along large spatial scales. The aim of this study is to show distribution patterns of littoral assemblages at a regional scale and to identify the most relevant abiotic factors associated to such patterns. The study is based on a detailed and extensive survey at a regional scale on a tideless rocky shore. Benthic macroflora and macrofauna of 750 relevés were described along the vertical axis of 143 transects distributed across the shoreline of Catalonia (NW Mediterranean). The Detrended Correspondence Analysis (DCA) first axis is highly related to the height on the shore: species, relevés, and assemblages grade from lower to upper height (infralittoral to supralittoral). As observed in nature, different assemblages co-occur at the same height at different sites, which is shown along DCA second axis. The abiotic variables that best explain the assemblage distribution patterns are: height (75% of the model inertia), longitude (14.6%), latitude (7.2%) and transect slope (2.9%). The Canonical Correspondence Analysis (CCA) first axis is related to height on the shore and explains four times more variance than CCA second axis, which is related to the horizontal gradient. Generalized Lineal Model (GLM) results show that height on the shore is the factor explaining most of the variance in species presence. Most studied species show distribution patterns re

The study of the relationships between vascular aquatic macrophyte occurrence, species richness andthe local environment are central for suitable ecosystem quality assessments, freshwater bodies manage-ment and assistance for macrophyte restoration. Here we quantify the importance of the local factors, bothwater column and sediment, to provide tools for lentic water systems management and conservation in aMediterranean region. We surveyed 90 water bodies along a 2500 m altitudinal gradient in Catalonia (NESpain). Despite its relatively small scale, the area of study exhibits large-scale environmental gradientsmainly related to a diverse geology and climate. In consequence, the response of aquatic macrophytesto a broad range of environmental conditions can be studied without interference of biogeographicalclines. We identified all vascular aquatic macrophytes and analyzed 35 environmental variables at eachsite. Local environmental factors accounted for only 19% of variance in aquatic macrophyte distribution.Even though water column variables explained more variance than sediment variables in a variance par-titioning analysis (pCCA), a mixed model integrating variables of both compartments performed better.The most important variables driving aquatic macrophyte distribution were water conductivity, waterDOC, water K, water pH, water Na, sediment organic matter, sediment Na and water nitrate. CCA betweenspecies and water and sediment variables clearly segregated coastal lagoons, temporary pools and alpinelakes over two main gradients: ionic content and water body productivity. Species richness was low(4.2 species per water body on average) and GAM showed weak correlations with sediment and mostwater column variables. The best factor explaining species richness was the geomorphological typology,but only temporary pools were significantly different from the other types and had the highest speciesrichness. Thus, temporary pools were unique and displayed a high biodiversit

Climate characteristics appear to play a key role in filtering organisms based on their biological traits. If this trait filtering by climate indeed occurs, it should have effects on the composition, dynamics, taxonomic relatedness and co-occurrence patterns of local assemblages, regardless of the taxonomic group considered. This preliminary study aimed to assess the extent to which environmental variables might determine these patterns in local communities and to evaluate whether the ultimate cross-taxon congruence relationships are consistent across, or dependent on, the selected region. To this end, we studied the bryophyte, macrophyte, macroinvertebrate, and amphibian communities in two clusters of temporary wetlands on the NE Iberian Peninsula under mesothermal and semiarid climates. We observed effects of environmental filtering, with the communities differing between the climatic regions not only in their compositions but also in their dynamics and taxonomic relatedness patterns. Although the cross-taxon congruence in terms of species richness was high in the mesothermal climate, most of the congruent relationships were disrupted in the semiarid environment. Overall, because climate-dependent patterns appear to prevail over climate-consistent ones, we suggest that the use of surrogate taxa may be of limited value when aiming to assess wetland biodiversity across large areas.

Even though aquatic macrophytes are key species in freshwater bodies and some of them are rare and vulnerable, aquatic macrophytic vegetation in the Mediterranean area is poorly known. Here we aim at identifying diversity patterns, both at the species and vegetation levels, from Catalonia (NE Spain), an area which holds a rich variety of aquatic ecosystems situated along a wide altitudinal range. More than 20,000 citations concerning 120 aquatic vascular plant species and 235 phytosociological relevés are studied. Data are obtained mainly from the Biodiversity Data Bank of Catalonia (BDBC) plus unpublished records. Aquatic macrophytes are present in 94% of the total 10 × 10 km2 UTM squares covering the studied area and 82% of the aquatic macrophytes reported from the Iberian Peninsula are listed in Catalonia. This illustrates that species richness in this small area is high, in accordance with its geomorphological and water body diversity. Coastal wetlands, deltas and alpine lakes arise as diversity hot spots, with altitude being a major factor in determining species distribution and richness. DCA ordination of the BDBC relevés also showed a high relevé dispersion for some submerged macrophyte associations like Potametum denso-nodosi, which can be explained either by inaccuracy when defining the association or by an erroneous identification of some relevés. Moreover, the compiled relevés come from a 8% of the studied territory, indicating that much effort has to be devoted to the study of these communities and their distribution.

Submersed vegetation is a common feature in about 70% Pyrenean high mountain (>1500 m a.s.l.) lakes. Isoetids and soft-water elodeids are common elements of this underwater flora and can form distinct vegetation units (i.e. patches of vegetation dominated by different species) within complex mosaics of vegetation in shallow waters (<7 m). Since isoetids exert a strong influence on sediment biogeochemistry due to high radial oxygen loss, we examined the small scale characteristics of the lake environment (water and sediment) associated to vegetation patches in order to ascertain potential functional differences among them. To do so, we characterised the species composition and biomass of the main vegetation units from 11 lakes, defined plant communities based on biomass data, and then related each community with sediment properties (redox and dissolved nutrient concentration in the pore water) and water nutrient concentration within plant canopy. We also characterised lake water and sediment in areas without vegetation as a reference. A total of twenty-one vegetation units were identified, ranging from one to five per lake. A cluster analysis on biomass species composition suggested seven different macrophyte communities that were named after the most dominant species: Nitella sp., Potamogeton praelongus, Myriophyllum alterniflorum, Sparganium angustifolium, Isoetes echinospora, Isoetes lacustris and Carex rostrata. Coupling between macrophyte communities and their immediate environment (overlying water and sediment) was manifested mainly as variation in sediment redox conditions and the dominant form of inorganic nitrogen in pore-water. These effects depended on the specific composition of the community, and on the allocation between above- and belowground biomass, and could be predicted with a model relating the average and standard deviation of sediment redox potential from 0 down to -20 cm, across macrophyte communities. Differences in pore-water total dissolved