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Este artículo contiene 5 páginas, 3 figuras., Small fish species such as minnows (Phoxinus sp.) are introduced into mountain lakes by anglers that use them as live bait for fishing salmonids that were previously introduced in these naturally fishless habitats. Introduced fish severely impact native biota but minnows are nevertheless released believing to provide forage for game fish, i.e., salmonids. However, our results indicate that minnows negatively interact with game fish, reducing their relative densities. On some occasions, minnows can remain the only present fish following trout extinction. We believe that this information should be urgently disseminated among anglers as a pragmatic argument to also convince anglers less sensitive to conservation issues that carrying minnows to the mountains is not a good idea whatever the main interest is, e.g., nature conservation or outdoor recreation., Funding was provided by the EU Projects LIFE BIOAQUAE (LIFE11 BIO/IT/000020) and LIFE LIMNOPIRINEUS (LIFE13 NAT/ES/001210), LIFE RESQUE ALPYR (LIFE20 NAT/ES/000369), MONOCLE (H2020-CLIMATE/ 0357), and Biodiversa FISHME (BiodivRestor-280), and by the Spanish Government projects FUNBIO (RTI2018- 096217-B-I00) and BIOOCULT (2413/2017).

Acknowledgements This study was funded by the European Commission, under the LIFE Nature and Biodiversity program, as part of the project LIFE-DIVAQUA (Proyecto LIFE18 NAT/ES/000121). We also like to thank all the Spanish government agencies and research institutions who provided information, answered the questionnaires and participated in the workshop “Synthesis of the monitoring programs of global change in aquatic ecosystems SMNP: Autonomous Organism of National Parks, MAPAMA-Dir. Gral. Agua, Universidad de Granada, Instituto Universitario de Investigación del Agua, (IdeA-UGR), Universidad Politécnica de Madrid, CISE-P.N. Sierra de Guadarrama, Fundación Biodiversidad, CEAB-CSIC, IGME, MNCN-CSIC, Universidad de Córdoba, Universidad de Barcelona and ICTA-UAB. We also like to thank the 28 European Nation Parks who responded our query. The authors finally thank the support provided by Christoph Wohner in the use of the DEIMS-SDR., Electronic supplementary material The online version contains supplementary material available at https://doi.org/10.1007/s10531-022-02466-x., Data Availability The datasets used to review the monitoring programs at the Global scale conducted in the ILTER nodes that are included in Rivers (ILTER-Rivers) or Lakes (ILTER-Lakes) are available at the DEIMS dataset registry (DEIMS-SDR) (for more details see: Wohner et al. 2019; https://deims.org/). The datasets used to review the monitoring programs at the European scale conducted in the EMNP are available by requesting them via email to the corresponding EMNP. The datasets used to review the monitoring programs at the National scale conducted in the five SMNP are mostly included in this article and it supplementary information file. In addition, meteorological data recorded by the Spanish Global Change Monitoring Network in available at the Meteorological data download web application (https://www.miteco.gob.es/es/redparques- nacionales/red-seguimiento/acceso-datos.aspx). Further and more detailed information is available from the corresponding author on reasonable request., Funding This study was carried out with the financial support of the EU LIFE programme, as part of the project LIFE-DIVAQUA (Proyecto LIFE18 NAT/ES/000121). The information showed in this publication only reflects the point of view of the authors. The European Comission and CINEA cannot be held responsible for any use which be made of the information contained here. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature., Identifying and quantifying global change impacts on biotic and abiotic components of ecosystems is critical to promote an effective adaptation that increases the success of conservation strategies. To achieve this goal, global and regional assessment efforts require certain degree of harmonization on local monitoring programs to establish relevant comparisons at different spatio-temporal scales. Otherwise, the lack of harmonization might hinder the detection and assessment on the effects of human impacts. In this work we have compiled information on freshwater monitoring programs located in areas of intensive research and conservation interest: International Long Term Ecological Research (ILTER) nodes and mountain National Parks. We aimed at evaluating the quality and robustness of these programs to assess the impact of global change, addressing from the worldwide to the European and Spanish national scale. Results highlighted that freshwater monitoring programs lack a common strategy to monitor these ecosystems. Even at the continental and national scales, contrasting strategies and level of detail have been historically applied. Water quality, habitat and biodiversity are more commonly monitored than community structure and ecosystem functioning. Monitoring efforts on the Spanish Mountain National parks indicated differences on the targeted aquatic ecosystems. Rivers and lakes received a higher attention, while mires were rarely considered. Our results provide evidence that greater efforts should be directed towards constructing a coordinated strategy to monitor freshwater ecosystems at national, continental, and global scales. This strategy should involve a shared backbone of biophysical and biogeochemical variables for each habitat type on agreed protocols that are implemented across regions and administrative borders. Achieving this will support a substantial advance on the ecological research to further delineate proper conservation strategies to face the challenges imposed by global change., European Commission LIFE18 NAT/ES/000121

Este artículo contiene 10 páginas, 2 figuras, 1 tabla., [EN]The corixid Sigara (Subsigara) distincta (Fieber, 1848) in the Pyrenees: a first record for Spain and an unsolved taxonomic puzzle The occurrence of Sigara (Subsigara) distincta (Fieber, 1848) in Spain is reported for the first time based on specimens collected in the Pyrenean municipality of Vielha e Mijaran (Central Pyrenees). Multiple captures between 2014-2018 indicate that S. distincta successfully established itself in Lake Vilac (1640 m a.s.l.), a small mesotrophic water body under Atlantic climate. High-throughput sequencing (HTS) technologies are valuable tools for freshwater bioassessment and detection of rare taxa. A DNA metabarcoding study carried out on macroinvertebrate samples supported the presence of S. distincta in the lake, thus corroborating morphological identification of imagines and greatly facilitating the identification of immature stages, which otherwise would be a difficult if not impossible task. By means of DNA barcode sequencing of individuals from Lake Vilac, we detected a rare haplotype of S. distincta previously recorded in Northern Germany. Our sequences showed to be clearly segregated from other publicly available S. distincta sequences, according to phylogenetic analysis. The results support the hypotheses of the existence of two highly divergent S. distincta lineages across Europe. A major taxonomic revision of Subsigara Stichel, 1935 species, combining both molecular and morphological approaches will be needed to shed light on the causes of high genetic intraspecific variation in S. distincta and related species.[ES]El coríxido Sigara (Subsigara) distincta (Fieber, 1848) en los Pirineos: una primera cita para España y un rompecabezas taxonómico no resuelto Se reporta por primera vez para España la especie Sigara (Subsigara) distincta (Fieber, 1848), en base a individuos recolectados en el municipio pirenaico de Vielha e Mijaran (Pirineos centrales). La captura de individuos durante 2014-2018 indica que S. distincta se ha establecido con éxito en la laguna de Vilac (1640 m s.n.m.), una pequeña masa de agua mesotrófica bajo la influencia de clima atlántico. Las tecnologías de secuenciación de alto rendimiento (HTS) demostraron ser herramientas valiosas para la monitorización de ecosistemas acuáticos continentales y la detección de taxones raros. Un estudio de metabarcoding llevado a cabo sobre las muestras de macroinvertebrados de la laguna apoyó la presencia de S. distincta, corroborando la identificación morfológica de los imagos y facilitando en gran medida la identificación de estadios inmaduros, que de otra forma hubiera sido muy difícil, si no imposible, identificar. Mediante la secuenciación del código de barras genético de individuos de la laguna de Vilac, detectamos un raro haplotipo previamente registrado en el norte de Alemania. Nuestras secuencias mostraron estar claramente segregadas respecto otras secuencias de S. distincta disponibles públicamente, según los análisis filogenéticos. Los resultados apoyan la hipótesis de la existencia de dos linajes altamente divergentes de S. distincta en Europa. Una revisión taxonómica de las especies de Subsigara Stichel, 1935, combinando aproximaciones moleculares y morfológicas, será necesaria para aportar más información sobre las causas de la alta variabilidad genética intraespecífica de S. distincta y las especies cercanas., This work was funded by the European Commission LIFE+ project LIMNOPIRINEUS (LIFE13 NAT/ES/001210), and the Spanish Government projects FUNBIO (RTI2018-096217-B-I00) and BIOOCULT (2413/2017).

1. Invasive alien species are among the most important threats to biodiversity. Plans for their eradication have been implemented worldwide but estimating residual population size and eradication probability to assess removal success is complicated by the imperfect detection of residual individuals. 2. Most methods to assess residual abundance and eradication probability rely on the often unrealistic assumption that a population is closed to mortality and recruitment processes during the implementation of removal actions. We extended existing removal models and developed a novel analytical approach to estimate residual population size and derive eradication probability in open populations, while accounting for multiple removal methods. 3. We apply this approach to 20 eradication projects in Europe and the United States that used mechanical methods to return high mountain lakes to their original fishless condition. 4. The new removal model incorporates i) a mechanistic description of the ecological process underlying survival and recruitment probabilities during the eradication period, and ii) the use of multiple, concomitant removal methods (i.e., electrofishing, gillnetting, fyke-netting) at multiple sites simultaneously. 5. We used a subset of “control” lakes where eradication success was confirmed by more than 5 years of post-removal surveys to validate the model. For these lakes, eradication success, evaluated by whether the 95% Bayesian credible interval for estimated residual population size encompassed values of less than 2 individuals, was confirmed in 13 out of 15 lake-by-species case studies. In addition, the model correctly assigned an eradication probabilities equal to 0 for the eradications that are still in progress. 6. Synthesis and applications. Our study provides insights into the dynamics of fish populations subject to eradication in high mountain lakes of different countries. In addition, the analytical approach proposed accounts for demographic processes and multiple removal methods in multiple sites and seasons. It can represent an informative tool to estimate residual population size and eradication probability of alien species to optimize eradication efforts and efficacy of conservation actions. The extension to open populations makes the approach useful to evaluate long-term eradication plans.

In alpine biogeographic regions, aquatic and semi-aquatic habitats are important biodiversity reservoirs and habitats for species of community interest, but they are often threatened by multiple factors. The conservation state of protected habitats and species in the EU is expected to worsen as long as no actions or conservation strategies are implemented. LIFE RESQUE ALPYR aims to restore mountain aquatic habitats by improving the conservation of several target habitats/species in four Nature 2000 sites from the alpine biogeographical regions of the Pyrenees (in northeastern Iberian Peninsula) and the Alps (in northwestern Italy). The target habitats include eleven aquatic and semi-aquatic habitats, of which five are prioritary: high mountain lakes (HCIs 3110 and 3130), alpine and subalpine grasslands, heaths and meadows (HCIs 4020*, 6230*, 6410, and 6520), mires (HCIs 7110*, 7140, 7230, and 91D0*) and petrifying springs (HCI 7220*). The target species include native amphibians found either in both areas (Rana temporaria) or solely in the Pyrenees (Euproctus asper and Alytes obstetricans); the semi-aquatic mammal Galemys pyrenaicus living in Pyrenean streams and lakes; and seven insectivorous bats, including Barbastella barbastellus, Myotis myotis, and Plecotus macrobullaris, which are present in the Pyrenees and the Alps, and Rhinolophus hipposideros, Myotis blythii, Myotis bachsteinii, and Nyctalus lasiopterus from the Pyrenees. The target habitats and most of the target species have naturally fragmented distributions, occurring in small areas of the European alpine biogeographic zone, and are affected by anthropogenic pressures. The introduction of trout or minnows in most alpine lakes caused the disappearance of native amphibians and invertebrates at local and landscape scales, indirectly affecting aquatic mammals and terrestrial species, such as bats, that rely on aquatic insects for feeding. Minnows can also cause the strong eutrophication of lakes, leading to drastic habitat degradation. The affected habitats and species are HCIs 3110 and 3130, R. temporaria, E. asper, A. obstetricans, G. pyrenaicus, R. hipposideros, P. macrobullaris, B. barbastellus, M. myotis, M. blythii, M. bachsteinii, and N. lasiopterus. The proposed actions and methods with regard to fish species involve the experimental eradication of non-native fish in high mountain lakes by means of both chemical (rotenone) and mechanical methods (traps, nets, and electrofishing). The project will provide data regarding replicable and exportable conservation actions and will increase awareness of pertinent conservation issues among stakeholders and the public. In addition, the project will promote the transfer of its background data and results to conservation authorities concerned with other European high mountain areas., This research was funded by the European Comission grant number LIFE20.

Paleoclimatological information derived from the study of lacustrine sedimentary records is not only biased by taphonomical processes but also by potential differences in the expression of climate variability in the sediments due to site-specific factors. Using a multiproxy approach (the elemental and isotopic compositions of organic matter, diatom assemblages, and marker pigments of algae and cyanobacteria), we study the different environmental signatures recorded since the Little Ice Age (LIA) in the sediments of two volcanic lakes located within the same caldera on S~ao Miguel Island (Azores Archipelago). Lake Santiago is a crater lake whose eutrophic status in the last stage of the LIA was linked to external nutrient inputs associated with this humid period. Its post-LIA evolution was forced by changes in the thermal structure of the water, which determined its degree of mixing and therefore nutrient availability through recycling from the hypolimnion. In contrast, the decadal to centennial limnological evolution of Lake Azul, a caldera lake 2.5 km from Lake Santiago, shows geochemical and micropaleontological signatures disconnected from climate variability until 1980/1990 CE due to its greater exposure to the fallout of tephra after a catastrophic eruption in c. 1290 CE. Only after 1980/1990 CE did a global warming scenario induce a common ecological restructuring of both lakes, involving the replacement of turbulence-loving algal taxa by species adapted to strengthening water column stratification. Nevertheless, this shift was relatively gradual in Lake Azul but more sudden in Lake Santiago, indicating that the local site-specific components still had an effect on the expression of climate change in the sediments. Despite the short history of anthropogenic pressure (compared to their continental counterparts) and the large atmospheric patterns operating over the Azores Archipelago, the sedimentary records of these two adjacent oceanic volcanic lakes reacted quite differently to climate changes., Spanish Ministry of Economy and Competitiveness projects PaleoNAO, RapidNAO and PaleoM-odes CGL 2010-15767 CGL 2013-40608-R, Fundacao para a Ciencia e a Tecnologia (FCT) PTDC/CTA-AMB/28 511/2017, Xunta de Galicia, European Social Fund (ESF), Spanish Ministry of Science and Innovation through the Ramon y Cajal Scheme RYC 2020-029253-I, Fundacao para a Ciencia e a Tecnologia (FCT) DL57/2016/ICETA/EEC 2018/25, Universidade da Coruna/CISUG

Este artículo contiene 9 páginas, 5 figuras, 1 tabla., 1. Introduced fish are a widespread ecological threat in originally fishless high mountain lakes. However, basic distribution data are largely missing for most high mountain regions. 2. Using time-consuming standard methods (e.g. Nordic standard fishing nets) to assess fish distribution and relative densities at a relevant spatial scale can be impracticable, because of the large number of high mountain lakes. To overcome this problem, alternative rapid monitoring methods would be helpful. 3. Visual encounter survey (VES) is a candidate method that enables observing fish from the shoreline. It takes only minutes to implement and is already widely used for amphibian monitoring in high mountain lakes and ponds. VES was evaluated as a method for monitoring introduced salmonids and cyprinids (the most widespread fish families) in 52 high mountain lakes. 4. The probability of detecting both families by VES rapidly approaches 100% as the relative densities of fish increase, and false absences are restricted to populations living at low relative densities. VES also provides simple indications about fish relative densities, distinguishing between high-density and low-density populations. 5. As VES usually does not enable fish species identifications, we propose VES as a useful method to describe large fish distribution inventories, not needing high taxonomic detail, but necessary for planning large-scale conservation measures., Funding was provided within the framework of the EU Projects LIFE BIOAQUAE (LIFE11 BIO/IT/000020), LIFE LIMNOPIRINEUS (LIFE13 NAT/ES/001210), LIFE RESQUE ALPYR (LIFE20 NAT/ES/000369), and Biodiversa FISHME (BiodivRestor-280), and of the Spanish Government projects FUNBIO (RTI2018-096217-B-I00) funded by MCIN/AEI/10.13039 and BIOOCULT (2413/2017) funded by MTERD/OAPN and by “ERDF A way of making Europe.” Additional funding was provided by the Confederaci on Hidrográfica del Ebro, Mont Avic Natural Park, and the University of Pavia.

Worldwide, increasing amounts of dams and weirs have been established in rivers in recent decades, often with drastic effects on their ecosystems. Between late 2009 and 2011, 16 large-scale dams were built in the main channels of the four largest rivers in South Korea, eight of these along the main channel of Nakdong River (300 km, 520 km in total). We studied the effect of these constructions on the fish community in the riparian zone based on intensive fish field surveys conducted in the littoral zone during 2007–2017, analysis of fishermen's catch data and molecular analysis of the diet of the keystone species, largemouth bass (Micropterus salmoides). Our results, based on RDA and GLM analyses, showed that environmental characteristics and fish species composition changed significantly with dam construction. Total fish abundance and biomass decreased after the start of the weir construction and fish richness decreased with time. The abundance and biomass of exotic fish decreased during construction but recovered afterwards, leading to higher proportions of exotics. Dominance and Shannon indices did not change significantly from before to after construction, while the Evenness index showed a significant decreasing trend. A comparison of the diet composition of largemouth bass showed decreasing genetic variation after construction. The changes in Functional Feeding Group (FFG) of the benthic communities at the study sites did not coincide with FFG changes in the prey items of largemouth bass, indicating a transition in feeding mode from before to after construction. In conclusion, the endemic and native fish species were most sensitive and showed lower resilience to disturbance by the large-scale dam construction than the translocated and exotic species, and the lake-like ecosystems after construction markedly improved the competitive capacity of these exotic fish over the native and endemic species in the riparian zone of the river.

Este artículo contiene 10 páginas, 4 figuras, 1 tabla., Despite being naturally fishless, the widespread introduction of trout and minnows is threatening the conservation of high mountain lakes all over the world. Previous studies have reported that amphibians quickly disappear after trout introduction, followed by many conspicuous invertebrates. Here, we have studied the effects of minnows versus trout on the littoral macroinvertebrate community of 54 high mountain lakes from the Pyrenees, covering a gradient of environmental characteristics. The relative importance of fish compared to other variables in explaining macroinvertebrate communities was assessed using distance-based redundancy analysis (dbRDA) and multivariate regression tree (MRT) to find the main environmental thresholds. Both dbRDA and MRT approaches revealed that minnow density was the most important variable negatively determining community structure, followed by aquatic macrophytes, which increased taxa richness. The occurrence and abundance of relevant taxa was analysed in relation to fish densities and other environmental factors using binomial and gamma generalized linear models (GLM). GLM suggested that trout had an impact on the distribution of swimmer taxa and caused declines in the abundance of conspicuous clinger and burrower taxa. Minnows restricted the occurrence of more taxa than trout and negatively affected a wide variety of body sizes and functional groups. Indeed, we found that minnows were responsible for a dramatic biodiversity loss in the littoral macroinvertebrate community. The fast spread of minnows in high mountain areas is of great concern for the conservation of lake macroinvertebrates. Urgent measures to stop minnow introductions are strongly recommended., Economic support was provided by the European Commission LIFE + LIMNOPIRINEUS (LIFE13 NAT/ES/001210), LIFE RESQUE ALPYR (LIFE20 NAT/ES/00347), BiodivERsA FISHME (BiodivRestor-280) and FUNBIO (RTI2018-096217-B-I00) funded by MCIN/AEI/10.13039/ 501100011033 and BIOOCULT (2413/2017) funded by MTERD/OAPN and by “ERDF A way of making Europe”

Este artículo contiene 19 páginas, 6 figuras, 1 tabla., Thermal variables are crucial drivers of biological processes in lakes and ponds. In the current context of climate change, determining which factors better constrain their variation within lake districts become of paramount importance for understanding species distribution and their conservation. In this study, we describe the regional and short-term interannual variability in surface water temperature of high mountain lakes and ponds of the Pyrenees. And, we use mixed regression models to identify key environmental factors and to infer mean and maximum summer temperature, accumulated degree-days, diel temperature ranges and three-days’ oscillation. The study is based on 59 lake-temperature series measured from 2001 to 2014. We found that altitude was the primary explicative factor for accumulated degree-days and mean and maximum temperature. In contrast, lake area showed the most relevant effect on the diel temperature range and temperature oscillations, although diel temperature range was also found to decline with altitude. Furthermore, the morphology of the catchment significantly affected accumulated degree-days and maximum and mean water temperatures. The statistical models developed here were applied to upscale spatially the current thermic conditions across the whole set of lakes and ponds of the Pyrenees., The authors want to aknowledge the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya and the European Social Fund for the doctoral scholarship FI (2015FI_B_01147) given to the first author, that has allowed this work. The projects provided by the Spanish Government projects; Fundalzoo (CGL2010-14841) and Invasivefish (427/2011) and by the European Commission LIFE+ project LimnoPirineus (LIFE13 NAT/ES/001210), and also the last project of the Spanish Government, FUNBIO (RTI2018-096217- B-I00) supported this research., With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI).

Este artículo contiene 8 páginas, 2 tablas, 3 figuras., Amphibians of high mountain lakes face many threats related to global change, including novel pathogens, development, climate change and overexploitation. However, the foremost threat is the presence of non-native fish. One of the objectives of the LIFE+ LIMNOPIRINEUS project (2014–2019) was the recovery of protected amphibian communities (including the endemic Calotriton asper) in eight naturally fishless Pyrenean high mountain lakes, by controlling or eradicating non-native trout or minnows. During the summer months of 2015 to 2019, we removed 95–100% of the fish present in these lakes, and monitored changes in their amphibian populations, as well as surveyed 56 nearby control lakes with or without fish. We found rapid natural recovery of amphibian communities as fish removal work progressed. The fish-removal lakes achieved typical richness figures for the area one year after fish removal began, and typical species abundances after three years (with the only exception of Rana temporaria). We documented a total of 16 colonisation events, all by amphibian species from the same valley. The two earliest colonisation events were observed in the year in which fish removal began, with eight events the following year. The lack of colonisation from nearby valleys in the study period highlights the crucial role of nearby residual populations not affected by human impacts. We show that whole amphibian communities from high mountain lakes recover rapidly after eliminating or reducing non-native fish, proving that this is a powerful tool to improve the conservation status of endangered amphibians., Economic support was provided by the European Commission LIFE + project LIMNOPIRINEUS (LIFE13 NAT/ES/001210), and by the Spanish Government projects FUNBIO (RTI2018-096217-B-I00) and BIOOCULT (2413/2017).

Este artículo contiene 6 figuras, 4 tablas., Historical factors (colonization scenarios, demographic oscillations) and contemporary processes (population connectivity, current population size) largely contribute to shaping species’ present‐day genetic diversity and structure. In this study, we use a combination of mitochondrial and nuclear DNA markers to understand the role of Quaternary climatic oscillations and present‐day gene flow dynamics in determining the genetic diversity and structure of the newt Calotriton asper (Al. Dugès, 1852), endemic to the Pyrenees. Mitochondrial DNA did not show a clear phylogeographic pattern and presented low levels of variation. In contrast, microsatellites revealed five major genetic lineages with admixture patterns at their boundaries. Approximate Bayesian computation analyses and linear models indicated that the five lineages likely underwent separate evolutionary histories and can be tracked back to distinct glacial refugia. Lineage differentiation started around the Last Glacial Maximum at three focal areas (western, central and eastern Pyrenees) and extended through the end of the Last Glacial Period in the central Pyrenees, where it led to the formation of two more lineages. Our data revealed no evidence of recent dispersal between lineages, whereas borders likely represent zones of secondary contact following expansion from multiple refugia. Finally, we did not find genetic evidence of sex‐biased dispersal. This work highlights the importance of integrating past evolutionary processes and present‐day gene flow and dispersal dynamics, together with multilocus approaches, to gain insights into what shaped the current genetic attributes of amphibians living in montane habitats., Economic support was provided by the European Commission LIFE+ project LimnoPirineus (LIFE13 NAT/ES/001210), by the Spanish Government project Funbio (RTI2018-096217-B-I00), by the Interreg POCTEFA ECTOPYR project (EFA031/15) and by the Societas Europaea Herpetologica (SEH, research grant awarded to F.L.). F.L. had a doctoral grant funded by Fundação para a Ciência e Tecnologia (FCT, grant number PD/BD/52598/2014). M.D. is research Director at Fonds de la Recherche Scientifique – FNRS.

Este artículo contiene 13 páginas, 6 figuras, 1 tabla., Varved sediments provide unique opportunities to carry out high-resolution paleoclimatic and paleoenvironmental reconstructions with accurate time control. To better interpret the sediment record it is necessary to understand the physical, chemical and biological factors that influence varve formation and preservation. We explored the link between the annual limnological cycle and current varve deposition in the oligotrophic hardwater Lake Montcortès (Central Pyrenees). The varves of this lake consist of couplets of dark organic and light calcareous laminae. A two-year limnological monitoring (10/2013–10/2015) combined with a sediment trap study were conducted at monthly resolution. Limnological and sedimentological measurements were compared with meteorological data. Although the lake was considered meromictic in the first limnological studies, we documented total mixing of the water column both winters. In spite of this, long periods of stratification and hypolimnetic anoxia create suitable conditions for varve formation and preservation. Sediment deposition followed a clear seasonal pattern related to biological processes in the euphotic zone. During summer and fall, calcite precipitation was favored by high calcite saturation indices and enhanced primary production that promoted relatively high pH values as a result of CO2 uptaking. There was considerable variability in the amount of calcite deposition between years, which was linked to seasonal temperature differences. In addition, calcite crystal sizes and diatom fluxes showed seasonal patterns related to calcite saturation index and changes in water stratification, which in turn were also related to temperature variability. Seasonal sedimentation patterns were strongly linked to primary producers and especially sensitive to temperature shifts. It results in a clear seasonal signal and varve formation. We compared our results with previous sedimentological interpretations of the varved record of this lake. This study improves the interpretation of Lake Montcortès sediment record extending back several millennia., This work was funded by the Ministry of Economy, Industry and Competitiveness (project MONT-500; reference CGL2012-33665 with an associated pre-doctoral research grant (FPI; BES-2013-065846); PI: Teresa Vegas-Vilarrúbia) and the Catalan University and Research Management Agency (AGAUR, project 2014 SGR 1207, PI: Meike Köhler).

Este artículo contiene 23 páginas, 10 figuras., In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of di erent modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Di erent biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortès as a case study and proposing new working hypotheses for future research., Research funding was granted by the Spanish Ministry of Economy and Competitivity (MINECO/FEDER) with the projects MONT-500, ref. CGL2012-33665; GLOBALKARST, ref. CGL2009-08145), the Institute of Catalan Studies with the projects PIRIMOD and POLMONT, and the Catalan University and Research Management Agency (AGAUR) with the projects 2014 SGR 1207, 2017 SGR 1116).

Seagrass ecosystems, which have important functions such as coastal protection and blue carbon sequestration, are threatened by anthropogenic pressure including climate change. Long-term data series from seagrass sedimentary archives (mats) can be used to understand natural cycles of environmental change and answer key questions related to contemporary management. A 7500 yr sediment record from Posidonia australis meadows in Oyster Harbour (Albany, SW Australia) was subjected to multiproxy reconstruction by means of pigment analysis (UHPLC), analytical pyrolysis (Py-GC–MS), carbonate content, δ13C and δ15N stable isotope ratios, organic C (Corg) content, Corg/N ratio and glomalin-related soil proteins (GRSP). The study revealed a brackish lagoon (7500–7000 cal yr BP) that was transformed in an open marine environment (7000–4100 cal yr BP) due to Holocene transgression. Earliest evidence of seagrass establishment was detected around 4500 cal yr BP, and meadow extension accelerated between 4100 and 3700 cal yr BP. The meadow environment was surprisingly resistant against environmental perturbations, as the mat, composed of P. australis seagrass fibres embedded within a siliciclastic mineral matrix containing biogenic carbonates, continued to develop steadily until 190 cal yr BP (1830 CE). Then, shifts in several proxies (pigments, GRSP) showed evidence of terrestrial runoff-triggered eutrophication/turbidity (likely driven by forest clearance and agricultural activities after European settlement), but the seagrass showed resilience (no decline of the proportion of seagrass-derived Corg). By contrast, since ~1930 CE seagrass retreat is evident in the biogeochemical record: lighter δ13C values, lower lignin abundance and shifts in pigment abundance and types, affecting the balance between seagrass inputs and alternative sources, as was observed in previous studies of the area. The findings show that pigment proxies are useful early indicators of shifts in seagrass ecosystem condition, while lignocellulose and other pyrolysis products are useful proxies of more profound ecosystem alterations that influence seagrass abundance. The record indicates that the climax seagrass ecosystem condition, which prevailed for several millennia, had been impacted over the last century. Management of seagrass and coastal ecosystems should aim to avoid crossing ecological thresholds and diminish local impacts aggravating those of global change.

Este artículo contiene 16 páginas, 6 figuras, 5 tablas., Non-native fish invasions threaten native fauna and ecosystem functioning, not least in isolated island lakes. In Tasmania, where the native fish are mostly galaxiids, 9 non-native freshwater fish species have been introduced over the past 150 years, with uncertain ecological outcomes. We evaluated the effects of non-native predatory fishes (NNPF) and various environmental and biological variables on the trophic niche of native fish (galaxiids) and potential cascading effects. We analysed Layman’s food web metrics based on both stable isotope (δ15N and δ13C) values and fish stomach contents in 14 shallow Tasmanian lakes along a NNPF abundance gradient. The food web metrics calculated were (1) range of δ13C (CR) and δ15N (NR) centroid distance (CD) and (2) standard ellipse area. Our results showed that NNPF relative abundance in the fish catch per unit effort was negatively related to the galaxiids’ trophic niche metrics (e.g., CRG, NR G, and CDG), trophic position, and the pelagic contribution to the diet. Moreover, the proportion of galaxiids in the diet of NNPF was higher in turbid lakes. The zooplankton standard ellipse area was negatively correlated with the pelagic contribution to the NNPF diet, and NNPF relative abundance was positively correlated with the maximum body size of calanoid copepods. While our results suggest a negative effect of NNPF on the trophic niche of galaxiids, the cascading effect on phytoplankton biomass was weak. Non-native predatory fish affect native fish prey, and the outcome of these interactions should be considered for conservation purposes, particularly for island lakes, such as those in Tasmania., The project was funded by Galathea 3, Carlsberg, Research Council of Nature and Universe (272-08-0406), the TK Foundation, Dronning Margrethes og Prins Henriks Fond, Torben og AliceFrimodts Fond, Christian og Ottila Brorsons Rejselegat, University of Copenhagen and Aarhus University. MM and NV were funded by SNI-ANII and the L’Oréal UNESCO Women for Science national award with support of DICYT, Uruguay. MV was supported by a Marie Curie post-doctoral grant (MEIF-CT-2005-010554) and TB by a Beatriu de Pinós post-doctoral grant (2005 BP-A 1004). EJ was supported by the MARS project (Managing Aquatic Ecosystems and Water Resources Under Multiple Stress) funded under the EU 7th Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), CIRCE and CRES. LAB was supported by the Australian Research Council (LP130100756). CT is a CONICET (Argentinean Council of Science) researcher; Fondation L’Oréal; Sistema Nacional de Investigadores (UY).

In the Quaternary paleosciences, the rationale behind analogical inference presupposes that former natural changes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesise synthetize the results of different modern analog studies and discuss their value to obtain the best inferences from high resolution past records. This synthesis is based on the following: 1) The monthly monitoring of calcite precipitation reveals a strong connection with primary producers and between-years variability; this precipitation produces a seasonal signal with imprint on varve formation. 2) Clear pollen sedimentation peaks occur in spring/summer and fall/winter that coincide with temperature, precipitation, relative humidity and winds; this pattern converges with the two-layer coupled varves representing the same seasonality. 3) We assess the lake’s contemporary oxygenation dynamics over a three- year period; a combination of sedimentary REDOX proxies revealed different scenarios of oxic/anoxic shifts since 1500 CE. 4) We investigate presence of seasonality in the production/distribution of glycerol dialkyl glycerol tetraethers and derived temperature estimates in soils and particulate matter. Branched glycerol dialkyl glycerol tetraethers signatures and some derived temperature estimates proxies appear to mainly depend on the non-seasonal shifts in soil properties. 5) Currently we examine relationships and similarities between extant phytoplankton and derived pigments in water and traps, and their correspondence with subfossil pigments; some preliminary results are presented here.Keywords: high resolution, endogenic varves, calcite precipitation, pollen sedimentation, meromixis, freshwater glycerol dialkyl tetraether, subfossil pigments, long-term ecology.

14 páginas, 2 tablas, 10 figuras., Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed formost pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns., This work was funded by the Ministry of Economy and Competitivity (project MONT-500; reference CGL2012-33665; PI: Teresa Vegas-Vilarru´bia).

Este artículo contiene 16 páginas, 6 figuras, 3 tablas., 1. Pigments in lake surface sediments integrate both benthic and pelagic primary producer composition at the whole‐lake ecosystem level. 2. We gathered a comprehensive set of water chemistry, morphometric, physical and biological lake variables, catchment and climate characteristics, and geographical descriptors. We used multiple regressions to relate whole‐lake algal pigment concentration to environmental conditions and multivariate statistical analyses to assess the factors most associated with photoautotrophic algal and bacterial community composition. The relative influence of environmental factors and spatial distribution was assessed by variance partitioning analysis among three groups of variables: (1) in‐lake factors, (2) external factors, and (3) geographic descriptors. 3. Pigment concentration and community composition were most sensitive to in‐lake factors. Pigment‐inferred abundance of algae, including cyanobacteria, tended to be highest in shallower systems with high nutrient concentrations, independent of the latitudinal temperature or irradiance gradients. Pigment‐inferred community composition was best explained by nutrients and biotic composition (zooplankton and fish communities). Only in maritime temperate lakes did a link with regional location occur due to their low dissolved inorganic nitrogen to soluble reactive phosphorus ratios (1.5 atomic ratio), suggesting nitrogen limitation of phytoplankton growth; accordingly, the sediment pigments revealed cyanobacteria to be the dominant group, although this may also be a consequence of the overall high nutrient levels in these 4. Despite the large climate gradient covered, in‐lake rather than external factors were associated with the patterns observed in pigment concentration (from benthic and pelagic microorganisms) and inferred composition and abundance in these shallow lakes. Our results suggest that pigment assemblages in sediments, which integrate both benthic and pelagic microbial photoautotrophic community and processes, are valuable indicators of changes in shallow (0.75–12 m depth) lake ecosystems., This research was funded by a post‐doctoral Beatriu de Pinós grant from the Departament d'Universitats, Recerca i Societat de la Informació, Generalitat de Catalunya (T.B.). Further support came from The Netherlands Organization for Scientific Research (NWO) grant W84‐549 and WB84‐586, The National Geographic Society grant 7864‐5; in Brazil by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) grants 480122, 490409, 311427; in Uruguay by PEDECIBA, Maestría en Ciencias Ambientales, Donación Aguas de la Costa S.A., and Banco de Seguros del Estado. N.M. was supported by Sistema Nacional de Investigadores. E.J. was supported by the MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change) and AU Centre for Water Technology (watec.au.dk).

Este artículo contiene 11 páginas, 8 figuras, 5 tablas., Submersed aquatic plants are a key component of shallow, clear water lakes contributing to primary production and water quality. High mountain lakes are naturally fishless although invasive trout and most recently minnows have been introduced causing a major impact on fauna richness. The Pyrenean high mountain range has preserved soft-water oligotrophic boreal isoetids in their southern limit of distribution but the recent fish introduction is a potential factor of stress that needs to be addressed. We here work under the hypothesis that due to contrasting ecological features, trout will not be heavily affecting quillwort populations while minnows will have a stronger effect on zooplankton and zoobenthos that will promote algal growth and reduce light availability for the underwater meadows. Ten Pyrenean shallow lakes representative of three scenarios -fishless, with trout and with minnows-, were sampled for meadow structure, water column and benthic environment characterization in mid-summer 2015 and 2016. Quillwort biomass allocation (above vs. belowground), epiphytic load, and composition of the algal community (abundant cyanobacteria) differed in the presence of minnows. In trout lakes biomass allocation and epiphytic load were average and the algal community composed by chlorophytes and diatoms as in fishless lakes. Biomass ratio was close to thresholds of negative buoyancy in minnow lakes indicating that meadows were at risk of uprooting and consequent de-vegetation. Total and soluble carbohydrates were lower and the sporangia contained significantly less reserves to constrain growth and expansion in the presence of minnows. Lake scenarios were coupled to physicochemical differences with low light, high phosphorus and Chl-a (mesotrophia) in minnow lakes, while trout and fishless lakes remained oligotrophic. This is the first study assessing the impact of non-native fish on soft-water isoetids from mountain lakes and shows that minnows are a major threat to quillworts. The impaired light environment (from epiphytic algal overgrow and water column Chl-a) entails consequent regression (i.e., no recruitment) and de-vegetation (uprooting) of themeadows. Since soft-water oligotrophic mountain lakes are protected under the Habitats Directive, some action needs to be urgently implemented not only to preserve quillworts but to the overall ecological integrity of the lakes., This work was funded by the European Commission LIFE+ project LimnoPirineus (LIFE13 NAT/ES/001210), EU H2020 eLTER ref. 999452014-EAA, and by Grup de Recerca de Canvis Ambientals GECA (SGR-DGR), Generalitat de Catalunya. SGR 1249. 2017-2020.

High mountain lakes are originally fishless, although many have had introductions of non-native fish species, predominantly trout, and recently also minnows introduced by fishermen that use them as live bait. The extent of these introductions is general and substantial often involving many lakes over mountain ranges. Predation on native fauna by introduced fish involves profound ecological changes since fish occupy a higher trophic level that was previously inexistent. Fish predation produces a drastic reduction or elimination of autochthonous animal groups, such as amphibians and large macroinvertebrates in the littoral, and crustaceans in the plankton. These strong effects raise concerns for the conservation of high mountain lakes. In terms of individual species, those adapted to live in larger lakes have suffered a higher decrease in the size of their metapopulation. This ecological problem is discussed from a European perspective providing examples from two study areas: the Pyrenees and the Western Italian Alps. Species-specific studies are urgently needed to evaluate the conservation status of the more impacted species, together with conservation measures at continental and regional scales, through regulation, and at local scale, through restoration actions, aimed to stop further invasive species expansions and to restore the present situation. At different high mountain areas of the world, there have been restoration projects aiming to return lakes to their native fish-free status. In these areas autochthonous species that disappeared with the introduction of fish are progressively recovering their initial distribution when nearby fish-free lakes and ponds are available.

Este artículo contiene 16 páginas, 9 figuras., Recent expansion of anoxia has becomea global issue and there is potential forworsening under global warming. At the same time, obtaining proper long-term instrumental oxygen records is difficult, thus reducing the possibility of recording long-term changes in oxygen shifts that can be related with climate or human influence. Varved lake sediments provide the better time frame to study this phenomenon at high resolution. We tracked the oxic/anoxic shifts of the varved LakeMontcortès since 1500 CE, and tried to recognise anthropogenic and climatic influences combining biological and geochemical proxies. Four main scenarios emerged: 1) years with abrupt sediment inputs (A); 2) years with outstanding mixing and oxygenation of the water column (B); 3) years with strong stratification, anoxia, intense sulfur bacterial activity and increased biomass production (C); 4) yearswith stratification and anoxia, but relatively less biomass production (D). In line with current limnologic trends, high supra-annual variability in the occurrence of oxygenation events was observed. Interestingly, at least 45.3% of the years were mixing years and, like the meromictic ones, were mostly clustered into groups of consecutive years, thus alternating years of monomixis with years of meromixis. Most years of D belong to the period 1500–1820 CE, when human activities were the most intense. Most years of A belonged to the climatic unstable period of 1850–1899 CE. Years of B were irregularly distributed but were best represented in the period 1820–1849 CE.Most years of C belonged to the 20th century. More than 90% of the years with climatic instrumental records belonged to B and C. Current climate warming seems to be taking control over the oxygenation capacity of the lake, especially since the second half of the 20th century. Our results support recent findings related to hypoxia spreading at the global scale., Funding was granted by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (projects MONT-500, ref. CGL2012-33665; GLOBALKARST, ref. CGL2009-08145), the Institute of Catalan Studies (PIRIMOD and POLMONT), and the CatalanUniversity and Research Management Agency (AGAUR) (project 2014 SGR 1207). Training research grantswere awarded toM. Carmen Trapote and Núria Pérez-Zanón and funded by MINECO (BES-2013-065846) and the University Rovira i Virgili (Martí Franquès program, 2104PMF-PIPF-22), respectively.

The composition of algal species and pigments and the structural and functional characteristics of the algal community were investigated in an acid stream of southwestern Spain, the Rio Tinto. The algal community had low diversity and showed few seasonal differences. It was mainly made up of Klebsormidium flaccidum Kutz. (Silva, Mattox & Blackwell) that produced long greenish or purplish filaments, Pinnularia acoricola Hust. (producing brown patches) and Euglena mutabilis Schmitz. The algal filaments made up a consistent biofilm that also included fungal hyphae, iron bacterial sheaths, diatoms, and mineral particles. HPLC analyses on Rio Tinto samples showed that undegraded chl accounted for 67% of the total chl in the filamentous patches but were a minority in the brown patch (2.6%). The brown patch had a concentration of carotenoids eight times lower than that observed in the green patch. When chl concentrations were weighted for the proportion of the different patches on the streambed, undegraded chl a accounted for 89.2 mg

10 páginas, 4 figuras., Increases in atmospheric temperature and nutrients from land are thought to be promoting the expansion of harmful cyanobacteria in lakes worldwide, yet to date there has been no quantitative synthesis of long-term trends. To test whether cyanobacteria have increased in abundance over the past ~ 200 years and evaluate the relative influence of potential causal mechanisms, we synthesised 108 highly resolved sedimentary time series and 18 decadal-scale monitoring records from north temperate-subarctic lakes. We demonstrate that: (1) cyanobacteria have increased significantly since c. 1800 CE, (2) they have increased disproportionately relative to other phytoplankton, and (3) cyanobacteria increased more rapidly post c. 1945 CE. Variation among lakes in the rates of increase was explained best by nutrient concentration (phosphorus and nitrogen), and temperature was of secondary importance. Although cyanobacterial biomass has declined in some managed lakes with reduced nutrient influx, the larger spatio-temporal scale of sedimentary records show continued increases in cyanobacteria throughout the north temperate-subarctic regions., This project was funded by the Natural Sciences and Engineering Research Council of Canada (I.G.-E., P.R.L., F.P., R.D.V.), Fonds Qu eb ecois de Recherche sur la Nature et les Technologies (Z.E.T.), Canadian Foundation for Innovation (I.G.-E., P.R.L.), Canada Research Chair (P.R.L.), Fundaci o Bosch i Gimpera, Universitat de Barcelona (T.B.), EU project BIOMASS (T.B., J.C.), Catalan government (GECA, 2014SGR1249) (T.B., J.C.), Spanish government (NitroPir, CGL2010-19373) (J.C.), Nexdata Project (P.G., A.L., G.M.), EU INTERREG IIIA (S.M., M.A.S.), Cheshire Wildlife Trust and Natural England (S.M.), UK Environment Agency and Freshwater Biological Association (S.M.), Engineering and Physical Sciences Research Council and Environment Agency (H.M.), International Commission for the Protection of Italian Swiss Waters (P.G., A.L., G.M.), ‘IperRetro’ ANR VULNS- 005 (I.D.), SOERE OLA IS (I.D.) data collection by INRA, CIPEL, CISALB and SILA (I.D.), EDYTEM for the sediment core LDB09_P2-02 code IGSN : EDYLDB005 (I.D.), and the Alberta Ingenuity Water Research grant (P.L.T., R.D.V.).

The ecosystem response of Lake Redo (Central Pyrenees) to fluctuations in seasonal air temperature during the last two centuries was investigated by comparison of reconstructed air temperatures with the sediment record. Fine slicing allowed a resolution of 3–6 years according to the 210Pb dating, although it was still difficult to easily investigate the response to air temperature forcing, since extreme fluctuations in temperature occur on interannual time-scales. However, the resolution was sufficient to show responses on decadal and century scales. An overall tendency to warming in mean annual temperature in the Central Pyrenees has been caused by summer and in particular by autumn increases. Many of the measured sediment variables apparently responded to these long term trends, but the significance of the relationships was highly conditioned by the structure of the data. The variables responding most on the finer time scales were the microfossils. For diatoms, chironomids and chrysophytes the main variability correlated to summer and to autumn temperatures. For two planktonic species, Fragilaria nanana and Cyclotella pseudostelligera, we found a link of their variability with temperature fluctuations in their growing months (September and October, respectively). This relationship appeared at a certain point during a general warming trend, indicating a threshold in the response. On the other hand, no significant changes in the dominant species could be linked to temperature, nor in any significant subgroup of the 180 diatom species present in the core. In contrast, for most chironomids (particularly Paratanytarsus austriacus, Heterotrissocladius marcidus and Micropsectra radialis) a negative relationship with summer temperature extended throughout the studied period. This response of the whole group gives chironomids a more robust role as indicators for recording temperature changes on long time-scales (e.g., through the Holocene) and for lake signal inter-comparison. Finally, our results indicated that, in all cases, there was a significant resilience to high frequency changes and hysteresis despite extreme fluctuations. Although we were dealing with organisms with one or many generations per year, their populations seemed to follow the decadal trends in air temperature.

Weather variation and climate fluctuations are the main sources of ecosystem variability in remote mountain lakes. Here we describe the main patterns of seasonal variability in the ecosystems of nine lakes in Europe, and discuss the implications for recording climatic features in their sediments. Despite the diversity in latitude and size, the lakes showed a number of common features. They were ice-covered between 5–9 months, and all but one were dimictic. This particular lake was long and shallow, and wind action episodically mixed the water column throughout the ice-free period. All lakes showed characteristic oxygen depletion during the ice-covered-period, which was greater in the most productive lakes. Two types of lakes were distinguished according to the number of production peaks during the ice-free season. Lakes with longer summer stratification tended to have two productive periods: one at the onset of stratification, and the other during the autumn overturn. Lakes with shorter stratification had a single peak during the ice-free period. All lakes presented deep chlorophyll maxima during summer stratification, and subsurface chlorophyll maxima beneath the ice. Phosphorus limitation was common to all lakes, since nitrogen compounds were significantly more abundant than the requirements for the primary production observed. The major chemical components present in the lakes showed a short but extreme dilution during thawing. Certain lake features may favour the recording of particular climatic fluctuations, for instance: lakes with two distinct productive periods, climatic fluctuations in spring or autumn (e.g., through chrysophycean cysts); lakes with higher oxygen consumption, climatic factors affecting the duration of the ice-cover (e.g., through low-oxygen tolerant chironomids); lakes with higher water retention time; changes in atmospheric deposition (e.g., through carbon or pigment burial); lakes with longer stratification, air temperature changes during summer and autumn (e.g., through all epilimnetic species).

14 páginas, 5 figuras, 2 tablas., Among the environmental factors affecting benthic algae and cyanobacteria in streams, the one often producing the largest effects is flow intermittency. This study aimed to characterize the responses of algal assemblages to flow intermittency in a Mediterranean intermittent stream during the drying, non-flow (112 days), and rewetting phases. Algae growing in the epilithic, epipsammic and hyporheic streambed compartments were analyzed for pigment composition, and for the existence of structural changes in cells. Chlorophyll-a concentrations decreased between 60 to 90 % during the non-flow phase, indicating low resistance of algal assemblages to desiccation. In contrast, fast recoveries of Chlorophyll-a when flow resumed indicated high resilience. Pigment composition revealed that the epilithic algal assemblage was considerably different than the epipsammic and hyporheic ones. These differences were mainly attributed to the physical conditions prevailing on each streambed compartment that allowed the growth of different algal assemblages. During the non-flow phase, the synthesis of protective carotenoids (i.e. echinenone and scytonemin) and the occurrence of cell resistance structures (i.e. enlarged membrane thickness and resistant spores) enhanced resistance of the epilithic biofilm. The resistance observed in the epilithic biofilm might also be related to the tightly adhered growth-form of algae on this substratum. Main results suggest that algal assemblages in the epilithic compartment, which were the most exposed to desiccation, were structurally and functionally better adapted to flow interruption than those colonizing other streambed compartments, and that this compartment plays a crucial role in maintaining ecosystem functions under varying flow periods., Xisca Timoner was recipient of a PhD fellowship from the Spanish Ministry of science and technology (AP- 2007-01945), and Teresa Buchaca was partially supported by the Spanish Government project Invasive fish (427/2011). This research was funded by the projects SCARCE (CONSOLIDER-INGENIO CSD2009-00065), and CARBONET (CGL2011-30474-C02-01) of the Spanish Ministry of Science and Innovation.

Lake ecosystems are nowadays often subjected to multi-stressors, such as eutrophication, climate change, and fish manipulations, the effects of which can be difficult to disentangle, not least from the usual short-term limnological time-series that are available. However, multi-proxy paleoecological approaches may offer such opportunities, especially in the study of remote island lakes characterized by being species poor and buffered somewhat against the recent climate change. We used a paleoecological multi-proxy approach to determine the relative importance of nutrient loading, meteorological forcing, and fish species introduction for recent lake ecosystem development in Lake Furnas on the island of São Miguel, the Azores. The lake was stocked with cyprinids in the late nineteenth century and recently also with piscivorous fish, and has been affected by increasing agricultural activities in its catchment. We analyzed marker pigments, cladoceran remains, and subfossil diatoms in a 46-cm core representing the last 40 years. Remains of large-bodied cladocerans were virtually absent until the introductions of piscivorous pike and pikeperch in 1980 and 1982, respectively, after which the zooplankton community composition changed abruptly. First Ceriodaphnia sp. appeared (ca. 1980), followed by Daphnia a few years later. Carotenoids from cyanobacteria (myxoxanthophyll, aphanizophyll) were regularly present in the lake sediment with a major shift occurring around 1994, from N2-fixing to non-fixing groups. This shift coincided with the onset of anoxia in the lake water, evidenced by the presence of pigments from Chlorobiaceae (BChl-e homologues and isorenieratene), and with a rapid decrease in benthic-tychoplanktonic diatoms and an increase in cyanobacteria, chlorophytes, dinoflagellates, and cryptophytes. The composition of microbial and algal assemblages changed rapidly after Daphnia appearance, and the covariance between fish stocking, nutrient loading, and enhanced temperatures captured most of the variability in algae accumulation, and thus likely in lake primary production as well. Thus, lake production apparently did not respond strongly to specific changes in temperature, food-web structure, or nutrient input, but rather to the combined effects of all the three forcing mechanisms, emphasizing the role of multi-stressors in lake ecosystem functioning. Our study demonstrates the sensitivity of these remote species-poor lakes to increased nutrient loading, introduction of non-native species, such as fish and climate change.

Fish introduction may have marked effects on the trophic dynamics and ecological state of former fishless lakes, but due to scarcity of historical data this can seldom be documented. We used remains of cladoceran, chironomid and pigment assemblages in the sediment archive to unravel the effect of introduction of carp (Cyprinus carpio), rainbow trout (Oncorhynchus mykiss) and a cyprinid (Chondrostoma oligolepis) in Lake Fogo, the Azores (Portugal). The stratigraphical record showed two major shifts in community assemblage coinciding with the time of introduction of carp (AD ca. 1890) and trout (AD 1941), respectively. Carp introduction was followed by an abrupt and major decline in the abundance of chironomids, a shift in the cladoceran community from a benthic to a more pelagic dominated community, and Daphnia size was significantly reduced. Pigment assemblages also indicated a shift from a benthic to a pelagic dominated ecosystem, as cryptophytes became markedly more abundant at the expense of benthic diatoms. Trout introduction was followed by a return to a more benthic cladoceran and benthic algae (pigments) dominated state, which we attribute to trout predation on carp leading to improved water clarity. A steady increase in the abundance of pigments and cladoceran remains followed, suggesting enhanced productivity, which may be attributed to enhanced atmospheric nitrogen deposition and introduction of C. oligolepis. We conclude that fish introduction has profoundly altered the trophic dynamics and the relative importance of benthic and pelagic production in this species poor and natural fishless lake in the Azores, and likely in most others lakes at the archipelago islands as fish stocking has been a widespread practice.

15 páginas, 7 figuras, 2 tablas., This study compares the marker pigment composition in three different lake compartments: the water column; the surface sediment biofilm (0–0.5 cm), where production and main degradation processes take place; and the deep sediment (15–17 cm), where the signal is finally stored and marker pigments are used as a proxy in paleolimnological studies. The aim was to evaluate which marker pigments better record in the sediment the relative contributions of planktonic and benthic production in high mountain lakes, taking into account the differential preservation existing among pigments. A survey of 82 high mountain lakes distributed along the major environmental gradients was carried out in the Pyrenees. Comparison of pigments between the three compartments revealed that both water column and sediment biofilm signals could be distinguished in old sediment layers, despite the observation that some of the most characteristic carotenoids that appeared frequently and in high concentrations in the water column were already less common or even absent from the sediment biofilm. In the shallowest lakes, pigment composition in the sediment biofilm was typical of photosynthetically active communities and their deep sediment samples were characterised by a substitution of fucoxanthin by diatoxanthin as the dominant diatom marker pigment. However, in the deepest lakes the pigment composition of the sediment biofilm and deep sediment was similar, characterised by marker pigments of mainly planktonic algal groups and pheophytins, which are typical pigments of decaying communities. Results are discussed in terms of how pigment source (planktonic or benthic) and pigment type (lability of molecule) interact to shape pigment composition in the sediment record of high mountain lakes., The study was supported by the European Union within the framework of the EMERGE (Contract No. EVK1-CT-1999–00032) and EUROLIMPACS (GOCE-CT-2003–505540).

15 páginas, 5 figuras, 4 tablas., 1. Surface sediment biofilm samples from 82 Pyrenean lakes were analysed for marker pigment composition using high performance liquid chromatography (HPLC). 2. Variability in the pigment composition among lakes was investigated by multivariate statistical analyses using a large data set of factors describing lake chemical, physical, morphological and catchment characteristics. 3. Due to the widely varying light penetration in the lakes, the most significant gradient of pigment composition extended from a benthic to a planktonic signal. The most important pigments in the gradient were alloxanthin (cryptophytes marker pigment, planktonic signal) and diatoxanthin (diatoms marker pigment, benthic signal). The molar ratio between these two marker pigments was positively correlated with lake depth. 4. Chlorophyll-a preservation was found to be positively related to light penetration and the development of an autothrophic biofilm on the surface sediment and negatively related to decreasing pH and the percentage of alpine meadows in the lake catchments. 5. Zooplankton marker pigments in the surface sediment, including grazing by-products (e.g. phaeophorbides) and carotenoids (astaxanthin, canthaxanthin, echinenone) incorporated into their tissues, were correlated with the areal abundance of zooplankton. 6. Marker pigments for photosynthetic bacteria, BChl-e and okenone, were found mainly in relatively shallow lakes with large catchments that are forested, probably because of their higher loading of allochthonous organic matter. 7. The evaluation of a preservation index (Chl-a expressed as a percentage of a-phorbins) and the alloxanthin/diatoxanthin ratios throughout the sediment record of mountain lakes can provide evidence of historical changes in the relative importance of planktonic versus benthic primary production and might ultimately be interpreted in terms of climatic or environmental changes., The study was supported by the European Union within the framework of the EMERGE (Contract No. EVK1-CT-1999- 00032) and EUROLIMPACS (GOCE-CT-2003-505540).

11 páginas, 4 tablas, 4 figuras., Assessment of the contribution of distinct algal groups to phytoplankton biomass in oligotrophic lakes by marker pigments is compared with assessment by cell-counting biovolume estimates. Seasonal samples from an oligotrophic alpine lake (Redon, Pyrenees) mostly included species of chrysophytes, dinoflagellates, cryptophytes and chlorophytes. The chlorophyl a (Chl a) corresponding to each algal group was estimated using HPLC pigment analyses and the CHEMTAX program. Chl a estimates and biovolume showed a significant correlation for all the groups during the ice-free season except for chlorophytes. However, some of the samples from the initial phase of the ice cover presented a clear departure from the relationship during the ice-free period in most groups. On the other hand, the ratios between a specific marker pigment and the biovolume of the marked algal group were significantly constant within the photic zone (>1% surface irradiance) for most of the pigments and groups, including chlorophytes. Nevertheless, the ratios increased and showed a large variability for samples below the photic depth or below the ice cover. The violaxanthin-chrysophyte biovolume ratio presented an opposed tendency to other pigment-biovolume ratios, which increased in inverse proportion to the depth of the sample. The results are discussed in terms of methodological limitations, acclimation responses and species composition., This study was supported by the European Union (Contract No. ENV4-CT95-007) within the framework of the European Union Environment and Climate project MOLAR (Measuring and modelling the Dynamic Response of Remote Mountain Lake Ecosystems to Environmental Change: a Program of Mountain Lake Research).

Lake Issyk-Kul constitutes one of the most important economic resources in the Republic of Kyrgyzstan, with more than 100 recreational centers along its shore. Some 370,000 holidaymakers visit the lake annually, and this number is expected to increase in the near future given the growing interest in natural environments (Romanovsky, 1990; Savvaitova and Petr, 1992). Thus, a fuller understanding of the past and present evolution of this ecosystem is essential for promoting and sustaining this natural habitat.

13 páginas, 7 figuras, 2 tablas., The Rano Aroi mire on Easter Island (also known as Rapa Nui; 27°09′S, 109°27′W, 430 m above sea level) provides a unique non-marine record in the central South Pacific Ocean for reconstructing Late Pleistocene environmental changes. The results of amultiproxy study on two cores fromthe center and margin of the Rano Aroimire, including peat stratigraphy, facies analysis, elemental and isotope geochemistry on bulk organic matter, X-ray fluorescence (XRF) core scanning and macrofossil analysis, were used to infer past water levels and vegetation changes. The chronology was based on 18 14C AMS dates for the upper 8.7 m. The extrapolated age for the base of the sequence is 70 kyr,which implies that this record is the oldest paleolimnological record on Easter Island. The recovered Rano Aroi sequence consists of a radicel peat formed primarily from the remains of sedges, grasses and Polygonaceae that have accumulated since Marine Isotopic Stage (MIS) 4 (70 kyr BP) to the present. From 60 to 40 kyr BP (MIS 3), high precipitation/runoff events were recorded as organicmud facies with lighter δ13C, low C/N values and high Ti content, indicating higher detritic input to themire. A gradual shift in δ13C bulk organic matter from −14% to −26%, recorded between 50 and 45 cal kyr BP, suggests a progressive change in local peat-forming vegetation from C4 to C3 plant types. Post-depositional Ca and Fe enrichment during sub-aerial peat exposure and very low sedimentation rates indicate lower water tables during Late MIS 3 (39– 31 cal kyr BP). During MIS 2 (27.8–19 cal kyr BP), peat production rates were very low, most likely due to cold temperatures, as reconstructed from other Easter Island records during the Last Glacial Maximum (LGM). Geochemical and macrofossil evidence shows that peat accumulation reactivates at approximately 17.5 cal kyr BP, reaching the highest accumulation rates at 14 cal kyr BP. Peat accretion decreased from 5.0 to 2.5 cal kyr BP, coinciding with a regional Holocene aridity phase. The main hydrological and environmental changes in Rano Aroi reflect variations in the South Pacific Convergence Zone (SPCZ), Southern Westerlies (SW) storm track, and South Pacific Anticyclone (SPA) locations., This research was funded by the Spanish Ministry of Science and Education through the projects LAVOLTER (CGL2004-00683/BTE), GEOBILA (CGL2007-60932/BTE) and CONSOLIDER GRACCIE (CSD2007-00067) and an undergraduate grant JAE (BOE 04/03/2008) to Olga Margalef.