Search

Here, we present the data obtained from the samples collected in a field campaign during the spring of 2015 which aims for a better understanding of the diversity and distribution patterns of freshwater diatoms in Madeira Island. Following European and Portuguese standards and recommendations for routine diatom sampling and analysis, we collected samples in 40 sites, distributed in 27 permanent streams and identified the diatom species present, using general diatom floras and studies in Portuguese freshwater diatoms. Little is known about the diversity and distribution of freshwater diatom assemblages from Madeira Archipelago. This study reports a survey in 40 sites in Madeira Island distributed in 27 permanent streams. A total of 965 diatom (Bacillariophyta) occurrences were recorded, belonging to 130 different taxa from 44 genera and 27 families. The families with the highest number of occurrences were Bacillariaceae (176), Achnanthidiaceae (135) and Naviculaceae (133). The two diatom endemisms, described previously in Madeira Island (Lange-Bertalot 1993), Nitzschia macaronesica Lange-Bertalot and Navicula madeirensis Lange-Bertalot, were only observed in a small number of sites, located mostly at Laurissilva forest. Sixty species are new records, not only to Madeira Island, but also to the Madeira Archipelago.

Shredders play a crucial role in litter decomposition in streams. However, in oceanic islands, many streams have low shredder density and richness, and microbes seem to be the main litter decomposers. Here, we evaluate the effects of shredders and aquatic hyphomycetes on litter decomposition in insular streams. Three leaf species differing in physical and chemical characteristics, Alnus glutinosa, Clethra arborea, and Cryptomeria japonica, were enclosed in bags of coarse and fine mesh to allow and avoid macroinvertebrate access to the litter, respectively, and incubated in six streams along a gradient of Limnephilus atlanticus (Trichoptera) density in Sao Miguel Island. In streams with higher L. atlanticus density, leaf mass loss was higher in coarse than fine mesh bags. However, no difference in litter mass loss was found between bag types in streams with no L. atlanticus, despite the presence of other shredder taxa. These results suggest that when L. atlanticus are present at relatively high densities, they significantly contribute to litter decomposition, while litter decomposition is mainly driven by microbes when L. atlanticus density is low, or they are absent. Moreover, litter decomposition depends on litter quality, with leaves with high nutrient concentration and low concentration of secondary compounds being preferred by shredders.

Freshwater diversity from Desertas islands (Madeira archipelago, Portugal) is poorly known, although the islands are protected and became a Natural Reserve in 1995. To fulfil this gap, several freshwater and terrestrial habitats were sampled during two field expeditions in 2013 and 2014 to Deserta Grande island. Our aim was to perform a biodiversity assessment of the freshwater biota present in Desertas islands. Here we present the freshwater and terrestrial diatom diversity in Deserta Grande island, including some notes on their ecology and distribution. This study contributes to improve the knowledge of Madeira archipelago freshwater diversity, particular in the Desertas subarchipelago. To our knowledge, we present the first diatom data for the Desertas sub archipelago. This work resulted in a list of 61 diatom taxa for Deserta Grande, from which 57 identified to species level. From the 61 new records for Desertas sub archipelago, 30 of them were also new records for Madeira archipelago. The majority of the species are strictly associated with freshwater, but several others are typically found in brackish environments revealing the influence of sea spray in inland surface water bodies of Deserta Grande, especially at lower altitudes.

The authors acknowledge COST Action ES 1105 "CYANOCOST Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management" and COST Action Global Change Biology ES 1201 NETLAKE -Networking Lake Observatories in Europe" for contributing to this study through networking and knowledge sharing with European experts in the field. We acknowledge the members of the Global Lake Ecological Observatory Network (GLEON) for their collaborative spirit and enthusiasm that inspired the grassroots effort of the EMLS. E.M. was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis. We thank Pieter Slot for assisting with the pigment analysis. We thank Dr. Ian Jones for valuable feedback on an earlier version of the manuscript. We thank the Leibniz Institute of Freshwater Ecology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart, and the Leibniz Association for financial support. H.P. was supported by the US National Science Foundation (1840715, 1831096). A.C.'s work was funded by the Spanish Agencia Estatal de Investigacion and EU funds through the project CLIMAWET (CGL2015-69557-R). The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland. We are grateful to Kristiina Vuorio from the Freshwater Centre of the Finnish Environment institute for her help in organizing, collecting and analysing samples by the University of Jyvaskyla and to Gerald Dorflinger from the Water Development Department of Cyprus for his assistance with the sampling in Cyprus and for granting the CUT team permission to use WDD's equipment. Finally, we would like to thank the numerous other assistants that helped realizing each local survey. Open access funding provided by Universite de Geneve., To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature., European Cooperation in Science and Technology (COST) ES 1105 ES 1201, Swiss State Secretariat for Education, Research and Innovation, University of Geneva, Leibniz Association, National Science Foundation (NSF) 1840715 1831096, Spanish Agencia Estatal de Investigacion, European Commission CGL2015-69557-R, Department of Agriculture, Environment and Rural Affairs, Northern Ireland

Background: Testate amoebae are a polyphyletic group of protists living preferentially in soils, freshwaters and wetlands. These Protozoa have a worldwide distribution, but their presence and diversity in the Azores (a remote oceanic archipelago) is poorly known, with only twelve taxa recorded so far. The published information reflects occasional collections from sporadic field visits from naturalists to São Miguel Island, mainly in the nineteenth century. To overcome this limitation, a standardised survey was carried out on the Island, sampling different types of habitats from several localities to provide the distribution and information on species ecology of testate amoebae. New information: In this study, 43 species of testate amoebae were recorded (within a total of 499 occurrences), belonging to two orders of Protista (26 Arcellinida and 17 Euglyphida). The most frequently occurring testate amoebae were Euglypha strigosa, Trinema lineare, Euglypha rotunda, Assulina muscorum and Cyclopyxis eurystoma. The most diverse genus was Euglypha (six species). A total of 38 species are new records for the Azores Archipelago. These data help to improve knowledge of the geographical distribution of testate amoebae in the northern hemisphere and their diversity in the Azores Archipelago This work was funded by FCT – Foundation for Science and Technology, the European Union, QREN, FEDER, COMPETE programmes (PMR - DL57/2016/ICETA/EEC2018/25; MSS - ICETA/EEC2018/25; DiscoverAzores Project - PTDC/CTA-AMB/28511/2017; UID/BIA/50027/2020 and POCI-01-0145-FEDER-006821), AZORESBIOPORTAL – PORBIOTA (ACORES-01-0145-FEDER-000072) and Consolidation and Structuring Project 2018 GRC-ED431C 2018/32 of Xunta de Galicia government SI

Background Aquatic hyphomycetes are a phylogenetically heterogeneous group of fungi living preferentially in fast flowing, well-aerated forest streams. These fungi have worldwide distribution, but with the exception of Articulospora tetracladia , no aquatic hyphomycete taxon was previously recorded on Madeira Island. Aquatic hyphomycetes were sampled from 40 sites, distributed by 27 permanent streams in 2015, to provide the distribution of aquatic hyphomycetes in Madeira Island streams. New information In this study, a total of 21 species of aquatic hyphomycetes were recorded belonging to three classes of Ascomycota . All taxa are new records for Madeira Archipelago, except Articulospora tetracladia and four are reported for the first time in Macaronesian biogeographic region.

The Azores are oceanic islands located in the Northern Atlantic Ocean and are particularly rich in aquatic systems, ranging from freshwater, brackish, marine and thermal habitats. Due to the increase in local anthropogenic pressures and global warming, several azorean lakes began to reveal signs of eutrophication that led to the implementation of monitoring programmes and management strategies on the most impacted lakes. Later, the Water Framework Directive (2000/60/EC) demanded the establishment of biomonitoring programmes for European freshwater ecosystems and the limited Azorean monitoring programmes were extended to a larger set of lakes. Since the establishment of the aquatic systems monitoring programme in the Azores archipelago, lakes have been regularly sampled, producing innumerous unpublished records of cyanobacteria that are difficult to access. Here we present the occurrences of cyanobacteria in Azorean lakes that result from 22 years of phytoplankton monitoring in a total of 1948 cyanobacteria occurrences from 968 phytoplankton sampling events on Azorean lakes done between 1996 and 2018 as part of regional inland aquatic ecosystems monitoring programmes. Forty two cyanobacteria taxa were identified in those events, 28 species and 14 at genus level. This information is crucial for conservation, biodiversity studies and lake management, as some of the cyanobacteria species present are bloom-forming and have the ability to produce toxins. This will also allow for the identification of invasive species and possible targeted control and mitigation programmes, according to the species present in the Azorean lakes.

Until recently, the distribution of diatom and chironomid assemblages and their attributes (species richness/diversity) in relation to water depth and sedimentary environments have been identified but not quantified. The influence of environmental variables on assemblage distribution and taxa richness in a deep, monomictic lake in São Miguel Island is assessed. Attention is given to community variation along a water-depth gradient. Sediment core samples were analysed for diatom content, chironomids, and grain-size clastic particles along three transects from the shoreline to the central deep basin of the lake at a resolution of 1 m water depth. Linear and unimodal regressions were used to test taxon richness, taxon diversity and taxon evenness versus water depth of each transect. A hump-shaped relationship between species richness and water depth was noted, with a peak occurring at mid-depth, meaning that samples located at that depth better represented the total subfossil assemblage living in lake Azul. Moreover, data indicate that both assemblages in Lake Azul, and taphonomic effects, were influenced by processes of clastic transport depending on the lake morphology. Results from this study allow us to access the spatial distribution of biological assemblages in clastic-dominated lakes with a high topographic gradient, and provide us with principal criteria that will allow us to determine coring locations that capture the true species diversity for studies in lakes. © 2018, Springer International Publishing AG, part of Springer Nature., Acknowledgements Part of this study was financed by Fundac¸ão para a Ciência e Tecnologia (SFRH/BPD/99461/2014) and the PaleoNAO, RapidNAO and PaleoModes projects of the Spanish Ministry of Education (CGL2010-15767, CGL2013-40608-R and CGL2016-75281-C2-1-R, respectively). We deeply thank to Nora Richter for the revision of the English along the manuscript. We also thank the two anonymous reviewers whose comments/suggestions helped improve and clarify this manuscript. Finally, we are grateful to the Freshwater Ecology Group from the University of the Azores for all the help in field and laboratory work. The surveys performed comply with the current laws of Portugal.

Oceanic freshwater communities tend to be species poor but rich in endemism due to their physical isolation. The ecology of endemic freshwater species is, however, poorly known. This study assessed allometric relationships, feeding preferences, growth and survival of larvae of the endemic stream insect Limnephilus atlanticus (Trichoptera, Limnephilidae) exposed to four leaf species differing in their physical and chemical characteristics (Ilex perado, Morella faya, Alnus glutinosa and Clethra arborea), in laboratory trials. All regression models used to estimate L. atlanticus dry mass from body and case dimensions and wet mass were significant, but wet mass and body length were the best predictors. Limnephilus atlanticus consumed all the four leaf species offered, but when given a choice, shredders significantly preferred A. glutinosa over the other three leaf species. Relative larval growth rate was significantly higher when L. atlanticus fed on A. glutinosa and I. perado leaves in comparison with the other leaf species. Survival of 95% was found when individuals fed on A. glutinosa leaves while it decreased to 75% when they fed on the other leaf species. Our results suggest that L. atlanticus can be an active shredder and that it exhibits the same basic patterns of food exploitation as its continental counterparts. The lack of an effect of shredders on litter decomposition in Azorean streams revealed by previous studies may thus be due to low densities or to a preference for food resources other than the low quality native litter species.

Raposeiro et. al., Little is known about the effect of top predator introduction in historically fishless communities, especially on remote islands. This issue is important because it might strongly affect climate reconstructions derived from biota assemblages such as chironomids. Head capsule larval remains of chironomids have been studied in a 660 years lacustrine sedimentary sequence from Lake Azul (Sao Miguel Island, Azores archipelago) to assess the extent and timescale of the effect of the predator introduction occurring in this historically fishless lake. Analysis of similarity showed that the chironomid assemblage was statistically different before and after predator introduction (R = 0.78; p < 0.001). Abundance of chironomids was about 40% greater in the fishless lake period compared to the period in the presence of predator. Results show major change in chironomid assemblage coinciding with the first time of goldfish introduction (around 1790 CE), followed by carp (1890 CE) and pike (1979 CE) introductions. The composition of feeding group guilds changed following a pattern characterized by a decrease in abundance of detritivorous and predaceous taxa and an increase in abundance of grazing chironomid taxa. This study suggests that predator introduction was the most important factor affecting the chironomid assemblages in this natural, Azorean fishless lake, but predators did not affect all chironomid species. Other external forcings like major climate oscillations, anthropogenic activities in the catchment basin, and volcanic eruptions seem to play an additional role. The latest stage of the warm and arid Medieval Climate Anomaly (1000–1300 CE) favoured the occurrence of some warm-adapted chironomid taxa, which were absent through the Little Ice Age (ca. 1450–1850 CE) cool period. © 2016, Part of this study was financed by the Fundo Regional da Ciência e Tecnologia (M3.1.7/F/009/2011) and the PaleoNAO and RapidNAO projects of the Spanish Ministry of Education (CGL2010-15767 and CGL2013-40608-R, respectively). PMR was supported by Fundação para a Ciência e Tecnologia (SFRH/BPD/99461/2014). AH was supported by the Portuguese Science Foundation (FCT) through a post-doctoral grant (SFRH/BPD/79923/2011). This work was also funded by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and by National Funds through FCT - Foundation for Science and Technology under the UID/BIA/50027/2013 and POCI-01-0145-FEDER-006821.

The decomposition of leaf litter of terrestrial origin is a fundamental process in aquatic ecosystems in forest contexts. Little is known about what drives leaf litter decomposition in oceanic islands. We examined the relative importance of leaf litter identity (Acacia melanoxylon, Pittosporum undulatum, Morella faya) and environmental conditions on litter decomposition in seven lakes in the oceanic archipelago of Azores for 28 and 56 days. Leaf litter was incubated in coarse and fine mesh bags for the assessment of the relative contribution of macroinvertebrates to leaf litter decomposition. Leaf litter mass loss generally did not differ between mesh sizes, suggesting that in these lakes macroinvertebrates generally have a negligible role on leaf decomposition. Leaf litter decomposition was in the order M. faya

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains. © 2018 by the authors. Licensee MDPI, Basel, Switzerland., The authors acknowledge COST Action ES 1105 “CYANOCOST—Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE—Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from the University of Geneva. We thank Clare Ahnlund, Ena Suarez and Irene Gallego for helping out with the Swiss survey. We thank Wendy Beekman and Els J. Faassen for the nutrient and toxin analysis.

Following environmental changes, communities disassemble and reassemble in seemingly unpredictable ways. Whether species respond to such changes individualistically or collectively (e.g. as functional groups) is still unclear. To address this question, we used an extensive new dataset for the lake communities in the Azores' archipelago to test whether: 1) individual species respond concordantly within trophic groups; 2) trophic groups respond concordantly to biogeographic and environmental gradients. Spatial concordance in individual species distributions within trophic groups was always greater than expected by chance. In contrast, trophic groups varied non-concordantly along biogeographic and environmental gradients revealing idiosyncratic responses to them. Whether communities respond individualistically to environmental gradients thus depends on the functional resolution of the data. Our study challenges the view that modelling environmental change effects on biodiversity always requires an individualist approach. Instead, it finds support for the longstanding idea that communities might be modelled as a cohort if the functional resolution is appropriate.

It has been widely reported that shredders play an important role in leaf decomposition, especially in continental temperate streams. However, the paucity of shredders in many oceanic island streams leads to a greater contribution of microbes to litter decomposition in these streams. In this study, we investigated the importance of shredder presence and density (three levels) and leaf litter identity (Alnus glutinosa, Clethra arborea and Acacia melanoxylon) on leaf litter decomposition in one stream located in the Azores Archipelago. Coarse and fine mesh bags were used to allow natural colonisation of leaf litter by benthic macroinvertebrates or to exclude macroinvertebrates respectively. Treatments with one and three shredders were accomplished by enclosing one or three shredders in the fine mesh bags. Rates of litter decomposition differed significantly among shredder density treatments only for A. glutinosa and C. arborea. Decomposition rates were significantly faster for the natural within-stream shredder density treatment than for other shredder treatments. Shredder density differed significantly among litter species, being higher in A. glutinosa than in C. arborea and A. melanoxylon. The results indicate that when shredders are present at high densities in oceanic island streams they can substantially contribute to the decomposition of high-quality leaf litter, whereas the decomposition of hard leaf litter is mostly performed by the microbial community.