Diatom preservation in peat sediments

[Abstract] This paper describes a comprehensive survey of the quality of diatom preservation in the recent sediment record from two close peatbogs but with different geomorphological features, Villaseca and La Mata (NW Spain). Twenty samples have been analysed from each core, focusing especially in the preservation of diatom frustules along the upper part of the core (from Late Glacial), which change during the main trophic events. In Villaseca peatbog, between 50 and 160 cm with high organic sediment, the diatoms are rare and bad preserved (from Boreal to present times). Between 160 and 260 cm, with a high clay content, the diatoms are abundant and well preserved (Late Glacial to Boreal). Between 50 and 200 cm (Preboreal to historical times) the diatom flora is made up of litoral species adapted to oligotrophic conditions. In La Mata the diatoms are absent from all samples except in the two samples from the upper-most part of the core where the valves are abundant but bad preserved. At this stage the diatom assemblages are also characteristic from oligotrophic and shallow waters. The data suggest that diatom preservation is controlled by the relationship between the geomorphology, the source of water and the trophic level

Registro isotópico de δ13 C y δ15 N de 12.000 años de antigüedad de Amboromena (Macizo de Andringitra, Madagascar)

[Abstract] Profiles of percent carbon, nitrogen and phosphorus, carbon/nitrogen (C/N) ratios, percent organic matter and carbonates, and stable carbon (δ13C) and nitrogen (δ15N) from a 176 cm core were used to reconstruct environments of deposition in the Amboromena basin (Madagascar)during last 12,000 yr BP. From these profiles three distinctively different stages in the basin evolution were apparent, which could have been result from the response to changes in the climatic conditions. Similar changes has been observed in other works about climate evolution in Madagascar and the African Tropics during the Late Quaternary

Diatom communities in thermo-mineral springs of Galicia (NW Spain)

[Abstract] The species composition of diatom assemblages was studied in five unpolluted thermo-mineral springs in Galicia (NW Spain). Three are considered hot and two cold, and some contain hydrogen sulphide. A total of 68 taxa (24 genera) have been recorded. The Shannon–Wiener diversity index (H′) ranged between 0.63 and 2.01. The nMDS ordination showed that diatom assemblage composition was influenced mostly by conductivity, temperature and hydrogen sulphide concentration. Diatom assemblages found in the Galician springs differed from those in springs of other geographical locations with similar physical and chemical characteristics. The most species-rich genera were Nitzschia and Achnanthidium with 10 and 8 species, respectively. Achnanthidium exiguum and Achnanthidium saprophilum had the widest distribution. Denticula thermalis and Achnanthidium caledonicum were found in environments with relatively low mineralization and low temperature, whereas Rhopalodia gibberula, Rhopalodia operculata and Fragilaria crotonensis were found in mineral-rich springs with high temperatures. Achnanthidium exiguum, A. saprophilum, Achnanthes coarctata, Achnanthes exigua var. elliptica, Mayamaea atomus, Eunotia implicata, Gomphonema minusculum, Gomphonema minutum and Cosmioneis pusilla were present in the spring with high H2S content

Postglacial evolution of the Lake of Villaseca (NW Iberian Peninsula) inferred from diatom analysis

[Abstract] The lake of Villaseca is located in the foothills of the southern Cantabrian Mountains, nearby Villaseca de Laciana (León,NWIberian Peninsula). This lake has a glacier origin and has been formed due to the obstruction of a lateral moraine of the glacier tongue that will be canalized through the Valley of Brañas de Roble. Once discovered during the Late Glacial (over 23,000 years), the linle basin beganto work as a catchment area. A 893 cm length record has been srudied. Ir shows the postglacial evolution of the lake. Most part of this record (beteween 260-893 cm) is represented by a detritic varved sedimentation, where the absence of diatoms is clear, although the pollen record is continous all through the sequence. In this period, the paleolimnological reconstruction can't be done, because the grains of pollen in the sediment proceed from an alloctonous source and they only reflect the landscape in the surroundings of the lake. With the begining of the Late Glacial the lake of Villaseca began to present an autoctonous diatom flora and the basin changed to mesotrophic and slightly alkaline conditions. The most important data proceed from the study of the diatoms succession, which points out and environment dominated by tychoplanktonic Fragilaria assemblages, only interrupted by a period ofperiphytic, acidophilous and oligotrophic assemblages. During this episode the pollen record points out a stepic vegetation, represented by Artemisia and Poaceae. During the Postglacial, the basin becomes completely filled and the number of acidophilous taxa increase. This is a typical final step of the filling process ofa lake before transforming into a bog as the presence of Sphagnum establishes

A Simple and Inexpensive Method to Gain Diatom Absolute Abundances from Permanent Mounts in Hydrobiological and Paleoecological Research

This article belongs to the Special Issue Advances in Hydrogeology[Abstract] Here, we describe and discuss a method based on microscopical field of view (FOV) area to estimate diatom absolute abundances (densities or concentrations), and we statistically verify its reliability, also comparing it to another commonly used method (microspheres). To test the new method, we purposely performed replicate counts, both with the FOV and with the microsphere method, on both subfossil and recent material (samples) from mires. Intraclass correlation (ICC) revealed a high degree of agreement between the measurements obtained for the replicates with each of the two methods, suggesting that both are reliable for measuring diatom valve concentrations. However, the FOV consistently overestimated diatom absolute abundances, as compared to the microsphere method, and the ICC value used to assess the reliability of the two methods combined suggested that the two methods cannot be used interchangeably. The FOV method is relatively simple, has a lower cost, wider applicability, higher resolution, and warrants compatibility with existing datasets. However, there may also be drawbacks, such as the potential for sample distortion during the concentration process. Therefore, it is important to carefully evaluate the strengths and limitations of the different methods before adopting one for specific research or applied questions

Heterogeneity of epiphytic diatoms in shallow lakes : implications for lake monitoring

Current diatom assessments of shallow lakes typically use littoral epiphytic diatoms as bioindicators for eutrophication pressure. However, challenges in establishing robust ecological assessments still exist because of the natural pressures that shallow lakes are subjected to which are difficult to quantify (e.g., water-level fluctuations or wave action). Information on the spatial and temporal variability of epiphytic communities within a shallow lake is limited although important for the development of robust bioassessment protocols. We compared epiphytic diatom taxa and functional group compositions between the littoral and pelagic zone of three least-disturbed shallow lakes in the northeastern part of South Africa along a temporal gradient. In comparison to the pelagic zone, the littoral zone was characterized by almost double in species richness. Temporal variability was significantly higher for littoral diatom communities and littoral water physico-chemistry than those of the pelagic. Overall, water depth was a good predictor of the epiphytic diatom taxa and functional group composition. We also found that pelagic diatom taxa and functional groups correlated better with pelagic physico-chemistry than littoral diatoms to littoral physico-chemistry. This could be attributed to un-modeled factors related to natural physical pressures that will have more of an impact on littoral habitats than less exposed pelagic habitats. Given these findings, using pelagic epiphytic diatoms as a bioindicator in shallow lake monitoring programs could be more efficient than littoral diatoms at providing robust ecological assessments due to their relatively low variability.Waterlab (Pty) Ltd. and J.C. Taylor, a recipient of South African National Research Foundation (NRF) incentive funding.http://www.elsevier.com/locate/ecolind2021-04-01hj2020Paraclinical Science

Stratification Strength and Light Climate Explain Variation in Chlorophyll at the Continental Scale in a European Multilake Survey in a Heatwave Summer

[Abstract] 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 ) 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 than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°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.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 Jyväskylä and to Gerald Dörflinger 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 GeneveEstados Unidos. US National Science Foundation; 1831096Estados Unidos. US National Science Foundation; 184071

Diatomeas epilíticas (Bacillariophyceae) de los cursos de agua corriente del NO de la península ibérica (Galicia, España)

A catalog of Bacillariophyceae for the rivers of NW of Spain is made for the first time. It includes a re-examination of the taxa reported in previous publications, taxa cited during the last years of the rivers of the Galicia-Costa Hydrographic Demarcation, and a revision of the taxonomy, in line with the systematic and nomenclature changes, which have occurred mainly in recent years. The epilethic diatoms of the river basins of Galicia-Costa were sampled during the years 2005, 2006, and 2007, in May-June and September. The study was carried out in 41 localities distributed along 31 rivers, samples were taken in upstream and downstream sections. Diatom communities were compared in all upstream sections of these rivers draining from siliceous substrates. We identified 141 taxa of diatoms from the coast of Galicia. In this paper we present 15 new citations for Galicia, two for Spain and three for the Iberian Peninsula, in addition to a new species recently described. The dominant taxa are: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, and Navicula minima. Achnanthes subhudsonis was the most abundant species during the spring and summer months. The remaining species showed no relevant changes regardless of the time of year. The results indicate that the river diatoms of Galicia are an important component of the diversity of the ecosystem.Se realiza por primera vez un catálogo de Bacillariophyceae para los ríos del NW de España. Se incluyen un nuevo examen de los táxones recogidos en publicaciones anteriores, datos de táxones citados durante los últimos años de los ríos de la demarcación hidrográfica de Galicia-Costa y una revisión de la taxonomía, en consonancia con los cambios sistemáticos y nomenclaturales, que se han producido sobre todo durante los últimos años. Se estudiaron las diatomeas epilíticas de las cuencas de los ríos de Galicia-Costa entre los años 2005, 2006 y 2007, durante dos temporadas diferentes: mayo-junio y septiembre. El estudio se llevó a cabo en 41 localidades distribuidas a lo largo de 31 ríos, donde se tomaron muestras en tramos aguas arriba y aguas abajo. Las comunidades de diatomeas de estos ríos que drenan de sustratos silíceos fueron comparadas en todos los tramos de aguas arriba. Se identificaron 141 táxones de diatomeas de la costa de Galicia. En este trabajo presentamos 15 nuevas citas para Galicia, dos para España y tres para la Península Ibérica, además de una nueva especie recientemente descrita. Los táxones dominantes son: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, y Navicula minima. Achnanthes subhudsonis fue la especie más abundante durante los meses de primavera y verano. Las especies restantes no mostraron cambios pertinentes independientemente de la época del año. Los resultados indican que las diatomeas de los ríos de Galicia son un componente importante de la diversidad del ecosistema

Phycological biodiversity at the Natural Park Serra da Enciña da Lastra (Ourense, Spain)

We have studied the phycological diversity at the Natural Park of Serra da Enciña da Lastra (Ourense, Spain) and present here the algae checklist of the Galir river, the only permanent fluvial course in the area. This geographical zone is a SCI (Site of Community Importance) and is located within an European Nature Reserve belonging to the “Nature 2000” network. Despite its environmental importance there is no previous phycological survey to this study. We collected samples in three points along the river, and measured physical and chemical water parameters (pH, conductivity, temperature, and dissolved oxygen). The checklist includes 88 taxa: 6 Cyanophyta, 4 Rhodophyta, 60 Heterokontophyta (58 Bacillariophyceae, 2 Xantophyceae), 1 Dinophyta, 2 Euglenophyta, and 15 Chlorophyta. Within the Rhodophyta we highlight the presence of Lemanea condensata, as a new record to the Iberian Peninsula. In addition, we have identified 8 new records for Galicia and 14 for OurenseSe ha estudiado la diversidad ficológica del río Galir, el único curso fluvial permanente del Parque Natural Serra da Enciña da Lastra (Orense, España). Es un Lugar de Importancia Comunitaria (LIC) incluido en la red de espacios naturales “Natura 2000”. A pesar de su importancia ambiental, no hay ningún estudio ficológico previo al presente. El catálogo de la flora ficológica incluye táxones recogidos de tres puntos del río y se han tenido en cuenta algunos parámetros físicoquímicos del agua: pH, conductividad, temperatura y oxígeno disuelto. El catálogo florístico incluye 88 táxones: 6 Cyanophyta, 4 Rhodophyta, 60 Heterokontophyta (58 Bacillariophyceae y 2 Xantophyceae), 1 Dinophyta, 2 Euglenophyta y 15 Chlorophyta. Entre las Rhodophyta destaca Lemanea condensata, por ser nueva cita para la Península Ibérica. Además, se han encontrado 8 nuevas citas para Galicia y 14 para la provincia de OrenseThis study was funded by the Consellería de Medio Ambiente e Desenvolvemento Sostible de la Xunta de Galicia (PGIDIT05RFO20002PR)S

Diatomeas epilíticas (Bacillariophyceae) de los cursos de agua corriente del NO de la península ibérica (Galicia, España)

A catalog of Bacillariophyceae for the rivers of NW of Spain is made for the first time. It includes a re-examination of the taxa reported in previous publications, taxa cited during the last years of the rivers of the Galicia-Costa Hydrographic Demarcation, and a revision of the taxonomy, in line with the systematic and nomenclature changes, which have occurred mainly in recent years. The epilethic diatoms of the river basins of Galicia-Costa were sampled during the years 2005, 2006, and 2007, in May-June and September. The study was carried out in 41 localities distributed along 31 rivers, samples were taken in upstream and downstream sections. Diatom communities were compared in all upstream sections of these rivers draining from siliceous substrates. We identified 141 taxa of diatoms from the coast of Galicia. In this paper we present 15 new citations for Galicia, two for Spain and three for the Iberian Peninsula, in addition to a new species recently described. The dominant taxa are: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, and Navicula minima. Achnanthes subhudsonis was the most abundant species during the spring and summer months. The remaining species showed no relevant changes regardless of the time of year. The results indicate that the river diatoms of Galicia are an important component of the diversity of the ecosystemSe realiza por primera vez un catálogo de Bacillariophyceae para los ríos del NW de España. Se incluyen un nuevo examen de los táxones recogidos en publicaciones anteriores, datos de táxones citados durante los últimos años de los ríos de la demarcación hidrográfica de Galicia-Costa y una revisión de la taxonomía, en consonancia con los cambios sistemáticos y nomenclaturales, que se han producido sobre todo durante los últimos años. Se estudiaron las diatomeas epilíticas de las cuencas de los ríos de Galicia-Costa entre los años 2005, 2006 y 2007, durante dos temporadas diferentes: mayojunio y septiembre. El estudio se llevó a cabo en 41 localidades distribuidas a lo largo de 31 ríos, donde se tomaron muestras en tramos aguas arriba y aguas abajo. Las comunidades de diatomeas de estos ríos que drenan de sustratos silíceos fueron comparadas en todos los tramos de aguas arriba. Se identificaron 141 táxones de diatomeas de la costa de Galicia. En este trabajo presentamos 15 nuevas citas para Galicia, dos para España y tres para la Península Ibérica, además de una nueva especie recientemente descrita. Los táxones dominantes son: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, y Navicula minima. Achnanthes subhudsonis fue la especie más abundante durante los meses de primavera y verano. Las especies restantes no mostraron cambios pertinentes independientemente de la época del año. Los resultados indican que las diatomeas de los ríos de Galicia son un componente importante de la diversidad del ecosistemaThe financial support for this work has been provided by Augas de Galicia (Xunta de Galicia) through a contract with the University of Santiago de Compostela for the assessment of the stream water quality in rivers of Galicia-Costa using diatom metrics (2005—2007). We are indebted to Juan Manuel Antelo Cortizas (Department of Química-Física) and Teresa García Bernadal (researcher of Santiago de Compostela University) for their assistance during fieldwork and insightful comments on stream chemistry and ecologyS