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

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

Recent and subfossil diatom assemblages as indicators of environmental change (including fish introduction) in a high-mountain lake

We investigated modern-littoral and subfossil sediment-core diatoms in the shallow (max depth 6.4 m) high-mountain Lake Balma in the Orsiera Rocciavrè Nature Park (Italian Western Alps). Our study provided evidence that might be related to the response of diatom assemblages to fish introduction, in particular the decreasing of the nutrient-enrichment sensitive low-profile life-form/ecological guild and the increase in species known to react positively to the augmented nutrient availability due to fish excretions (e.g., Fragilaria nanana, Pseudostaurosira brevistriata, Staurosirella neopinnata). We are, however, aware that some of these effects could as well have been caused by pastures and cattle watering, and by increased temperatures due to global warming, and we acknowledge the typical complex-interaction pattern among different stressors. High-mountain lakes are ‘‘early warning systems’’ for the whole alpine system and can contribute valuable information also on the interactions between environmental global changes and anthropogenic impacts. Benthic diatoms, in particular, can provide useful indications on the deleterious effects of non-native fish introduction, cattle grazing, and global warming, and thus support an adaptive and sustainable management of high-mountain lakes for the sake of nature conservation

Chemical Quality and Hydrogeological Settings of the El-Farafra Oasis (Western Desert of Egypt) Groundwater Resources in Relation to Human Uses

In the Egyptian deserts, new land reclamation projects have been recently established to meet the increasing-population growth rate and food demand. These projects mainly depend on the different groundwater aquifers. El-Farafra Oasis is one of the "1.5-million-feddan reclamation project" areas recently established in the Western Desert of Egypt where the only available water source is the world's largest fossil freshwater reservoir "the Nubian Sandstone Aquifer System (NSAS)". Groundwater-dependent springs, and their artificial counterpart "drilled wells", are reliable water systems throughout the world. In the present study, hydrochemical parameters were collected in 2015 from 16 different springs and wells of the El-Farafra Oasis, and analyzed using the different water quality indices. The calculated water quality index (WQI), its correlations with the water quality parameters Gibbs, Piper, US Salinity-Lab Staff and Wilcox diagrams, and Principal Component Analysis (PCA) were used to evaluate the groundwater suitability for human drinking and irrigation purposes. WQI values revealed good-to-excellent groundwater quality for human drinking. In addition, the spring and well water samples investigated showed good indices for irrigation activities. Gibbs and Piper's diagrams were presented, with most samples falling into the rock-dominance category, and belonging to hydrogeochemical facies determining the following water types: Mg(HCO3)(2) type water (37.5% of the samples), no dominant ions (mixed water-type category; Ca/MgCl2) (50% of the samples), and, finally, NaCl water type (the remaining 12.5%). The groundwater chemistry in the study area is mainly controlled by rock-water interactions, particularly the dissolution of carbonate rocks and silicate weathering. The elevated nutrient concentrations, in particular nitrates, are most likely due to agricultural activities, indicating substantial anthropogenic activities in the area studied

Benthic algae assessments in the EU and the US: Striving for consistency in the face of great ecological diversity

Freshwaters face multiple environmental problems including eutrophication, acidification, salinization, and climate-change, all of which can lead to impairment of ecosystem structure and function. Furthermore, these stressors often act in combination. Benthic algal-based assessments to quantify impairment are used in both the EU and US. In this review, we use case studies, experience, and the literature to compare concepts, approaches, and methods between the EU and US to offer an updated picture of benthic algal-based assessments. Both the US and EU are composed of numerous constituent states having considerable flexibility to adopt individual methods. The goal of this work is to synthesize the various approaches that are used across the EU and US. Specifically, we compare and contrast benthic algal assessment performed in response to core legislation – the Water Framework Directive in the EU and the Clean Water Act in the US, with a particular focus on the steps taken to ensure consistency at different stages of the process. This includes consideration of approaches to sampling design and field methods, taxonomic resolution and laboratory harmonization, metric selection and choice of algal groups, assessment of stressors and stressor/response relationships. A number of commonalities emerged during this process, particularly the focus on diatoms over other algal groups. However, there are also a number of key differences, including more widespread use of multimetric indices in the US compared with the EU. Finally, we consider emerging opportunities, including the potential for using metagenomic approaches for bioassessment in the future

Analysis of the Fragilaria rumpens complex (Fragilariaceae, Bacillariophyta) with the description of two new species

The former Synedra rumpens complex has long puzzled diatom taxonomists. In the nineteenth century, many infraspecific taxa were described as varieties or forms of S. rumpens. In the present study, type material of Synedra rumpens and several infraspecific taxa such as S. rumpens var. fragilarioides and S. familiaris f. parva and f. major was investigated using LM and SEM observations. For comparison, the original material of several other relevant diatom taxa (such as Fragilaria perdelicatissima, F. spinaspeciosa, Synedra campyla, S. vaucheriae var. distans) was also analysed. The results based on these comparisons show that all infraspecific taxa should be split from Fragilaria rumpens. Fragilaria campyla is a new combination within the genus Fragilaria with F. parva and S. (rumpens var.?) familiaris f. major as synonyms. Fragilaria scotica is likewise a new combination in Fragilaria. Fragilaria metcalfeana is proposed as new name for Synedra familiaris var. neogena. The analysis of F. distans and F. fragilarioides confirmed their conspecificity, with F. fragilarioides having priority as name. Finally, two new species, F. pseudofamiliaris Van de Vijver, T.M.Schuster, Kusber et D.M.Williams sp. nov. and F. bahlsiana Van de Vijver, C.E.Wetzel et Ector sp. nov. are described. Using an analysis of the associated diatom flora, the ecological preferences of each taxon are briefly discussed

Ecohydrogeology: The interdisciplinary convergence needed to improve the study and stewardship of springs and other groundwater-dependent habitats, biota, and ecosystems

This essay discusses the need for, advantages and challenges of integrating the scientific disciplines of ecology and hydrogeology in the study of groundwater-dependent ecosystems (GDEs). We provide a definition for ecohydrogeology as \u201ca unifying, synthetic field of study integrating the approaches from the ecological and hydrogeological sciences in the study of groundwater (GW)-related ecosystems, habitats, and organisms to advance science, stewardship, and policy\u201d. We selected specific case studies to illustrate first how hydrogeological approaches can favour in-depth understanding and modelling of springs and crenobiontic (spring-dependent) species distribution, assemblage composition and organization. Second, this essay also examines how taxa and assemblages serve as bioassays and ecosystem indicators to infer hydrogeological aspects of GW flow and discharge, as well as quantitative and qualitative human impacts. We consider both types of features and parameters as ecohydrogeological indicators. The examples presented include topics related to springs and other GDE geomorphological types and classification, GW quality influences on crenobiont distribution, phreatophyte (= plant species the roots of which reach to and into the water table) ecophysiology in relation to water table depth, and flow variability in karstic systems, to nutrient dynamics in relation to dinoflagellate blooms in GDE montane lakes. Conceptual approaches that integrate ecology with hydrogeology include the investigation of GDE distribution and ecology, groundwater-surface water (GW-SW) interactions, and the development of the discipline of ecohydrology. Despite widespread applications, the scientific community still lacks a complete or effective integration of the principles described in the fields of groundwater hydrogeology with ecology, ecophysiology, and environmental biology. Springs are aquatic-wetland-riparian habitats that link shallow subsurface-surface processes and assemblages, often functioning as biodiversity hotspots, ecotones, keystone, and refugial ecosystems, for which coordination between studies of hydrogeology and ecology are both obvious and essential. Over the past century, springs ecosystem ecology has been largely ignored by hydrologists, and, conversely, hydrogeology has been under-emphasized by ecologists. Recent global recognition of the extraordinary biodiversity and socio-cultural significance of springs, coupled with their globally highly threatened conservation status, stimulated this inquiry into how to better integrate hydrogeology with springs ecosystem ecology. Acknowledging the highly threatened status of springs ecosystems around the world, there is an urgent need to integrate and invigorate the union of these disciplines into ecohydrogeology, the study of groundwater-dependent organisms, habitats, ecosystems, and management policy

Integrative taxonomic, ecological and genotyping study of charophyte populations from the egyptian western-desert oases and sinai peninsula

Present-day information available on the charophyte macroalgae in Egypt, including their phylogenetic affinities, remains largely incomplete. In this study, nine charophyte populations were collected from different aquatic biotopes across the Egyptian Western-Desert Oases and Sinai Peninsula. All populations were investigated using an integrative polyphasic approach including phylogenetic analyses inferred from the chloroplast-encoded gene (rbcL) and the internal transcribed spacer (ITS1) regions, in parallel with morphotaxonomic assignment, ultrastructure of the oospore walls, and autecology. The specimens identified belonged to the genera Chara, Nitella, and Tolypella, with predominance of the first genus to which five species were assigned though they presented some interesting aberrant taxonomic features: C. aspera, C. contraria, C. globata, C. tomentosa, and C. vulgaris. Based on our integrative study, the globally rare species C. globata was reported for the second time for the whole African continent. The genus Nitella was only represented by N. flagellifera, and based on the available literature, it is a new record for North Africa. Noteworthy, an interesting Tolypella sp., morphologically very similar to T. glomerata, was collected and characterized and finally designated with the working name ‘Tolypella sp. PBA–1704 from a desert, freshwater wetland’, mainly based on its concatenated rbcL+ITS1 phylogenetic position. This study not only improved our understanding on the diversity, biogeography and autecological preferences of charophytes in Egypt, but it also broadened our knowledge on this vulnerable algal group in North Africa, emphasizing the need of more in-depth research work in the future, particularly in the less–impacted desert habitats

Fragilaria radians (Kützing) D.M.Williams et Round, the correct name for F. gracilis (Fragilariaceae, Bacillariophyta): a critical analysis of this species complex in Europe

Fragilaria gracilis is one of the most reported Fragilaria species in Europe, observed in a broad range of water bodies, ranging from (ultra)oligotrophic rivers to even eutrophic lakes. A revision of this im-portant taxon based on the analysis of the morphology of a large number of historic and recent populations was highly needed. In the present study, type material of Fragilaria gracilis and several related taxa such as Synedra radians, Fragilaria pseudolaevissima, S. utermoehlii, F. aquaplus, F. boreomongolica and F. tridentina together with more than 10 modern populations were investigated using LM and SEM observations. The results based on these comparisons show that Fragilaria (Synedra) radians is the name for the taxon formerly known as F. gracilis. Moreover, detailed analysis demonstrated that F. pseudolaevissima and Synedra utermoehlii are conspecific with F. radians and should be considered as heterotypic synonyms. The observations made in this study also resulted in the description of several new species, often with distinct ecologies and distribution ar-eas: Fragilaria huerlimannii Van de Vijver sp. nov., F. acerosa Van de Vijver, C.E.Wetzel, Jarlman et Ector sp. nov., F. neglecta Van de Vijver, C.E.Wetzel, Jarlman et Ector sp. nov., F. heudreana Van de Vijver, C.E.Wetzel et Ector sp. nov., F. eutraphenta Van de Vijver, Kusber et D.M.Williams sp. nov., and F. mertensiana Van de Vijver, C.E.Wetzel et Ector sp. nov. Using an analysis of the associated diatom flora, the ecological preferences of each taxon are briefly discussed

Seminavis aegyptiaca sp. Nov., a new amphoroid diatom species from estuary epilithon of the river–nile damietta branch, Egypt

During a recent floristic–taxonomic study on the algal flora, including diatoms, from the estuary of the Damietta Branch of the Nile in Egypt, an interesting epilithic diatom species belonging to the genus Seminavis (Naviculaceae) was collected and investigated using both light and scanning electron microscopy. This new diatom species shares morphologically some taxonomic diagnostic features with other related taxa such as S. insignis, S. robusta, and S. ventricosa. However, it still differs by having ventral central striae that are shorter and more or less straight in the middle of the smaller frustules to be clearly radiate in the larger ones and then become geniculate and only radiate near the poles, the central raphe endings are externally more distantly spaced than in the similar species, the elongate central nodule is internally less prominent, and the areola density is much denser. Therefore, we here describe it as Seminavis aegyptiaca sp. nov. Hydrochemical analyses revealed that S. aegyptiaca commonly inhabits typical marine, with a weak tendency towards brackish water, habitats. It was found to be tolerant to meso–eutrophic, nutrient–enriched conditions, based on the data available on seasonal concentrations of N and P compounds. These findings not only contribute to the inventory of Egyptian diatoms, but also increase our understanding of the autecology and distribution of this relatively poorly–known diatom genus

Diatoms from the Spring Ecosystems Selected for the Long-Term Monitoring of Climate-Change Effects in the Berchtesgaden National Park (Germany)

We studied diatoms from the fifteen springs selected in the Berchtesgaden National Park on behalf of the Bavarian State Ministry for the Environment to be sentinel environments of climate-change effects. For three of these springs, diatom data based on samples taken in 1997 were also available. A total of 162 species belonging to 49 genera were found sampling three microhabitat types (lithic materials, bryophytes, surface sediments). The cumulative percentage of all species included in a threat category including endangered species was 43%, confirming previous findings for comparable environments of the Alps. We could find a statistically significant positive association between the Meinzer variability index for discharge and the cumulative relative abundance of aerial diatom species. This study thus highlighted once again the relevance of discharge (and associated water-level) variability as an environmental determinant of diatom assemblages in spring ecosystems. Increased nitrate concentrations in some springs, likely due to diffuse airborne pollution and, locally, to impacts such as forest management, game, and cattle, led to a relevant occurrence of eutraphentic diatom species. Our results show a segregation of the older data in non-parametric diatom-based ordinations, suggesting a strong potential for the use of spring diatoms in studies aiming at tracking the effects of climate and environmental change