Three new species of Delicatophycus M.J. Wynne (Bacillariophyta) from China, all possessing apical pore fields

[EN] Delicatophycus wulingensis sp. nov., D. qinghainensis sp. nov., and D. menyuanensis sp. nov., are described, illustrated, and compared to similar taxa. Two types of apical pore fields (APFs) in the genus Cymbella are defined. The three new Delicatophycus all possess the type II APF found in some species of Cymbella, i.e. the APF is divided by the distal raphe fissure into two areas, one larger than the other. They also share a further three distinct features: variable central dorsal portion of valve, stigmata, and a notch on the dorsal side of the distal raphe fissure. Since there are many species of Delicatophycus without APFs, such as D. sinensis M.J. Wynne, D. williamsii M.J. Wynne and D. chongqingensis M.J. Wynne; D. williamsii and D. liuweii Li both possess stigmata, thus proposed diagnostic characters for Delicatophycus are the tilde-shaped areolae and the dorsally curved distal fissuresSIThis research was supported by the National Natural Science Foundation of China [grant number 31760051] and the graduate program of Jishou University [grant number Jdy20074

Diffeomorphic transforms for data augmentation of highly variable shape and texture objects

[EN] Background and objective: Training a deep convolutional neural network (CNN) for automatic image classification requires a large database with images of labeled samples. However, in some applications such as biology and medicine only a few experts can correctly categorize each sample. Experts are able to identify small changes in shape and texture which go unnoticed by untrained people, as well as distinguish between objects in the same class that present drastically different shapes and textures. This means that currently available databases are too small and not suitable to train deep learning models from scratch. To deal with this problem, data augmentation techniques are commonly used to increase the dataset size. However, typical data augmentation methods introduce artifacts or apply distortions to the original image, which instead of creating new realistic samples, obtain basic spatial variations of the original ones. Methods: We propose a novel data augmentation procedure which generates new realistic samples, by combining two samples that belong to the same class. Although the idea behind the method described in this paper is to mimic the variations that diatoms experience in different stages of their life cycle, it has also been demonstrated in glomeruli and pollen identification problems. This new data augmentation procedure is based on morphing and image registration methods that perform diffeomorphic transformations. Results: The proposed technique achieves an increase in accuracy over existing techniques of 0.47%, 1.47%, and 0.23% for diatom, glomeruli and pollen problems respectively. Conclusions: For the Diatom dataset, the method is able to simulate the shape changes in different diatom life cycle stages, and thus, images generated resemble newly acquired samples with intermediate shapes. In fact, the other methods compared obtained worse results than those which were not using data augmentation. For the Glomeruli dataset, the method is able to add new samples with different shapes and degrees of sclerosis (through different textures). This is the case where our proposed DA method is more beneficial, when objects highly differ in both shape and texture. Finally, for the Pollen dataset, since there are only small variations between samples in a few classes and this dataset has other features such as noise which are likely to benefit other existing DA techniques, the method still shows an improvement of the resultsSIThe authors acknowledge financial support of the Spanish Government and Junta de Comunidades de Castilla-La Mancha under projects AQUALITAS (Ref. CTM2014-51907-C2-R-MINECO), HYPERDEEP (Ref. SBPLY/19/180501/000273), and APRENDAMOS (Ref. SBPLY/17/180501/000543). They would also like to extend the acknowledgment to technicians Enrique Cepeda and Jesus Diaz for their help in running some experiment

DNA metabarcoding and morphological methods show complementary patterns in the metacommunity organization of lentic epiphytic diatoms

[EN] Diatoms are important organisms in freshwater ecosystems due to their position as primary producers and therefore, analyzing their assemblages provides relevant information on ecosystem functioning. Diatoms have historically been identified based on morphological traits, which is time-consuming and requires well-trained specialists. Nevertheless, DNA barcoding offers an alternative approach to overcome some limitations of the morphological method. Here, we assess if both approaches are comparable methods to study patterns and mechanisms (including environmental filtering and dispersal limitation) of epiphytic diatom metacommunities using a comprehensive dataset from 22 Mediterranean ponds at different taxonomic resolutions. We used a fragment of rbcL barcode gene combined with High-Throughput Sequencing to infer diatom community composition. The overall degree of correspondence between both approaches was assessed by Procrustean rotation analysis and Procrustean randomization tests, whereas the role of local environmental variables and geographical distances was studied using a comprehensive combination of BIOENV, Mantel tests and distance-based redundancy analysis. Our results showed a relatively poor correspondence in the compositional variation of diatom metacommunity between both approaches. We speculate that the incompleteness of the reference database and the bioinformatics processing are the biases most likely affecting the molecular approach, whereas the limited counting effort and the presence of cryptic species are presumably the major biases related with the morphological method. On the other hand, variation in diatom community composition detected with both approaches was strongly related to the environmental template, which may be related with the narrow community-environment relationships in diatoms. Nevertheless, we found no significant relationship between compositional variation and geographical distances. Overall, our work shows the complementary nature of both approaches and highlights the importance of DNA metabarcoding to address empirical research questions of community ecology in freshwaters, especially once the reference databases include most genotypes of occurring taxa and bioinformatics biases are overcomeSIThis study was supported by the project METAPONDS (CGL2017-84176R), grant by the Spanish Ministry of Economy and Industry, by the project BT-2019, grant by the Biodiversity Foundation and the Spanish Ministry for Ecological Transition and Demographic Challenge and by the project LE004G18, grant by the Junta of Castile and Leó

Improving the performance of recycled concrete by biodeposition of biogenic silica as a surface coating

[EN] This study addresses the challenges of sustainability and the implementation of a circular economy in the construction and maintenance of concrete structures used in clean-water applications. Specifically, it examines the use of an innovative surface treatment based on a biofilm comprising diatom biosilica deposition as a waterproofing agent and surface pore sealant to improve the longevity of recycled concrete. To this end biofilm-treated and untreated (control) samples of a concrete mix containing 50% recycled aggregates were subject to four performance tests directed at assessing the durability of concrete structures under environmental conditions: resistance to carbonation, freeze–thaw durability, resistance to water penetration, and electrical resistivity as an indicator of the corrosion resistance of concrete. In addition, the protective biofilm was characterised using SEM. Results suggest that the biogenic silica surface treatment significantly improves the durability of recycled concrete, in particular, for treated compared to untreated samples there was a 56 % reduction of the carbonation front, 26% lower mass loss in freeze–thaw cycles, 57% reduction in the water penetration front under pressure, and 44% higher electrical resistivity. Together these findings confirm that the biofilm used in this study constitutes an effective treatment to improve the properties of recycled concrete and ensure its durability, particularly when used in the construction of structures in contact with constant water fluctuations

Innovative approach for the protection of recycled concrete by biogenic silica biodeposition

[EN] Over the past few years, the construction industry has sought to be more sustainable through use of more economically responsible materials and the use of environmentally friendly techniques such as bio-remediation. One promising area in this regard is that of surface treatments, particularly bio-repair techniques, to reduce the deterioration suffered by cement-based materials as a result of environmental conditions. This study presents original work on the use of silicaceous biodeposition by diatoms as a waterproofing surface treatment for recycled concrete. A recycled concrete mix containing a 50% substitution of recycled aggregates (RA) was used as a test substrate and the effectiveness of the bio-treatment was assessed using four different tests: capillary absorption, high-pressure water penetration, low-pressure water absorption and also characterised the biodeposited layer using SEM. Results demonstrate reductions of up to 33% in the capillary absorption test, while high-pressure water penetration decreased by 54.7%, compared to controls. In addition, Karsten tube tests showed low-pressure water absorption was delayed by up to 436 times relative to control samples. In combination these tests confirm the efficacy of diatom biodeposition as a protective surface treatment for cement-based construction materials.S

The ecology of diatoms inhabiting cryoconite holes in Antisana Glacier, Ecuador

Published for International Glaciological Society, IGS[EN] In the ablation zone of glacier habitats, cryoconite holes are known to harbor diverse microbial communities, including unique diatom floras distinct from those of surrounding aquatic and terrestrial systems. Besides descriptive studies, little is known about the diversity of cryoconite diatoms and their response to environmental stressors, particularly in low-latitude glaciers. This paper documents an extremely diversified diatom community in Antisana Glacier (Ecuador), reporting 278 taxa found in 54 surface holes, although with low individual abundances. Contrary to our expectations, assemblage structure did not respond to water physical or chemical characteristics, nor to cryoconite hole morphology, but to elevation. We demonstrate that elevation is a driver of diatom assemblages. Both alpha diversity (measured as Fisher's index) and species richness (corrected for unequal sample sizes) correlated negatively with elevation, suggesting a replacement toward simplified, poorer communities along this gradient. The taxonomic composition also changed significantly, as revealed by multivariate statistics. In summary, cryoconite holes are sites of high taxonomic diversity composed of taxa that are allochthonous in originSIThe authors are thankful to the ‘Fonag’, EPMAPS” and ‘Ministerio del Ambiente’, Ecuador, for collection permission No. MAE-DNB-CM 2018-0028-0093. The research was funded by Proyecto de Investigación DII-UISEK-P041516_3, (SC) ‘Índice Biótico de Calidad de Agua para el Ecuador’, Universidad Internacional SEK and Convenio Marco de Cooperación entre la Universidad de León, España y La Universidad Internacional SEK, Ecuado

Anaerobic digestion of food waste coupled with biogas upgrading in an outdoors algal-bacterial photobioreactor at pilot scale

[EN] This work aimed at integrating the anaerobic digestion of food waste (FW) with photosynthetic biogas upgrading at pilot scale in order to obtain a high quality biomethane and a nutrient-laden algal biomass as the main byproducts from FW treatment. The performance of a 100 L anaerobic digester treating food waste integrated via raw biogas and digestate injection with a 1.2 m2 outdoors high-rate algal pond (HRAP) was evaluated. Biogas production in the digester averaged 790 ± 89 mL g VSin-1 (68 ± 8 L d-1) (35 ◦C, 1 bar) at a loading rate of 0.86 g VS L-1 d-1 and a steady state chemical oxygen demand removal efficiency of 83 ± 7%. The biogas produced (60% CH4 / 39% CO2) was upgraded in a 2.5 L absorption column interconnected with the HRAP via culture broth recirculation at a liquid to biogas ratio of 2, resulting in a maximum CO2 removal efficiency of 90% and a maximum CH4 content of 93.9%. The HRAP, supplied with the centrifuged liquid digestate supplemented with synthetic wastewater (5.0 ± 1.1 L d-1, Total nitrogen (TN) = 793 ± 110 mg N L-1, P-PO43- = 39 ± 19 mg P L-1), supported TN and total phosphorus maximum removal efficiencies of 100% in both cases. Pseudoanabaena sp. and Chlorella vulgaris were identified as the dominant speciesSIEste trabajo contó con el apoyo de la Junta de Castilla y León y EU-FEDER (CLU 2017-09, CL-EI-2021-07, UIC 315). También se reconoce al Ministerio de Ciencia, Innovación y Universidades de España (FJC 2018-038402-I) por la financiación del contrato de investigación Juan de la Cierva-Formación de Lara Ménde