Articles de revues : « Diatom test »

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Winter, Jennifer G., et Hamish C. Duthie. « Stream biomonitoring at an agricultural test site using benthic algae ». Canadian Journal of Botany 78, n^o 10 (1 octobre 2000) : 1319–25. http://dx.doi.org/10.1139/b00-104.

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The percent cover and composition of benthic macroalgal growths and the structure of epilithic diatom communities were analyzed in 1995 at four sites in a stream flowing through a cultivated field near Kintore, Ontario, Canada. The dominant epilithic diatom taxa did not differ greatly among sites. However, a correspondence analysis of the diatoms sampled monthly between July and September separated an upstream site from those receiving agricultural runoff. Sites downstream of agricultural inputs showed an increase in the cover of Cladophora glomerata (L.) Kütz and other green algae, and in general a reduction in the cover of diatoms and crusts dominated by Oscillatoriaceae (aff. Oscillatoria sp.) and the red alga Audouinella violacea (Kütz.) Hamel. In particular, there was a positive correlation between the cover of Cladophora and nitrate concentration.Key words: biomonitoring, diatoms, periphyton, agriculture, correspondence analysis (CA).

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Jakovljević, Olga S., Slađana S. Popović, Danijela P. Vidaković, Katarina Z. Stojanović et Jelena Ž. Krizmanić. « The Application of Benthic Diatoms in Water Quality Assessment (Mlava River, Serbia) ». Acta Botanica Croatica 75, n^o 2 (1 octobre 2016) : 199–205. http://dx.doi.org/10.1515/botcro-2016-0032.

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AbstractThe main objective of this study was to assess the ecological status of the Mlava River based on epilithic diatoms and to test the use of diatom indices as a tool for estimating the quality of flowing waters in Serbia. Quantitative analysis showed that in AprilAchnanthidium minutissimumwas dominant at each site, except at the fifth site, whereAmphora pediculuswas dominant. In July and September,Achnanthidium minutissimum, Achnanthidium pyrenaicum,Amphora pediculus,Denticula tenuis,Diatoma vulgaris,Gomphonema elegantissimum,Cocconeis pseudolineataandCocconeis placentulavar.lineatadominated. Detrended correspondence analysis (DCA) was used to detect the major patterns of variation in species composition. The first DCA axis summarizes the distribution of the diatom community, mainly through temperature, conductivity, oxygen and water hardness gradient. The second DCA axis was weakly correlated with few variables. Based on the average values of the pollution sensitivity index (IPS), commission for economical community metric (CEE) and biological diatom index (IBD), the water of the Mlava River belonged to water class I during all three seasons. Values of the diatom-based eutrophication/pollution index (EPI-D) indicated class II water quality. According to calculated trophic diatom index (TDI) values, water of the Mlava River was characterized by intermediate nutrient concentrations during three seasons. Principal components analysis was used to represent the correlation between diatom indices, and the highest correlation among the selected diatom indices is seen between EPI-D, IPS and IBD.

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Ha, Hongil, et Yun Taek Sim. « A False-positive Diatom Test in a Non-drowned Victim of Multiple Stab Wounds ». Korean Journal of Legal Medicine 46, n^o 2 (31 mai 2022) : 55–58. http://dx.doi.org/10.7580/kjlm.2022.46.2.55.

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For the diagnosis of drowning in immersed bodies, the diatom test has been controversial due to false-negative and false-positive results. Causes of false positive results include antemortem penetration of diatoms, and postmortem contamination during the submersion or the diatom preparation process. Herein, we report a false-positive case in a 30-year-old woman who died from homicidal multiple stab wounds and was thrown into a shallow farm waterway approximately 10 days after her death. In addition, a discussion on the false-positive diatom test results in immersed bodies with penetrating wounds is provided.

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Bigelow, P. R., et C. G. Alexander. « Diatoms on the cirri of tropical barnacles ». Journal of the Marine Biological Association of the United Kingdom 80, n^o 4 (août 2000) : 737–38. http://dx.doi.org/10.1017/s0025315400002599.

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Two species of large extension feeding barnacles are abundant on exposed tropical rocky shores of northern Australia. The cirri of many specimens carry varying numbers of a commensal diatom in some cases with as many as 2000 individuals on a single cirrus. The araphid diatom resembles the genus, Lichmophora within the family Fragilariaceae although no description has yet been published. Species of Lichmophora are common benthic diatoms in these waters as an epiphyte on macroalgae and common primary fouling diatoms on test panels. The diatom reported here has not been found on any substratum other than the barnacles Tetraclita squamosa and Australobalanus imperator, very rarely on Balanus amphitrite. Analysis of the diatom distribution on the cirri shows significantly higher numbers on the posterior captorial cirri. The effect of commensal diatoms on the feeding efficiency of the barnacles is discussed.

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Horton, Benjamin P. « Diatoms and Forensic Science ». Paleontological Society Papers 13 (octobre 2007) : 181–90. http://dx.doi.org/10.1017/s1089332600001534.

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The application of diatom analysis in determining whether drowning was the cause of death has proved to be a valuable tool in forensic science. The basic principal of the “diatom test” in drowning is based on inference that diatoms are present in the medium where the possible drowning took place and that the inhalation of water causes penetration of diatoms into the alveolar system and blood stream, and thus, their deposition into the brain, kidneys, and other organs.I provide an informal assessment of “reliability” of the “diatom test” through correlations between control samples and samples from organs and clothing in two case studies. In studies, all organ and clothing samples except one had matching analogues in the modern diatom dataset from the body recovery sites, reinforcing drowning as the cause of death. The analogue matching provides further information on the precise site of drowning, in particular differentiating between drowning in a bathtub versus a naturally occurring body of water.

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Mall, Ashutosh. « Study of Diatom Flora of Kaalesar Ghat of Rapti River at Gorakhpur for Forensic Consideration ». International Journal for Research in Applied Science and Engineering Technology 9, n^o 10 (31 octobre 2021) : 555–59. http://dx.doi.org/10.22214/ijraset.2021.38444.

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Abstract: Diatoms are unique algae. They are scientifically known as Bacillariophyceae. Diatoms have been used in forensic science in a variety of ways, the most frequent being the diagnosis of death by drowning. When a person drowns, water will enter the lungs and then enter the bloodstream through ruptures in the peripheral alveoli before being carried to the other organs such as the liver and heart. Naturally, the microscopic contents of the water, which will include diatoms, will pass into the blood as well. The detection of diatoms in the organs can contribute to a diagnosis of death by drowning, a process referred to as the ‘diatom test’. A study was conducted in the department of Forensic Science, SHUATS, Prayagraj which included the extraction and identification of diatoms from the collected water samples from three different sites of Kaalesar Ghat of Rapti River in Gorakhpur. The acid digestion method was used for diatom extraction. And, after analysis total 13 diatom species were found. The identified diatoms were of great ecological assessment that plays an important role in criminal investigations related to premortem or ante-mortem drowning. Keywords: Diatom, Drowning, D-mapping, Rapti-River

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Erkan, Çiler Fulya, et Gürsel Çetin. « Comparison of Diatoms Which Were Obtained from The External Surface of The Body and Internal Organs in the Corpses Pulled Out of Water Using Colloidal Silica Gradient Centrifuge Method ». Bulletin of Legal Medicine 24, n^o 2 (13 octobre 2019) : 83–92. http://dx.doi.org/10.17986/blm.2019252241.

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Objective: Diatom analysis is a valuable tool in forensic science and it is useful in diagnosis of drowning and determination of the drowning site. The basic principal of the “diatom test” in investigation of drowning is based on correlation between diatoms are present in the medium where the possible drowning took place and inhalation of water causes penetration of diatoms into the alveolar system and blood stream and consequently their deposition into brain, kidneys and other organs, like the bone marrow of large bones. There are various extraction methods that are used to isolate diatoms from water and tissues. Nitric acid digestion is a worlwide known method for the extraction of diatoms. In this study, instead of acid digestion method, colloidal silica gradient centrifuge method was used to extraction diatom and the advantages of this technique has been aimed to be discussed. Materials and Methods: Therefore, 30 visceral and body fluid samples that have been obtained from corpses which were removed from the water and brought to the Council of Forencic Medicine to perform autopsy, were examined and diatom were obtained from samples of 19 cases. Moreover, the diatoms that were obtained from the swab samples taken from the outer body surfaces and the diatoms obtained from the visceral organs were compared. Results: When the diatoms which were obtained from internal organs tissues and body fluids were evaluated numerically, it was seen that the diatoms that were obtained lungs were in high numbers and it was followed by pleural liquid...

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Shibabaw, Tebkew, Abebe Beyene, Aymere Awoke, Mulat Tirfie, Muluken Azage et Ludwig Triest. « Diatom community structure in relation to environmental factors in human influenced rivers and streams in tropical Africa ». PLOS ONE 16, n^o 2 (3 février 2021) : e0246043. http://dx.doi.org/10.1371/journal.pone.0246043.

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The contemporaneous effect of natural and anthropogenic factors involved in a watershed contribution to the seasonal and spatial variation of diatom community composition is widely discussed in the scientific literature. Yet, there is a paucity of scientific evidence indicating the effect of these factors on diatoms in tropical African regions characterized by distinct dry and wet seasons and season associated human activities like rainfed agriculture are commonly practiced. We applied multivariate techniques to determine the spatio-temporal drivers of diatom assemblage and diatom species richness in human influenced rivers and streams in Ethiopia. We simultaneously collected water and diatom samples from 24 sampling points during the wet (July) and dry (February) seasons. Both water and diatom samples were processed following standard procedures. We identified 169 species belonging to 45 genera in the studied lotic systems. We found that both season and land use factors were important in defining diatom composition (PERMANOVA, p<0.05) and species richness (ANOVA, p<0.05) patterns. Diatom community composition was driven by conductivity, dissolved oxygen, pH, and turbidity parameters (Monte Carlo permutation test, p<0.05). Besides, diatom species richness was driven by dissolved oxygen, soluble reactive phosphorus, and turbidity (GLMM, p<0.05). The study highlighted physicochemical parameters influenced by seasonal variation and human activity determined the composition of diatoms. This implies that the unique feature of heavy rain during the rainy season in the region followed by extensive flooding aggravated by the steep slope from the highlands to the lowlands plays a major role in shaping the diatom autecology in the region. Therefore, in applying biomonitoring in such regions considering the effect of runoff and dilution is imperative.

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Bogusz, Marek, Iwona Bogusz, Magdalena Kwiatkowska, Agnieszka Siwińska et Joanna Żelazna-Wieczorek. « Does occurrence of diatoms in internal organs always prove a case of drowning ». Issues of Forensic Science 302 (2018) : 38–43. http://dx.doi.org/10.34836/pk.2018.302.1.

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Diatoms (Bacillariophyta) are unicellular algae inhabiting in aquatic ecosystems and marsh habitats on the entire Earth. This group of algae, variable in terms of species, comprises both cosmopolitan ones but also those whose occurrence is limited to specific environmental conditions, i.e. stenotopic species. Diatoms are distinguished by unique cell walls making so-called, frustules, whose structures constitute the bases for differentiation between species. Frustules are resistant to the majority of environmental conditions that destroy other algae. Due to the above characteristics diatoms have been incorporated in forensic investigations and they can be the conclusive component of the proceedings by indicating drowning as the cause of death. In those cases, it is important to answer the question whether finding diatoms in internal organs of corpses found in water always proves drowning. The publication uses reports from forensic medical examinations of corpses and reports from detecting presence of diatoms in internal organs performed in years 2013-2017 in the Institute of Forensic Medicine of Warsaw Medical University, which is presently the only centre in Poland that routinely performs the diatom test. It has been demonstrated that a positive result of the diatom test generally coincides with the conclusive indications of the cause of death in the forensic medical autopsy reports. Only in few individual well-explainable cases the results of the diatom tests did not confirm conclusions from the forensic autopsies, which excluded drowning as the cause of death.

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Zahajská, Petra, Sophie Opfergelt, Sherilyn C. Fritz, Johanna Stadmark et Daniel J. Conley. « What is diatomite ? » Quaternary Research 96 (29 avril 2020) : 48–52. http://dx.doi.org/10.1017/qua.2020.14.

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AbstractDifferent types of biogenic remains, ranging from siliceous algae to carbonate precipitates, accumulate in the sediments of lakes and other aquatic ecosystems. Unicellular algae called diatoms, which form a siliceous test or frustule, are an ecologically and biogeochemically important group of organisms in aquatic environments and are often preserved in lake or marine sediments. When diatoms accumulate in large numbers in sediments, the fossilized remains can form diatomite. In sedimentological literature, “diatomite” is defined as a friable, light-coloured, sedimentary rock with a diatom content of at least 50%, however, in the Quaternary science literature diatomite is commonly used as a description of a sediment type that contains a “large” quantity of diatom frustules without a precise description of diatom abundance. Here we pose the question: What is diatomite? What quantity of diatoms define a sediment as diatomite? Is it an uncompacted sediment or a compacted sediment? We provide a short overview of prior practices and suggest that sediment with more than 50% of sediment weight comprised of diatom SiO2 and having high (>70%) porosity is diatomaceous ooze if unconsolidated and diatomite if consolidated. Greater burial depth and higher temperatures result in porosity loss and recrystallization into porcelanite, chert, and pure quartz.

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Cejudo-Figueiras, Cristina, Irene Álvarez-Blanco, Eloy Bécares et Saúl Blanco. « Epiphytic diatoms and water quality in shallow lakes : the neutral substrate hypothesis revisited ». Marine and Freshwater Research 61, n^o 12 (2010) : 1457. http://dx.doi.org/10.1071/mf10018.

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For bioassessment of freshwaters, diatom indices have been mainly used in streams although their applicability in shallow lakes has been demonstrated in several studies. However, the influence of sampling substrata on periphytic diatom communities and on the ecological quality inferred from them has been paid little attention. In this paper, we test the ‘neutral substrate hypothesis’, which predicts no relevant influence of host plant type on their epiphytic community. Nineteen shallow permanent lakes from north-west Spain were studied and classified into three trophic levels. Epiphytic diatom communities growing on three different macrophytes for each trophic level were sampled and analysed. We assess: (1) which of the most common diatom indices provides a reliable water quality assessment, (2) how different plant substrata influence the diatom communities growing on them and (3) how these differences affect water quality assessment. Similarity tests showed significant differences in the composition of diatom assemblages among nutrient concentrations and host macrophytes. In contrast, ANOVA results for selected diatom-based metrics showed significant differences among trophic levels but not between different plant substrata. This supports the use of epiphytic diatoms as biological indicators for shallow lakes irrespective of the dominant macrophyte.

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Dedić, Anita, Ana Antunović, Jasmina Kamberović, Svjetlana Stanić-Koštroman, Dragan Škobić, Anđelka Lasić et Dubravka Hafner. « USING DIATOMS IN BIOLOGICAL ASSESSMENT OF THE WATER QUALITY ON THE EXAMPLE OF SMALL KARSTIC RIVER IN BOSNIA AND HERZEGOVINA ». Radovi Šumarskog fakulteta Univerziteta u Sarajevu 49, n^o 1 (1 novembre 2021) : 52–68. http://dx.doi.org/10.54652/rsf.2019.v49.i1.25.

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UDK: 574.5(282.249 Bunica) Research into the benthic diatoms in the Bunica River was performed during the period from 5th May 2013 to 9th January 2014 on three different sites, from the headwaters to the mouth. The Bunica River is located in the south-eastern part of the Mostar valley, in the south of Bosnia and Herzegovina. The aim of this research was to test the use of benthic diatoms as indicators and the use of diatom indices as a tool for estimating water quality in an example of a small karstic river. For that purpose, diatom indices were calculated using OMNIDIA GB 5.3 software. This was the first testing of diatom indices for a small karstic river. Diatom indices showed different results and huge variations between sites on the Bunica River. According to the results, the indices in the OMNIDIA software are not applicable for karstic rivers in Bosnia and Herzegovina and they must be modified for this purpose. This paper can be the first step towards calibration indices for karstic region. Also, it can be useful for the development of biomonitoring tool for karstic rivers in Bosnia and Herzegovina.

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Bao, Roberto, Henko De Stigter et Tjeerd C. E. Van Weering. « Diatom fluxes in surface sediments of the Goban Spur continental margin, NE Atlantic Ocean ». Journal of Micropalaeontology 19, n^o 2 (1 décembre 2000) : 123–31. http://dx.doi.org/10.1144/jm.19.2.123.

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Abstract. Continental slopes are presumed key areas for deposition of organic carbon exported from the shelf. Analysis of across-slope differences in diatom and silicoflagellate fluxes recorded in bottom sediments of the Goban Spur margin, a typical North Atlantic slope environment, was carried out to test if they can provide information on the magnitude of advection of material from the shelf into deeper waters. Total diatom and silicoflagellate accumulation rates showed strong across-slope differences. Minimum values are recorded at the shelf break where maximum surface productivity conditions occur while the deeper sampling stations record fluxes as high as 183×106 valves cm–2 ka–1. While high diatom fluxes show a clear correspondence with the activity of a permanent bottom nepheloid layer operating in the region, they do not correlate with productivity patterns observed in the water column. Diatom assemblages are mainly composed of Chaetoceros resting spores and Thalassionema nitzschioides (Grunow) Grunow ex Hustedt, typical indicators of spring bloom conditions in the area. The absence of clear across-slope trends in the diatom assemblages is interpreted as the effect of random mixing driven by the strong hydrodynamic regime provoked by the activity of the bottom nepheloid layer. The dominance of Chaetoceros resting spores across the slope is related to important exportation of shelf-derived production. However, due to the broad ecological tolerances of the main taxa composing the diatom assemblages, they do not allow precise estimations on the magnitude of the primary vertical flux vs. the secondary lateral flux in this slope environment. Use of the tychoplanktonic and benthic diatoms, which are restricted to the neritic realm, allows only the estimation of the minimum amount of shelf-derived diatoms reaching the slope sediments (at least 13% of the total diatom assemblage for the upper slope area of the Goban Spur). This study shows that major limitations exist for the use of diatoms preserved in surface sediments of this area as tracers of shelf-derived production transported to the continental slope.

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Kamberović, Jasmina, Amela Kišić, Dubravka Hafner et Anđelka Plenković-Moraj. « COMPARATIVE ANALYSIS OF EPILITHIC DIATOM ASSEMBLAGES OF SPRINGS AND STREAMS IN THE KONJUH MOUNTAIN (BOSNIA AND HERZEGOVINA) ». Radovi Šumarskog fakulteta Univerziteta u Sarajevu 46, n^o 2 (1 décembre 2016) : 54–67. http://dx.doi.org/10.54652/rsf.2016.v46.i2.73.

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UDK: 574.587:582.26/.27(234.422 Konjuh) Springs are recognized as hotspots for freshwater biodiversity conservation. The study objective was to analyze and compare the biodiversity of epilithic diatom communities of spring and stream habitats in the Konjuh Mountain (B&H). The measuring of basic water physical and chemical parameters and diatom sampling were carried out during summer and autumn period in 2013. Diatom assemblages were collected from 10 locations: (i) five locations were placed in small mountain springs that flow into headwater streams, where another 5 localities were placed. Diatoms were collected by scrubbing the rocks using standard methodology. Relative diatom cell abundances were established by counting up to 400 frustules on permanent slides prepared in Naphrax. Spring habitats were more diverse in diatoms (H' loge =1.67 average) in comparison with headwater stream habitats (H' loge=1.15 average), which was confirmed by t-test (t=2.79; p=0.013). The similarities of community structure from different habitats were investigated by non-metric multidimensional scaling, on the Bray-Curtis similarity matrix in software package Primer 6. Using Permutational Manova test, a different diatom composition was proved between spring and stream communities (Pseudo F=2.66, p=0.012), while the seasonal difference in the community structure was not confirmed (F=0.586, p=0.876). The most abundant and frequent species in spring habitats were: Achnanthidium minutissimum (Kützing) Czarnecki, Cocconeis pseudolineata (Geitler) Lange-Bertalot, Gomphonema pumilum var. elegans E.Reichardt & Lange-Bertalot, Meridion circulare (Greville) C.Agardh and Planothidium lanceolatum (Brébisson ex Kützing) Lange-Bertalot. The most frequent and abundant species in headwater stream habitats were: Achnanthidium minutissimum (Kützing) Czarnecki, Cocconeis placentula var. euglypta (Ehrenberg) Grunow, Cocconeis placentula var. lineata (Ehrenberg) van Heurck and Cymbella tridentina Lange-Bertalot, M.Cantonati & A.Scalfi. In comparison with streams habitats, the springs are heterogeneous with specific diatom composition due to more stable water flow. Although the springs cover very small areas, the diversity of species that inhabit them must not be neglected in planning the use of these natural resources.

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Kakizaki, Eiji, Shuji Kozawa, Masahiro Sakai et Nobuhiro Yukawa. « Numbers, Sizes, and Types of Diatoms Around Estuaries for a Diatom Test ». American Journal of Forensic Medicine and Pathology 32, n^o 3 (septembre 2011) : 269–74. http://dx.doi.org/10.1097/paf.0b013e318221b857.

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Bonfantine, Krista L., Stacey M. Trevathan-Tackett, Ty G. Matthews, Ana Neckovic et Han Ming Gan. « Dumpster diving for diatom plastid 16S rRNA genes ». PeerJ 9 (1 juillet 2021) : e11576. http://dx.doi.org/10.7717/peerj.11576.

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High throughput sequencing is improving the efficiency of monitoring diatoms, which inhabit and support aquatic ecosystems across the globe. In this study, we explored the potential of a standard V4 515F-806RB primer pair in recovering diatom plastid 16S rRNA sequences. We used PhytoREF to classify the 16S reads from our freshwater biofilm field sampling from three stream segments across two streams in south-eastern Australia and retrieved diatom community data from other, publicly deposited, Australian 16S amplicon datasets. When these diatom operational taxonomic units (OTUs) were traced using the default RDPII and NCBI databases, 68% were characterized as uncultured cyanobacteria. We analysed the 16S rRNA sequences from 72 stream biofilm samples, separated the chloroplast OTUs, and classified them using the PhytoREF database. After filtering the reads attributed to Bacillariophyta (relative abundance >1%), 71 diatom OTUs comprising more than 90% of the diatom reads in each stream biofilm sample were identified. Beta-diversity analyses demonstrated significantly different diatom assemblages and discrimination among river segments. To further test the approach, the diatom OTUs from our biofilm sampling were used as reference sequences to identify diatom reads from other Australian 16S rRNA datasets in the NCBI-SRA database. Across the three selected public datasets, 67 of our 71 diatom OTUs were detected in other Australian ecosystems. Our results show that diatom plastid 16S rRNA genes are readily amplified with existing 515F-806RB primer sets. Therefore, the volume of existing 16S rRNA amplicon datasets initially generated for microbial community profiling can also be used to detect, characterize, and map diatom distribution to inform phylogeny and ecological health assessments, and can be extended into a range of ecological and industrial applications. To our knowledge, this study represents the first attempt to classify freshwater samples using this approach and the first application of PhytoREF in Australia.

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Maitland, Victoria Carley, Chloe Victoria Robinson, Teresita M. Porter et Mehrdad Hajibabaei. « Freshwater diatom biomonitoring through benthic kick-net metabarcoding ». PLOS ONE 15, n^o 11 (18 novembre 2020) : e0242143. http://dx.doi.org/10.1371/journal.pone.0242143.

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Biomonitoring is an essential tool for assessing ecological conditions and informing management strategies. The application of DNA metabarcoding and high throughput sequencing has improved data quantity and resolution for biomonitoring of taxa such as macroinvertebrates, yet, there remains the need to optimise these methods for other taxonomic groups. Diatoms have a longstanding history in freshwater biomonitoring as bioindicators of water quality status. However, multi-substrate periphyton collection, a common diatom sampling practice, is time-consuming and thus costly in terms of labour. This study examined whether the benthic kick-net technique used for macroinvertebrate biomonitoring could be applied to bulk-sample diatoms for metabarcoding. To test this approach, we collected samples using both conventional multi-substrate microhabitat periphyton collections and bulk-tissue kick-net methodologies in parallel from replicated sites with different habitat status (good/fair). We found there was no significant difference in community assemblages between conventional periphyton collection and kick-net methodologies or site status, but there was significant difference between diatom communities depending on site (P = 0.042). These results show the diatom taxonomic coverage achieved through DNA metabarcoding of kick-net is suitable for ecological biomonitoring applications. The shift to a more robust sampling approach and capturing diatoms as well as macroinvertebrates in a single sampling event has the potential to significantly improve efficiency of biomonitoring programmes that currently only use the kick-net technique to sample macroinvertebrates.

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Aritonang, Simon Hasintongan, Yusni Ikhwan Siregar et Irvina Nurrachmi. « Vertical Distribution of Nitrate, Phosphate, and Abundance of Planktonic Diatoms in Pandan Waters, Tapanuli Tengah Regency, North Sumatra ». Journal of Coastal and Ocean Sciences 3, n^o 1 (10 janvier 2022) : 9–16. http://dx.doi.org/10.31258/jocos.3.1.9-16.

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This research was conducted in February 2021 in Pandan Waters, Central Tapanuli Regency, North Sumatra Province. The purpose of this study was to analyze the concentration of nitrate and phosphate, analyze the composition distribution and abundance of planktonic diatoms, and analyze the relationship between nitrate and phosphate concentrations with an abundance of planktonic diatoms at different depths in Pandan Waters. The method used is the survey method. The results of the analysis of vertical concentrations of nitrate and phosphate in Pandan waters tend to increase with increasing depth, while the results of vertical analysis of planktonic diatom abundance in Pandan waters tend to decrease with increasing depth. The results of a simple linear regression test showed that the relationship between nitrate concentration and abundance of planktonic diatoms at different depths had a strong (negative) relationship, while the relationship between phosphate concentration and planktonic diatom abundance at different depths had a very weak (negative) relationship

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Vélez-Agudelo, Camilo, et Marcela A. Espinosa. « Benthic diatoms in relation to environmental factors in an allochthonous river from Patagonia, Argentina ». Marine and Freshwater Research 72, n^o 9 (2021) : 1340. http://dx.doi.org/10.1071/mf20249.

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Natural and human pressures increasingly threatening the biodiversity and water resources of dryland rivers. Fluvial environments of Patagonia harbour high diatom diversity, but their management value is overlooked. The aim of this study is to explore the diatom distribution in surface sediments of the Chubut River and evaluate their relationship with environmental variables. In total, 243 diatom taxa were identified in 16 littoral zone sites. The physical and chemical variables independently explained the variance in diatom data, whereas sediment texture had a low influence. Conductivity, major ions (HCO3–, Cl–, SO42–, Na+, K+, Ca2+ and Mg2+) and pH were the main environmental drivers explaining the diatom composition. As the highlighted variables increased near the mouth, so did the relative abundances of marine–brackish taxa such as Amphora copulatoides, Sarcophagodes alfred-wegeneri, Nitzschia fonticola and Tryblionella apiculata. Meanwhile, the presence of high pollution-tolerant diatoms can be put forward to explain the river health deterioration towards downstream areas. The marine–brackish taxa found at freshwater sites reflect a weak tidal influence in the estuary compared with other coastal systems of Patagonia. This study provides valuable information to test the hypothesis on the ecological status of aquatic resources and the potential effects of climatic and hydrological changes in the area.

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Ryves, David B., Annemarie L. Clarke, Peter G. Appleby, Susanne L. Amsinck, Erik Jeppesen, Frank Landkildehus et N. John Anderson. « Reconstructing the salinity and environment of the Limfjord and Vejlerne Nature Reserve, Denmark, using a diatom model for brackish lakes and fjords ». Canadian Journal of Fisheries and Aquatic Sciences 61, n^o 10 (1 octobre 2004) : 1988–2006. http://dx.doi.org/10.1139/f04-127.

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Diatoms in surface sediments from a data set of 27 brackish lakes and nine fjords in Jutland, Denmark (range 0.2 31 g·L1 total dissolved solids (TDS)), were analysed using multivariate methods to determine response to measured parameters (depth, total phosphorus (TP), total nitrogen (TN), TN/TP, salinity, water body type). Water body type, salinity, depth and TP together explained 25.3% of the variation in the diatom data and were all independently significant predictors. A diatomsalinity model (r2jack = 0.887, root mean square error of prediction = 0.246 log salinity, g·L1) was developed from the 36 sample training set and applied to fossil diatom assemblages in three sediment cores from the east Vejlerne wetland, Denmark, a nature reserve created after the damming of an embayment of the polyhaline Limfjord (~26 g·L1 TDS) in the late 19th century. The diatominferred salinity reconstructions reflect the known salinity history of the Limfjord and the freshwatersubsaline Vejlerne lakes, and appear sensitive to documented North Sea storms in the 16th and 17th centuries, which had major impacts on the brackish Limfjord herring fishery. Diatomsalinity models may be useful tools in long-term studies of coastal and estuarine areas to test hypotheses concerning aquatic resources and ecological, hydrographic, and cultural change.

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Zimmermann, Heike H., Kathleen R. Stoof-Leichsenring, Stefan Kruse, Juliane Müller, Ruediger Stein, Ralf Tiedemann et Ulrike Herzschuh. « Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30 000 years ». Ocean Science 16, n^o 5 (7 septembre 2020) : 1017–32. http://dx.doi.org/10.5194/os-16-1017-2020.

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Abstract. The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (sedaDNA) metabarcoding. Amplifying a short, partial rbcL marker from samples of sediment core MSM05/5-712-2 resulted in 95.7 % of our sequences being assigned to diatoms across 18 different families, with 38.6 % of them being resolved to species and 25.8 % to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom sedaDNA richness is highest in the Late Weichselian and lowest in Mid- and Late Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice-associated diatoms and suggests several reorganisations – after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, Chaetoceros socialis indicate the detectability of intra-specific diversity using sedaDNA. We detect no clear pattern between our diatom sedaDNA record and the previously published IP25 record of this core, although proportions of pennate diatoms increase with higher IP25 concentrations and proportions of Nitzschia cf. frigida exceeding 2 % of the assemblage point towards past sea-ice presence.

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Majewska, Roksana, Maria Cristina Gambi, Cecilia Maria Totti et Mario De Stefano. « Epiphytic diatom communities of Terra Nova Bay, Ross Sea, Antarctica : structural analysis and relations to algal host ». Antarctic Science 25, n^o 4 (10 janvier 2013) : 501–13. http://dx.doi.org/10.1017/s0954102012001101.

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AbstractEpiphytic diatoms are important constituents of the Southern Ocean coastal water ecosystem, being a key element in many of the Antarctic trophic chains. However, only limited information exists relating to these microalgal communities. Here we describe our findings of a study on epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica) based on material collected during the summer campaigns spanning from 1990–2004. Observations of diatoms associated with three rhodophyte species (Iridaea cordata (Turner) Bory, Phyllophora antarctica Gepp & Gepp, and Plocamium cartilagineum (L.) Dixon) were carried out with the use of a scanning electron microscope. A total of 73 diatom taxa (32 genera) were distinguished, of which 20 taxa exceeded 3% of total abundance. Cocconeis fasciolata (Ehrenberg) Brown, Navicula perminuta Grunow, and Fragilariopsis nana (Steemann Nielsen) Paasche appeared in every sample. The analysis of similarities (ANOSIM) test as well as non-metric multidimensional scaling analysis indicated the nature of host organism as a major factor influencing associated diatom community structure, whereas depth, site, and time of sampling seemed to be less important. The epizooic communities associated with sessile fauna epiphytic on macroalgae differed significantly from those associated with macroalgal surface. A pronounced difference between the communities epiphytic on various host macroalgae species was also observed, although most of the dissimilarities occurred between diatom taxa of the same growth form.

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Pollanen, M. S. « The Diatom Test for Drowning in Ontario ». Canadian Society of Forensic Science Journal 29, n^o 4 (janvier 1996) : 205–11. http://dx.doi.org/10.1080/00085030.1996.10757063.

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Olsen, Brianna K., Michael F. Chislock, Anja Rebelein et Alan E. Wilson. « Nutrient enrichment and vertical mixing mediate 2-methylisoborneol and geosmin concentrations in a drinking water reservoir ». Water Supply 17, n^o 2 (24 septembre 2016) : 500–507. http://dx.doi.org/10.2166/ws.2016.159.

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Few ecosystem-level studies have experimentally determined the physicochemical and biological factors that mediate concentrations of off-flavor compounds in drinking water reservoirs. Consequently, the watershed-scale mechanisms determining production of these compounds are still poorly understood. In a recent study, the addition of both nitrogen and phosphorus significantly increased 2-methylisoborneol (MIB). Not surprisingly, MIB was correlated with cyanobacterial abundance (a well-known producer of off-flavor compounds); however, MIB was most strongly correlated with diatom abundance. To empirically test for differences in the production of two important off-flavor compounds, specifically MIB and geosmin, by either cyanobacteria or diatoms, we conducted a fully factorial experiment that manipulated two factors that typically promote cyanobacteria (nitrogen and phosphorus fertilization) or diatoms (vertical mixing of the water column). As predicted, fertilization promoted cyanobacteria, and vertical mixing favored diatoms. Interestingly, the production of geosmin was rapid and consistent with an increase in cyanobacteria while MIB production increased later in the experiment when cyanobacterial biovolume tended to decline and diatom biovolume increased. Based on our current and previous studies, MIB and geosmin production is associated with cyanobacteria, but the direct or indirect influence of diatoms on production should not be ignored.

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Wolfe, Alexander P. « Spatial patterns of modern diatom distribution and multiple paleolimnological records from a small arctic lake on Baffin Island, Arctic Canada ». Canadian Journal of Botany 74, n^o 3 (1 mars 1996) : 435–49. http://dx.doi.org/10.1139/b96-054.

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The assumption that within-lake, deep-water sedimentary diatom assemblages are relatively uniform and that a single core is sufficient to depict lake ontogeny was tested for a small tarn on the southwestern Cumberland Peninsula of Baffin Island, Northwest Territories. Diatom transport and deposition were evaluated through analyses of periphytic, planktonic, and epipelic habitats. Diatom stratigraphies of four cores were used to test whether or not trends are comparable in different regions of the lake and throughout the Holocene. Among 12 surface-sediment stations, diatom distributions were alternately highly equitable or variable. Valves of evenly distributed genera (Aulacoseira and Achnanthes) are mixed in the water column prior to deposition. This is supported by plankton tow and periphyton samples, which were respectively dominated by Aulacoseira distans (and varieties) and Achnanthes altaica. Conversely, frequencies of several benthic taxa (e.g., Pinnularia biceps, species of Eunotia) varied up to 30% between stations, in patterns unrelated to water depth, and reflecting habitat specificity and minimal transport prior to burial. Of the four cores (38.0–95.5 cm), analysis of the two longest revealed three distinct zones: (i) a zone dominated by species of Fragilaria (> 9000 BP); (ii) a zone containing benthic acidophilic diatoms indicating natural acidification (9000–7000 BP); and (iii) a zone characterized by numerous species of Aulacoseira ranging from the mid to late Holocene. Clear differentiation of the lower two zones was impossible in the shorter cores, and radiocarbon dates suggest that sediment reworking truncated the earliest records of organic sedimentation at these sites. Correspondence analysis facilitated comparisons of the diatom stratigraphies and enabled the evaluation of core reproducibility. Central cores preserve the most useful paleolimnological records in this environment. Keywords: diatoms, paleolimnology, Arctic Canada, Baffin Island.

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Eilertsen, Hans Chr, Edel Elvevoll, Ingeborg Hulda Giæver, Jon Brage Svenning, Lars Dalheim, Ragnhild Aven Svalheim, Birthe Vang et al. « Inclusion of photoautotrophic cultivated diatom biomass in salmon feed can deter lice ». PLOS ONE 16, n^o 7 (29 juillet 2021) : e0255370. http://dx.doi.org/10.1371/journal.pone.0255370.

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The aim of this study was to evaluate the potential of diatom (microalgae) biomass as a lice-reducing ingredient in salmon feed. The original hypothesis was based on the fact that polyunsaturated aldehydes (PUAs), e.g. 2-trans, 4-trans decadenial (A3) produced by diatoms can function as grazing deterrents and harm copepod development. Salmon lice (Lepeophtheirus salmonis) is a copepod, and we intended to test if inclusion of diatom biomass in the feed could reduce the infestation of lice on salmon. We performed experiments where salmon kept in tanks were offered four different diets, i.e. basic feed with diatoms, fish oil, Calanus sp. oil or rapeseed oil added. After a feeding period of 67 days a statistically representative group of fishes, tagged with diet group origin, were pooled in a 4000L tank and exposed to salmon lice copepodites whereafter lice infestation was enumerated. Salmon from all four diet groups had good growth with SGR values from 1.29 to 1.44% day-1 (increase from ca. 130 g to 350 g). At the termination of the experiment the number of lice on salmon offered diatom feed were statistically significantly lower than on salmon fed the other diets. Mean lice infestation values increased from diatom feed through Calanus and fish oil to standard feed with terrestrial plant ingredients. Analysis of the chemical composition of the different diets (fatty acids, amino acids) failed to explain the differences in lice infestation. The only notable result was that diatom and Calanus feed contained more FFA (free fatty acids) than feed with fish oil and the control feed. None of the potential deleterious targeted polyunsaturated aldehydes could be detected in skin samples of the salmon. What was exclusive for salmon that experienced reduced lice was diatom inclusion in the feed. This therefore still indicates the presence of some lice deterring ingredient, either in the feed, or an ingredient can have triggered production of an deterrent in the fish. An obvious follow up of this will be to perform experiments with different degrees of diatom inclusion in the feeds, i.e. dose response experiments combined with targeted PUA analyses, as well as to perform large scale experiments under natural conditions in aquaculture pens.

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Glaviano, Francesca, Nadia Ruocco, Emanuele Somma, Giuseppe De Rosa, Virginia Campani, Pasquale Ametrano, Davide Caramiello, Maria Costantini et Valerio Zupo. « Two Benthic Diatoms, Nanofrustulum shiloi and Striatella unipunctata, Encapsulated in Alginate Beads, Influence the Reproductive Efficiency of Paracentrotus lividus by Modulating the Gene Expression ». Marine Drugs 19, n^o 4 (17 avril 2021) : 230. http://dx.doi.org/10.3390/md19040230.

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Physiological effects of algal metabolites is a key step for the isolation of interesting bioactive compounds. Invertebrate grazers may be fed on live diatoms or dried, pelletized, and added to compound feeds. Any method may reveal some shortcomings, due to the leaking of wound-activated compounds in the water prior to ingestion. For this reason, encapsulation may represent an important step of bioassay-guided fractionation, because it may assure timely preservation of the active compounds. Here we test the effects of the inclusion in alginate (biocompatible and non-toxic delivery system) matrices to produce beads containing two benthic diatoms for sea urchin Paracentrotus lividus feeding. In particular, we compared the effects of a diatom whose influence on P. lividus was known (Nanofrustulum shiloi) and those of a diatom suspected to be harmful to marine invertebrates, because it is often present in blooms (Striatella unipunctata). Dried N. shiloi and S. unipunctata were offered for one month after encapsulation in alginate hydrogel beads and the larvae produced by sea urchins were checked for viability and malformations. The results indicated that N. shiloi, already known for its toxigenic effects on sea urchin larvae, fully conserved its activity after inclusion in alginate beads. On the whole, benthic diatoms affected the embryogenesis of P. lividus, altering the expression of several genes involved in stress response, development, skeletogenesis and detoxification processes. Interactomic analysis suggested that both diatoms activated a similar stress response pathway, through the up-regulation of hsp60, hsp70, NF-κB, 14-3-3 ε and MDR1 genes. This research also demonstrates that the inclusion in alginate beads may represent a feasible technique to isolate diatom-derived bioactive compounds.

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Gili, Josep-Maria, Alicia Duró, Josep García-Valero, Josep M. Gasol et Sergio Rossi. « Herbivory in small carnivores : benthic hydroids as an example ». Journal of the Marine Biological Association of the United Kingdom 88, n^o 8 (décembre 2008) : 1541–46. http://dx.doi.org/10.1017/s0025315408003214.

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Previous evidence has shown that benthic hydroids capture all kinds of available prey and the only known constraint was prey size. Among the prey captured are phytoplankton cells but it is not known whether they are digested and assimilated. To test the hypothesis that benthic hydroids assimilate phytoplankton cells, a series of feeding experiments was carried out with the Mediterranean species Eudendrium racemosum. Ingestion rates and assimilation efficiency were determined by analysing the 14C incorporated from a labelled population of the diatom species Thalassiosira weissflogii. Eudendrium racemosum fed on T. weissflogii, after a period of starvation, and with the diatoms as the sole food item. In the presence of approximately 15,000 diatoms ml−1, Eudendrium fed at rates ranging from 16 to 55 diatoms polyp−1 hour−1. Accumulation of radioactivity in the hydrocaulus and the polyps of the hydroids were observed. A maximum ingestion of 31.6 diatoms per μgC of polyp (i.e. 175 diatoms per polyp) was observed in the experiments. Most of the diatom 14C ingested would have ended up in the Eudendrium tissue (efficiency 94%), and it was expected that a certain percentage would have been respired by the polyps. These data show that Eudendrium feed on phytoplankton, which can satisfy almost 100% of their energy demand when this type of food is sufficiently abundant.

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Guo, Liliang, Zhenghong Sui, Shu Zhang, Yuanyuan Ren et Yuan Liu. « Comparison of potential diatom ‘barcode’ genes (the 18S rRNA gene and ITS, COI, rbcL) and their effectiveness in discriminating and determining species taxonomy in the Bacillariophyta ». International Journal of Systematic and Evolutionary Microbiology 65, Pt_4 (1 avril 2015) : 1369–80. http://dx.doi.org/10.1099/ijs.0.000076.

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Diatoms form an enormous group of photoautotrophic micro-eukaryotes and play a crucial role in marine ecology. In this study, we evaluated typical genes to determine whether they were effective at different levels of diatom clustering analysis to assess the potential of these regions for barcoding taxa. Our test genes included nuclear rRNA genes (the nuclear small-subunit rRNA gene and the 5.8S rRNA gene+ITS-2), a mitochondrial gene (cytochrome c-oxidase subunit 1, COI), a chloroplast gene [ribulose-1,5-biphosphate carboxylase/oxygenase large subunit (rbcL)] and the universal plastid amplicon (UPA). Calculated genetic divergence was highest for the internal transcribed spacer (ITS; 5.8S+ITS-2) (p-distance of 1.569, 85.84 % parsimony-informative sites) and COI (6.084, 82.14 %), followed by the 18S rRNA gene (0.139, 57.69 %), rbcL (0.120, 42.01 %) and UPA (0.050, 14.97 %), which indicated that ITS and COI were highly divergent compared with the other tested genes, and that their nucleotide compositions were variable within the whole group of diatoms. Bayesian inference (BI) analysis showed that the phylogenetic trees generated from each gene clustered diatoms at different phylogenetic levels. The 18S rRNA gene was better than the other genes in clustering higher diatom taxa, and both the 18S rRNA gene and rbcL performed well in clustering some lower taxa. The COI region was able to barcode species of some genera within the Bacillariophyceae. ITS was a potential marker for DNA based-taxonomy and DNA barcoding of Thalassiosirales, while species of Cyclotella, Skeletonema and Stephanodiscus gathered in separate clades, and were paraphyletic with those of Thalassiosira. Finally, UPA was too conserved to serve as a diatom barcode.

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Chaudhary, Rinkal, et Vinod Dhingra. « Forensic significance in the cases of drowning deaths : An elaborative study ». IP International Journal of Forensic Medicine and Toxicological Sciences 6, n^o 4 (15 janvier 2022) : 122–26. http://dx.doi.org/10.18231/j.ijfmts.2021.026.

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Drowning is a form of asphyxia which is caused by submersion/immersion of the body in water or any other fluid that occurs due to the aspiration of fluid into air passages and is mostly accidental. The main question arises in the case of a body recovered from water is whether the individual was alive at the time he entered water. If a body is found in water is does not necessarily mean, that this person has drowned. The bodily external and internal findings are necessary in medicolegal investigation of drowning deaths. Drowning is difficult to determine and are often diagnosed by eliminating other potential causes of death whereas diatom test is significant for the concluding analysis of drowning deaths. Diatoms found inside the body may serve as corroborative evidence in the diagnosis of the cause of drowning death. It can be ascertained whether the drowning is ante-mortem or post-mortem. The diatom test considered as the only tool to examine drowning cases. The present study highlights some specific points to drag conclusive results in the investigation of deaths due to drowning.

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Rukiana, Syahril Nedi et Irvina Nurachmi. « ANALYSIS CONCENTRATION OF SURFACTANT ANIONIC AND THE RELATION WITH DIATOM ABUNDANCE IN BUNGUS WATER, PADANG WEST SUMATERA ». Asian Journal of Aquatic Sciences 3, n^o 1 (9 avril 2020) : 1–10. http://dx.doi.org/10.31258/ajoas.3.1.1-10.

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This research aims to analyze surfactant anionic concentration and diatom abundance that has been implemented at May 2018 in Bungus rivers, Padang. This Research were conducted in survey method, four station were eshtablished with three replication of each sampling station. Analysis of surfactant anionic and diatom content was done at Chemistry Oceanography Laboratory and diatom identification was performed at Biology Oceanography Laboratory. The results showed that surfactant content in the waters ranged from 0,309-0,773 ppm and diatom abundance based on laboratory test on ranged 40,7407-81,4815 Ind/l. The correlation of surfactant and diatom content in waters by using linear regression y = Y = 94.56 -66.8x with correlation coefficient r = 0,809 and correlation water quality parameters with diatom abundance by using multiple linear regression Y= 787,189 -238,828X1 -9,032X2 -6,185X3 +5,371X4 +303,081X5 -35,631X6 with determination regression 0,995 and correlation coefficient r = 0,997.

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Blanco, Saúl, Irene Álvarez et Cristina Cejudo. « A test on different aspects of diatom processing techniques ». Journal of Applied Phycology 20, n^o 4 (22 décembre 2007) : 445–50. http://dx.doi.org/10.1007/s10811-007-9292-2.

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Pociecha, Agnieszka, Agata Z. Wojtal, Ewa Szarek-Gwiazda, Anna Cieplok, Dariusz Ciszewski et Sylwia Cichoń. « Neo- and Paleo-Limnological Studies on Diatom and Cladoceran Communities of Subsidence Ponds Affected by Mine Waters (S. Poland) ». Water 12, n^o 6 (2 juin 2020) : 1581. http://dx.doi.org/10.3390/w12061581.

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Plankton assemblages can be altered to different degrees by mining. Here, we test how diatoms and cladocerans in ponds along a river in southern Poland respond to the cessation of the long-term Pb-Zn mining. There are two groups of subsidence ponds in the river valley. One of them (DOWN) was contaminated over a period of mining, which ceased in 2009, whereas the other (UP) appeared after the mining had stopped. We used diatoms and cladocerans (complete organisms in plankton and their remains in sediments) to reveal the influence of environmental change on the structure and density of organisms. The water of UP pond was more contaminated by major ions (SO42−, Cl−) and nutrients (NO3−, PO43−) than the DOWN ponds. Inversely, concentrations of Zn, Cd, Cu and Pb were significantly higher in sediment cores of DOWN ponds in comparison to those in the UP pond. Ponds during mining had higher diversity of diatoms and cladocerans than the pond formed after the mining had stopped. CCA showed that diatom and cladoceran communities related most significantly to concentrations of Pb in sediment cores. Comparison of diatom and cladoceran communities in plankton and sediment suggests significant recovery of assemblages in recent years and reduction of the harmful effect of mine-originating heavy metals. Some features of ponds such as the rate of water exchange by river flow and the presence of water plants influenced plankton communities more than the content of dissolved heavy metals.

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Gibson, A. M. « Diatom Analysis of Clays and Late Neolithic Pottery from the Milfield Basin, Northumberland. » Proceedings of the Prehistoric Society 52 (1986) : 89–103. http://dx.doi.org/10.1017/s0079497x00006599.

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The suitability of diatom analysis for provenancing British late neolithic and early Bronze Age ceramics is examined. The Milfield Basin, Northumberland, was chosen for a test programme, as an area with well documented clay sources, defined geology and available pottery samples. The bulk of the pottery sampled was of local origin, or at least need not have been made elsewhere; one sherd, the only possible Beaker sherd sampled, seems to be an import. It is concluded that it is possible to use diatoms in this way, and some of the problems of the technique are discussed, together with possible solutions. Sampling and counting strategies are also discussed.

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Liu, Shuangshuang, Min Yao, Shiyue Chen et Xingzhong Yuan. « Surface Sediment Diatom Assemblages Response to Water Environment in Dongping Lake, North China ». Water 13, n^o 3 (29 janvier 2021) : 339. http://dx.doi.org/10.3390/w13030339.

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The relationship between the diatom taxa preserved in surface lake sediments and environmental variables in Dongping Lake was explored using multivariate statistical methods. The statistical analysis showed that the lake was eutrophicated in all seasons. Transparency, chlorophyll a (Chla) and total phosphorus (TP) were the dominant environmental factors in spring and summer, and NH4+-N and chemical oxygen demand (COD) were the dominant environmental factors in autumn and winter. Sixteen genera and 43 species of diatom were found in the surface sediments, and the dominant diatom genera were Aulacoseira, Ulnaria, Cyclotella, Navicula and Fragilaria. A redundancy analysis (RDA) and Monte Carlo permutation 20 test revealed that COD, pH, TP, conductivity and transparency were significant factors influencing diatom assemblage change, meaning that the distribution of the diatom assemblages were mostly influenced by nutrient composition, light intensity and ion concentrations.

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Kang, Lee-Kuo, Feng-Hsiu Tsui et Jeng Chang. « Quantification of Diatom Gene Expression in the Sea by Selecting Uniformly Transcribed mRNA as the Basis for Normalization ». Applied and Environmental Microbiology 78, n^o 17 (15 juin 2012) : 6051–58. http://dx.doi.org/10.1128/aem.00935-12.

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ABSTRACTTo quantify gene expressions by quantitative reverse transcription-PCR (Q-RT-PCR) in natural diatom assemblages, it is necessary to seek a biomass reference specific to the target species. Two housekeeping genes,TBP(encoding the TATA box-binding protein) andEFL(encoding the translation elongation factor-like protein), were evaluated as candidates for reference genes in Q-RT-PCR assays. Transcript levels ofTBPandEFLwere relatively stable under various test conditions including growth stages, light-dark cycle phases, and nutrient stresses inSkeletonema costatumandChaetoceros affinis, andTBPexpression was more stable than that ofEFL. Next, the sequence diversity of diatom assemblages was evaluated by obtaining 32EFLand 29TBPhomologous gene fragments from the East China Sea (ECS). Based on sequence alignments,EFLandTBPprimer sets were designed forChaetocerosandSkeletonemagroups in the ECS. An evaluation of primer specificity and PCR efficiency indicated that theEFLprimer sets performed better. To demonstrate the applicability ofEFLprimer sets in the ECS, they were employed to measure mRNA levels of the FcpB (fucoxanthin-chlorophyll protein) gene in diatoms. The results correctly revealed prominent diel variations inFcpBexpression and confirmedEFLas a good reference gene.

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Reed, J. M., A. Cvetkoska, Z. Levkov, H. Vogel et B. Wagner. « The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania) : testing diatom response to climate ». Biogeosciences Discussions 7, n^o 3 (17 juin 2010) : 4689–714. http://dx.doi.org/10.5194/bgd-7-4689-2010.

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Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 15–7.4 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, following by a post-Medieval cooling trend. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom concentration data in future studies.

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Reed, J. M., A. Cvetkoska, Z. Levkov, H. Vogel et B. Wagner. « The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania) : testing diatom response to climate ». Biogeosciences 7, n^o 10 (13 octobre 2010) : 3083–94. http://dx.doi.org/10.5194/bg-7-3083-2010.

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Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 14.7–6.9 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, followed by a post-Medieval loss of diversity which is consistent with cooling, but not definitive. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom accumulation data in future studies.

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Bielczyńska, Aleksandra. « Bioindication on the basis of benthic diatoms : Advantages and disadvantages of the Polish phytobenthos lake assessment method (IOJ – the Diatom Index for Lakes) / Bioindykacja na podstawie okrzemek bentosowych : Mocne i słabe strony polskiej metody oceny jezior na podstawie fitobentosu (IOJ – Indeks Okrzemkowy Jezior) ». Ochrona Srodowiska i Zasobów Naturalnych 26, n^o 4 (1 décembre 2015) : 48–55. http://dx.doi.org/10.1515/oszn-2015-0027.

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Abstract Diatoms are widely used for bioindication because of their sensitivity to anthropogenic pressures (e.g. eutrophication or acidity of waters). In many countries in the world, work has been undertaken to develop and implement diatom indices. Since 2000, in the Member States of the European Union, this has been done as part of the implementation of the Water Framework Directive. The results of lake assessment obtained using the Polish method based on epiphytic diatoms (IOJ - Indeks Okrzemkowy Jezior = the Diatom Index for Lakes) are greatly different from those provided by the other ecological status assessment methods. The purpose of this article is to review the scientific literature on the use of phytobenthos for bioindication in order to identify the advantages and disadvantages of the Polish IOJ method and to indicate the possible directions of improvements in this method. The literature evidencing the variability of phytobenthos related to its habitat, the spatial variability at the scale of a lake and the variability in the growing season was reviewed. The cited writings indicate that the further specification of guidelines for the sampling procedure and an increase in the number of survey sites could enhance the functionality of the Polish lake assessment method. It has also been suggested that it may be useful to test the effect of the seasonal variability of a phytobenthos assemblage on its bioindicator value.

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Memmolo, Pasquale, Pierluigi Carcagnì, Vittorio Bianco, Francesco Merola, Andouglas Goncalves da Silva Junior, Luis Marcos Garcia Goncalves, Pietro Ferraro et Cosimo Distante. « Learning Diatoms Classification from a Dry Test Slide by Holographic Microscopy ». Sensors 20, n^o 21 (7 novembre 2020) : 6353. http://dx.doi.org/10.3390/s20216353.

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Diatoms are among the dominant phytoplankters in marine and freshwater habitats, and important biomarkers of water quality, making their identification and classification one of the current challenges for environmental monitoring. To date, taxonomy of the species populating a water column is still conducted by marine biologists on the basis of their own experience. On the other hand, deep learning is recognized as the elective technique for solving image classification problems. However, a large amount of training data is usually needed, thus requiring the synthetic enlargement of the dataset through data augmentation. In the case of microalgae, the large variety of species that populate the marine environments makes it arduous to perform an exhaustive training that considers all the possible classes. However, commercial test slides containing one diatom element per class fixed in between two glasses are available on the market. These are usually prepared by expert diatomists for taxonomy purposes, thus constituting libraries of the populations that can be found in oceans. Here we show that such test slides are very useful for training accurate deep Convolutional Neural Networks (CNNs). We demonstrate the successful classification of diatoms based on a proper CNNs ensemble and a fully augmented dataset, i.e., creation starting from one single image per class available from a commercial glass slide containing 50 fixed species in a dry setting. This approach avoids the time-consuming steps of water sampling and labeling by skilled marine biologists. To accomplish this goal, we exploit the holographic imaging modality, which permits the accessing of a quantitative phase-contrast maps and a posteriori flexible refocusing due to its intrinsic 3D imaging capability. The network model is then validated by using holographic recordings of live diatoms imaged in water samples i.e., in their natural wet environmental condition.

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Huh, Gi Yeong. « Progress in Method and Reliability of Diatom Test in Drowning ». Korean Journal of Legal Medicine 44, n^o 3 (31 août 2020) : 115–22. http://dx.doi.org/10.7580/kjlm.2020.44.3.115.

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Nolte, Kim Alexander, Jana Schwarze, Cindy Denise Beyer, Onur Özcan et Axel Rosenhahn. « Parallelized microfluidic diatom accumulation assay to test fouling-release coatings ». Biointerphases 13, n^o 4 (août 2018) : 041007. http://dx.doi.org/10.1116/1.5034090.

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Litchman, E., C. A. Klausmeier, J. R. Miller, O. M. Schofield et P. G. Falkowski. « Multi-nutrient, multi-group model of present and future oceanic phytoplankton communities ». Biogeosciences Discussions 3, n^o 3 (19 juin 2006) : 607–63. http://dx.doi.org/10.5194/bgd-3-607-2006.

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Abstract. Phytoplankton community composition profoundly influences patterns of nutrient cycling and the structure of marine food webs; therefore predicting present and future phytoplankton community structure is of fundamental importance to understanding how ocean ecosystems are influenced by physical forcing and nutrient limitations. In this paper, we develop a mechanistic model of phytoplankton communities that includes multiple taxonomic groups, test the model at two contrasting sites in the modern ocean, and then use the model to predict community reorganization under different global change scenarios. The model includes three phytoplankton functional groups (diatoms, coccolithophores, and prasinophytes), five nutrients (nitrate, ammonium, phosphate, silicate and iron), light, and a generalist zooplankton grazer. Each taxonomic group was parameterized based on an extensive literature survey. The model successfully predicts the general patterns of community structure and succession in contrasting parts of the world ocean, the North Atlantic (North Atlantic Bloom Experiment, NABE) and subarctic North Pacific (ocean station Papa, OSP). In the North Atlantic, the model predicts a spring diatom bloom, followed by coccolithophore and prasinophyte blooms later in the season. The diatom bloom becomes silica-limited and the coccolithophore and prasinophyte blooms are controlled by nitrogen, grazers and by deep mixing and decreasing light availability later in the season. In the North Pacific, the model reproduces the low chlorophyll community dominated by prasinophytes and coccolithophores, with low total biomass variability and high nutrient concentrations throughout the year. Sensitivity analysis revealed that the identity of the most sensitive parameters and the range of acceptable parameters differed between the two sites. Five global change scenarios are used to drive the model and examine how community dynamics might change in the future. To estimate uncertainty in our predictions, we used a Monte Carlo sampling of the parameter space where future scenarios were run using parameter combinations that produced adequate modern day outcomes. The first scenario is based on a global climate model that indicates that increased greenhouse gas concentrations will cause a later onset and extended duration of stratification and shallower mixed layer depths. Under this scenario, the North Atlantic spring diatom bloom occurs later and is of a smaller magnitude, but the average biomass of diatoms, coccolithophores and prasinophytes will likely increase. In the subarctic North Pacific, diatoms and prasinophytes will likely increase along with total chlorophyll concentration and zooplankton. In contrast, coccolithophore densities do not change at this site. Under the second scenario of decreased deep-water phosphorus concentration, coccolithophores, total chlorophyll and zooplankton decline, as well as the magnitude of the spring diatom bloom, while the average diatom and prasinophyte abundance does not change in the North Atlantic. In contrast, a decrease in phosphorus in the North Pacific is not likely to change community composition. Similarly, doubling of nitrate in deep water does not significantly affect ecosystems at either site. Under decreased iron deposition, coccolithophores are likely to increase and other phytoplankton groups and zooplankton to decrease at both sites. An increase in iron deposition is likely to increase prasinophyte and diatom abundance and decrease coccolithophore abundance at both sites, although more dramatically at the North Pacific site. Total chlorophyll and zooplankton are also likely to increase under this scenario at both sites. Based on these scenarios, our model suggests that global environmental change will inevitably alter phytoplankton community structure and potentially impact global biogeochemical cycles.

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Zhao, Jian, Yuzhong Wang, Yanji Zhang, Sunlin Hu et Chao Liu. « Types of diatoms in China’s three major rivers and the possible application for an automatic forensic diatom test ». Australian Journal of Forensic Sciences 47, n^o 3 (18 juillet 2014) : 268–74. http://dx.doi.org/10.1080/00450618.2014.937456.

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Jantschke, Anne, Katrin Spinde et Eike Brunner. « Electrostatic interplay : The interaction triangle of polyamines, silicic acid, and phosphate studied through turbidity measurements, silicomolybdic acid test, and 29Si NMR spectroscopy ». Beilstein Journal of Nanotechnology 5 (6 novembre 2014) : 2026–35. http://dx.doi.org/10.3762/bjnano.5.211.

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The discovery of long-chain polyamines as biomolecules that are tightly associated to biosilica in diatom cell walls has inspired numerous in vitro studies aiming to characterize polyamine–silica interactions. The determination of these interactions at the molecular level is of fundamental interest on one hand for the understanding of cell wall biogenesis in diatoms and on the other hand for designing bioinspired materials synthesis approaches. The present contribution deals with the influence of amines and polyamines upon the initial self-assembly processes taking place during polyamine-mediated silica formation in solution. The influence of phosphate upon these processes is studied. For this purpose, sodium metasilicate solutions containing additives such as polyallylamine, allylamine and others in the presence/absence of phosphate were investigated. The analyses are based mainly on turbidity measurements yielding information about the early aggregation steps which finally give rise to the formation and precipitation of silica.

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Blanco, Saúl, María Borrego-Ramos et Adriana Olenici. « Disentangling diatom species complexes : does morphometry suffice ? » PeerJ 5 (11 décembre 2017) : e4159. http://dx.doi.org/10.7717/peerj.4159.

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Accurate taxonomic resolution in light microscopy analyses of microalgae is essential to achieve high quality, comparable results in both floristic analyses and biomonitoring studies. A number of closely related diatom taxa have been detected to date co-occurring within benthic diatom assemblages, sharing many morphological, morphometrical and ecological characteristics. In this contribution, we analysed the hypothesis that, where a large sample size (number of individuals) is available, common morphometrical parameters (valve length, width and stria density) are sufficient to achieve a correct identification to the species level. We focused on some common diatom taxa belonging to the genusGomphonema. More than 400 valves and frustules were photographed in valve view and measured using Fiji software. Several statistical tools (mixture and discriminant analysis, k-means clustering, classification trees, etc.) were explored to test whether mere morphometry, independently of other valve features, leads to correct identifications, when compared to identifications made by experts. In view of the results obtained, morphometry-based determination in diatom taxonomy is discouraged.

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Saini, Shivam, et Bhuvnesh Yadav. « Current techniques used for diatom test in diagnosis of drowning deaths ». Journal of Punjab Academy of Forensic Medicine & ; Toxicology 19, n^o 2 (2019) : 186. http://dx.doi.org/10.5958/0974-083x.2020.00041.2.

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Sidari, Laura, Nunzio Di Nunno, Fulvio Costantinides et Mauro Melato. « Diatom test with Soluene-350 to diagnose drowning in sea water ». Forensic Science International 103, n^o 1 (juillet 1999) : 61–65. http://dx.doi.org/10.1016/s0379-0738(99)00056-0.

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Bortolotti, Federica, Giovanna Del Balzo, Riccardo Calza, Fernando Valerio et Franco Tagliaro. « Testing the specificity of the diatom test : search for false-positives ». Medicine, Science and the Law 51, n^o 1_suppl (octobre 2011) : 7–10. http://dx.doi.org/10.1258/msl.2010.010057.

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González-Paz, Lorena, Josué Gestido, Cristina Delgado, Nuria Pedrol et Isabel Pardo. « Short-Term Effect of Eucalyptus Leachates on Green Food Webs in Headwaters ». Water 15, n^o 1 (29 décembre 2022) : 115. http://dx.doi.org/10.3390/w15010115.

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Despite the reported allelopathic nature of the Eucalyptus genus, eucalypt leachates have unknown effects on the trophic base of stream green food webs. Eucalypt plantations have increased worldwide, including riparian ecosystems. We aimed to test whether short-term eucalypt leachates might alter water chemistry, periphytic algal biomass and diatoms, and herbivorous invertebrates’ (i.e., scrapers). We studied two oligotrophic and well-preserved headwaters from NW Spain. The experiment followed a before-after control-impact paired (BACIp) design, with weekly sampling before and after eucalypt leaves addition to streams. In the stream with lower discharge, the eucalypt treatments seemed to affect increases in biomass accrual (Chl-a) and diatom assemblages, disfavouring sensitive species (e.g., Eunotia minor and Achnanthidium pyrenaicum). Therefore, the ecological status was reduced from high to good. In the stream with higher discharge, invertebrate assemblages changed with scrapers having their abundances modified in comparison with the control (e.g., Habrophlebia sp. and Elmidae). Results suggest that eucalypt leaves leachates exert toxic effects on periphyton and on diatom and invertebrate assemblages, and this effect might be mediated by discharge. Alterations at the base of stream food webs may compromise their good ecological status. Further studies are necessary to identify whether this toxicity is due to allelopathic processes.

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