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Mulenga M, Monde C, Johnson T, Ouma KO, Syampungani S. Advances in the integration of microalgal communities for biomonitoring of metal pollution in aquatic ecosystems of sub-Saharan Africa. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:40795-40817. [PMID: 38822177 PMCID: PMC11190019 DOI: 10.1007/s11356-024-33781-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 05/16/2024] [Indexed: 06/02/2024]
Abstract
This review elucidated the recent advances in integrating microalgal communities in monitoring metal pollution in aquatic ecosystems of sub-Saharan Africa (SSA). It also highlighted the potential of incorporating microalgae as bioindicators in emerging technologies, identified research gaps, and suggested directions for further research in biomonitoring of metal pollution. Reputable online scholarly databases were used to identify research articles published between January 2000 and June 2023 for synthesis. Results indicated that microalgae were integrated either individually or combined with other bioindicators, mainly macroinvertebrates, macrophytes, and fish, alongside physicochemical monitoring. There was a significantly low level of integration (< 1%) of microalgae for biomonitoring aquatic metal pollution in SSA compared to other geographical regions. Microalgal communities were employed to assess compliance (76%), in diagnosis (38%), and as early-warning systems (38%) of aquatic ecological health status. About 14% of biomonitoring studies integrated microalgal eDNA, while other technologies, such as remote sensing, artificial intelligence, and biosensors, are yet to be significantly incorporated. Nevertheless, there is potential for the aforementioned emerging technologies for monitoring aquatic metal pollution in SSA. Future monitoring in the region should also consider the standardisation and synchronisation of integrative biomonitoring and embrace the "Citizen Science" concept at national and regional scales.
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Affiliation(s)
- Mary Mulenga
- Department of Biological Sciences, School of Mathematics & Natural Sciences, Copperbelt University, P. O. Box 21692, Kitwe, Zambia.
- Chair-Environment & Development, Oliver R Tambo Africa Research Chair Initiative (ORTARChI), Copperbelt University, P. O. Box 21692, Kitwe, Zambia.
| | - Concillia Monde
- Department of Zoology & Aquatic Sciences, School of Natural Resources, Copperbelt University, P. O. Box 21692, Kitwe, Zambia
- Chair-Environment & Development, Oliver R Tambo Africa Research Chair Initiative (ORTARChI), Copperbelt University, P. O. Box 21692, Kitwe, Zambia
| | - Todd Johnson
- Department of Biological Sciences, School of Mathematics & Natural Sciences, Copperbelt University, P. O. Box 21692, Kitwe, Zambia
| | - Kennedy O Ouma
- Department of Zoology & Aquatic Sciences, School of Natural Resources, Copperbelt University, P. O. Box 21692, Kitwe, Zambia
| | - Stephen Syampungani
- Department of Plant & Environmental Sciences, School of Natural Resources, Copperbelt University, P. O. Box 21692, Kitwe, Zambia
- Chair-Environment & Development, Oliver R Tambo Africa Research Chair Initiative (ORTARChI), Copperbelt University, P. O. Box 21692, Kitwe, Zambia
- Forest Science Postgraduate Program, Department of Plant & Soil Sciences, Plant Sciences Complex, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0002, South Africa
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Silva C, Santos JI, Vidal T, Silva S, Almeida SFP, Gonçalves FJM, Abrantes N, Pereira JL. Potential effects of the discharge of wastewater treatment plant (WWTP) effluents in benthic communities: evidence from three distinct WWTP systems. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:34492-34506. [PMID: 38709406 PMCID: PMC11136724 DOI: 10.1007/s11356-024-33462-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 04/21/2024] [Indexed: 05/07/2024]
Abstract
Wastewater treatment plant (WWTP) effluents can be sources of environmental contamination. In this study, we aimed to understand whether effluents of three different WWTPs may have ecological effects in riverine recipient ecosystems. To achieve this, we assessed benthic phytobenthos and macroinvertebrate communities at three different locations relative to the effluent discharge: immediately upstream, immediately downstream and 500-m downstream the effluent discharge. Two approaches were employed: the ecological status classification as defined in the Water Framework Directive (WFD) based on biological indicators; constrained multivariate analysis to disentangle the environmental drivers (physicochemical variables and contaminants, namely metals, polycyclic aromatic hydrocarbons, pharmaceuticals, and personal care products) of ecological changes across the study sites. The results showed inconsistencies between the WFD approach and the multivariate approach, as well as between the responses of macroinvertebrates and diatoms. The WWTP effluents impacted benthic communities in a single case: macroinvertebrates were negatively affected by one of the WWTP effluents, likely by the transported pharmaceuticals (other stressors are essentially homogeneous among sites). Given the findings and the scarcity of consistent evidence on ecological impacts that WWTP effluents may have in recipient ecosystems, further research is needed towards more sustainable regulation and linked environmental protection measures.
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Affiliation(s)
- Carlos Silva
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Joana Isabel Santos
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Tânia Vidal
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Susana Silva
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Salomé Fernandes Pinheiro Almeida
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- GeoBioTec - Geobiociências, Geotecnologias E Geo-Engenharias, University of Aveiro, Aveiro, Portugal
| | - Fernando José Mendes Gonçalves
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Nelson Abrantes
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
| | - Joana Luísa Pereira
- CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal.
- Department of Biology, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal.
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Blanco S. What do diatom indices indicate? Modeling the specific pollution sensitivity index. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:29449-29459. [PMID: 38580872 PMCID: PMC11058767 DOI: 10.1007/s11356-024-33115-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/24/2024] [Indexed: 04/07/2024]
Abstract
Diatoms are commonly used in environmental assessments to detect pollution and eutrophication. The specific pollution sensitivity index (SPI) is one of the most frequently used indices, which assigns scores to diatom taxa based on their sensitivity to pollution. The study analyzed diatom communities in the Duero River basin in Spain to examine the relationship between SPI scores and various limnological variables. A GLM model showed that phosphates, nitrites, and water temperature were the main factors explaining SPI variability. The study also reviews previous results using SPI for water quality monitoring in different world regions, highlighting the role of nutrients in general as major drivers of SPI values worldwide. Overall, the findings reinforce the reliability of SPI as a metric for biological monitoring in various watercourses.
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Affiliation(s)
- Saúl Blanco
- Diatom Laboratory, University of Leon, La Serna 58, 24007, Leon, Spain.
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Novais MH, Penha AM, Catarino A, Martins I, Fialho S, Lima A, Morais M, Palma P. The usefulness of ecotoxicological tools to improve the assessment of water bodies in a climate change reality. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 901:166392. [PMID: 37597569 DOI: 10.1016/j.scitotenv.2023.166392] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 07/22/2023] [Accepted: 08/16/2023] [Indexed: 08/21/2023]
Abstract
This study aimed to analyse the added value of using ecotoxicological tools to complement and improve the assessment of natural water bodies status, in situations of climate change, with a higher frequency of extreme events as floods or droughts. Four water bodies of streams in the Guadiana Basin (Álamos, Amieira, Lucefécit, Zebro) were studied in 2017 and 2018 and classified based on the Water Framework Directive (WFD) parameters: Biological Quality Element - Phytobenthos (diatoms), General chemical and physicochemical elements, Specific pollutants, and Priority Substances. Complementarily, bioassays (including lethal and sublethal parameters) were carried out with organisms of different trophic levels: (i) the bacteria Aliivibrio fischeri; (ii) the microalgae Pseudokirchneriella subcapitata; (iii) the crustaceans Daphnia magna, Thamnocephalus platyurus and Heterocypris incongruens. A classification system with 5 scores was developed, permitting to classify water bodies from non-toxic (EC50 > 100 %; growth and feeding rate > 80 %; blue) to highly toxic (EC50 < 10 %; growth and feeding rate < 10 %; red). The comparison between the classification based on the WFD parameters and on ecotoxicological endpoints showed similar results for 71 % of the samples, and significant positive Pearson correlations were detected between the diatom-based Specific Polluosensitivity Index (SPI) and EC50V.fisheri, the algae growth rate and Shannon diversity index. These results indicate that when the biological quality elements cannot be used (namely under drought or flooding conditions) the application of ecotoxicological bioassays may be a good alternative. Further, when ecotoxicological parameters were included, an increase of worse classifications (Bad and Poor) was observed, revealing an improvement in the sensitivity of the classification, mainly in presence of specific and priority substances. So, the ecotoxicological analysis appears to provide useful information regarding the potential presence of both known and unknown contaminants at concentrations that cause biological effects (even within the WFD limits), in agreement with several authors that have already suggested its use in biomonitoring.
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Affiliation(s)
- M H Novais
- ICT, Institute of Earth Sciences, University of Évora, Rua Romão Ramalho 59, Évora, Portugal; Water Laboratory, University of Évora, P.I.T.E. Rua da Barba Rala N(o) 1, 7005-345 Évora, Portugal.
| | - A Marchã Penha
- ICT, Institute of Earth Sciences, University of Évora, Rua Romão Ramalho 59, Évora, Portugal; Water Laboratory, University of Évora, P.I.T.E. Rua da Barba Rala N(o) 1, 7005-345 Évora, Portugal
| | - A Catarino
- ICT, Institute of Earth Sciences, University of Évora, Rua Romão Ramalho 59, Évora, Portugal; Department of Technologies and Applied Sciences, Polytechnic Institute of Beja, 7801-295, Portugal
| | - I Martins
- Department of Technologies and Applied Sciences, Polytechnic Institute of Beja, 7801-295, Portugal
| | - S Fialho
- Department of Technologies and Applied Sciences, Polytechnic Institute of Beja, 7801-295, Portugal
| | - A Lima
- Department of Technologies and Applied Sciences, Polytechnic Institute of Beja, 7801-295, Portugal
| | - M Morais
- ICT, Institute of Earth Sciences, University of Évora, Rua Romão Ramalho 59, Évora, Portugal; Water Laboratory, University of Évora, P.I.T.E. Rua da Barba Rala N(o) 1, 7005-345 Évora, Portugal
| | - P Palma
- ICT, Institute of Earth Sciences, University of Évora, Rua Romão Ramalho 59, Évora, Portugal; Department of Technologies and Applied Sciences, Polytechnic Institute of Beja, 7801-295, Portugal; GeoBioTec, NOVA School of Science and Technology, Campus da Caparica, 2829-516 Caparica, Portugal
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Mobasher A, Bayrami A, Asadi‐Sharif E, Rahim Pouran S. Ecological indicators for qualitative assessment of Ojarud River: A case study. Ecol Evol 2023; 13:e10310. [PMID: 37465610 PMCID: PMC10350820 DOI: 10.1002/ece3.10310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 06/10/2023] [Accepted: 06/30/2023] [Indexed: 07/20/2023] Open
Abstract
Today, the application of ecological indicators based on organisms has replaced traditional saprobic approaches for assessment of the quality of rivers impaired due to organic pollution and some other environmental disturbances. This study aimed to weigh the quality of the Ojarud River in Ardabil, Iran, applying biological and physiological indices of macro-invertebrates. A total of 12,524 samplings were fulfilled at four stations (S1, S2, S3, S4) from the headstream to downstream by a Surber sampler (30 × 30 cm2) from June/2020 to April/2021. All year round, the highest frequent families were Chironomidae (2658), Simuliidae (1025) from Diptera and Caenidae (1855), and Baetidae (724) from Ephemeroptera. The diversity pattern was analyzed by PAST software, and Primer 7 (BIO-ENV analysis) was utilized to understand what factor has the most impact on the distribution of macro-invertebrates. The least similarity of S4 to other stations was recognized by Cluster analysis. As per the ANOSIM (analysis of similarities), a statistically significant difference in the macroinvertebrates' frequency was established between S3 and other stations (p = .0001, r = .63). Moreover, the relationship between heavy metals and macro-invertebrate showed that the three families of Simuliidae, Gomphidae, and Caenidae had a positive correlation with the concentrations of heavy metals in the sediment. As per the Ephemeroptera, Plecoptera and Trichoptera index, the water quality was placed in the "excellent" class, but the Biological Monitoring Working Party and Hilsenhoff Family Biotic Index indices scored the water quality "good" class at S1 and the "poor" class at S3. Based on the results of this study, the use of physicochemical and hydro-morphological indicators can support the biological indicators but cannot replace them. In addition, careful evaluation of biological indicators is required to develop conservation strategies.
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Affiliation(s)
- Aydin Mobasher
- Department of Biology, Faculty of ScienceUniversity of Mohaghegh ArdabiliArdabilIran
| | - Abolfazl Bayrami
- Department of Biology, Faculty of ScienceUniversity of Mohaghegh ArdabiliArdabilIran
| | - Ehsan Asadi‐Sharif
- Department of Soil and Water ResearchGilan Agricultural and Natural Resources Research and Education Center, AREEORashtIran
| | - Shima Rahim Pouran
- Department of Environmental and Occupational Health, Social Determinants of Health Research CenterArdabil University of Medical SciencesArdabilIran
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Heß S, Hof D, Oetken M, Sundermann A. Effects of multiple stressors on benthic invertebrates using Water Framework Directive monitoring data. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 878:162952. [PMID: 36948311 DOI: 10.1016/j.scitotenv.2023.162952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 05/13/2023]
Abstract
Multiple stressors affect freshwater systems and cause a deficient ecological status according to the European Water Framework Directive (WFD). To select effective mitigation measures and improve the ecological status, knowledge on the stressor hierarchy and individual and joined effects is necessary. However, compared to common stressors like nutrient enrichment and morphological degradation, the relative importance of micropollutants such as pesticides and pharmaceuticals is largely unaddressed. We used WFD monitoring data from Saxony (Germany) to investigate the importance of 85 environmental variables (including 34 micropollutants) for 18 benthic invertebrate metrics at 108 sites. The environmental variables were assigned to five groups (natural factors, nutrient enrichment, metals, micropollutants and morphological degradation) and were ranked according to their relative importance as group and individually within and across groups using Principal Component Analyses (PCAs) and Boosted Regression Trees (BRTs). Overall, natural factors contributed the most to the total explained deviance of the models. This variable group represented not only typological differences between sampling sites but also a gradient of human impact by strongly anthropogenically influenced variables such as electric conductivity and dissolved oxygen. These large-scale effects can mask the individual importance of the other variable groups, which may act more specifically at a subset of sites. Accordingly, micropollutants were not represented by a few dominant variables but rather a diverse palette of different chemicals with similar contribution. As a group, micropollutants contributed similarly as metals, nutrient enrichment and morphological degradation. However, the importance of micropollutants might be underestimated due to limitations of the current chemical monitoring practices.
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Affiliation(s)
- Sebastian Heß
- Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecystr. 12, 63571 Gelnhausen, Germany; Goethe University Frankfurt, Faculty of Biology, Institute of Ecology, Evolution and Diversity, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany.
| | - Delia Hof
- Goethe University Frankfurt, Faculty of Biology, Department of Aquatic Ecotoxicology, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
| | - Matthias Oetken
- Goethe University Frankfurt, Faculty of Biology, Department of Aquatic Ecotoxicology, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
| | - Andrea Sundermann
- Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecystr. 12, 63571 Gelnhausen, Germany; Goethe University Frankfurt, Faculty of Biology, Institute of Ecology, Evolution and Diversity, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
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Mhlarhi N, Gitari WM, Ayinde WB, Tavengwa NT, Mudzielwana R, Izevbekhai OU. Biosorption of toxic metal ions (Cr +6, Cd 2+) and nutrients (PO 43-) from aqueous solution by diatom biomass. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2023; 58:483-497. [PMID: 37021346 DOI: 10.1080/10934529.2023.2196929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 03/08/2023] [Accepted: 03/17/2023] [Indexed: 06/19/2023]
Abstract
This paper evaluates diatom biomass as a biosorbent for removing Cr+6, Cd2+, and PO43- ions from water. The diatom was characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscopy (SEM-EDS) for its crystallinity, functional groups, and morphology. A batch sorption study was conducted to evaluate the parameters influencing Cr+6, Cd2+, and PO43- ions adsorption, and the mechanisms were explored. The FTIR spectra revealed Si-O, O-H, N-H, and C-O as the main functional groups present on the surface of the adsorbent. The SEM showed a rough and irregular-shaped morphology, while the EDS indicated that the diatom biomass is an aluminosilicate material. The rate-limiting steps for Cr+6 and Cd2+ were pseudo-first order, and pseudo-second order sorption favored PO43- based on their R2 values. Moreover, the dominant adsorption model that best described the equilibrium data was the Freundlich isotherm. The maximum adsorption capacities obtained for Cr+6 was 5.66 (mg/g), and Cd2+ was 5.27 (mg/g) at 313 K while PO43- was 19.13 (mg/g) at 298 K. The thermodynamic data revealed that the reaction was endothermic for Cd2+ and exothermic for Cr+6 and PO43-, respectively. Diatom biomass was observed to be a promising bio-sorbent for removing Cr6+, Cd2+ and PO42- from wastewater.
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Affiliation(s)
- Nsovo Mhlarhi
- Department of Geography and Environmental Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
- Department of Water and Sanitation, Resource Quality Information Services (RQIS), Roodeplaat, Pretoria, South Africa
| | - Wilson Mugera Gitari
- Department of Geography and Environmental Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
- School of Chemical Sciences, Technical University of Kenya, Nairobi, Kenya
| | - Wasiu Babatunde Ayinde
- Department of Geography and Environmental Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
| | - Nikita Tawanda Tavengwa
- Department of Chemistry, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
| | - Rabelani Mudzielwana
- Department of Chemistry, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
| | - Oisaemi Uduagele Izevbekhai
- Department of Chemistry, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
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ZORZAL-ALMEIDA STÉFANO, LEHMKUHL ELTONA, MARQUARDT GISELEC, MORAIS KRYSNAS, TRANCOSO MATEUSS, SILVA-LEHMKUHL ANGELAM. 177 years of diatom studies in Brazil: knowledge, gaps, and perspectives. AN ACAD BRAS CIENC 2022; 94:e20210959. [DOI: 10.1590/0001-3765202220210959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/18/2021] [Indexed: 11/22/2022] Open
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Pissaridou P, Cantonati M, Bouchez A, Tziortzis I, Dörflinger G, Vasquez MI. How can integrated morphotaxonomy- and metabarcoding-based diatom assemblage analyses best contribute to the ecological assessment of streams? METABARCODING AND METAGENOMICS 2021. [DOI: 10.3897/mbmg.5.68438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Environmental conditions, such as nutrient concentrations, salinity, elevation etc., shape diatom assemblages of periphytic biofilms. These assemblages respond rapidly to environmental changes, a fact which makes diatoms valuable bioindicators. Hence, freshwater biomonitoring programmes currently use diatom indices (e.g. EU Water Framework Directive - WFD). To date, microscopy-based assessments require high taxonomic expertise for diatom identification at the species level. High-throughput technologies now provide cost-effective identification approaches that are promising, complementary or alternative tools for bioassessment. The suitability of the metabarcoding method is evaluated for the first time in the Cyprus streams WFD monitoring network, an eastern Mediterranean country with many endemic species and results are compared to the results acquired from the morphotaxonomic analysis. Morphotaxonomic identification was conducted microscopically, using the most updated taxonomic concepts, literature and online resources. At the same time, DNA metabarcoding involved the use of the rbcL 312 bp barcode, high-throughput sequencing and bioinformatic analysis. The ecological status was calculated using the IPS Index. Results show a positive correlation between morpho-taxonomic and molecular IPS scores. Discrepancies between the two methodologies are related to the limitations of both techniques. This study confirmed that Fistulifera saprophila can have a crucial role in key differences observed, as it negatively influences IPS scores and microscopy methods frequently overlook it. Importantly, gaps in the DNA barcoding reference databases lead to a positive overestimation in IPS scores. Overall, we conclude that DNA metabarcoding offsets the morphotaxonomic methodology for the ecological quality assessment of freshwaters.
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Epiphytic Diatom-Based Biomonitoring in Mediterranean Ponds: Traditional Microscopy versus Metabarcoding Approaches. WATER 2021. [DOI: 10.3390/w13101351] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Benthic diatoms have traditionally been used as bioindicators of aquatic ecosystems. Because diatom-based monitoring of water quality is required by European legislation, molecular-based methods had emerged as useful alternatives to classical methods based on morphological identification using light microscopy. The aim of this study was to test the reliability of DNA metabarcoding combined with High-Throughput Sequencing (HTS) techniques in the bioassessment of the trophic status of 22 Mediterranean shallow ponds in NW Spain. For each pond, the Trophic Diatom Index (TDI) was calculated from inventories obtained by identification using light microscopy (LM) followed by high-throughput sequencing (HTS) at the molecular level. Ponds were subsequently classified into five water quality classes. The results showed a good correspondence between both methods, especially after applying a correction factor that depended on the biovolume of the cells. This correspondence led to the assignment to the same quality class in 59% of the ponds. The determination and quantification of valves or DNA sequences was one of the main pitfalls, which mainly included those related to the variability in the relative abundances of some species. Accordingly, ponds with similar relative abundances for the dominant species were assigned to the same quality class. Moreover, other difficulties leading the discrepancies were the misidentification of some species due to the presence of semi-cryptic taxa, the incompleteness of the reference database and the bioinformatic protocol. Thus, the validation of DNA-based methods for the identification of freshwater diatoms represents an important goal, as an alternative to using traditional methods in Mediterranean shallow ponds.
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