RESUMEN
The study of microalgal communities is critical for understanding aquatic ecosystems. These communities primarily comprise diatoms (Heterokontophyta), with two methods commonly used to study them: Microscopy and metabarcoding. However, these two methods often deliver different results; thus, their suitability for analyzing diatom communities is frequently debated and evaluated. This study used these two methods to analyze the diatom communities in identical water samples and compare the results. The taxonomy of the species constituting the diatom communities was confirmed, and both methods showed that species belonging to the orders Bacillariales and Naviculales (class Bacillariophyceae) are the most diverse. In the lower taxonomic levels (family, genus, and species), microscopy tended to show a bias toward detecting diatom species (Nitzschia frustulum, Nitzschia inconspicua, Nitzschia intermedia, Navicula gregaria, Navicula perminuta, Navicula recens, Navicula sp.) belonging to the Bacillariaceae and Naviculaceae families. The results of the two methods differed in identifying diatom species in the communities and analyzing their structural characteristics. These results are consistent with the fact that diatoms belonging to the genera Nitzschia and Navicula are abundant in the communities; furthermore, only the Illumina MiSeq data showed the abundance of the Melosira and Entomoneis genera. The results obtained from microscopy were superior to those of Illumina MiSeq regarding species-level identification. Based on the results obtained via microscopy and Illumina MiSeq, it was revealed that neither method is perfect and that each has clear strengths and weaknesses. Therefore, to analyze diatom communities effectively and accurately, these two methods should be combined.
Asunto(s)
Código de Barras del ADN Taxonómico , Diatomeas , Estuarios , Microscopía , Diatomeas/clasificación , Diatomeas/crecimiento & desarrollo , Microscopía/métodos , República de Corea , Biodiversidad , Filogenia , EcosistemaRESUMEN
Karst ecosystems play a unique role as exceptional natural habitats in sustaining biodiversity. This study focuses on diatoms, a diverse group of microeukaryotes in the periphytic community of a karstic river. In a multi-microhabitat study along the Krka River (Croatia), our goal was to obtain a detailed overview of diatom diversity and community structure using morphological and molecular approaches, and to assess the applicability of eDNA metabarcoding as a reliable tool for biomonitoring assessment. The results revealed a relatively low agreement in the diatom community composition between the two approaches, but also provided complementary information, with no differences in beta diversity detected between microhabitats. The SIMPER analysis underlined the importance of the molecular approach in identifying diatom community composition, due to errors in distinguishing between deposited diatom cells that occurred in the morphological analysis. In contrast, the morphological approach indicated a clear diatom community separation along the river with a strong location effect. Despite certain differences, both approaches provided a feasible assessment of the ecological status according to the relationship to environmental pressures, classifying the Krka River as High (morphological approach) or Good (molecular approach) throughout the most of its course. Moreover, diatom diversity based on both approaches provides a reliable dataset applicable in routine monitoring assessment and offers a deeper understanding of the presented ecological status. The incompleteness of a reference database presents one major drawback of the molecular approach, which needs further updating in order to improve routine diatom metabarcoding.
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ADN Ambiental , Diatomeas , Biodiversidad , Código de Barras del ADN Taxonómico , Diatomeas/genética , Ecosistema , Monitoreo del Ambiente/métodos , RíosRESUMEN
In recent decades, intense human activities have caused a decline in many lake ecosystems in Yunnan Province, rendering the transformation of the lake from a clear macrophyte-dominated state to a turbid phytoplankton-dominated state. Improved understanding of the ecological changes in lake ecosystem has significant implications for management. In this study, a small lake in Dali Prefecture of Yunnan Province, i.e., Lake Xihu, was selected. Combined with diatom records and physicochemical proxies from the lake sediments, this paper focuses on the long-term ecological changes in Lake Xihu, Dali since the mid-1960s. The results show that the Lake Xihu, Dali has undergone a significant shift in stable states over the past 50 years. Prior to 2000, the benthic-epiphytic species (i.e., Cocconeis placentula, Staurosira construens, Gomphonema angustum, and Achnanthidium minutissimum) dominated in diatom assemblages, indicating oligotrophic conditions; since 2000, benthic-epiphytic species (i.e., Encyonopsis microcephala and Navicula cryptocephala) and planktonic species (i.e., Cyclotella atomus, Cyclotella meneghiniana, Stephanodiscus hantzschii, and Aulacoseira granulata) dominated successively, indicating mesotrophic to eutrophic conditions. Principal component analysis based on the diatom assemblages in temporal scale showed the response of diatoms succession to nutrients. Redundancy analysis also confirmed that nutrient enrichment was the main driving force for the succession of diatom assemblages in Lake Xihu, Dali. In the past 50 years, climate change and human activities (i.e., agricultural reclamation, fertilization, animal husbandry, and fishery) have enhanced the accumulation of nutrients in the lake. The continuous loading of nutrients promoted the propagation of planktonic algae, and also the productivity of the lake, rendering the transformation to a turbid phytoplankton-dominated state.
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Diatomeas , Lagos , Animales , China , Cambio Climático , EcosistemaRESUMEN
Diatoms play an important role as ecological indicators, and some species of diatoms can easily cause water blooms, thereby decreasing the production capacity of water treatment plants and endangering drinking water safety. Mastering the diatom community dynamics is crucial for water supply. In this study, diatom composition, spatial distribution and succession were investigated in Datun Reservoir, Donghu Reservoir and Shuangwangcheng Reservoir, which are important drinking water sources in Shandong province, China. Results showed that the three reservoirs could be classified as being between mesotrophic and moderately eutrophic. The diatom community in each of the three reservoirs exhibited no obvious seasonal succession. The diatom communities in the three reservoirs were relatively simple in composition, with Synedra and Cyclotella being the most dominant groups all year round. Synedra had a negative relationship with NO2-N. Cyclotella had a positive association with NO3-N, but was negatively associated with NH4-N and CODMn in the three reservoirs. Through the analysis of diatom and environmental factors, the three reservoirs have the potential of hosting diatom blooms in summer, when the higher temperature combines with reduced water flow.
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Diatomeas/crecimiento & desarrollo , Monitoreo del Ambiente , Abastecimiento de Agua/estadística & datos numéricos , China , Fósforo/análisis , Estaciones del AñoRESUMEN
Environmental contamination has become a global problem of increasing intensity due to the exponential growth of industrialization. One main debated issue is the metal contamination of rivers receiving Acid Mine Drainage (AMD) from active/abandoned mines. In order to assess the quality of lotic systems, diatoms are commonly used, as their assemblage modifies on the basis of changes in environmental parameters. Benthic diatom changes were analyzed along the metal-impacted Gromolo Torrent (Liguria, NW Italy) with the aim of understanding the effects of input from the abandoned Libiola Cu mine. The results support the hypothesis that metals from AMD lead to massive changes in diatoms, resulting in low biological diversity and in a shift of dominance, passing from the genera Cymbella and Cocconeis to more tolerant and opportunistic species, such as Achnanthidium minutissimum and Fragilaria rumpens. The high concentrations of labile metals, measured through Diffusion Gradients in Thin-films (DGT) immediately downstream of the two AMD inputs in the torrent, corresponded to a sudden decrease in the presence of diatoms, indicating the possible reaching of acute toxic levels. In particular, A. minutissimum dominated the mining area and was positively correlated with Cu and Zn; whereas F. rumpens bloomed downstream of this area, where the metal content was diluted, and was positively correlated with As and Pb. Finally, an important abundance of Nitzschia palea and teratological forms of A. minutissimum and F. rumpens were observed downstream from the mine, indicating that metals may have an important impact on diatoms up to the torrent mouth.
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Diatomeas/fisiología , Monitoreo del Ambiente , Metales Pesados/toxicidad , Contaminantes Químicos del Agua/toxicidad , Sedimentos Geológicos , Italia , MineríaRESUMEN
Fuxian Lake is an important deep lake in China with trophic status generally categorized as class I. However, there exists a trend of degradation in its ecological and environmental health under the increasing impacts derived from catchment development and recent global warming. Therefore, it is important to evaluate the community composition, distribution patterns, and driving factors of lake biota. In order to uncover the spatio-temporal variations in water quality and diatom communities, a monthly survey of diatom community composition and limnological characteristics was carried out in the surface waters of three sampling sites from the south, middle, and north of the lake basin in Fuxian in 2015. A total of 166 diatom species belonging to 31 genera were identified, which was dominated by planktonic diatoms with the extirpation of Cyclotella rhomboideo-elliptica, an endemic species for Yunnan. Diatom community structure showed significant seasonal succession across the three sites, which were dominated by Fragilaria crotonensis in January and February, by Aulacoseira granulata in March, by Cyclotella ocellata and F. crotonensis in April, and by C. ocellata for other months (i.e., relative abundance of ~80%). Over the spatial scale, the distribution of the dominant diatoms displayed a high degree of similarity. Principal component analysis further showed that there existed significant difference in the diatom community structure and lake environment over the temporal scale, but no significant deviance was found across the three sites. The results of redundancy analysis and variation partitioning revealed that the key driver included meteorological and physical factors (i.e., water temperature, wind velocity, and Secchi depth), which accounted for 27.6% of the total variance in diatom community changes. In combination with the thermocline analysis, the change in lake hydrodynamics may have influenced the thickness and duration of the thermal stratification of lake water, resulting in the reorganization of the diatom community. At the same time, the lake-water nutrients and ions also exerted an important influence on community structuring, which explained the 21.2% and 9.4% of the diatom variation, respectively. Therefore, regional warming and catchment development have significantly structured the biological community and ecosystem health of Fuxian Lake. In all, measures should be taken not only to control the watershed input of pollutants but also to actively mitigate the long-term impact of climate change for the protection and ecological remediation of Fuxian Lake.
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Diatomeas/crecimiento & desarrollo , Lagos , China , Diatomeas/clasificación , Ecosistema , Estaciones del Año , Análisis Espacio-TemporalRESUMEN
Diatom abundance, biovolume and diversity were measured over a 2-year period along the Straits of Malacca at two stations with upper (Klang) and lower (Port Dickson) states of eutrophication. Diatom abundance, which ranged from 0.2 × 104 to 21.7 × 104 cells L-1 at Klang and 0.9 × 103- 41.3 × 103 cells L-1 at Port Dickson, was influenced partly by nutrient concentrations. At Klang, the diatoms were generally smaller and less diverse (H' = 0.77 ± 0.48) and predominated by Skeletonema spp. (60 ± 32% of total diatom biomass). In contrast, diatoms were larger and more diverse (H' = 1.40 ± 0.67) at Port Dickson. Chaetoceros spp. were the most abundant diatoms at Port Dickson but attributed only 48 ± 30% of total diatom biomass. Comparison of both Klang and Port Dickson showed that their diatom community structure differed and that eutrophication reduced diatom diversity at Klang. We also observed how Si(OH)4 affected the abundance of Skeletonema spp. which in turn influenced the temporal variation of diatom community at Klang. Our results highlighted how eutrophication affects diatom diversity and community structure.
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Diatomeas , Eutrofización , Biomasa , Diatomeas/genética , Diatomeas/crecimiento & desarrollo , Monitoreo del Ambiente , Malasia , Clima TropicalRESUMEN
The effects of multiple stressors on marine diatom assemblages are still poorly understood. The interactive effects of metals and nutrients were assessed in two coastal biofilms grown at a reference site and a historically contaminated site. The biofilms were exposed in situ to pulse exposures of metals (Zn and Pb) and nutrients (N and P) individually and in combination to mimic patterns of discharge in the study area. The reference community's structure (composition and abundance of taxa) was modified after metals and/or nutrients exposure, but each stressor acted in different way. Irrespective of the stressors or scenario, the abundance of the dominant species Opephora krumbeinii declined, and it is proposed as sensitive species. Nutrient supply favoured the proliferation of certain species with high nutrient tolerances (Fragilaria famelica, Tabularia ktenoeides), whereas metals promoted the colonisation of metal-tolerant species, e.g., Berkeleya fennica, Opephora marina. Simultaneous exposure induced an amplification of levels of accumulated metals, chlorophyll a and EPS contents and triggered the succession of species towards tolerant species with specific growth. Metals seemed to act as a selective factor of metal-tolerant species, and nutrients favoured the proliferation of those species forming zig-zag colonies (Neosynedra provincialis), mucous tubes (Berkeleya spp.) and motile diatoms (Navicula salinicola, Nitzschia incognita), resulting in biofilms with a more complex architecture. The diatom communities from the historically contaminated site were more resistant to pulse exposure, but metals or nutrients loads induced overproduction of mucilage. We propose that growth forms may complement taxonomic approaches and provide a quick and easy way to detect community changes related to metal and nutrient pollution.
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Biopelículas , Diatomeas/fisiología , Plomo/análisis , Zinc/análisis , Clorofila , Clorofila A , Diatomeas/efectos de los fármacosRESUMEN
This work presents a combination of geochemical, mineralogical, and biological data obtained in water reservoirs located in one of the most paradigmatic mining regions, suffering from acid mine drainage (AMD) problems: the Iberian Pyrite Belt (IPB). Four water reservoirs located in the Spanish sector of the IBP, storing water for different purposes, were selected to achieve an environmental classification based on the effects of AMD: two mining dams (Gossan and Águas Ácidas), a reservoir for industrial use (Sancho), and one with water used for human supply (Andévalo). The results indicated that the four reservoirs are subject to the effect of metallic loads from polluted rivers, although with different levels: Águas Ácidas > Gossan > Sancho ≥ Andévalo. In accordance, epipsammic diatom communities have differences in the respective composition and dominant taxa. The dominant diatoms in each reservoir indicated acid water: Pinnularia acidophila and Pinnularia aljustrelica were found in the most acidic dams (Gossan and Águas Ácidas, with pH <3), Pinnularia subcapitata in Sancho (pH 2.48-5.82), and Eunotia exigua in Andévalo (pH 2.34-6.15).