Eco-Assessment of Streams of Konya Closed River Basin (Turkey) Using Various Ecoregional Diatom Indices

Ecological assessments of freshwater ecosystems based on diatom metrics are an important issue to attain environmental sustainability. The present study aimed to evaluate differences in the diatom-stressors relationship in relatively least disturbed streams in the Konya closed river basin using multivariate analyses and to bio-assess streams by application of different ecoregional diatom indices. Cocconeis euglypta, Cymbella excisa, Cocconeis placentula, and Achnanthidium minutissimum are the most contributing species to the dissimilarity of sampling stations between rainy and dry seasons and also between altitude (A2 800-<1600 m and A3 ≥1600 m) groups. A strong (82.8%) correlation between diatom species and stressors was expressed by the first two axes of canonical correspondence analysis. Diatom species displayed distinct responses to environmental variables (electrical conductivity, Ni, Cu, B, and altitude) playing important roles on the distribution of diatom species. Diatom indices indicated different ecological statuses of stations from a bad to a high. European diatom indices except Duero Diatom Index-DDI and Trophic Diatom Index-TDI showed well responses to the eco-assessment of streams and indicated high ecological status for the least disturbed sampling stations symbolized as S16, S20, S24, S25, S27-29, S37, and 39. These results were also supported by abiotic evaluation. Among diatom indices, although TIT was more competitive in the bio-assessment of streams, it is necessary to increase its species list by determining their trophic weights in future studies. This indicates that the revision of ecoregional specific diatom metrics with the enhancement of diatom species numbers according to their ecological preferences is needed to correctly interpret the water quality.

Development of a Periphytic Diatom-Based Comprehensive Diatom Index for Assessing the Trophic Status of Lakes in the Lower Reaches of the Yangtze River, China

Periphytic diatoms play important functional roles in aquatic ecosystems. Their community compositions are widely used in water quality monitoring due to their wide distribution, short reproductive cycles, and sensitivity to environmental changes. In this study, 116 samples of periphytic diatom samples were collected from lakes in the lower reaches of the Yangtze River. The weighted average without tolerance down-weighting regression method was used to develop total phosphorus (r2 = 0.661), total nitrogen (r2 = 0.699), and chemical oxygen demand (r2 = 0.423) models, and the optimal and tolerance values of 78 periphytic species were calculated. Then, a new index, the comprehensive diatom index (CDI), was established on the basis of the optima and tolerances of these 78 species concerning the three environmental variables (TP, TN, and COD) to assess the water trophic status of the lakes in this region. According to the CDI, the trophic statuses of 8, 17, 23, 30, 22, and 14 sample sites were oligotrophic, mesotrophic, light eutrophication, moderate eutrophication, heavy eutrophication, and ultra-eutrophication, respectively. The CDI was more strongly correlated with the conductivity, pH, TP, TN, COD, and TDS than other diatom indices. These results demonstrate that the CDI is a useful metric for assessing the water trophic status of the lakes in the lower reaches of the Yangtze River.

Epiphytic diatoms on herbarium material from the Central Forest phytogeographic region of the Democratic Republic of the Congo

Background and aims – Epiphytic diatoms are excellent bio-indicators of the present and past ecological condition of aquatic ecosystems. In order to reconstruct the diatom history and to evaluate its diversity in the Democratic Republic of the Congo, epiphytic diatoms were sampled from herbarium specimens of aquatic plants deposited at the National Herbarium of the Congo at Yangambi (YBI) and at the herbarium of Meise Botanic Garden (BR).Material and methods – In YBI, nine specimens belonging to the Nymphaeaceae, three to the Ceratophyllaceae, and 12 to the Lentibulariaceae collected in the Central Forest phytogeographic region were sampled for diatom investigation. In addition, nine Nymphaea lotus specimens were sampled in BR. Semi-quantitative analyses were performed by light microscopy on permanent diatom slides.Key results – Analyses of the epiphytic diatom communities on YBI and BR materials showed a large diversity of 132 species belonging to 44 genera. Taxa belonging to the genus Eunotia were relatively the most abundant in all studied samples followed by Frustulia saxonica and a Desmogonium sp. The diatom communities on Nymphaea were as varied as on Ceratophyllum, while on Utricularia, a significant lower diversity was observed. The Trophic Diatom Index (TDI) and Generic Diatom Index (GDI) showed that the water quality in the Central Forest phytogeographic region was overall good during the 20th century. They point to oligotrophic conditions for the running waters with a slight increase towards more mesotrophic conditions from the 1950s onwards. The only sample in the present study indicating mesotrophic condition was from a swamp.Conclusions – The results on the epiphytic diatoms present on herbarium material can serve as a basis for sustainable management of aquatic ecosystems in D.R. Congo. In absence of an in-depth knowledge of the species and their ecological preferences, a genus-based TDI and IDG have proven to be valuable tools for water quality monitoring in tropical Africa.

DiaThor: R package for computing diatom metrics and biotic indices

1- Diatoms are widely used to detect changes in water quality due to their specific sensibility to a variety of environmental conditions. Among the different diatom-based tools to measure water quality, the biotic indices, ecological and morphological traits are the most commonly used. 2- DiaThor, contains 19 functions that provide morphological data of the samples (number and shape of chloroplasts, total biovolume), ecological data (species richness, evenness, diversity, size classes, ecological guilds, ecological preferences) and biotic indices (Descy Index, EPID Index, Indice Diatomique Artois-Picardie, Swiss Diatom Index, Pampean Diatom Index, ILM index, Specific Pollution sensitivity Index, Lobo Index, Sladecek index, SPEAR(herbicides) index and the Trophic index). A web application (in Shiny) was also developed to provide access to the package for those users not familiar with the R environment. 3- The structure of the package, how it functions and the structure of the input and output data are explained. To demonstrate the most common use of DiaThor, an example of the package performance is also provided. 4- The DiaThor package aims to contribute to the water quality assessment based on diatom assemblages, while also providing researchers with an open platform to suggest new statistics and functionalities to be integrated into future builds.

Applicability of diatom metabarcoding in the ecological status assessment of Hungarian lotic and soda pan habitats

Diatoms, eukaryotic algae with silica cell wall have been proved to be reliable bioindicators and are applied in ecological status assessment of aquatic ecosystems using indices calculated from pollution sensitivity and indicator values of species. Traditional method of identification of diatom species is based on morphological features of frustule that requires in-depth taxonomical knowledge and expertise. Metabarcoding that combines barcodes and high-throughput sequencing offers a promising alternative. In this pilot study we tested the applicability of metabarcoding of benthic diatom assemblages for ecological status assessment of water bodies in Hungary comparing its performance to that of morphology-based identification of species. Samples from 78 rivers and streams arranged along a trophic gradient and 14 soda pans representing unique types of habitats were investigated. Sequences of the barcode region of rbcL gene suggested by Vasselon et al. (2017) were acquired revealing 1135 diatom amplicon sequence variants (ASVs) of which 54% could be assigned at species level using Diat.barcode (Rimet et al. 2019) as reference database. Morphological investigation detected more species and intraspecific taxa in the lotic and lentic samples (413 and 78, respectively) than metabarcoding (190 and 75). Correspondence between taxa detected based on morphology and DNA sequences was relatively low (on average 24% in lotic and 26% in lentic samples) but considerably increased (on average 66% and 56%, respectively) when taking into account only the taxa reaching higher than 5% relative abundance in microscopy counting. The differences mainly derived from that a considerable portion (59% and 32%, respectively) of the morphologically identified taxa were not recorded in the reference database. Community structure of samples from both running and standing waters based on microscopy and DNA sequence analysis showed significant correlation as revealed using Mantel test. For rivers and streams diatom index IPS (Specific Pollution Sensitivity Index, (Coste in Cemagref, 1982) for soda pans indices H (Ziemann et al., 2001) and IBD (Indice Biologique Diatomées, Lenoir and Coste, 1996) were calculated from the results of the two aspects. Strong correlation was found between morphology- and sequence-based indices and in about half of the samples, the ecological status class obtained with the two methods coincided. Our results suggest that metabarcoding inheres a great opportunity and could be successfully applied in benthic diatom-based ecological status assessment of Hungarian waters after the reference database is supplemented with taxa frequently occurring in these habitats. References Cemagref, 1982. Etude des méthodes biologiques quantitativesd’appréciation de la qualité des eaux, Rapport Division Qualité des Eaux Lyon. Agence financière de Bassin Rhône-Méditerranée-Corse, Pierre-Bénite, France. Lenoir, A., Coste, M., 1996. Development of a practical diatom index of overall water quality applicable to the French National Water Board Network. Presented at the International symposium, Volksbildungsheim Grilhof Vill, AUT, 17-19 September 1995, Universität Innsbruck, pp. 29–43. Rimet, F., Gusev, E., Kahlert, M., Kelly, M.G., Kulikovskiy, M., Maltsev, Y., Mann, D.G., Pfannkuchen, M., Trobajo, R., Vasselon, V., Zimmermann, J., Bouchez, A., 2019. Diat.barcode, an open-access curated barcode library for diatoms. Sci. Rep. 9, 15116. Vasselon, V., Rimet, F., Tapolczai, K., Bouchez, A., 2017. Assessing ecological status with diatoms DNA metabarcoding: Scaling-up on a WFD monitoring network (Mayotte island, France). Ecol. Indic. 82, 1–12. Ziemann, H., Kies, L., Schulz, C.-J., 2001. Desalinization of running waters: III. Changes in the structure of diatom assemblages caused by a decreasing salt load and changing ion spectra in the river Wipper (Thuringia, Germany). Limnologica 31, 257–280.

Applicability of Benthic Diatom Indices Combined with Water Quality Valuation for Dish Lake from Nanjishan Nature Reserve, Lake Poyang

Benthic diatom indices developed in the Europe Union have been widely accepted as indicators of the trophic state and water quality in freshwater ecosystems. In China, most of the benthic diatom-based indices have not been widely tested or evaluated before. For this purpose, the water quality parameters and benthic diatoms community structures at 20 sample sites in the dish lake of Nanjishan Nature Reserve in Poyang Lake were investigated in this study and 18 widely-applied diatom indices were established. The statistical results indicated that most water quality parameters including Total Nitrogen (TN), Total Phosphorus (TP), ammonia nitrogen (NH4+), Chemical Oxygen Demand (COD) and Chlorophyll (Chl) were highly correlated with each other at a confidence level of 0.05. Water quality sampling sites from 8 lakes could be classified into 4 groups based on the integrated comprehensive scores using principal components analysis (PCA). Monitoring sites could also be divided into 4 groups based on clustering analysis with hierarchical methods for diatom dominant species in 20 sampling sites. According to the status of water ecological health recognition and box plot analysis in different water quality groups and diatom dominant species groups, only 3 diatom indices including the Biological Diatom Index (IBD), Specific Pollution Sensitivity Index (IPS) and Louis Leclercq Diatom Index (IDSE) demonstrated good evaluation suitability and good correlation within different water quality grades at the final stage. The above results revealed that IBD, IPS and IDSE were the most suitable diatom indices for the water quality evaluation of the dish lake in the Nanjishan Nature Reserve, Lake Poyang.

Using Diatom Indices to Evaluate Water quality In Abu-Zirig Marsh Thi-Qar Province /south of Iraq

The study attempts to assess water quality in Abu-Zirig Marsh which used epiphytic Diatom community for assessing water quality. Many of Diatom indices {Trophic diatom index (TDI), Diatom index (DI), Generic diatom index (GDI) have been used to give qualitative information about the status of the freshwater ecosystem(good, moderate, high pollution). In this study, the epiphytic diatoms on both host aquatic plants Phragmites australis and Typha domengensis were collected from Abu-Zirig Marsh within Thi-Qar Province at three sites in Autumn, 2018 and winter, 2019. Epiphytic diatoms were Identified by the preparation of permanent slides method, some species of epiphytic diatom showed dominance such as Cyclotella meneghiniana, Gomphonema angustatum, Cocconies placentula, Cymbella affinis, Navicula cryptoephala, Nitzschia linearis, N. dissipata, Surirella ovalis. Abundant diatoms indicated trophic conditions of the Marsh. The results of diatom indices revealed that IPS (10-12.5) is a moderate pollution condition of marsh, DI (2.9-3.4) range from high to moderate pollution condition, TDI (47.2-60.8) indicates trophic condition ranging from (oligo-mesotrophic to eutrophic) condition of marsh while GDI a range between (11.6-13.7) moderate pollution condition, the aim of the study that is about evaluating water quality of Abu-Zirig Marsh by using Diatom indices (IPS,DI,TDI and GDI), as well as due to scarce local previous studies of epiphytic diatoms and used as bio-indicator of water quality in Abu-Zirig Marsh, therefor suggested this study .

Use of Diatoms in Monitoring the Sakarya River Basin, Turkey

The Sakarya River basin is one of the largest basins in Turkey, and encompasses the Kocaeli, Düzce, Sakarya, Bursa, Bilecik, Bolu, Kütahya, Eskişehir, Ankara, Afyon, and Konya provinces. In this study, the water quality status of the basin was investigated using 18 diatom indices, calculated in Omnidia software. For this purpose, a total of 46 stations were surveyed in the rivers and streams of the basin in May 2018. As a result, 41 of 195 diatom taxa were found to be the most frequent (>10% share in assemblage). According to Detrented Correspondence Analysis (DCA), three subgroups were described as the spring section, Ankara and Polatlı section, and lowland section. The river basin quality was evaluated as moderate or lower quality status, while only a few sites had good status. The diatom index scores showed that the Descy’s Index (DES), Pampean Diatom Index (IDP), Artois-Picardie Diatom Index (IDAP), and Specific Pollution Sensitivity Index (IPS) appear best suited to water quality assessment in this area, showing the largest number of significantly important correlation with environmental variables.