A comparative Study of Diatom Flora of the Taleghan River in Iran with Other Studies Around the World

It is important to compare the flora of different parts of the world which have the various environmental condition. The flora of Taleghan dam and River was identified from November 2017 to October 2018 and the result is compared with 15 regions of recent studies in different continents. The flora of Africa with 66 percent common taxa was the highest similar to our study. Based on the comparison the Ulnaria ulna ( Nitzsch) Compère, Navicula cryptotenella Lange-Bertalot Gomphonema acuminatum Ehrenberg and Nitzschia palea (Kü tzing) W Smith was the cosmopolitan species and Achnanthidium eutrophilum (Lange-Bertalot) Lange-Bertalot , Frustulia tugelae Cholnoky , Nitzschia acula (Kützing) Kü tzing in Rabenhors, and some other species were rare taxon. 45 out of 203 diagnosed species and genus Seminavis D.G.Mann is new record for diatoms flora of Iran. Also, the species Cymbella pernodensis Maillard , Cymbella novazeelandiana Krammer and Achnanthidium druartii Rimet & Couté were new records for Asia.


Introduction
The changeability of different organisms including the diatoms in various habitats shows the biodiversity comprising species, genetic, and ecosystem diversity. It is necessary to understand the biodiversity to utilize the natural resources for human applications. There is a mutual relation between biodiversity and environment as the alteration in the physicochemical variables, impacts on the diversity of organisms and frequently are responsible for fluctuations the species assemblages. The diatoms are widespread organisms that occurred in various environments like soil, marine, freshwater, and even in extreme conditions. Mann [1] estimated their species number between 30,000 and 200,000 as of the most species-rich in the algal group. They prefer special environmental conditions, such as many other organisms which besides their fast reproduction and their resistant siliceous cell wall (useful for the rebuilding of previous environments) make them a good candidate as bioindicator. Therefore, it is important to study the flora of diatom communities that are influenced by the environmental condition and land-water interactions [2].
It is feasible to evaluate the environment in the aquatic ecosystem with the help of species diversity. Also, the diversity of species is an effective factor in ecosystem functioning, food chain, integrity, and process. The environmental condition such as temperature, humidity, geology, physicochemical elements, substrates (stone, sands, plants, and etc.), anthropogenic factors, water velocity and light intensity influences on the diatom community and their species richness [3,4]. According to the phylogenetic tree the epiphytic and epilithic lifestyle is an ancestral character in which many planktonic diatom species have been evolved from their lineage [5]. The major evolution (lifestyle, morphology, and ecology) of different diatom classes have occurred in the benthic lifestyle. The majority of diatom species live in benthic communities due to their heavy silicified frustule.
Comparing the present flora with the previous studies can reflect climate change and anthropogenic influences on the earth. Iran with 1.6 million km 2 has a diverse climate and the Zagros

Material and Methods
Taleghan River is one of the main tributaries of Sefid Rud, the second-longest river in Iran with approximately 670 km length. It rises in the Alborz Mountain in the northwest of Iran and flows into the Caspian Sea. Taleghan River begins in the Kahar and Kandovan mountains located in the western part of the Alborz domain. It is one of the longest rivers in the center of Iran with 180 km length; they form the Shah Roud River after joining to Alamut River. This study was carried out at eight sites on the Taleghan River  and Taleghan Dam from November 2017 to October 2018 (Table  1, Figure 1). The number of sediments were160 ml, collected from each station in three replicates. The sediment samples were fixed with a 4% formaldehyde solution in the sampling field and then transferred to the laboratory. Ten ml of suspension was prepared from the samples based on the protocol Van der Werff [11].
The samples were treated with 25 ml of hydrogen peroxide (H 2 O 2 ) (1.5 h at 100 °C) and then 10 ml hydrochloric acid (HCl) (2 h at 120 °C) to remove organic matters. The oxidized by-products were removed by recurrent and settling with distilled water. To neutralize electrostatic charges on the suspended particles, one drop of 10% NH 4 CL was added for every 10 mL of suspension [12]. Coverslips were prepared with diatom suspension and installed on slides in Naphrax glue. The Olympus microscope (Model CX31) via 100x oil immersion was used to investigate the diatom cells. Finally, the Canon camera (Model EOS 5D Mark III) was used to capture the images. The slides were examined to evaluate the abundance of species based on 300 valves counts for each site. Each month, three permanent slides were prepared for eight stations (Table 1, Figure 1).

Results and Discussion
In this study some research of diatom flora was chosen which were representative of continents (Asia, Europe, Africa, America). The study of Brazil diatoms was conducted to increase the biodiversity and ecology of tropical diatoms. In the Czech Republic study, the region includes pristine habitat with clean and unpolluted waters. The sampling in the Serbian study was done from different substrates including epiphyte and epilithic which two genera (Microfissurata and Fistulifera) were new for their flora. The sampling stations in Iraq and its geographical position were highly diverse from cold to hot and mountains to deserts areas which make it special. The characteristics of the sampling area in the United States were diverse regarding pH, temperature, salinity, nutrient, and a vast area which can be the reason for the diversity of diatom species.

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A very small diatom linear shape and other individual characteristics with strongly concave valve margins, poorly elongated, rounded to sub-capitate apices and if not focused on, it may not be observed by diatomists in microscopic investigation. In our samples, it occurred in slightly alkaline pH (7.25), moderate electrolyte to high electrolyte content with conductivity (309-890 μs cm -1 ) and eutrophic conditions, with DO (7. 25 -9.74 mg.l -1 ), ORP (-32.2-to -101.6), NO 3 2-(1.7-7 mg.l -1 ), Si (2.23-8.57 mg.l -1 ) & Mg 2+ (11.48-24 mg.l -1 ). It was observed only in winter and autumn (temperature 4.3-19.7°C) (Figure 3, Table 2).  [18,23,31,32,[36][37][38][39][41][42][43]. The Ulnaria ulna (Nitzsch) Compère is the most frequent species which has been occurred in 12 out of 15 compared studies. Following this species in frequency is Navicula cryptotenella Lange Bertalot, Gomphonema acuminatum Ehrenberg, and Nitzschia palea (Kützing) W Smith, which were common in 11 studies. So, it can be concluded that these species are cosmopolitan and probably they can be seen in the normal environment of whole the world. Some taxa were only reported from Iran's rivers, but not present in other compared regions, such as Nitzschia subtilis (Kützing) Grunow, N. oligotraphenta Lange Bertalot, A. minutissima W. Smith. Cymbella compacta Østrup, C. diversistigmata Krammer, Gomphonema venusta Passy, Navicula notha Wallace. So, they may be, found in special geographical regions. The other objective was to compare the flora of Taleghan River with other studies in Iran and the other 15 areas in the world ( Table 2). The highest and the lowest similarity was between Africa's rivers (66%) and Serbia's diatoms (3%) respectively. Bacillarophyta  to  three  classes Coscinodiscophyceae, Mediophyceae, and Bacillariophyceae which it is supported by the molecular analysis, however, we have used the Guiry & Guiry diatoms classification [44][45][46] (Figure 4, Table 3). Probably the high diversity of the Taleghan River can be related to the presence of 10 mines in the upstream which release the inorganic elements.

Medlin & Kaczmarska and Medlin have classified the
The assembly of ecosystems and species diversity is affected by anthropogenic activities such as destroying habitats, organic, and inorganic pollution.

Conclusion
Based on the performed comparison, the Ulnaria ulna, Navicula cryptotenella, Gomphonema acuminatum and Nitzschia palea was the cosmopolitan species and Achnanthidium standeri, Frustulia tugelae, Nitzschia acula, and some other species were rare taxon. Sixty-four species and two genera were new records for diatoms flora of Iran and for Asia the species Cymbella pernodensis, Cymbella novazeelandiana, and Achnanthidium druartii were new recorded. According to the comparison of Taleghan diatom flora with 15 other environments, it can be concluded that the flora of Africa and the USA are the most similar and the flora of Serbia is the least similar to the Taleghan River. Also, the rare and cosmopolitan species was visible in Table 2.