Introduction: One of the main problems associated with mining activities is run-off, which adversely effects the quality of surface and underground waters. Golestan province has various mines and since that most of these are located in forest areas, monitoring their effects on neighboring ecosystems is essential. Due to the abundance in every ecosystem, short life cycle, and quick response to the environmental changes, diatoms are considered as suitable bioindicators and extensively have been used for water quality assessment. These organisms can serve as good Indicators in heavily polluted areas affected by mining. This survey studied the effects of the mining drainage from the Zemestan Yurt and Razi mines in East Golesta on diatom assemblages. No studies have been conducted on the relationship between diatoms and coal mines in Iran. This survey specifically examined the impact of drainage from Zemestan Yurt and Razi coal mines on diatom assemblages.
Material and methods: In this study in each mine two sites werer selected: the first site in the outlet of mine and the second downstream form the outlet where the drainage flows into the Khormarud (in Zemestan Yurt Mine) and Ghareh Cheshmeh Rivers (in Razi Mine). Sampling was carried out during the winter season from stony substrates. The sampling stations were located downstream from the outlets of the Zemestan Yurt (Azadshahr City) and Razi (East Alborz, Ramian City) coal mines, where the drainage flows into the Khormarud and Ghareh Cheshmeh Rivers. Alongside algal samples, water samples were also collected and in darkness with ice were carried out to the laberatory for further analysis. Diatom samples were studied and identified under a light microscope after preparation and the production of permanent slides. Water parameters were measured both in situ and in the laboratory.
Results and discussion: In total 27 diatom taxa belonging to 16 genera were identified in this study; these taxa have also been reported from other aquatic ecosystems in Golestan Province. The most abundant taxa included Achnanthidium minutissimum, Diatoma moniliformis and Gomphonema pumilum which more or less were among the most abundant taxa in other studied ecosystems of Golestan Province. Hydrochemical results showed that the pH was alkaline and greater than 8, which aligns with the identified diatom taxa, as 60.71% of which were alkalifilous which are found in pH more than 7 and the last are taxa which are found in pH 7. Although salinity levels increased as one moved away from the mines, however its level was in the freshwater range and this increase was not significant enough to have a remarkable effect on the diatom assemblage. In terms of tolerance to organic pollution, most of the identified taxa in both mines were found to be pollution-tolerant. Regarding tropHic status, most species were indicators of eutropHic waters, followed by species capable of surviving in various tropHic conditions.
Conclusion: Among the effects of mining which can remarkably affect the diatom assemblages is the obvious change in water pH and salinity; according to findings of this study no significant change were observed in terms of the mentioned parameters and the identified taxa were also reported from other studied ecosystems of Golestan Province. However the studied sites exhibited low taxonomic richness, which is characteristic ecosystems affected by mining; all identified taxa were either pollution-tolerant or taxa with extensive ecological niches. Therefore more experiments on rivers pollution are suggested specially in terms of possible heavy metals that may have entered this rivers through mine runoffs.