Using benthic diatom assemblages to assess sedimentary nutrient status in Tri An reservoir, Dong Nai province, Vietnam

Abstract

Tri An Reservoir plays an important role in the water supply for Dong Nai province and Ho Chi Minh city. It also contributes significantly to increase underground water reserves in the vicinity, especially in the dry season. However, recently, the increase of nutritional compounds in the lake has contributed to eutrophication, causing serious deterioration of the quality of the environment, creating conditions for microalgae to thrive. Therefore, this study aimed to evaluate and zoning the sediment quality of the Tri An reservoir based on using benthic diatom communities as biological indicators as an indicator tool. Sediment and algae samples were collected from 8 survey locations in the Ho Tri An area from March to August in 2019. The results showed that the dominance of several species belonging to the genera that prefer to live in nutrient-rich environment such as Navicula, Nitzschia. The TDI index indicated the sediment environment had high nutrient contents. Water quality in the lower section of the reservoir was classified from eutrophic (even hyper-eutrophic) status, particularly stations into the reservoir. Meanwhile, upstream and downstream sites had lower nutrient levels, mainly excessive phosphorus but still in eutrophic class. Additionally, the initial analysis results also revealed that NH4 +, TN, PO4 3ô€€€ and DO played a major role to regulate the development of benthic diatom assemblages.