Self-purification plays an important role in water regulating ecosystem services aimed at protecting river water quality from pollutant inputs. The Citarum River is the longest river in West Java, Indonesia where the water quality has declined due to pollutant inputs from domestic and non-domestic activities. This study aims to investigate the status of self-purification ecosystem services and the influence of water quality in the upstream of the Citarum River, in the Cihawuk and Majalaya segments, which are rural and urban areas. The self-purification status was determined by the deoxygenation rate using Thomas’s slope method, and by the reaeration rate according to O’Connor and Dobbins’ method. The polynomial component regression (PCR) was performed to determine the significance of the influence of physicochemical factors on self-purification. The deoxygenation rates (k₁) in the rural and urban areas upstream of the Citarum River were 0.044 per day and 0.058 per day, respectively, while the reaeration rates (k₂) in the rural and urban areas were 0.196 per day and 0.156 per day, respectively. These deoxygenation and reaeration rates indicate that the self-purification status upstream of the Citarum River has been disturbed. This result also indicates that chemical factors have a significant influence on the deoxygenation process, while the reaeration process is most significantly influenced by physical factors. The deterioration of self-purification in the Citarum River poses a risk to the long-term availability of water resources. Therefore, this research encourages the reduction in the input of organic pollutants and develops a strategic plan for river management.

Pratiwi D, Oktavia D, Sumiarsa D, Sunardi S. 2024. Water quality assessment of river based on phytoplankton biological integrity index in rural areas of the upstream Citarum River, West Java, Indonesia. Biodiversitas 25: 881-889. The deterioration of water quality in the upstream Citarum River is one of the consequences of agricultural practices characterized by fertilizer and pesticide runoff that disrupts the ecological balance of aquatic ecosystems. The research area was on agricultural land use in the Cihawuk segment, Kertasari, Bandung District. The present study attempts to community structure and assess the water quality using the biological indexes of rural areas in upstream Citarum River through phytoplankton studies. A purposive sampling technique was used to collect data on physico-chemical parameters and phytoplankton community structure from stations selected on the basis of agricultural land use. Furthermore, biological indexes such as pollution levels based on the Shannon Wienner diversity index (H'), Palmer algae index, and Diatomeae index are examined using the data community structure of phytoplankton. The findings show that the abundance of phytoplankton in rural areas is 4,105 cells/L. The community structure of phytoplankton was dominated by Coelastrum sp. and Trachellomonas sp. The Palmer algae index ranges from 23-26, indicating that the water was a highly organic pollutant. The pollution level of upstream Citarum River based on the diversity index shows moderately polluted water. Meanwhile, the diatomeae index showed less than 0.2, which sites water bodies were mesotrophic. Phytoplankton and their indexes serve as valuable tools for evaluating the quality of the water environment.

Understanding soil physicochemical properties is fundamental to ecosystem functioning, agriculture, and land management (Schoenholtz et al. 2000; Olorunfemi et al. 2018). Soil develops through the ...