Abstract :
Illegal gold mining (PETI) carried out by the community in the Batang
Masumai River is becoming increasingly alarming. The dredging activities
conducted by miners have caused the river flow to become turbid and experience a
decline in water quality. This study aims to determine the water quality of the
Batang Masumai River using biological, physical, and chemical parameters. Water
quality monitoring can be carried out through various methods, namely chemically,
physically, and biologically. Biological monitoring can be done by utilizing
bioindicators. Biological indicators can continuously monitor and provide easy-to-
observe signs of pollution.
Plankton plays a crucial role in ecosystem balance as it is a component in
the aquatic food chain. The life of plankton is highly influenced by the physical
and chemical parameters of water, including salinity, pH, dissolved oxygen levels,
carbon dioxide (CO2), and water clarity. As a biological indicator, the composition
and abundance of plankton can provide insights into pollution levels using the
saprobity index, which is employed to assess the saprobity level of water.
Saprobity describes the water quality related to the composition of organisms in
the river. The biota community varies based on their living time and location. In
this system, an organism can act as an indicator characterizing the water.
Sampling was conducted using purposive random sampling at three
research locations. Physical-chemical parameter measurements at the three
locations showed average temperatures of 30°C, average pH of 8, turbidity
ranging from 252.18 to 577.33 NTU, brightness ranging from 6 to 8 cm, and
dissolved oxygen levels ranging from 0.3 to 0.4 mg/L. The research results using
bioindicators indicated three classes of phytoplankton: Cyanophyceae,
Chlorophyceae, Bacillariophyceae. The phytoplankton diversity index (H') at the
three locations ranged from 0.4505 to 1.0251, and the dominance index (D) of
phytoplankton ranged from 0.4650 to 1. Based on measurements of physical,
chemical, and biological parameters with phytoplankton as a bioindicator, the
water of the Batang Masumai River is classified as heavily polluted.