Water Quality Assessment of Lake Maninjau After the Mass Fish Kill Event Taofik Jasalesmana(a*, d), Sulung Nomosatryo(d), Ira Akhdiana(d), Mutiara Rachmat Putri(b), Mirzam Abdurrachman(c), Cynthia Henny(d)
a) Earth Science Doctor Program, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia
*t.jasalesmana[at]gmail.com
b) Research Group of Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia
c)Geological Engineering Study Program, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia
d)Research Center for Limnology and Water Resources, National Research and Innovation Agency (BRIN), Cibinong 16911, West Java, Indonesia
Abstract
Mass fish kill is often occurring in Lake Maninjau. A decreased oxygen content has reportedly resulted in many fish kills, including the lake Maninjau condition recently. Deoxygenation of lake water is a natural phenomenon that often occurs after heavy rain events and low sunlight intensity. In addition, the decrease in oxygen chemically is triggered by the rise of sulfide from the bottom layer of the water column when the wind blows hard over a long period. Furthermore, this study examines water quality parameters after mass fish mortality occurred across locations in Lake Maninjau. Field surveys were conducted by measuring psychochemical parameters and total sulfide on the five of the middle and ten points around of the lake from 26 November - 02 December. They were measured directly using the HORIBA water quality checker (WQC), DO meter YSI ProDO and the HACH spectrophotometer DR3900 method. The results showed that DO levels at each observation point averaged close to 0 mg/L with an average sulfide level on the surface of 21.5 micro g/L. The average Oxidation Reduction Potential (ORP) of -79.26 mV indicates that the lake is in a reduced state and signifies that a lot of dead and decaying material in the water cannot be cleared or decomposed. Low ORP values indicate that the compound in the water is available in reduced form, which is more toxic. Our productivity primer experiment showed that sunlight intensity is effective in increasing oxygen concentration in the lake.
Keywords: Dissolved oxygen, fish death, Lake Maninjau, sulfide.
