Dissolved organic matter and its correlation with phytoplankton abundance for monitoring surface water quality

BACKGROUND AND OBJECTIVES: Dissolved organic matter has a fundamental role in supporting phytoplankton abundance and growth in aquatic environments. However, these organisms produce dissolved organic matter with varied quantities or characteristics depending on the nutrient availability and the species composition. Therefore, this study aims to assess the characteristic of dissolved organic matter on surface water and its correlation with phytoplankton abundance for monitoring water quality.METHODS: The sample was obtained at four Kali Surabaya River stations for further dissolved organic matter analysis and phytoplankton species analysis. The analysis was presented through bulk parameters of total organic, ultraviolet at 254 nm wavelength (UV254), specific ultraviolet absorbance value, and fluorescence spectroscopy using excitationemission matrices with fluorescence regional integration analysis.FINDINGS: The results showed the bulk parameters of dissolved organic matter at all stations were significantly different, as Station 1 and 2 were higher, while 3 and 4 had a lower concentration. Furthermore, the fluorescence spectroscopy identified four components of dissolved organic matter at all stations, namely aromatic proteinslike (APlike), humic acidlike (HAlike), soluble microbial byproductslike (SMPslike), and fulvic acidlike (FAlike). Also, stations 1 and 2 were grouped in the high percentage FRI of humic substance (FAlike and HAlike), while 3 and 4 were classified in the high percentage FRI of nonhumic substances (APlike and SMPslike).CONCLUSION: The main phytoplankton species, namely Plectonema sp., Pinularia sp., Nitzchia sp., Navicula sp., had the highest abundance at Stations 1, 3, and 4, respectively. A strong correlation between dissolved organic matter analysis and phytoplankton abundance led to the usage of these methods for monitoring surface water quality.