Total organic carbon and dissolved organic nitrogen in the upper water column of Keunekai Waters, Weh Island, Indonesia: an overview of mass coral mortality impacts

Abstract

Keunekai waters located in the southern Weh Island are directly bordered by the Indian Ocean. Due to the climatic anomaly occurred in the Indian ocean in 2016 where the temperature raised dramatically, resulting in mass-bleached coral colony. This study aims to evaluate the impact of carbon organic resulted from mass coral mortality on the availability of dissolved nitrogen in Keunekai waters. Non-dispersive infrared – supercritical water oxidation (NDIR-SCWO) and Kjeldahl methods are employed to analyze the total organic carbon (TOC) and dissolved organic nitrogen (DON) that the concentrations respectively ranged 9.67 - 14.19 mg C/L and 0.13-0.53 mg N/L. The ratio of C:N shows the N-relative content which the observation station with higher TOC indicates the N limitation probably influenced by the competition between autotroph biota and microbes indicating the decomposition level variation and the water fertility. In several stations, the N concentration is slightly low in accordance with the higher TOC concentration identified. The relatively high C:N ratio indicates that Keunekai water is in the imbalanced condition.