Organic matter and organic carbon levels in sediments of Lake Maninjau, West Sumatra

The organic matter content of lake sediments provides a variety of indicators, or proxies that can be used to reconstruct paleoenvironments of lakes and their watersheds. Particularly, in this study it will provide information that is important to interpretations of both natural and human-induced changes in lake ecosystems. The abundance of organic matter in sediments is described from the total organic carbon (TOC) because it's a primary parameter. Moreover, Algae is the main source of organic carbon in the eutrophic lake. Lake Maninjau that located in West Sumatra has been eutrophic due to increasing of lake water utilization for floating fish cages, in recent years Lake Maninjau has faced an algal bloom frequently. Four sediments core were collected in Lake Maninjau from the lowest (near coastal) and deepest part (30 cm long core in average). Total organic matter (TOM) was performed using Lost on Ignition method (LoI) in whole cores, while total organic carbon (TOC) was analyzed using combustion analyzer method in one core that was taken in the deepest part of Lake Maninjau. TOM in Lake Maninjau among the cores varied between 21 to 34% at the surface, then decreased slowly as a depth. The percentage of surface TOM in the near coastal is elevated to the deepest part (21% to 34%). The TOC content in the surface was 9%. According to the Mid-Atlantic Integrated Assessment (MAIA) Estuaries the TOC concentrations in the sediments was in the range of high organic carbon level (>3%). The high value of TOC level in the surface sediment was controlled by algal productivity.