Paleolimnological approach infers past environmental changes archived in lake sediments of Bukit Merah Reservoir, Malaysia.

Human activities in the watershed of Bukit Merah Reservoir, have significantly increased, placing unprecedented pressure on this important system. However, long-term records of the ecological effects are scarce. Thus, this research aims to examine the impact of human-induced environmental change on the reservoir using a paleolimnological approach. Two 25 cm sediment cores were extracted from the reservoir using a Uwitech corer, and analysed for 210Pb, elemental geochemistry, and diatom remains. Using 210Pb and the Constant rate of Supply Model (CRS) the oldest sediments (22.5-24.5 cm) were dated to AD 1985 ± 34 years. The mean concentration of metals (As, Cd, Cu, Pb, and Zn), total nitrogen (TN), total organic carbon (TOC), and total phosphorus (TP) increased from the bottom of the core and fluctuated to the top. This may be ascribed to increasing usage of agrochemicals, tourism, industry contributions, sand excavation, and inputs from small and medium-scale companies in the catchment area. In this study, the dominance of diatom species (Aulacoseira granulata, Aulacoseira ambigua, Discostella stelligera, and Cyclotella meneghiniana) throughout the length of the core, indicates high productivity of the reservoir due to continuous human impacts. As a result, immediate action is needed to further ameliorate the degradation of the reservoir.