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Stratification and mixing dynamics in tropical lakes differ from those in temperate systems, owing to their continuously warm climate and distinct geographical settings. Using high-frequency water column temperature and meteorological measurements, together with chemical profiles collected from October 2022 to October 2023 in tropical eutrophic Lake Batur, Bali, Indonesia, we investigated the timing and key drivers of stratification and related indices, including epilimnion and hypolimnion temperature, Schmidt stability and Wedderburn number, and the magnitude of surface heating and cooling at subdaily to annual timescales. Changepoint analysis was used to identify 4 seasonal periods: early stratification (Oct–Dec), mixing (Dec–Mar), strong stratification (Mar–May), and frequent mixing (May–Oct), confirming the polymictic regime of the lake. Mixing events were associated with high rates of heat loss, strong wind events, or both. Analysis of dissolved oxygen and sulfide concentrations indicated that ∼20% of the available oxygen in the water column was consumed by sulfide oxidation following a mixing event, which likely represents a conservative estimate of the actual oxygen demand. Our study indicates that in-lake aquaculture in tropical eutrophic systems like Lake Batur faces heightened risks from frequent mixing-induced anoxia, which may intensify under climate warming and shifting wind regimes.
Santoso et al. (Wed,) studied this question.