Oxygen depletion of Hamilton Harbour

Processes involved in the oxygen cycles of the highly eutrophic Hamilton Harbour were studied. Sediment oxygen demand k_s(O₂ m⁻² day⁻¹) was measured by an in situ method and was determined to be dependent on oxygen concentrations c (m l⁻¹) in the water phase. This dependence was expressed by the equation k_s = 0.72 + 0.26 c. The water column oxygen demand of the harbour was determined experimentally and revealed a significant dependence on oxygen concentration. It was estimated that over 80% of the oxygen supplied to the harbour was used within the water column. The sediment oxygen consumed about 18% of the oxygen entering the harbour and was relatively most important in the early stages of stratification when the hypolimnetic dissolved oxygen concentrations were high. The main sources of oxygen were atmospheric reaeration (80%), lake-harbour exchange (10%) and photosynthesis (10%).