Seasonal Changes in Sediment Oxygen Demand Across Intensive and Extensive Aquaculture Ponds

Sediment Oxygen Demand (SOD) is a substantial sink of dissolved oxygen in aquaculture ponds and an important coupling between the benthic organic matter mineralization and water quality, production risk, and ecosystem functioning. In this study, the SOD rate has been quantified in three intensive and three extensive freshwater aquaculture ponds for one year of operation using intact-core incubation method (n = 72 cores), in addition to sediment organic matter content, nitrogen content, acid-volatile sulfide content and water column chlorophyll-a. The SOD rate varied from 0.38 to 2.14 g O₂ m⁻² d⁻¹ and was significantly higher in intensive (annual mean = 1.44 g O₂ m⁻² d⁻¹) than in extensive (0.69 g O₂ m⁻² d⁻¹) ponds. The effect of both the pond type and the season was significant, and the SOD in summer was 2.6-2.8 times higher than in winter. SOD responded in an exponential manner depending on the temperature (Q₁₀ value of 1.77 in intensive and 1.85 in extensive ponds). SOD was significantly correlated with water temperature, sediment OM, and chlorophyll-a. It is clearly evident that oxygen consumption by the benthos occurs at the time when oxygen concentration in the water column is lowest and hence requires a specific season-based sediment and aeration management approach.