Winter Sediment Oxygen Demand and Sediment Characteristics in Pools 4, 8, and 13 of the Upper Mississippi River, 2022

Many ecological processes affect availability of winter dissolved oxygen (DO) concentrations in rivers, a key feature of overwintering fish habitat. Sediment oxygen demand (SOD) contributes to DO depletion, particularly during ice-covered periods, and may cause hypoxic conditions in backwater lakes, affecting availability of suitable overwintering habitat. Understanding drivers of SOD on habitat conditions during winter is critical for management of the Upper Mississippi River System (UMRS). We measured SOD rates in three different habitat types (shallow, non-vegetated; deep, non-vegetated; and vegetated) within 12 backwater lakes in Pools 4, Pool 8, and Pool 13 of the UMRS in January and February 2022. Sediment physicochemical characteristics were measured to identify potential drivers of winter SOD rates. Measured SOD rates ranged from 0.04 – 0.44 g O2/(m2d) at in situ temperatures, and 0.14 – 1.46 g O2/(m2d) when corrected to 20°C.