Role of Aquatic Plant Nutrients in Causing Sediment Oxygen Demand Part I – Origin of Rapid Sediment Oxygen Demand 1

Some urban streams experience rapid depletion of dissolved oxygen (DO) associated with major stormwater runoff events. In some situations, the DO depletion can be sufficient to rapidly cause low DO that can lead to fish kills. This report is Part I of a three-part discussion that examines the role of aquatic sediments in causing the rapid depletion of DO in some urban and rural streams associated with stormwater runoff events that suspend sediments into the watercolumn where they exert oxygen demand. Also, focus is given to the potential for similar, rapid DO depletion in US navigable waterways (river and harbor systems) associated with the exertion of sediment oxygen demand when sediments become suspended into the watercolumn during storms and open water disposal of dredged sediments. While sediment oxygen demand is typically said to be associated with relatively slow biotic reactions (decomposition of organics), there are situations in which abiotic (inorganic) reactions play a major role in DO depletion in a waterbody watercolumn. Examples of these situations are discussed herein. Part II expands on the discussion of sediment oxygen demand and includes examination of the role of planktonic (suspended) algal death/decomposition in causing oxygen demand in the watercolumn of lakes and channels. Part III discusses the role of aquatic plant nutrients in causing low DO in waterbodies that leads to sediment toxicity. Impact of Low DO on Fish. Lee and Jones-Lee (2003) summarized the effects of decreased DO on fish and other aquatic life based on the information in the US EPA guidance document for the DO water quality criteria (US EPA, 1986). According to C. Delos (Health and Ecological Criteri