As in many other urban areas centered around rivers and harbors, water pollution problems have been documented in the tidal river since the turn of the century (e.g., Newell, 1897). In the late 1950s USPHS officials described the Potomac near Washington, DC, as "malodorous ... with gas bubbles from sewage sludge over wide expanses of the river . . . and coliform content estimated as equivalent to dilution of 1 part raw sewage to as little as 10 parts clean water." Dissolved oxygen levels near Washington, DC, were typically less than 1 mg/L during summer low-flow conditions, and nuisance algal blooms and fish kills were commonplace during the 1940s, 1950s, and 1960s. Between 1955 and 1960, the stock abundance of American shad in the Potomac River dropped precipitously despite favorable hydrographic conditions for spawning and development. American shad in northeastern estuaries such as the Potomac River, although influenced by spawning success, may be influenced to a larger extent by mortality suffered by young fish as they pass seaward through regions of poor water quality (Summers and Rose, 1987).
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