Biological Oxygen Demand Dynamics in the Lower San Joaquin River, California

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• 作者：Emily C. Volkmar ; Randy A. Dahlgren
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：September 15, 2006
• 年：2006
• 卷：40
• 期：18
• 页码：5653 - 5660
• 全文大小：370K
• 年卷期：v.40,no.18(September 15, 2006)
• ISSN：1520-5851

文摘

Dissolved oxygen less than 5 mg L^-1 (U. S. EPA advisorylevel) commonly occurs in the lower San Joaquin River (SJR),California. Most acute episodes typically occur in latesummer and fall. The oxygen deficit can stress and killaquatic organisms, often inhibiting the upstream migrationof Chinook salmon (Oncorhynchus tshawytscha). This 5year study examined watershed-scale spatial and temporalbiological oxygen demand (BOD) loads and the primarycomponents believed to contribute to BOD: ammonium,algal biomass, nonalgal particulate organic carbon, dissolvedorganic carbon, and dissolved organic nitrogen. Sampleswere collected bimonthly at 15 sites during the summers of2000 and 2001 and from three lower mainstem sites fromMay 2002 to March 2005. BOD loads showed a downstreamincrease in parallel with increasing algal biomass loadsresulting primarily from in-stream growth. BOD loads frommeasured tributaries and drains accounted for 28% and39% of the BOD load at the downstream Vernalis site in 2000and 2001, respectively. Algal C was positively correlated(r = 0.80) with BOD, explaining 64% of BOD variance for datacollected from 2001 to 2005. Less than 20% of BOD wasfound in the dissolved fraction (<0.45 m). We conclude thatalgal biomass is the primary contributor to BOD loads inthe lower SJR, upstream of Mossdale.