HR: 0800h
AN: B51D-0243    [Abstracts]
TI: Algal Biomass as an Indicator for Biochemical Oxygen Demand in the San Joaquin River, California.
AU: * Volkmar, E C
EM: ecvolkmar@ucdavis.edu
AF: Land, Air, and Water Resources University of California, Davis, 1 Shields Ave, Davis, CA 95616 United States
AU: Dalhgren, R A
EM: radahlgren@ucdavis.edu
AF: Land, Air, and Water Resources University of California, Davis, 1 Shields Ave, Davis, CA 95616 United States
AB: Episodes of hypoxia (DO < 2 mg/L) occur in the lower San Joaquin River (SJR), California, and are typically most acute in the late summer and fall. The oxygen deficit can stress and kill aquatic organisms, and often inhibits the upstream migration of fall-run Chinook salmon. Hypoxia is most pronounced downstream from the Stockton Deep Water Ship Channel, which has been dredged from a depth of 2-3 m to about 11 m to allow ocean-going ships to reach the Port of Stockton. To protect aquatic organisms and facilitate the upstream migration of fall-run Chinook salmon, the minimum water quality standard for DO is 6 mg/L during September through November, and 5 mg/L for the remainder of the year. A five year study examined components contributing to biochemical oxygen demand (BOD): ammonia, algal biomass, non-algal particulate organic matter, and dissolved organic carbon. BOD shows a significant increase in loading rates as the SJR flows downstream, which parallels the load of algal biomass due to instream growth. BOD loading rates from tributaries accounts for 28% in a wet year and 39% in a dry year. Regression analysis revealed that chlorophyll-a + pheophyton-a was the only significant (p<0.05) predictor for BOD (r² = 0.71). Less than 20% of the BOD was found in the dissolved fraction (<0.45 μm). The average BOD decomposition rate of the SJR and tributaries is 0.0841 d^-1. We conclude that algal biomass is the primary contributor to BOD loads in the San Joaquin River.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
SC: Biogeosciences [B]
MN: Fall Meeting 2005