Kratzer – Directed Action Proposal

Study Element: Evaluation of nutrients and oxygen-demanding substances in the San Joaquin River upstream of Vernalis

February 20, 2001

1. How does the carbon isotope work fit in with the overall program to evaluate sources of oxygen demand? (Alan Jassby had a similar question)

The reason for analyzing the carbon 12/13 isotope ratios in dissolved and suspended organic carbon as part of the FY00 program was to help define the significance of terrestrial sources (surface runoff) versus aquatic sources (algae) of carbon to the river. The proposed USGS monitoring in FY01 will include a variety of isotopes and tracers. The following is from the FY01 USGS monitoring portion of the CALFED Directed Action:

"Isotopic measurements and tracers of possible dissolved oxygen-depleting compounds are important in that their analysis may provide insight to the metabolic pathways of algae and bacteria, within the DWSC, and thereby be important to the management of upstream sources of nutrients and other potential oxygen-depleting compounds. A final decision on the suite of isotopic measurements and other tracers for sampling and analysis will be made prior to the June sampling season following a review of existing data on nutrient sources and the availability of laboratory methods with sufficient quality assurance and within budgetary guidelines. Isotopic measurements under consideration include carbon 12/13 ratios in dissolved and suspended organic carbon and within inorganic carbon (carbonate and bicarbonate ions dissolved in water). Carbon isotope ratios can provide information on the source of the material (in-stream from algae), or terrestrial (derived from surface runoff), and the examination of the ratios in both the organic and inorganic pools will provide some information on which material is being utilized in algal and bacterial metabolism. Isotopes of nitrogen and oxygen in nitrate ions are also powerful tracers of the source of the nitrogen and have been used in other studies to distinguish nitrate from biological versus inorganic fertilizer sources. New analytical techniques are being developed by the U.S. Geological Survey National Water Quality Laboratory for the analysis of trace amounts of pharmaceutical compounds, some of important agricultural use, that are also useful in distinguishing the source or sources of oxygen-depleting compounds."

1. Has the fertilizer application and manure production data shown in Kratzer and Shelton (1998) been updated and is it available?

In Kratzer and Shelton (1998), data on fertilizer application and manure production in the San Joaquin River Basin is presented (by county) for 1950 to 1990 on page 83. Additional information and some updated data is available from the following public USGS website: http://water.usgs.gov/nawqa/nutrients/othdat.html . Click on the reference listed as Alexander and Smith (1990) for additional fertilizer information and on Puckett and others (1998) for additional manure information.

2. Will phosphorus be measured in a USGS study of ground-water inputs to the San Joaquin River?

Yes, if the Burow and Phillips USGS study is funded as part of this CALFED Directed Action it does include dissolved orthophosphate as a constituent to be analyzed.

1. The investigators might consider a greater effort at determining the relative BOD of the constituents they measure, especially DOM.

The USGS Principal Investigator did suggest to the Regional Board in FY00 that dissolved BOD analyses be run in addition to the whole-water BOD analyses. However, the Regional Board decided that this would be too expensive in FY00.

2. Since the responsibility for phytoplankton BOD cannot be laid at anyone’s doorstep with confidence, perhaps the resources currently being expended to identify nutrient sources (at least within the context of the DWSC TMDL process) could be better spent on trying to understand what really affects phytoplankton biomass at Vernalis.

The analysis of nutrients is a relatively small part of the expense in both the FY00 and FY01 USGS monitoring programs. Many other constituents are being analyzed in the collected samples, including volatile suspended solids, dissolved and suspended organic carbon, ultra-violet light absorption at 254 nm, chlorophyll a and pheophytin a, major ions, BOD, and a variety of isotopes and tracers. In addition, nutrients and their sources are still a potentially important TMDL-related issue for this project.