Nutrient Data 
Nutrient analysis for nitrate+nitrite, nitrite, ammonium, phosphate and silicate was 
performed by the Marine Science Institute Analytical Laboratory (MSIAL) of University of 
California at Santa Barbara. Nutrient analysis was carried out with a Lachat Instruments Model 
QuickChem 8000 Flow Injection Analyzer. Data quality indicators include representative 
calibration data, reagent blanks, replicate analysis and percent recovery analyses of spiked and 
control samples. Acceptable levels for these parameters are detailed in the MSIAL QA 
guidelines and provide means of monitoring data quality (MSIAL Quality Assurance Manual 
2005). In addition to these internal QA checks samples obtained from the National Institute of 
Sampling and Technology and other producers of certified reference material are analyzed 
periodically to audit performance. Deionized water blanks and sea water blank (low-nutrient 
natural sea water, aged to allow nutrient values to drop to near-zero levels) are also run. An 
independently-prepared “control” solution containing an intermediate concentration of each of 
the nutrients is also prepared. The chemistries used in determining the various nutrient species 
on this instrument have been developed by the manufacturer to have little or no salt effect, so the 
analytical response is the same for fresh, DI water samples, and standards as for salt water 
samples and standards. Saltwater samples, however, exhibit a refractive index-related response 
in the flow-through detector, so the sea water blank is used to adjust the measurement timing 
parameters to compensate for the refractive index effect. Instrument calibration is checked at the 
beginning of a sample-batch run, at the end of the run, and periodically during the run. Each 
calibration sample is analyzed in duplicate, and the resulting data is used to establish calibration 
curves for each nutrient species. If the mean of the two replicates of any standard differs from 
the known concentration of that standard by more than ten percent or more than one-half the 
concentration of the lowest standard, whichever, is greater, the calibration for that species is 
considered invalid and the calibration run is repeated. (See MSIAL Quality Assurance Manual 
2005 for more details) 
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