Results (2)


Project Summary

Experimental Design

Results (1)

Results (2)



Slough Bacteria Data

Slough abundances greater than ocean observations













Bacteria abundances rose dramatically during the first 12 hours. 

The red line represents the single limit standard for each organism: 

  • 10,000 MPN/ 100ml for total coliforms 
  • 400 MPN / 100 ml for E coli 
  • 104 MPN / 100 ml for enteroccoccus












Breach Water Quality Impacts

Summary of Total Violations for Each Indicator Organism and Sampling Location (yards relative to the Slough Mouth)



Indicator Organism Total Coliforms E coli Enterococcus
No. of violations 6 11 15



Sampling Location -250 -50 0 50 100 200 400
No. of Violations 1 8 5 5 5 5 3



The total number of water quality violations for each indicator organism was summed.  Enterococcus single limit standard was exceeded the most often and was the most conservative indicator in this study.

The number of violations for each sampling location was summed regardless of the indicator organisms responsible for the exceedences or the time of the exceedences.  -50 yards had the most violations with 8 while the 0 and 200 yards locations had 5, and the ends of the sampling regime had less.  Looking at this table and the graphs present in Results (1), the majority of the occurrences were around the mouth, except at the 12 hour sampling period.  

Relationships between Indicator Organisms and Tracer Parameters

Tracer parameters used: Nitrate, Salinity, and temperature

Indicator Organisms

Tracers R squared Values

Nitrate Salinity Temperature
E. coli 0.87 0.92 0.57
Enterococcus 0.57 0.61 0.32




The numbers in the table represent the R squared values derived from the linear regression relationship between the tracers and the indicator organisms. The R squared value can be interpreted as the proportion of the indicator organism variance that can be explained by the tracer parameter variance. 

Total coliforms were removed from the regression analysis as a 1:10 dilution did not dilute the water sample enough to determine the exact MPN number. Instead the concentration of total coliforms topped off at 25,000 MPN/ 100 ml. 

Nitrate and salinity showed a high correlation with the indicator organisms compared to temperature. 

All three tracers were better predictors for E coli as compared to enterococcus.






























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Last updated April 28, 2001