More Information about Dissolved Oxygen:

    The instantaneous measures of surface and bottom DO were, on average, slightly lower than the mean DO values obtained from the 25-hr deployment of water quality meters at each site (Appendix 2.1). These differences were not statistically significant based on a comparison of the mean versus instantaneous bottom measures (p > 0.05). However, the instantaneous DO measures did result in a higher percentage of the state's coastal water habitat coding as marginal or potentially stressful to marine biota (Appendix 2.5). The instantaneous bottom DO measure was also poorly correlated to the mean bottom DO obtained from the 25-hr instrument deployment (r²< 0.41). These results indicate that a single daytime measure of DO is not as good an indicator of average conditions compared to observations collected over a longer period that includes both day and night measures during all tidal stages. The SCECAP program will rely on mean values obtained from a 25-hr deployment as the best measure of dissolved oxygen conditions.
 

Typical dissolved oxygen concentrations observed during various tidal and diurnal periods in tidal creek versus open water habitats during 1999-2000. Shaded areas represent nighttime periods. Dotted lines show tidal stage.