Modeling results were consistent with analysis of seagrass depth limits which indicated that the 
median kj provided for persistence of seagrass at depths within the two estuarine zones that were 
comparable to current depth distributions. 
The current Oregon DO criterion of 6.5 mg l' 1 should be adequately protective of 
estuarine resources, but is closer to the 25 th percentile value rather than the median value for DO 
data in Zone 2. Recent DO measurements demonstrate that hypoxic water is imported into the 
estuary from the coastal shelf during the dry season. As a result, exceedances of the DO 
criterion should be expected particularly in Zone 1. The current Oregon chlorophyll a criterion 
of 15 pg l' 1 is approximately 3 times greater than the median value for Zone 2. The chlorophyll a 
criterion is determined as a 3-month average, and if chlorophyll a levels were to approach the 
present criterion for such a time period, significant trophic shifts in the estuary would be likely. 
Thus, the current chlorophyll a criterion may not prevent some impacts on designated use. 
Potential dry season criteria for the Yaquina Estuary based on median values for all parameters 
except for DO. 
Parameter (units) 
Zone 1 
Zone 2 
DIN (nM) 
14 
14 
Phosphate (pM) 
1.3 
0.6 
Chlorophyll a (pg f 1 ) 
3 
5 
Water Clarity (m 1 ) 
0.8 
1.5 
Dissolved Oxygen (mg f 1 ) 
6.5 
v 
