criterion observations in Zone 1 are probably related to the oceanic import of hypoxic water, but 
possibly not in Zone 2. In the continuous data, there is not significant difference in dry season DO 
levels (median =7.0 mg 1 ') between the two locations (Mann Whitney Rank Sum, p>0.05). However, 
median DO levels expressed as percentage of saturation are significantly lower in Zone 1 than in Zone 
2 (Mann Whitney Rank Sum, p<0.001). The ODEQ (1995) review of the state DO criterion notes that 
in some bays, the 6.5 mg f 1 criterion may not always be achievable due to natural background 
conditions. This conclusion is consistent with the analyses in this section. 
Table 8.1 Percentiles for dissolved oxygen (mg l' 1 ) calculated Yaquina (1998-2006), 
Classification (2004-2005), and NCA Oregon Estuaries (1999-2000) data sets. NCA and 
Classification values are for dry season only, while Yaquina include dry and wet 
season 
values. 
Percentiles for Dissolved Oxygen (mg \ ) 
Data set 
Sample Size 
25 th 
50 lh 
75 lh 
Zone 1 
Yaquina 
Dry 
Discrete 
6.5 
7.8 
8.5 
46 
Continuous 
5.9 
7.0 
8.0 
2856 
Wet 
9.0 
9.4 
9.5 
36 
Classification 
6.7 
7.3 
8.3 
37 
NCA 
7.2 
7.8 
8.4 
35 
NCA excluding Columbia 
7.3 
8.0 
8.5 
32 
Zone 2 
Yaquina 
Dry 
Discrete 
6.7 
7.2 
7.6 
259 
Continuous 
6.4 
6.9 
7.5 
2862 
Wet 
10.2 
11.0 
11.6 
184 
Classification 
6.9 
8.1 
9.3 
53 
NCA 
7.6 
8.5 
9.0 
88 
NCA excluding Columbia 
6.7 
7.3 
8.3 
26 
11 - 
59 
