Estuary. Naymik et al. (2005) found a similar relationship between stream total nitrogen and 
broadleaf cover (which is primarily red alder in the Coast Range) in the Tillamook watershed. In 
the Yaquina Estuary watershed, 23% of the watershed is vegetated with red alder (Brown and 
Ozretich, in review). Brown and Ozretich (in review) estimated that > 80% of the riverine 
nitrogen loading to Yaquina Estuary is related to red alder cover. Thus, riverine nutrient loading 
in the PNW is influenced by forest species composition. 
3.2.2 Ocean Input 
Brown and Ozretich (in review) estimated oceanic input of DIN to the Yaquina Estuary 
during the dry season of 2002 and 2003. The oceanic input of DIN was calculated using the 
time-series of flood tide input of DIN multiplied by the volume of water entering the inlet during 
each tidal cycle. The volume of water entering the inlet was calculated using a two-dimensional, 
laterally averaged hydrodynamic and water quality model (described in Brown and Ozretich, in 
review). Daily water samples were collected during flood tide approximately 0.5 m below the 
surface at a station about 3.7 km from the mouth of the estuary. These samples were analyzed 
+ 3 - 
for dissolved inorganic nutrients (NO3 + NO2, NH4 , PO 4 and Si(OH) 4 ). During the dry season 
of 2002, the amount of DIN entering the estuary from the ocean during each flood tide varied 
from 8.8 x 10 3 mol N to 6.7 x 10 5 mol N with a mean value of 2.4 x 10 5 mol N, and the mean 
daily flood tide input of DIN was 4.7 x 10 5 mol N d 1 . During the 2003 dry season, the mean 
oceanic input of DIN is 3.7 x 10 5 mol N d " 1 or 21% less than 2002 dry season. Sigleo et al. 
(2005) calculated the flood tide input of NO3 to Yaquina Estuary during August of 2000 to be 13 
x 10 5 mol N d’ 1 , which is about triple our estimate. However, these ocean input numbers were 
calculated using a constant flood tide NO 3 of 30 pM. 
22 
