Epiphyte Methods 
Epiphytes growing on Z marina leaves were collected within the Yaquina Estuary from 
2000 though 2004. Data were collected at six stations distributed between 3.5 and 17 km upriver 
from the mouth of the Yaquina Estuary. Leaves from collected plants were subdivided into outer 
(older) and inner (younger) leaves. Epiphytes were scraped from these leaf groups with dry 
weights (24-36 hours at 60-70 °C) of the removed material determined for each individual plant. 
The effect of epiphyte cover in terms of reducing light (PAR) availability to eelgrass was 
estimated in the laboratory using a LI-COR LI-190S A quantum sensor. Freshly removed 
epiphytes from a single leaf were washed into a Plexiglas cylinder with distilled water (60 mL). 
A light source was placed above this cylinder with the PAR sensor below the chamber and the 
amount of irradiance was determined. This value was then compared to a similarly measured 
irradiance value obtained using the same cylinder containing 60 mL of distilled water without 
epiphytes. 
Station Location 
The geoposition of each station was collected in the field with a Global Positioning 
System (GPS) and differentially corrected in post processing with data form the nearest National 
Geodetic Survey (NGS) Continuously Operating Reference Station (CORS). The GPS data 
collection device (CMT March II) published post-processed differentially corrected two 
dimension root mean square error (spatial accuracy) ranges from 1-5 m. 
Distance Upriver Calculations 
The distance from the mouth of the Yaquina to each station was calculated using GIS 
mapping software Arcview. After a center line shape file extending the length of the river was 
converted into a route file, the orthogonal distance from each station to the nearest point along 
that route file was calculated. The ArcToolBox linear referencing tool, 
LocateFeaturesAlongRoutes, was used to calculate the distances in meters for each station from 
the mouth of the estuary to the nearest point along the centerline route feature. 
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