than 26° Celsius may occur in the summer over tidal flats and marshlands 

 (Table 1) . Logging on the watershed from 1951 to 1971 caused extensive 

 siltation in the bay, but sediment input now is apparently low and stable 

 (Kreag, 1979). 



High and low marshes fringe the inner shore of the spit, and a large 

 area of high marsh occupies the southern end of the bay. This marsh was 

 once diked and used for pasture; however, the marsh has since reverted to 

 nearly natural drainage patterns under State ownership. 



3. Bay Study Areas . 



Nine study areas were established in the two estuaries (Fig. 1). 

 Areas 1 to 5 were chosen to represent the specific vegetation types 

 listed by Jefferson (1974), and were sampled most thoroughly. Substrate 

 characteristics of the marsh soil in these areas are given in Table 2. 

 The other areas are open bay and low marsh habitats, sampled once for fish. 

 Elevation data for areas 1, 3, and 4 are based on nearby EPA study sites 

 (H. Kibby, personal communication, 1979). 



a. Area 1, Low Sand Marsh (Netarts Spit) . This sandy beach (Table 



2) supports a mixed cover of pickleweed and saltgrass {Distichtis spicata) . 

 The lower edge of the marsh is lined with three-square bulrush. Inverte- 

 brate samples were taken in the pickleweed-saltgrass zone (about 2.4 meters 

 above MLLW) , and fish samples in the three-square bulrush zone and the 

 adjacent tidal flat (<2.1 meters above MLLW). A debris line of dead 

 eelgrass [Zostera marina) frequently forms at varying levels along this 

 marsh. 



b. Area 2, Low Silt Marsh (North of Siletz River) . This is an area 

 of prograding low marsh along Highway 101. The substrate in the marsh and 

 the adjoining tidal flat is mud (Table 2). The lower edge of the marsh is 

 composed of interrupted colonies of seaside arrowgrass invaded by Lyngbye's 

 sedge, which is the dominant species at higher elevations. Aquatic inver- 

 tebrate samples were taken in this transition zone which is characterized 

 by frequent flooding, pools of standing water among the plants, and dense 

 populations of amphipods and isopods. Terrestrial invertebrate samples 

 were collected higher in the sedge stand. Fish samples were collected 

 about 100 meters south of these sites in a series of small tidal creeks 

 that extend from high marsh through the sedge community and through the 

 bulrush community at the edge of the marsh. 



c. Area 3, Sedge Marsh (South of the Siletz River) . This marsh has 

 muddy soil (Table 2) with vegetation dominated by sedge, but floods less 

 frequently than the low silt sedge marsh. Elevation in the region of 

 level marsh invertebrate sampling site is about 2.3 meters above MLLW. A 

 dendritic system of small tidal creeks laces the marsh and apparently 

 receives some seepage through earthen dikes. A major creek (maximum 10 

 meters wide, 0.7 meter deep) dissects the marsh in an east-west direction. 

 The channel is deep at both marsh edges and shallow at the marsh center. 

 Therefore marsh drainage water in the channel flows in both directions 

 away from the center. Fish and aquatic invertebrate samples were taken in 

 various creek, pan, and tidal flat habitats, as well as in Millport ■ 

 Slough which borders the marsh on the southwest. All these habitats have 

 muddy substrates. 



