• 



• 



than they were at the two upstream sites. The dominant species here was Navicula symmetrica, 

 which indicates brackish, eutrophic waters with moderate organic loading (Lange-Bertalot 2001). 



Several ecological attributes were selected from the diatom reports in the appendix and 

 modal categories of these attributes were extracted to characterize water quality tendencies at 

 these four sites (Table 5). The majority of diatoms at all of the sites indicated alkaline and 

 eutrophic waters, but the sites differed with respect to other ecological attributes. 



Most of the diatoms in Dog Creek were highly motile, which corresponds to the severe 

 impairment from sedimentation that was noted at this site (Table 5). Motile diatoms are able to 

 maintain their position on aggrading substrates in depositional habitats. Similarly, the modal 

 category for motility at Eagle Creek site 3 was moderately motile, which corresponds to the 

 moderately impaired status for this site. The upper two sites on Eagle Creek supported mostly 

 non-motile diatoms, which are not adapted to living on aggrading substrates. 



The modal category for salinity was fresh-brackish at the upper two sites on Eagle Creek 

 (Table 5). Brackish-fresh, the modal category at the downstream site on Eagle Creek, indicated a 

 significant increase in salinity at this site. The modal category in Dog Creek was also brackish- 

 fresh. 



Most diatoms in Dog Creek have moderate requirements for dissolved oxygen and 

 indicate elevated loads of organic matter (alpha-mesosaprobous). At Eagle Creek site 1, most 

 diatoms also indicate moderate demand for dissolved oxygen, but the loading of organic matter 

 here is smaller (beta-mesosaprobous). The modal category for dissolved oxygen at Eagle Creek 

 site 2 was "continuously high", which indicates well-aerated water with only somewhat elevated 

 organic loads (beta-mesosaprobous). The modal category for oxygen demand and saprobity at 

 Eagle Creek site 3 was "not classified". 



Most diatoms in Dog Creek were facultative nitrogen heterotrophs, meaning that they are 

 capable of using organic nitrogen (urea and amino acids) as a source of nutrition (Table 5). In 

 contrast, most diatoms at the upper two sites on Eagle Creek were nitrogen autotrophs, meaning 



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