FIELD AND SAMPLE NOTES 



Big Dry Creek Site #9. The periphyton sample from this 

 site consisted mainly of plant roots. The stream here formed 

 long pools of variable depth. The substrate was a mix of small 

 gravels and silt. Macrophytes were present along the channel 

 edges. Channel alterations and sediment accumulations were 

 minimal. Point bars were active but with little long-term 

 enlargement. The sinuosity was about 2.0-2.5. Banks were stable 

 with good vegetative cover. (Field notes by Warren Kellogg, 

 NRCS, 8/23/00.) 



Little Dry Creek above Highway 200. The sample from this 

 site was very silty and was composed primarily of plant roots. 

 About 20% of the diatom cells were empty. Branching was observed 

 in Rhizoclonium, but it was rare. Two species of Oedogonium were 

 present. The habitat score for this site (115.5) was 68% of the 

 maximum possible (Carol Endicott, MDEQ, personal communication) . 



NON- DIATOM ALGAE 



Big Dry Creek 



Big Dry Creek supported a mix of green algae, euglenoid 

 algae {Euglena) , diatoms, and cyanobacteria (formerly called 

 blue-green algae) (Table 4) . Eight genera of non-diatom algae 

 were present, which is less than the average number (13) recorded 

 for reference streams in Great Plains Montana (Bahls 1993). 



Diatoms were the most abundant algae, followed by greens, 

 cyanobacteria, and euglenoids . Dominance by diatoms and greens 

 and the occasional cell of Euglena indicate moderate nutrient 

 enrichment and organic loading at this site. Nitrogen- fixing 

 cyanobacteria cannot compete successfully with diatoms and greens 

 under such conditions. 



Anahaena was one of three nitrogen- fixing cyanobacteria in 

 Big Dry Creek. Under certain conditions, AnaJbaeria can produce 

 waterblooms that release neurotoxins into the water. These 

 toxins can be lethal to livestock, pets, and wildlife. However, 



