METHODS 



Periphyton samples were collected following standard 

 operating procedures of the MDEQ Planning, Prevention, and 

 Assistance Division. Using appropriate tools, microalgae were 

 scraped, brushed, or sucked from natural substrates in proportion 

 to the rank of those substrates at the study site. Macroalgae 

 were picked by hand in proportion to their abundance at the site. 

 All collections of microalgae and macroalgae were pooled into a 

 common container and preserved with Lugol ' s solution. 



The samples were examined to estimate the relative abundance 

 and rank by biovolume of diatoms and genera of soft (non-diatom) 

 algae according to the method described in Bahls (1993) . Soft 

 algae were identified using Dillard (1999) , Prescott (1978) , 

 Smith (1950) , and Whitford and Schumacher (1984) . These books 

 also served as references on the ecology of the soft algae, along 

 with Palmer (1969, 1977) . 



After the identification of soft algae, the raw periphyton 

 samples were cleaned of organic matter using sulfuric acid, and 

 permanent diatom slides were prepared using Naphrax, a high 

 refractive index mounting medium, following Standard Methods for 

 the Examination of Water and Wastewater (APHA 1998) . Between 400 

 and 494 diatom cells (800 to 988 valves) were counted at random 

 and identified to species. The following were used as the main 

 taxonomic and autecological references for the diatoms: Krammer 

 and Lange-Bertalot 1986, 1988, 1991a, 1991b; Patrick and Reimer 

 1966, 197-5. Lowe (1974) was also used as an ecological reference 

 for the diatoms . 



The diatom proportional counts were used to generate an 

 array of diatom association metrics (Table 2) . A metric is a 

 characteristic of the biota that changes in some predictable way 

 with increased human influence (Barbour et al . 1999). 



