METHODS 



Periphyton samples were collected by Michael Pipp (Water 

 Monitoring Section, MDEQ Monitoring and Data Management Bureau) 

 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 by 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 418 diatom cells (800 to 836 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, 1975. Lowe (1974) was also used as an ecological reference 

 for the diatoms. 



The diatom proportional counts were used to generate an 



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