Central stonerollers (Campostoma anomalum) and crayfish (Orconectes meeki) are common in the Boston Mountains of Arkansas and can have substantial effects on stream structure and function. Summer drying is extensive in these systems and may alter interactions between grazers and benthic communities. We used electric exclusion quadrats in the Little Mulberry River to manipulate grazer densities during 2006 and 2007. Paired exclusion/open treatments were placed in multiple pools for two 30-day periods in early and mid-summer of each year. In 2006, exclusion increased chlorophyll, ash-free dry mass (AFDM), and chironomid abundance on tiles. Effects were greater in the second period but differed among pools. In 2007, chlorophyll abundance was greater on grazed than exclusion tiles in August, but not in June. AFDM, net primary production, and chironomid abundance did not differ among treatments. Leaf packs decayed faster in grazed than exclusion treatments (k_grazed=0.038±0.013, k_exclusion=0.007 ± 0.002), but grazer effects were stronger in some pools than others. Differences in grazer effects among years may be related to a higher frequency of spates in 2007. While grazing fish and crayfish can modify stream structure and functioning, these effects vary across both short (among pools and during stream drying) and longer (interannual) scales.