<p> This thesis qualifies functional and ecological aspects of mucus trails deposited by <i>Elimia potosiensis</i> collected from the Meramec River. Freshwater snails are most often recognized for their significant role in river and stream ecosystem function as primary consumers and prey items. However, their form of locomotion is the most energetically expensive found in the animal kingdom. Found in large numbers and densities, <i> E. potosiensis</i> is capable of coating large swaths of substratum with carbohydrate- and protein-rich mucus. This has the potential to affect ecosystem function at the most basal trophic level both energetically, by contributing nutrients and energy to the surrounding water body, and functionally, as a sticky substance to which microheterotrophs become adhered. </p><p> In marine studies, researchers have found that bacteria can readily degrade gastropod mucus and that it can act as the basis for biofilm formation. There have also been studies that show unique employment of energy saving strategies by snails that use their trails to capture food items and to reduce production needs by following trails laid by conspecifics. Very little research has been conducted on freshwater gastropods. This study is the first to focus solely on the ecological and functional aspects of freshwater snail mucus. </p><p> For this study, collections of <i>E. potosiensis</i> were made from a single site along the Meramec River to qualify the effect deposited mucus has on the adherence of microalgae and its potential for formation of biofilms. Overall, mucus-coated surfaces significantly more particles in flow than non-coated surfaces. The water velocity at which a trail is laid was not found to have an affect on the thickness, adhesive ability or persistence of a trail. However, the water velocity in which a trail is incubated in stream does have effect on the adherence rate of a trail. In this study, it was found that this was most likely due to the fact that trails in high water velocity come into contact with more particles during a given period of time due, in part, to its higher carrying capacity.</p>