Author: Landon P. Falke,   (UW-Madison)

Description:
In lotic ecosystems, free-living community structure is expected to change predictably from upstream to downstream in association with environmental changes. Yet how parasite communities change along river continua remains relatively unknown. We examined trematode parasite communities in aquatic snail hosts (Juga plicifera) at 130 sites ranging from first-order streams to an eighth-order river in the Willamette River Basin, Oregon. Increasing stream order coincided with decreasing elevation, increasing algal abundance, and a shift in dominant land use from forest to agriculture. We dissected 14,372 snails and found 17 trematode species across all sites. Trematode richness and infection prevalence showed a unimodal relationship with stream-order with peak levels in mid-order reaches, and were positively related to snail size and negatively related to snail density. We also found shifts in relative composition of trematode species across stream orders, likely due to species-specific differences in life cycle characteristics. For instance, prevalence of Nanophyetus salmincola, a trematode associated with mortality in salmonids, showed a negative relationship with stream order. Our results suggest that watershed-level environmental changes are associated with significant shifts in parasite richness, infection prevalence, and community composition in streams. These findings have implications for our understanding of disease dynamics in lotic ecosystems and provide motivation for further integration of parasites into the River Continuum Concept.

Category: Scientific Program Abstract > Special Session > CS33 River and Stream Ecology