PS 37-36 - Metagenomic Survey of Fish Parasite Communities of the Grand Canyon

Abstract: Parasites are seldom considered essential components of a biological community. At best they are grouped within the disease ecology of a system with other pathogens. Concern for the health of host populations or zoonotic spillover are two situations where parasites are obvious. Yet the opposite scenario, where the parasite populations themselves are disrupted, can go unnoticed. This project aims to characterize the intestinal parasite communities of fish in the Grand Canyon, as part of an effort to create a modern snapshot of this American landmark’s ecology.

Understanding the parasite community of this ecosystem is important for three reasons. First, parasites are significant drivers of host population dynamics, including through direct mortality, manipulation of host behavior, and parasite avoidance behavior. Second, parasites with complex life cycles rely on multiple hosts at different trophic positions to complete their lifecycles, making them sensitive indicators for functional food chains. Third, the Grand Canyon aquatic ecosystem is entering a state of flux, as drought and water management challenges in the American Southwest reduce Colorado River flow to historic lows. The transition from a cold river defined by dam reservoirs to a warm river with more constant flow occurs alongside a new wave of invasive species and within the global context of climate change.

We hypothesize that a longitudinal gradient will be evident in parasite diversity moving downstream within the canyon, as well as increased diversity near the mouths of relatively undisturbed tributaries. Previous lab research shows that macroinvertebrate diversity follows this pattern, and a broad food base for fish will also support a broad variety of parasites. In contrast, the most ecologically damaged areas of the canyon such as those close to Glen Canyon Dam or far from tributaries will show low parasite diversity, with generalist single host parasites making up a larger proportion of that diversity.

Feces were sampled from over 80 fish, most commonly Catostomus latipinnis, longitudinally along 450 river-kilometers of the Colorado River near and within Grand Canyon National Park. DNA was extracted from samples using Qiagen Blood and Tissue kits and sequenced using 18s primers to detect the presence of diverse parasite taxa, then bioinformatically classified to the most precise possible level, given the high diversity and species-specificity of wild parasites.

The unique sensitivity of parasites to trophic disturbance, and their permeating effects on ecosystem dynamics, demand a thorough understanding of anthropogenic impacts, past and future, on their communities.