COS 102-1 - Assessing Future Habitat Quality for Thymallus arcticus Utilizing a Bioenergetics Model across a Latitudinal Gradient

Background/Question/Methods

The transfer of basal resources to apex predators within Arctic stream environments occurs through complex food web pathways. For example, arctic graying feed on drifting benthic macroinvertebrates (BMI) with particular invertebrates possessing traits that increase their propensity to drift, making them more favourable to feeding grayling. With climate change expected to impact stream conditions and the BMI communities within them, we asked 1) how will these changes in BMI community composition impact prey availability and potential growth for grayling and, 2) will the future stream conditions in the western Canadian Arctic be more, or less suited to drift feeders such as Arctic grayling? These questions were addressed using a boreal-to-tundra latitudinal gradient as a space for time analysis and assessing change in BMI taxonomic and trait composition in 10 Arctic streams located along the gradient.

Results/Conclusions

BMI composition within the study streams was sampled in August 2019 and taxonomy evaluated using meta-barcoding technology. Total abundance within tundra streams is significantly higher than boreal streams (p< 0.001), mostly driven by the presence of Chironomidae and Branchycentridae, known drifters. PERMANOVA results showed significant differences in community compositions is based on their location in either boreal or tundra streams (p=0.002). In space for time analysis, southern communities (i.e., boreal streams), are considered indicative of future northern communities. If abundances of drift prone taxa will drop with the encroachment of the boreal ecozone into the tundra, this should be cause for concern as BMI abundance is the best predictor of drift density, and therefore prey availability for grayling. We will quantify how this potential drop in abundance may impact the growth of apex predators by sampling drifting BMI and applying a drift feeding bioenergetics model designed for arctic grayling. Grayling are a key apex predator that are critical to ecosystem health in Arctic streams, thus understanding how the suitability to their habitat may change in the future is crucial.