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SFS Annual Meeting

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Habitat modifications from ecosystem engineering can have profound legacy effects on ecological processes and communities. Our research identifies a hydraulic effect stemming from net-spinning caddisfly (Hydropsychidae) retreat structures and describes the longevity of this effect over ecologically relevant timescales. We hypothesized that water velocity would be reduced immediately downstream (5mm) of caddisfly retreat structures and that this effect would diminish overtime if retreats were abandoned by their caddisfly. We measured water velocity in front of and behind retreats and then simulated abandonment by removing caddisfly larvae and measuring 8 times over a 45-day post abandonment period in an artificial stream. Water velocity was significantly lower behind retreats by as much 90%, suggesting retreats have strong effects on local hydraulics. Reductions in flow behind abandoned retreats were also maintained for 45 days suggesting a potential ecologically relevant legacy effect on near bed hydraulics. The legacy of these local changes to hydrology may provide important refugia for less flow-tolerant benthic macroinvertebrate taxa and especially to those with rapid life histories and high turnover rates. Future work will focus on defining the persistence of caddisfly structures in the field and rates of deterioration.

Zachary Maguire (Primary Presenter/Author), Montana State University,;