Climate change is expected to increase in frequency, duration and magnitude of floods potentially driving substantial change in river ecosystems. Knowledge of flood effects on river biological communities is generally focused on individual high-magnitude floods. Here we demonstrate multiple effects of repeated atypical summer floods across three rivers in Glacier Bay, southeast Alaska at different stages of development following glacier retreat. Immediate short-term impacts (1st year post-flood) reduced mean invertebrate taxonomic richness from 22.3 (95% CI: 17.7, 27.0) to 13.6 (95% CI: 7.0, 20.3) and density from 9045 (ind/m2, 95% CI: 5431,14765) to 1636 (95% CI: 812, 3641) across the three rivers. Recovery of these richness and density metrics occurred over two subsequent years of post-flood community response. Persistent shifts in community composition were recorded in all rivers, with a decline in Jaccard’s dissimilarity within each site from pre-flood 0.40 (95% CI: 0.25, 0.56) to 0.19 (95% CI: 0.03, 0.35) and between the three rivers from pre-flood 0.64 (95% CI: 0.56, 0.71) to 0.45 (95% CI: 0.38, 0.51) during the post-flood response. Convergence of community composition was associated with the predominant colonisation/re-establishment of chironomids and some small ephemeropterans in all rivers post-flood. Overall, these findings lead us to suggest that the flood sequences, including repeated atypical summer floods, can influence river biological community reassembly by favouring a core group of disturbance tolerant taxa.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)