Evidence for lasting alterations to aquatic food webs with short-duration reservoir draining

• DOI: 10.1371/journal.pone.0211870
• Publication Date: 2019-02-07T20:32:27Z
• Authors: Christina A. Murphy; Ivan Arismendi; Gregory A. Taylor; Sherri L. Johnson
• Keywords: Trophic cascade; Chinook wind

Large dams and their respective reservoirs provide renewable energy water security, but also can profoundly alter riverine ecosystems. Here, we present evidence of changing aquatic food web structure in the seasons following short-duration, extreme manipulation levels a reservoir (i.e., draining to original riverbed during fall assist outmigration juvenile Chinook Salmon). We find unintended lagged consequences transitioning from lake river, even temporarily, that resulted trophic shifts away piscivory towards feeding at lower for two common piscivorous fishes reservoirs. Using natural abundances nitrogen stable isotopes, observed level invasive Largemouth Bass (Micropterus salmoides) native Rainbow Trout (Oncorhynchus mykiss) summers refilling than nearby reference were not temporarily drained fall. Declines top predators have been rarely documented outside controlled laboratory conditions. While useful assisting salmonids, temporary result novel foodweb dynamics including reduced piscivory. As large continue be operated constructed worldwide, increased understanding community ecosystem-level effects management will critical evaluating trade-offs between human needs, conservation high value species, ecosystem services impacted by river fragmentation.