Pulsed flows, tributary inputs and food-web structure in a highly regulated river

John L. Sabo, Melanie Caron, Rick Doucett, Kimberly L. Dibble, Albert Ruhi, Jane C Marks, Bruce A Hungate, Ted A. Kennedy

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Dams disrupt the river continuum, altering hydrology, biodiversity and energy flow. Although research indicates that tributary inputs have the potential to dilute these effects, knowledge at the food-web level is still scarce. Here, we examined the riverine food-web structure of the Colorado River below Glen Canyon Dam, focusing on organic matter sources, trophic diversity and food chain length. We asked how these components respond to pulsed flows from tributaries following monsoon thunderstorms that seasonally increase streamflow in the American Southwest. Tributaries increased the relative importance of terrestrial organic matter, particularly during the wet season below junctures of key tributaries. This contrasted with the algal-based food-web present immediately below Glen Canyon Dam. Tributary inputs during the monsoon also increased trophic diversity and food chain length: food chain length peaked below the confluence with the largest tributary (by discharge) in Grand Canyon, increasing by >1 trophic level over a 4-5 km reach possibly due to aquatic prey being flushed into the mainstem during heavy rain events. Our results illustrate that large tributaries can create seasonal discontinuities, influencing riverine food-web structure in terms of allochthony, food-web diversity and food chain length. Synthesis and applications. Pulsed flows from unregulated tributaries following seasonal monsoon rains increase the importance of terrestrially derived organic matter in large, regulated river food webs, increasing food chain length and trophic diversity downstream of tributary inputs. Protecting unregulated tributaries within hydropower cascades may be important if we are to mitigate food-web structure alteration due to flow regulation by large dams. This is critical in the light of global hydropower development, especially in megadiverse, developing countries where dam placement (including completed and planned structures) is in tributaries.

Original languageEnglish (US)
JournalJournal of Applied Ecology
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

food web
tributary
river
food chain
dam
canyon
monsoon
organic matter
allochthony
flow regulation
energy flow
confluence
thunderstorm
wet season
trophic level
streamflow
discontinuity
hydrology
developing world
biodiversity

Keywords

  • Allochthonous inputs
  • Dams
  • Food chain length
  • Hydrologic alteration
  • Maximum trophic position
  • Pulsed flow
  • Serial discontinuity

ASJC Scopus subject areas

  • Ecology

Cite this

Pulsed flows, tributary inputs and food-web structure in a highly regulated river. / Sabo, John L.; Caron, Melanie; Doucett, Rick; Dibble, Kimberly L.; Ruhi, Albert; Marks, Jane C; Hungate, Bruce A; Kennedy, Ted A.

In: Journal of Applied Ecology, 01.01.2018.

Research output: Contribution to journalArticle

Sabo, John L. ; Caron, Melanie ; Doucett, Rick ; Dibble, Kimberly L. ; Ruhi, Albert ; Marks, Jane C ; Hungate, Bruce A ; Kennedy, Ted A. / Pulsed flows, tributary inputs and food-web structure in a highly regulated river. In: Journal of Applied Ecology. 2018.
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