TY - JOUR
T1 - Pulsed flows, tributary inputs and food-web structure in a highly regulated river
AU - Sabo, John L.
AU - Caron, Melanie
AU - Doucett, Rick
AU - Dibble, Kimberly L.
AU - Ruhi, Albert
AU - Marks, Jane C.
AU - Hungate, Bruce A.
AU - Kennedy, Ted A.
N1 - Funding Information:
We thank the Arizona Game and Fish Department for fish tissues and specimens. Colden Baxter, Mike Booth, Wyatt Cross, Bob Hall, Emma Rosi-Marshall and Mike Yard provided invaluable logistic support in the field. We thank Caley Boone, Matt Moan, Wendy Steward and Allison Bair for countless hours sampling, sorting and preparing samples for stable isotope analysis. Finally, we thank Scott Vanderkooi and J. Ryan Bellmore for their reviews and thoughtful comments on this manuscript. This work was supported by the Bureau of Reclamation’s Glen Canyon Dam Adaptive Management Program via US Geological Survey cooperative agreement 04HQAG0122 to Northern Arizona University. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Publisher Copyright:
© 2018 The Authors. Journal of Applied Ecology © 2018 British Ecological Society
PY - 2018/7
Y1 - 2018/7
N2 - 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.
AB - 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.
KW - allochthonous inputs
KW - dams
KW - food chain length
KW - hydrologic alteration
KW - maximum trophic position
KW - pulsed flow
KW - serial discontinuity
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U2 - 10.1111/1365-2664.13109
DO - 10.1111/1365-2664.13109
M3 - Article
AN - SCOPUS:85042646487
SN - 0021-8901
VL - 55
SP - 1884
EP - 1895
JO - Journal of Applied Ecology
JF - Journal of Applied Ecology
IS - 4
ER -