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Sediment-phosphorus dynamics can shift aquatic ecology and cause downstream legacy effects after wildfire in large river systems

Sediment-phosphorus dynamics can shift aquatic ecology and cause downstream legacy effects after wildfire in large river systems
Sediment-phosphorus dynamics can shift aquatic ecology and cause downstream legacy effects after wildfire in large river systems
Global increases in the occurrence of large, severe wildfires in forested watersheds threaten drinking water supplies and aquatic ecology. Wildfire effects on water quality, particularly nutrient levels and forms, can be significant. The longevity and downstream propagation of these effects as well as the geochemical mechanisms regulating them remain largely undocumented at larger river basin scales. Here, phosphorus (P) speciation and sorption behavior of suspended sediment were examined in two river basins impacted by a severe wildfire in southern Alberta, Canada. Fine-grained suspended sediments (<125 µm) were sampled continuously during ice-free conditions over a two-year period (2009-2010), 6 and 7 years after the wildfire. Suspended sediment samples were collected from upstream reference (unburned) river reaches, multiple tributaries within the burned areas, and from reaches downstream of the burned areas, in the Crowsnest and Castle River basins. Total particulate phosphorus (TPP) and particulate phosphorus forms (nonapatite inorganic P, apatite P, organic P), and the equilibrium phosphorus concentration (EPC0 ) of suspended sediment were assessed. Concentrations of TPP and the EPC0 were significantly higher downstream of wildfire-impacted areas compared to reference (unburned) upstream river reaches. Sediments from the burned tributary inputs contained higher levels of bioavailable particulate P (NAIP) - these effects were also observed downstream at larger river basin scales. The release of bioavailable P from postfire, P-enriched fine sediment is a key mechanism causing these effects in gravel-bed rivers at larger basin scales. Wildfire-associated increases in NAIP and the EPC0 persisted 6 and 7 years after wildfire. Accordingly, this work demonstrated that fine sediment in gravel-bed rivers is a significant, long-term source of in-stream bioavailable P that contributes to a legacy of wildfire impacts on downstream water quality, aquatic ecology, and drinking water treatability.
1354-1013
1168-1184
Emelko, Monica B.
d5da725d-57fd-4229-a74e-8519ca7294b9
Stone, Micheal
6548f74b-b538-4741-81c4-e18d148bd8c2
Silins, Uldis
a9dd55c9-d39f-45b5-ae1f-6e714adad182
Allin, Don
4a5119b6-f3b3-4cbe-b7a0-89c61fbebae5
Collins, Adrian L.
700e5f6a-4de3-4406-ad7a-d9d8ec0a5069
Williams, Chris H. S.
03e8e586-496d-4dd9-a364-ae1da819d29a
Martens, Amanda M.
64148390-e82a-4d93-8ace-5a1a45238a20
Bladon, Kevin D.
053d5bed-f30d-40a8-98d4-18ec6202cf93
Emelko, Monica B.
d5da725d-57fd-4229-a74e-8519ca7294b9
Stone, Micheal
6548f74b-b538-4741-81c4-e18d148bd8c2
Silins, Uldis
a9dd55c9-d39f-45b5-ae1f-6e714adad182
Allin, Don
4a5119b6-f3b3-4cbe-b7a0-89c61fbebae5
Collins, Adrian L.
700e5f6a-4de3-4406-ad7a-d9d8ec0a5069
Williams, Chris H. S.
03e8e586-496d-4dd9-a364-ae1da819d29a
Martens, Amanda M.
64148390-e82a-4d93-8ace-5a1a45238a20
Bladon, Kevin D.
053d5bed-f30d-40a8-98d4-18ec6202cf93

Emelko, Monica B., Stone, Micheal, Silins, Uldis, Allin, Don, Collins, Adrian L., Williams, Chris H. S., Martens, Amanda M. and Bladon, Kevin D. (2016) Sediment-phosphorus dynamics can shift aquatic ecology and cause downstream legacy effects after wildfire in large river systems. Global Change Biology, 22 (3), 1168-1184. (doi:10.1111/gcb.13073).

Record type: Article

Abstract

Global increases in the occurrence of large, severe wildfires in forested watersheds threaten drinking water supplies and aquatic ecology. Wildfire effects on water quality, particularly nutrient levels and forms, can be significant. The longevity and downstream propagation of these effects as well as the geochemical mechanisms regulating them remain largely undocumented at larger river basin scales. Here, phosphorus (P) speciation and sorption behavior of suspended sediment were examined in two river basins impacted by a severe wildfire in southern Alberta, Canada. Fine-grained suspended sediments (<125 µm) were sampled continuously during ice-free conditions over a two-year period (2009-2010), 6 and 7 years after the wildfire. Suspended sediment samples were collected from upstream reference (unburned) river reaches, multiple tributaries within the burned areas, and from reaches downstream of the burned areas, in the Crowsnest and Castle River basins. Total particulate phosphorus (TPP) and particulate phosphorus forms (nonapatite inorganic P, apatite P, organic P), and the equilibrium phosphorus concentration (EPC0 ) of suspended sediment were assessed. Concentrations of TPP and the EPC0 were significantly higher downstream of wildfire-impacted areas compared to reference (unburned) upstream river reaches. Sediments from the burned tributary inputs contained higher levels of bioavailable particulate P (NAIP) - these effects were also observed downstream at larger river basin scales. The release of bioavailable P from postfire, P-enriched fine sediment is a key mechanism causing these effects in gravel-bed rivers at larger basin scales. Wildfire-associated increases in NAIP and the EPC0 persisted 6 and 7 years after wildfire. Accordingly, this work demonstrated that fine sediment in gravel-bed rivers is a significant, long-term source of in-stream bioavailable P that contributes to a legacy of wildfire impacts on downstream water quality, aquatic ecology, and drinking water treatability.

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More information

e-pub ahead of print date: 26 December 2015
Published date: 1 March 2016
Organisations: Geography & Environment

Identifiers

Local EPrints ID: 389580
URI: https://eprints.soton.ac.uk/id/eprint/389580
ISSN: 1354-1013
PURE UUID: 1adaf6e0-9f9c-46da-bcfd-cce6aa6a1865

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Date deposited: 09 Mar 2016 11:38
Last modified: 15 Jul 2019 20:42

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