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| Titel |
Sedimentation and salmon: Salmon-mediated floc formation and biofilm sediment trapping ability can drive lotic primary productivity |
| VerfasserIn |
Sam Albers, Ellen Petticrew |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056870
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| Zusammenfassung |
| Each year, as millions of Pacific salmon (Oncorhynchus spp.) return to their natal streams to
spawn and die, their decaying bodies release significant amounts of marine-derived nutrients
(MDN), fertilizing surrounding aquatic ecosystems. This nutrient release tends to stimulate
an increase in productivity. Spatial patterns of MDN-driven productivity increases, however,
remain poorly understood. This is partially because the interaction between in-stream
spawning activity and benthic biofilms remains unclear. An in-stream floc delivery
mechanism driven partially by salmon-mediated sediment resuspension has been previously
identified and post-spawning biofilm abundance increases are well documented. Delivery
mechanisms of MDN and biofilm organic matter processing, however, have not been
sufficiently examined in concert. Our objectives were to quantify, over the course of a
salmon spawning cycle, (i) changes in biofilm abundance, (ii) patterns of sediment
trapping by biofilms and (iii) in-stream particle size changes within a spawning
channel.
An opportunity to utilize the Horsefly River spawning channel (HFC) in the summer and
fall of 2009 allowed for characterization of both marine derived nutrients (MDN) and fine
sediment trapped by benthic biofilms during both the active-spawn and post-spawn periods of
salmon. The HFC is located in the Central interior region of British Columbia and is part of
the larger Fraser River basin. The HFC represents a unique research tool that spans the
manipulability of an artificial stream with the realism of a natural habitat. This type of
ecological realism has been previously highlighted as vitally important for making consistent
observations.
Using the HFC, the role of biofilm in trapping fine sediment was evaluated as a
mechanism of nutrient processing and retention. In the active spawn period, biofilm was
reduced in abundance while the streambed sediment infiltration was at its highest level.
During the post-spawn period, downstream biofilm abundance recovered to pre-spawn values
indicating a nutrient pulse over a small downstream scale. With the re-established biofilm
layer, sediment was increasingly trapped at the streambed surface by biofilms driving
biofilm abundance increases. Biofilms transfer increases in abundance to higher
trophic levels. This transfer has a positive effect on the next generation of juvenile
salmon growth and survivorship. This work identifies the importance to stream
ecosystems of both the nutrient delivery and physical reworking of the gravel bed
by salmon and may have consequences for both salmon and river management
goals. |
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