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| Titel |
Bream (\textit{Abramis brama} (L.)) as zoogeomorphic agents and ecosystem engineers: Implications
for fine sediment transport in lowland rivers |
| VerfasserIn |
James Smith, Stephen Rice, Richard Hodgkins |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147629
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| Publikation (Nr.) |
 EGU/EGU2017-11820.pdf |
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| Zusammenfassung |
| Despite increasing recognition that animals play important roles in geomorphological
systems (zoogeomorphology), with important ecological implications for the animals and
their ecosystems (ecosystem engineering), sediment transport continues to be regarded as
an abiotic process. This research challenges that orthodoxy by investigating the
biotic processes associated with bioturbation in rivers caused by feeding bream
(Abramis brama (L.)) and quantifying their impact on fine sediment suspension and
sediment yield. Experiments in lakes have demonstrated that bream negatively
influence ecosystem dynamics through bottom up mechanisms as a result of physical
bioturbation caused by benthivorous feeding. Although this level of bioturbation, and
thus sediment entrainment, can alter the fundamental biogeochemical cycles and
food web dynamics in lentic ecosystems, research is yet to assess this potential
effect in riverine ecosystems or evaluate this bioturbation mechanism as a driver of
fluvial sediment flux – even though they are common in rivers across mainland
Europe.
A series of ex-situ mesocosm experiments have investigated the controls of fine sediment
entrainment by bream, assessing the roles of both biomass (size and number) and food
density on suspended sediment concentration and turbidity. Bream create large volumes of
suspended sediment during feeding (highest recorded turbidity 1172 NTU) and there are
significant (p < 0.001) increases in turbidity associated with each experimental
parameter: number of fish, fish size and food density. Supplementary experiments have
assessed bream as ecosystem engineers in the presence of the congener species, roach
(Rutilus rutilus (L.)), which share the same ecological niche. In the presence of roach,
the impact of bream on turbidity increased by an average of 120% (6.6 NTU to
15 NTU) and increased further at the 90th percentile by 240% (32 NTU to 110
NTU).
In light of these findings, the extensive geographical distribution of bream and the
observation that shoals of bream commonly exceed one thousand individuals, it is plausible
that bream are an important biological constituent of the fine sediment cascade within riverine
systems. Complementary field work is underway to quantify the frequency-magnitude
characteristics of the fine sediment plumes that feeding shoals of bream generate in lowland
UK rivers. |
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