Influence of natural amphipod (<Emphasis Type="Italic">Victoriopisa</Emphasis><Emphasis Type="Italic">australiensis</Emphasis>) (Chilton, 1923) population densities on benthic metabolism,nutrient fluxes,denitrification and DNRA in sub-tropical estuarine sediment |
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Authors: | Ryan J K Dunn David T Welsh Mark A Jordan Peter R Teasdale Charles J Lemckert |
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Institution: | (1) Griffith School of Engineering, Griffith University, Gold Coast Campus, Gold Coast, QLD, 4222, Australia;(2) Griffith School of Environment and Australian Rivers Institute, Griffith University, Gold Coast Campus, Gold Coast, QLD, 4222, Australia |
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Abstract: | The influence of natural populations of the sub-surface deposit-feeding amphipod Victoriopisa
australiensis on sediment biogeochemistry was assessed by randomly collecting 21 sediment cores in a zone of Coombabah Lake, southern Moreton
Bay, Australia, where the benthic infauna was dominated by this species. Cores were incubated sequentially to determine sediment–water
column fluxes of oxygen, dissolved inorganic carbon and inorganic N species, followed by incubations to determine rates of
denitrification and dissimilatory nitrate reduction to ammonium (DNRA) using the isotope pairing technique. Finally, each
core was sieved in order to determine the population and biomass of amphipods present. Whilst all measures of overall benthic
metabolism (sediment oxygen demand, and effluxes of inorganic carbon and nitrogen) showed increased with amphipod density,
with rates being stimulated 70–220% at the highest categorised density range of 2,500–3,500 ind m−2, only the correlation with dissolved inorganic carbon was statistically significant. In contrast, there were no discernable
trends between amphipod densities and any of the N-cycle processes with the slopes of all correlations being very close to
zero. These results highlight the differences in mesocosm simulations of fauna effects, which primarily relate to shifts in
rates of organic matter turnover, compared to natural sediments where fauna effects relate more to induced changes in rates
of organic matter deposition. Therefore, while mesocosms represent a powerful tool to investigate the mechanisms by which
fauna influences microbial metabolism in the sediment, only studies of natural sediments can determine to what extent these
mechanisms function in situ.
Handling editor: Pierluigi Viaroli |
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Keywords: | Bioturbation Victoriopisa australiensis Sediment– water column fluxes Denitrification DNRA |
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