Abstract
Marine sediments, particularly those located in estuarine
and coastal zones, are key locations for the burial
of organic carbon (C). However, organic C delivered to the
sediment is subjected to a range of biological C-cycling
processes, the rates and relative importance of which vary
markedly between sites, and which are thus difficult to predict. In this study, stable isotope tracer experiments were used
to quantify the processing of C by microbial and faunal communities
in two contrasting Scottish estuarine sites: a subtidal,
organic C rich site in Loch Etive with cohesive finegrained
sediment, and an intertidal, organic C poor site on an
Ythan estuary sand flat with coarse-grained permeable sediments. In both experiments, sediment cores were recovered and
amended with 13C labelled phytodetritus to quantify whole
community respiration of the added C and to trace the isotope
label into faunal and bacterial biomass. Similar respiration
rates were found in Loch Etive and on the Ythan
sand flat (0.64 ± 0.04 and 0.63 ± 0.12 mg C m−2h
−1
, respectively),
which we attribute to the experiments being conducted
at the same temperature. Faunal uptake of added C
over the whole experiment was markedly greater in Loch
Etive (204 ± 72 mg C m−2
) than on the Ythan sand flat
(0.96 ± 0.3 mg C m−2
), and this difference was driven by a
difference in both faunal biomass and activity. Conversely,
bacterial C uptake over the whole experiment in Loch Etive
was much lower than that on the Ythan sand flat (1.80 ± 1.66
and 127 ± 89 mg C m−2
, respectively). This was not driven
by differences in biomass, indicating that the bacterial community
in the permeable Ythan sediments was particularly
active, being responsible for 48 ± 18 % of total biologically
processed C. This type of biological C processing appears
to be favoured in permeable sediments. The total amount of
biologically processed C was greatest in Loch Etive, largely
due to greater faunal C uptake, which was in turn a result
of higher faunal biomass. When comparing results from this
study with a wide range of previously published isotope tracing
experiments, we found a strong correlation between total
benthic biomass (fauna plus bacteria) and total biological
C processing rates. Therefore, we suggest that the total Ccycling
capacity of benthic environments is primarily determined
by total biomass.
| Original language | English |
|---|---|
| Pages (from-to) | 4343-4357 |
| Number of pages | 15 |
| Journal | Biogeosciences |
| Volume | 13 |
| Issue number | 15 |
| DOIs | |
| Publication status | Published - 4 Aug 2016 |
Bibliographical note
Acknowledgements.The authors would like to thank Eva-Maria Zetsche, Val Johnson, Owen McPherson, Caroline Gill, and Gwylim Lynn for assistance with the Ythan sand flat fieldwork, and Matthew Schwartz, Rachel Jeffreys, Kate Larkin, Andy Gooday, and Christine Whitcraft for assistance with the Loch Etive fieldwork. Jonathan Carrivick created Fig. 1. The work was funded by the Natural Environment Research Council and the Netherlands Earth System Science Center. We would also like to thank two anonymous reviewers for their comments which helped to improve the manuscript.
Access to Document
- Patterns of carbon processing at the seafloor: the role of faunal and microbial communities in moderating carbon flows
© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. https://creativecommons.org/licenses/by/3.0/