Organic-carbon-rich sediments: benthic foraminifera as bio-indicators of depositional environments
<p>Fjords have been described as hotspots for carbon burial, potentially playing a key role within the carbon cycle as climate regulators over multiple timescales. Nevertheless, little is known about the long-term fate of the carbon that may become stored in fjordic sediments. One of the main...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-11-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/16/4183/2019/bg-16-4183-2019.pdf |
| Summary: | <p>Fjords have been described as hotspots for carbon burial,
potentially playing a key role within the carbon cycle as climate regulators
over multiple timescales. Nevertheless, little is known about the long-term
fate of the carbon that may become stored in fjordic sediments. One of the
main reasons for this knowledge gap is that carbon arriving on the seafloor
is prone to post-depositional degradation, posing a great challenge when
trying to discriminate between an actual change in the carbon deposition rate
and post-depositional carbon loss. In this study, we evaluate the use of
modern benthic foraminifera as bio-indicators of organic carbon content in
six voes (fjords) on the west coast of Shetland. Benthic foraminifera are
known to be sensitive to changes in organic carbon content in the sediments,
and changes in their assemblage composition therefore reflect synchronous
variations in the quantity and quality of carbon reaching the seafloor. We
identified four environments based on the relationship between benthic
foraminiferal assemblages and organic carbon content in the sediments: (1) land-locked regions influenced by riverine and/or freshwater inputs of organic
matter, namely the head of fjords with a restricted geomorphology; (2) stressed environments with a heavily stratified water column and sediments
rich in organic matter of low nutritional value; (3) depositional
environments with moderate organic content and mild or episodic current
activity; and (4) marginal to coastal settings with low organic content, such as
fjords with an unrestricted geomorphology. We conclude that foraminifera
potentially provide a tool to disentangle primary organic carbon signals
from post-depositional degradation and loss of organic carbon because of
their environmental sensitivity and high preservation potential in the
sedimentary record.</p> |
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| ISSN: | 1726-4170 1726-4189 |