Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks

Macreadie,Peter I, Allen,Katie, Kelaher,Brendan P, Ralph,Peter J and Skilbeck,Charles G 2012, Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks, Global change biology, vol. 18, no. 3, pp. 891-901, doi: 10.1111/j.1365-2486.2011.02582.x.

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Title Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks
Author(s) Macreadie,Peter IORCID iD for Macreadie,Peter I
Kelaher,Brendan P
Ralph,Peter J
Skilbeck,Charles G
Journal name Global change biology
Volume number 18
Issue number 3
Start page 891
End page 901
Total pages 11
Publisher Wiley
Place of publication London, Eng.
Publication date 2012-03
ISSN 1354-1013
Keyword(s) Biosequestration
Blue carbon
Carbon capture and storage
Organic carbon
Stable isotopes
Summary Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO 2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney - the site of European settlement of Australia - to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (~6000 years) according to 210Pb profiles and radiocarbon ( 14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 30-50 years were considerably higher than during the rest of the Holocene. C : N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/ 13C showed that the relative contribution of seagrass and C 3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (~1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication. Given the lower carbon burial efficiencies of microalgae (~0.1%) relative to seagrasses and C 3 terrestrial plants (up to 10%), such changes represent a substantial weakening of the carbon sink potential of Botany Bay - this occurrence is likely to be common to human-impacted estuaries, and has consequences for the role these systems play in helping to mitigate climate change. © 2011 Blackwell Publishing Ltd.
Language eng
DOI 10.1111/j.1365-2486.2011.02582.x
Field of Research 060205 Marine and Estuarine Ecology (incl Marine Ichthyology)
Socio Economic Objective 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts)
HERDC Research category C1.1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2012, Wiley
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