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Reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs

Johnson, J.A.; Perry, C.T.; Smithers, S.G.; Morgan, K.M.; Woodroffe, S.A.

Reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs Thumbnail


Authors

J.A. Johnson

C.T. Perry

S.G. Smithers

K.M. Morgan



Abstract

Declining water quality represents a major threat to the coral reefs of Australia's Great Barrier Reef (GBR). Due to their close proximity to river point sources, reefs situated on the inner-shelf of the GBR are widely perceived to be most susceptible to the increased discharge of nutrients and sediments from coastal catchments, many of which have been modified since European settlement. However, the magnitude and impact of water quality change on the GBR's inner-shelf reefs remains unclear. Much of the uncertainty can be attributed to a paucity of long-term records with which to assess ecological and environmental change over appropriate reef-building timescales. Here, we present benthic foraminiferal palaeo-records from three proximal nearshore turbid reefs from the central GBR. Bayesian age-depth modelling was used to identify the core intervals corresponding to the timing of European settlement in the region (c. 1850 CE), enabling the investigation of: (1) the composition and variability of benthic foraminiferal assemblages during reef shallowing towards sea level; and (2) whether any signal of increased nutrient and sediment inputs, as the result of historical land-use change, can be discerned on the most nearshore reefs of the central GBR. Multivariate analyses identified two assemblage groups, delineated by a significant increase in the relative abundance of Pararotalia spp. up-core. Our results suggest that post-European settlement associated increases in nutrient and sediment inputs are unlikely to have driven the observed shifts in benthic foraminiferal assemblage composition. Rather, we interpret changes in the composition of benthic foraminiferal assemblages as being linked to changes in hydrodynamic energy, light availability and the carbonate content of reef-matrix sediments during reef shallowing towards sea level. Our findings support the hypothesis that nearshore turbid reefs have a higher resistance to increased nutrient and sediment inputs than those located further offshore, towards the inner/mid-shelf boundary.

Citation

Johnson, J., Perry, C., Smithers, S., Morgan, K., & Woodroffe, S. (2019). Reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs. Palaeogeography, Palaeoclimatology, Palaeoecology, 533, Article 109240. https://doi.org/10.1016/j.palaeo.2019.109240

Journal Article Type Article
Acceptance Date Jun 11, 2019
Online Publication Date Jun 15, 2019
Publication Date Nov 1, 2019
Deposit Date Jun 18, 2019
Publicly Available Date Jul 17, 2019
Journal Palaeogeography, Palaeoclimatology, Palaeoecology
Print ISSN 0031-0182
Electronic ISSN 1872-616X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 533
Article Number 109240
DOI https://doi.org/10.1016/j.palaeo.2019.109240
Public URL https://durham-repository.worktribe.com/output/1299109

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Copyright Statement
© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).






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