Can storms and shore armouring exert additive effectson sandy-beach habitats and biota?
Serena Lucrezi A , Thomas A. Schlacher A C and Wayne Robinson BA Faculty of Science, Health & Education, University of the Sunshine Coast, Maroochydore DC, Qld 4558, Australia.
B School of Environmental Sciences, Charles Sturt University, Old Sydney Road, Thurgoona,NSW 2641, Australia.
C Corresponding author. Email: tschlach@usc.edu.au
Marine and Freshwater Research 61(9) 951-962 https://doi.org/10.1071/MF09259
Submitted: 13 October 2009 Accepted: 26 January 2010 Published: 23 September 2010
Abstract
Increased storminess is a likely consequence of global climate change; its effects may be most dramatic on coasts dominated by sandy beaches. This scenario demands that the impacts of storms and the role of armouring structures, constructed as storm defences, are better understood. Here, we assess how a relatively small storm affected beach morphology and macrobenthos, and whether a seawall can modulate such impacts. The study system was a small (<1.5 km long) beach, bisected into parts with and without a seawall. The beach became narrower and steeper during the storm, when 26% of the subaerial sediment prism eroded from the armoured section; sand losses on the unarmoured part were one-fifth of those on the armoured part. Densities of ghost crabs (Ocypode) dropped significantly (36%) and were to some extent modulated by shore armouring; losses were high (62%) just seawards of the seawall where post-storm densities remained consistently lower. There was no ecological recovery in the short term, with most (83%) post-storm density values of crabs being lower, and crab counts in front of the seawall being depressed up to 3 months after the storm. Seawalls can change the resilience of beaches to storms, which may result in stronger ecological effects on armoured coasts.
Additional keywords: climate change, erosion, ghost crabs, Ocypode, recovery, sandy shores, storm impacts.
Acknowledgements
We greatly appreciate the help of our field assistants, especially Paul Cashion, Tara Nielsen, Luke Thompson and Lee Clarke who surveyed beaches come storm or sunshine. Neil Tindale gave freely of his meteorology expertise on storms. The assistance of Sue Nicholls with the Trend software is greatly appreciated, as well as the provision of wave-monitoring data (Environmental Protection Agency), weather information (Bureau of Meteorology) and beach visitor numbers (Sunshine Coast Regional Council). This work was partly financed by a Ph.D. scholarship to S.L. by the University of the Sunshine Coast. We appreciate the constructive feedback by reviewers, which greatly improved the manuscript.
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