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Decadal trends in a coral community and evidence of changed disturbance regime

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Wakeford, M and Done, TJ and Johnson, CR (2008) Decadal trends in a coral community and evidence of changed disturbance regime. Coral Reefs, 27 (1). pp. 1-13.

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Abstract

A 23 year data set (1981–2003 inclusive) and
the spatially explicit individual-based model ‘‘Compete’’
were used to investigate the implications of changing disturbance
frequency on cover and taxonomic composition of
a shallow coral community at Lizard Island, Australia.
Near-vertical in situ stereo-photography was used to estimate
rates of coral growth, mortality, recruitment and
outcomes of pair-wise competitive interactions for 17
physiognomic groups of hard and soft corals. These data
were used to parameterise the model, and to quantify
impacts of three acute disturbance events that caused significant
coral mortality: 1982—a combination of coral
bleaching and Crown-of-Thorns starfish; 1990—cyclone
waves; and 1996—Crown-of-Thorns starfish. Predicted
coral community trajectories were not sensitive to the
outcomes of competitive interactions (probably because
average coral cover was only 32% and there was strong
vertical separation among established corals) or to major
changes in recruitment rates. The model trajectory of coral
cover matched the observed trajectory accurately until the
1996 disturbance, but only if all coral mortality was confined
to the 3 years of acute disturbance. Beyond that date
(1997–2003), when the observed community failed to
recover, it was necessary to introduce annual chronic
background mortality to obtain a good match between
modelled and observed coral cover. This qualitative switch
in the model may reflect actual loss of resilience in the real
community. Simulated over a century, an 8 year disturbance
frequency most closely reproduced the mean
community composition observed in the field prior to
major disturbance events. Shorter intervals between disturbances
led to reduced presence of the dominant hard
coral groups, and a gradual increase in the slow growing,
more resilient soft corals, while longer intervals (up to
16 years) resulted in monopolization by the fastest growing
table coral, Acropora hyacinthus.

Item Type: Article
Keywords: Resilience, chronic disturbance, Community structure, climate change, diversity
Journal or Publication Title: Coral Reefs
Page Range: pp. 1-13
Identification Number - DOI: 10.1007/s00338-007-0284-0
Additional Information:

The original publication is available at www.springerlink.com

Date Deposited: 26 Feb 2008 11:04
Last Modified: 18 Nov 2014 03:30
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