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

• Published in: Coral reefs Vol. 27; no. 1; pp. 1 - 13
• Main Authors: Wakeford, M., Done, T. J., Johnson, C. R.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-03-2008; Springer; Springer Nature B.V
• Subjects: Acanthaster planci; Acropora hyacinthus; Animal and plant ecology; Animal, plant and microbial ecology; Asteroidea; Biodiversity; Biological and medical sciences; Biomedical and Life Sciences; Climate change; Cnidaria. Ctenaria; Community composition; Coral bleaching; Coral reefs; Disturbance; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Invertebrates; Life Sciences; Marine; Marine ecology; Mortality; Oceanography; Sea water ecosystems; Synecology; ISEW, Australia, Queensland, Great Barrier Reef, Lizard I; Australia; Community structure; Climate change; Chronic disturbance; Diversity; Resilience; Coral reef; Perturbation; Dynamical climatology; Coelenterata; Chronic; Coral; Cnidaria; Invertebrata; Community
• ISSN: 0722-4028; 1432-0975
• DOI: 10.1007/s00338-007-0284-0

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
.