Harris, Alasdair (2010) Analysis of recovery patterns of Indian Ocean coral reefs through examination of scleractinian communities and populations. PhD thesis, University of Warwick.

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Abstract

This thesis examines the colony size structure and taxonomic composition of coral
communities from eight regions of the Indian Ocean approximately 10 years after
thermal stress-induced mass mortality events. Coral community composition and
population structure differed widely within and between regions, reflecting the
different climatic and anthropogenic impacts experienced by each over the past
decade.
Coral communities in most areas started from a similarly depleted condition but after
1998 their recovery trajectories varied significantly, reflecting different surviving adult
communities and continuing, different local stressors; some have remained highly
depleted, while others have shown marked recovery. Profound differences between
coral communities at intra and inter-regional spatial scales are identified and related to
diversity and taxonomic composition, colony abundance, surface area, size frequency
distributions, and population demographic parameters within taxa. These are
analysed through multivariate techniques and univariate graphical representations to
illustrate the significantly different size frequency distributions, taxonomic
composition, taxonomic richness and dominance patterns at different spatial scales.
A novel technique is assessed for surveying juvenile coral communities, using
ultraviolet light, which causes new, growing tissue to fluoresce. This method
significantly increases detected juveniles, with important consequences to size
frequency patterns and to some previously published views on juvenile densities.
The surveying methodologies used are far more revealing than most commonly-used
conventional benthic assessments such as intercept surveys, cover values and
diversity, which rarely capture discriminatory information on overall composition of
coral communities, let alone the structure of populations within them. These colony
size-based studies of individual genera are extremely sensitive for interpreting spatial
and temporal variations in reefs and greatly enhance understanding of coral reef
condition and complexity.
The spatial differences demonstrate the applicability of the methods for advising reef
management, specifically in identifying areas where ecological resilience is impeded by
recruitment failure. Long-term consequences of changes in coral communities may
include reduced ecological functional redundancy, reduced structural complexity,
reduced carbonate accretion and reef growth, and impaired recovery potential.

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