Model of coral population response to accelerated bleaching and mass mortality in a changing climate

Bernhard M. Riegl, Samuel J. Purkis

Research output: Contribution to journalArticle

78 Scopus citations

Abstract

We model coral community response to bleaching and mass mortality events which are predicted to increase in frequency with climate change. The model was parameterized for the Arabian/Persian Gulf, but is generally applicable. We assume three species groups (Acropora, faviids, and Porites) in two life-stages each where the juveniles are in competition but the adults can enter a size-refuge in which they cannot be competitively displaced. An aggressive group (Acropora species) dominates at equilibrium, which is not reached due to mass mortality events that primarily disadvantage this group (compensatory mortality, >90% versus 25% in faviids and Porites) roughly every 15 years. Population parameters (N individuals, carrying capacity) were calculated from satellite imagery and in situ transects, vital rates (fecundity, mortality, and survival) were derived from the model, field observations, and literature. It is shown that populations and unaltered community structure can persist despite repeated 90% mortality, given sufficiently high fecundity of the remaining population or import from connected populations. The frequency of disturbance determines the dominant group-in low frequency Acropora, in high frequency Porites. This is congruent with field observations. The model of an isolated population was more sensitive to parameter changes than that of connected populations. Highest sensitivity was to mortality rate and recruitment rate. Community composition was sensitive to spacing of disturbances and level of catastrophic mortality. Decreased mortality led to Acropora dominance, increased mortality led to Acropora extinction. In nature, closely spaced disturbances have severely disadvantaged Acropora populations over the last decade. Unless a longer (>10 years) disturbance-free interval can be maintained, a permanent shift away from Acropora dominance will be observed. A mortality rate of 99% in Acropora, as observed in 1996, is not sustainable if repetitive and neither is a disturbance frequency <15 years-each leading to population collapse. This shows that the severity and/or the spacing of the 1996-1998-2002 disturbances were unusual in frequency and duration.

Original languageEnglish (US)
Pages (from-to)192-208
Number of pages17
JournalEcological Modelling
Volume220
Issue number2
DOIs
StatePublished - Jan 24 2009
Externally publishedYes

Keywords

  • Arabian/Persian Gulf
  • Bleaching
  • Coral population model
  • Coral reef
  • Global climate change
  • Mass mortality
  • Satellite imagery

ASJC Scopus subject areas

  • Ecological Modeling

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