Coral population dynamics across consecutive mass mortality events. (23rd September 2015)

• Record Type: Journal Article
• Authors: Riegl, Bernhard; Purkis, Sam
• Is Part Of: Global change biology. Volume 21:Number 11(2015:Nov.)
• Page Start: 3995
• Page End: 4005
• Publication Date: 2015-09-23
• Subjects: Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13014
• Languages: English
• ISSNs: 1354-1013

Abstract

<abstract abstract-type="main" id="gcb13014-abs-0001"> <title>Abstract</title> <p>Annual coral mortality events due to increased atmospheric heat may occur regularly from the middle of the century and are considered apocalyptic for coral reefs. In the Arabian/Persian Gulf, this situation has already occurred and population dynamics of four widespread corals (<italic>Acropora downingi</italic>, <italic> Porites harrisoni</italic>, <italic> Dipsastrea pallida</italic>, <italic> Cyphastrea micropthalma</italic>) were examined across the first‐ever occurrence of four back‐to‐back mass mortality events (2009–2012). Mortality was driven by diseases in 2009, bleaching and subsequent diseases in 2010/2011/2012. 2009 reduced <italic>P. harrisoni</italic> cover and size, the other events increasingly reduced overall cover (2009: −10%; 2010: −20%; 2011: −20%; 2012: −15%) and affected all examined species. Regeneration was only observed after the first disturbance. <italic>P. harrisoni</italic> and <italic>A. downingi</italic> severely declined from 2010 due to bleaching and subsequent white syndromes, while <italic>D. pallida</italic> and <italic>P. daedalea</italic> declined from 2011 due to bleaching and black‐band disease. <italic>C. microphthalma</italic> cover was not affected. In all species, most large corals were lost while fission due to partial tissue mortality bolstered small size classes. This general shrinkage led to a decrease of coral cover and a dramatic reduction of fecundity. Transition matrices for disturbed and undisturbed conditions were evaluated as Life Table Response Experiment and showed that <italic>C. microphthalma</italic> changed the least in size‐class dynamics and fecundity, suggesting they were 'winners'. In an ordered 'degradation cascade', impacts decreased from the most common to the least common species, leading to step‐wise removal of previously dominant species. A potentially permanent shift from high‐ to low‐coral cover with different coral community and size structure can be expected due to the demographic dynamics resultant from the disturbances. Similarities to degradation of other Caribbean and Pacific reefs are discussed. As comparable environmental conditions and mortality patterns must be expected worldwide, demographic collapse of many other coral populations may soon be widespread.</p> </abstract>