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Title: Corals and climate change in the Cenozoic : a case study based on the staghorn coral Acropora
Author: White, Clare Hannah
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2013
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There is currently widespread concern about the deterioration of living reef corals, such as Acropora, and tropical reefs. Much of their demise appears to be related to coral bleaching, the underlying cause is probably global climatic warming. Future predictions about the responses of modern coral reefs lack data from the geological record. This thesis documents the history of one individual taxon, Acropora, and demonstrates how a particularly important reef coral genus has responded to global change through its geological range. Existing fossil Acropora records have been databased, and revised as necessary to bring the names and stratigraphy into line with current classifications. Comparisons have been made with known patterns of climate change and with palaeogeographical reconstructions of availability of suitable habitat. A taxonomic review provides new descriptions and records that provide evidence that the genus diversified rapidly after its appearance in the fossil record. The development of a new working taxonomy for fossil Acropora is based on how the surface characters used for modern species recognition correspond (or not) to characters seen in sectional preparations and computed tomography of fossil specimens. Field work in selected areas in France and England improves distributional data of Acropora and provides an understanding of Acropora taphonomy and palaeoecology. Unaltered coral and mollusc specimens from the Eocene of the Paris and Hampshire basins are assessed for their preservational state and diagenesis, and their stable isotopic and trace element compositions provide palaeoenvironmental data. Taxonomic uniformitarianism and geochemical data confirm that Acropora existed in high palaeolatitude tropical-like climatic conditions in Northwest Europe during the Eocene. Overall the record suggests origination and diversification in the north AfricanMediterranean region. Cenozoic global climatic cooling and palaeogeographical reorganisation led to a latitudinal restriction of the genus in the Miocene and to the emergence of Acroporadominated communities from the Pliocene in the Caribbean and Southeast Asian regions. Nonframework building, high latitude coral assemblages have recently received increased attention as a potential refuge during global change, as a proxy for these changes and for testing the tolerances of these coral species (e.g. northern Gulf of California, Mexico, 29°N; Halfar et al., 2005). The fossil record of Acropora shows that during previous globally warm periods, the genus has survived in higher latitudinal positions than seen today in marginal environments, suggesting that this genus at least may have the potential to adapt and acclimatise to globally warm conditions deemed more environmentally marginal than those seen today. The fossil record appears to imply that warmer climates ameliorate pre-existing marginal and unfavourable environments (for z corals) by making them more suited to z-corals. The major difference at present, and for future predictions, is the unprecedented affect of human activity on these ecosystems. However, understanding a coral's ecological response to global climate change in the geological record undoubtedly helps to understand the future of coral reefs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available