Geographical variation in the growth rate of the hermatypic coral Porites in the Great Barrier Reef Province, Australia

Isdale, Peter James (1981) Geographical variation in the growth rate of the hermatypic coral Porites in the Great Barrier Reef Province, Australia. PhD thesis, James Cook University.

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Abstract

This thesis examines the growth rate of 452 colonies of the massive reef-building coral Porites from the Great Barrier Reef Province, Australia. The corals were collected from thirty-four different reefs, and from different zones within those reefs.

Five species of the genus were used in the project, each being a massive, hemispherical form, with a relatively smooth surface, small corallites, and a readily-identifiable point of origin of colonial growth.

The mean annual growth rate for each colony was measured using X-radiography of coral sections, and densitometry on the X-ray plates. The density variations found within the coral skeleton were used to identify periods of lunar and seasonal extension. Growth was measured radially, along maximum colony diameter.

The time of deposition of maximum density skeleton was found to differ with latitude, occurring in October/November in the south of the Province, but later, in April, north of Cooktown.

Colony growth rate was found to vary by a factor of two on a year to year basis, and that of similar colonies, varied, even under “uniform” conditions. Despite this, broader patterns of growth rate variation were found within the Province. Colony growth varied according to location on reef platforms, with maximum rates on the leeward reef flat and slowest growth on the more exposed central reef flat and windward crest areas. Growth was faster and more variable on the fringing reefs of the inner continental shelf than at the outer barrier, where rates were depressed and stable. Annual growth also varied with depth and according to species.

Examination of the spatial patterns of growth variability at each of the scales employed provides a background to the discussion of the relationships between scleractinian skeletogenesis and environmental and genetic factors. These findings are discussed in the context of modern reef investigations, in the light of their contribution to the study of reef development within the Province

Item ID: 12130
Item Type: Thesis (PhD)
Keywords: hermatypic corals, Porites, Great Barrier Reef Province, Wheeler Reef, growth, geographic variation, skeleton density, density banding, colony growth, reef development
Additional Information:

Peter Isdale received a JCU Outstanding Alumni Award in 2010.

Date Deposited: 28 Oct 2010 21:37
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060806 Animal Physiological Ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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