Adaptive variation in coral geometry and the optimization of internal colony light climates

Anthony, K.R.N., Hoogenboom, M. O., and Connolly, S.R. (2005) Adaptive variation in coral geometry and the optimization of internal colony light climates. Functional Ecology, 19 (1). pp. 17-26.

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Abstract

1. The ability of photosynthetic organisms to adjust their light climate has high adaptive significance because irradiance can vary spatially by orders of magnitude. Using a plating (foliaceous) coral species (Turbinaria mesenterina), we tested the hypothesis that plasticity of colony geometry optimizes internal irradiance distributions.

2. We developed a two-dimensional model to predict the internal irradiance distribution of a foliaceous colony as a function of its geometry. Field tests showed that the model explained 85% of the variation in irradiance within colonies of T. mesenterina with minimal bias.

3. Colony plate angle, plate spacing and range of tissue distributions into the colony were exponential functions of water depth. In shallow water plates tended to be nearly vertical, narrowly spaced, and had living tissue only near the growing edge of the plate. In deep water plates grew more horizontally, were more widely spaced, and had living tissue extending well into the colony interior. This pattern of phenotypic plasticity effectively evens out differences in within-colony irradiances.

4. We compared within-colony irradiance distributions across light habitats (depth), based on the observed variation in colony geometry with water depth. Despite fourfold differences in environmental irradiance, within-colony irradiances had a common mode of 100–200 µmol m−2 s−1. This is near the hypothesized photosynthetic optimum defined by the upper limit of the subsaturation parameter (Ek) of the photosynthesis–irradiance curve.

5. Our study demonstrates that phenotypic plasticity of colony geometry is an important mechanism for regulating light capture during growth in T. mesenterina, and facilitates near-optimal internal irradiances across a wide range of environmental light regimes.

Item ID: 6347
Item Type: Article (Refereed Research - C1)
Keywords: mathematical model; phenotypic plasticity; photosynthetic optimum; Scleractinian corals; turbinaria mesenterina
ISSN: 1365-2435
Date Deposited: 10 Feb 2010 23:39
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 100%
SEO Codes: 96 ENVIRONMENT > 9699 Other Environment > 969999 Environment not elsewhere classified @ 100%
Citation Count from Web of Science Web of Science 28
Downloads: Total: 3
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