Implications of geometric plasticity for maximizing photosynthesis in branching corals

Kaniewska, P., Anthony, K. R. N., Sampayo, E. M., Campbell, P. R. and Hoegh-Gulberg, O. (2014) Implications of geometric plasticity for maximizing photosynthesis in branching corals. Marine Biology, 161 2: 313-328. doi:10.1007/s00227-013-2336-z

Author Kaniewska, P.
Anthony, K. R. N.
Sampayo, E. M.
Campbell, P. R.
Hoegh-Gulberg, O.
Title Implications of geometric plasticity for maximizing photosynthesis in branching corals
Journal name Marine Biology   Check publisher's open access policy
ISSN 0025-3162
Publication date 2014-02-01
Year available 2013
Sub-type Article (original research)
DOI 10.1007/s00227-013-2336-z
Volume 161
Issue 2
Start page 313
End page 328
Total pages 16
Place of publication Heidelberg, Germany
Publisher Springer
Language eng
Formatted abstract
Reef-building corals are an example of plastic photosynthetic organisms that occupy environments of high spatiotemporal variations in incident irradiance. Many phototrophs use a range of photoacclimatory mechanisms to optimize light levels reaching the photosynthetic units within the cells. In this study, we set out to determine whether phenotypic plasticity in branching corals across light habitats optimizes potential light utilization and photosynthesis. In order to do this, we mapped incident light levels across coral surfaces in branching corals and measured the photosynthetic capacity across various within-colony surfaces. Based on the field data and modelled frequency distribution of within-colony surface light levels, our results show that branching corals are substantially self-shaded at both 5 and 18 m, and the modal light level for the within-colony surface is 50 μmol photons m−2 s−1. Light profiles across different locations showed that the lowest attenuation at both depths was found on the inner surface of the outermost branches, while the most self-shading surface was on the bottom side of these branches. In contrast, vertically extended branches in the central part of the colony showed no differences between the sides of branches. The photosynthetic activity at these coral surfaces confirmed that the outermost branches had the greatest change in sun- and shade-adapted surfaces; the inner surfaces had a 50 % greater relative maximum electron transport rate compared to the outer side of the outermost branches. This was further confirmed by sensitivity analysis, showing that branch position was the most influential parameter in estimating whole-colony relative electron transport rate (rETR). As a whole, shallow colonies have double the photosynthetic capacity compared to deep colonies. In terms of phenotypic plasticity potentially optimizing photosynthetic capacity, we found that at 18 m, the present coral colony morphology increased the whole-colony rETR, while at 5 m, the colony morphology decreased potential light utilization and photosynthetic output. This result of potential energy acquisition being underutilized in shallow, highly lit waters due to the shallow type morphology present may represent a trade-off between optimizing light capture and reducing light damage, as this type morphology can perhaps decrease long-term costs of and effect of photoinhibition. This may be an important strategy as opposed to adopting a type morphology, which results in an overall higher energetic acquisition. Conversely, it could also be that maximizing light utilization and potential photosynthetic output is more important in low-light habitats for Acropora humilis.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Communicated by R. Hill. Published online: 8 October 2013.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Global Change Institute Publications
Official 2014 Collection
School of Biological Sciences Publications
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Created: Thu, 13 Feb 2014, 19:07:36 EST by Michelle Hall on behalf of School of Biological Sciences