Coral Reef Science:  Development Highlights

Ronald L. Shimek, Ph. D.

This month, I will discuss an interesting article on morphological change in aquarium corals...

Todd, P.A., R.C. Sidle, and N.J.I. Lewin-Koh, 2004. An Aquarium Experiment For Identifying The Physical Factors Inducing Morphological Change In Two Massive Scleractinian Corals. Journal of Experimental Marine Biology and Ecology. 299: 97- 113.

Abstract:

Previous research has demonstrated that the massive corals Favia speciosa (Dana, 1846) and Diploastrea heliopora (Lamark, 1816) are phenotypically plastic; i.e., the phenotype of these species can be altered by environmental conditions within their life span. Many researchers have suggested that light, water movement and/or sediment can affect coral morphology, but no work to date has attempted to separate these variables in a controlled aquarium experiment. To ascertain whether any of these three factors could induce morphological change in F. speciosa and D. heliopora, fragments (clone-mates) of both species were maintained in five aquariums, representing: high water energy, high sedimentation, and three different light regimes. After four months, the architecture of 12 randomly chosen corallites from each fragment was measured. Reaction norms suggest a relationship between corallite morphology and light, but no consistent pattern could be detected for fragments kept in the sediment regime tank or the high water energy tank. Corallites expand, extend and deepen in high light conditions, and possible functional explanations for this response are presented. However, more research is necessary to confirm that light is the primary controlling factor inducing small-scale morphological change in F. speciosa and D. heliopora.

Comments:

Many aquarists would benefit from taking a look at this article. There are many glib statements in the aquarium literature and on various forums about testing various factors and their effects on corals. This study actually does some of those tests, in aquaria, no less. More than just showing the results of this particular study of the effects of changes in light, water movement and sediment between two corals, this study illustrates some of the complicated equipment and methodology needed to examine some of these simple questions in an aquarium situation.