Coral Reef Science:  Development Highlights

Eric Borneman

Marubini F, Ferrier-Pages C, and Cuif J-P. 2003. Suppression of skeletal growth in scleractinian corals by decreasing ambient carbonate-ion concentration: a cross-family comparison. Proc Roy Soc Lond B 270: 179-184.

Abstract:

Biogenic calcification is influenced by the concentration of available carbonate ions. The recent confirmation of this for hermatypic corals has raised concern over the future of coral reefs because [CO₃^2-] is a decreasing function of increasing pCO₂ in the atmosphere. As one of the overriding features of coral reefs is their diversity, understanding the degree of variability between species in their ability to cope with a change in [CO₃^2-] is a priority. We cultured four phylogenetically and physiologically different species of hermatypic coral (Acropora verweyi, Galaxea fascicularis, Pavona cactus and Turbinaria reniformis) under 'normal' (280 micromol kg^-1 and 'low' (140 micromol kg^-1 carbonate-ion concentrations. The effect on skeletogenesis was investigated quantitatively (by calcification rate) and qualitatively (by microstructural appearance of growing crystalline fibres using scanning electron microscopy (SEM)). The 'low carbonate' treatment resulted in a significant suppression of calcification rate and a tendency for weaker crystallization at the distal tips of fibres. However, while the calcification rate was affected uniformly across species (13-18% reduction), the magnitude of the microstructural response was highly species specific: crystallization was most markedly affected in A. verweyi and least in T. reniformis. These results are discussed in relation to past records and future predictions of carbonate variability in the oceans.

Comments:

This article addresses the role of carbonate as a factor in calcification. The authors note that coral growth is "intimately linked to calcification and is determined by a number of factors, including light, temperature, feeding and…the saturation state of the sea water." They describe how Ca²⁺ is conserved and how the precipitation of CaCO₃ is largely a function of CO₃^2-, which in turn is largely a function of pH. One purpose of the article was to determine if increasing CO₂ levels will affect calcification across scleractinian corals, in general, and the cross-family comparison suggests that it does. The experiments were performed as high and low carbonate treatments by varying the pH levels of the aquaria. It was interesting to note that the highest rate of calcification occurred in Pavona cactus, with lower rates in Turbinaria reniformis, Galaxea fascicularis, and Acropora verweyi.

Invertebrate Tidbits

Ronald L. Shimek, Ph.D.

This month, rather than highlighting a couple of articles in technical peer-reviewed journals, I would like to recommend that aquarists examine the current (November-December, 2005) issue of American Scientist. This is a magazine published by the Society of Sigma Xi, the Scientific Research Society, and it is often available on newsstands or from magazine sellers.

This magazine contains "review" or summary articles by researchers describing, and often summarizing, their research. These articles are written in clear, non-technical prose so that readers outside the author's discipline can understand and appreciate them. Consequently, the articles are generally understandable by non-specialists such as the general public.

This issue contains one real gem of an article for aquarists (Shadwick, R. E. 2005. How Tunas and Lamnid Sharks Swim: An Evolutionary Convergence. American Scientist. 93: 524-531). In this article, the author compares the swimming actions, bodily shapes and anatomies of tunas and lamnid sharks. The latter fish are animals like the Great White shark of "Jaws" fame. Both of these types of fish may swim at very high velocities, probably the fastest of any fishes, and both are warm-blooded animals. One of the interesting findings is that when these fish swim, their body is essentially rigid and the tail fins move rapidly from side to side. The tail doesn't really "push" water backwards, consequently moving the fish forward, as happens in many fish. Instead, the tail acts hydrodynamically in a manner similar to that of an airplane propeller's blade. In effect, an area of lower pressure is generated on the leading surface of the fin and this pulls the fish forward through the water, just as a rapidly moving propeller can pull an airplane through the air.

Other articles that may be of interest include one on biofilms (Harrison, J. J., R. J. Turner, L. L. R. Marques and H. Ceri. 2005. Biofilms. American Scientist. 93: 508-515) and their importance in biological communities; read that as "denitrification areas" of coral reef aquaria, and an article on yawning (Provine, R. R. 2005. Yawning. American Scientist. 93: 532-539) that is just plain fun to read.

The magazine also contains columns (including one on the development of supermarkets), book reviews and cartoons.

Additional information is available online at http://www.americanscientist.org/. Full access to the site, however, requires either a subscription to the magazine or membership in the Society of Sigma Xi.