Reef Science: Development Highlights
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.
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 [CO32-]
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
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.
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
state of the sea water." They describe how Ca2+
is conserved and how the precipitation of CaCO3
is largely a function of CO32-,
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
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.