[Coral-List] Coral growth

[Derek Manzello]

Hello Nassir and Coral-list,

Coral growth can mean several things.  If you are interested in linear
skeletal extension, that is something that is relatively easy to do.  One
of the easiest ways to do that is by staining the corals with Alizarin
Red-S (Lamberts 1978), albeit you will have to collect, kill and saw the
coral in half to figure out how much they grew if you are dealing with
corals of the "massive" morphology. This method has some inherent
problems, as Dick Dodge and colleagues showed that alizarin staining
actually depresses calcification to some extent (see Dodge et al. 1984). 
For some branching species (e.g., Pocillopora spp.) you may be able to
determine linear extension without any sawing, but just make sure you only
measure from the top of the stain line to the tip of the branch as the
stain will permeate down the porous skeleton a few mm, which can make
short-term (weeks-months) growth studies very difficult to interpret.  If
you are interested in calcification (g CaCO3 per unit area per time) you
can still utilize the Alizarin method, but will have to measure density (g
CaCO3 per volume) as well.   This can be done with the corals already used
to determine linear skeletal extension by the following equation (Lough
and Barnes 1997):

Calcification rate = linear extension X skeletal density
(g CaCO3 cm^-2 yr^-1) = (cm yr^-1) X (g CaCO3 cm^-3)

Another way to measure calcification is with the alkalinity anomaly
method.  A -2 microequiv change in alkalinity is equal to 1 mole of CaCO3
deposited (see Smith 1973; Smith and Kinsey 1978).  Yet, another way is
the buoyant weight technique (see Jokiel et al., 1978), which is good b/c
you don't have to kill any corals to get calcification estimates.

As you can see, it really depends on what "part" of coral growth you are
interested in in regards to what way you tackle the problem.  I hope this
helps with your work and I wish you the best of luck!

My two cents,
Derek Manzello

References

Dodge, R.E., S. Wyers, H.R. Frith, A.H. Knap, C. Cook, R. Smith, and T.D.
Sleeter, 1984. Coral calcification rates by the buoyant weight technique:
effects of alizarin staining. J. Exp. Mar. Biol. Ecol. 75, 217-232

Jokiel, P. L, Maragos, J. E., Franzisket, L. (1978). Coral growth: buoyant
weight technique. In Coral Reefs: Research Methods. Monographs on
Oceanographic Methodology, vol. 5 (ed. D. R. Stoddart and R. E. Johannes),
pp. 379-396. Paris: UNESCO.

Lamberts, A.E. 1978. Coral growth: Alizarin method. In: Stoddart, D.R.,
and R.E. Johannes, editors, Coral Reefs: Research methods, pp. 523-527,
UNESCO, Paris.

Lough JM, Barnes DJ (1997) Several centuries of variation in skeletal
extension, density and calcification in massive Porites colonies from the
Great Barrier Reef: A proxy for seawater temperature and a background of
variability against which to identify unnatural change. J Exp Mar Bio Ecol
211: 29-67

Smith, S.V. 1973. Carbon dioxide dynamics: a record of organic carbon
production, respiration, and calcification in the Eniwetok reef flat
community.  Limnology and Oceanography, 18, 106-120.

Smith, S.V., and K.W. Kinsey. 1978. Calcification and organic carbon
metabolism as indicated by carbon dioxide. In: Stoddart, D.R., and R.E.
Johannes, editors, Coral Reefs: Research methods, pp. 469-484, UNESCO,
Paris