Measuring growth of shape in stony corals

[Tim Pickering]

Dear Coral Listers

I am following this thread about measurement of coral growth with
interest.  My MSc student Kalo Pakoa wants to compare growth of
corallimorphs (Discosoma) cultivated under different conditions. 
Corallimorphs are relatively simple in that the discs can be regarded
as a 2-D shape and area measured by digital photography or even 
its diameter directly by vernier if one gets the measurement quickly
before touching the organism.

However corallimorphs and soft corals have an additional problem 
not faced by researchers of hard corals - their morphology is quite
plastic.  Under different lighting conditions, corallimorphs will
change their shape, eg become flattened out, or form a trumpet 
shape.  The same crittur can thus have different sizes under 
different lighting, which makes it hard to compare the effect of light 
on growth. 

I know Simon Ellis in Poehnpei has adopted an approach of 
"harrassing" a soft coral until it shrinks down to a "standard size",
then measuring it.

Has anyone else faced this problem, and found ways to overcome 
it?



Tim Pickering
The University of the South Pacific
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