[Coral-List] Re: Measuring growth

Danny Bucher dbucher at scu.edu.au
Mon Mar 29 19:55:30 EST 2004

Hi Craig,

I firmly believe that any study of growth of branching corals should
incorporate several different measures. Branching species increase colony
size by linear and radial extension of existing branches and by initiation
of new branches. Infilling of skeletal voids can also be considered as
growth in the broader sense but does not in itself increase colony size and
in acroporids may even reduce the internal space available for living
tissue. Simply measuring linear extension does not take into account the
possibility that other processes may have changed at the same time.

Morphology, as well as size, may be important if your aquaculture project
is providing live coral for the aquarium trade. Rapid extension with little
new branch formation may not provide the morphology demanded by clients.
Buoyant weight integrates all these growth processes including infilling.
It is possible with almost any kind of laboratory scales if you make up a
suitable bridle to sit over the weighing pan or hook. If this is really not
possible, perhaps you should consider measuring changes in displacement
volume as an alternative integrative growth measure (assuming skeletal
density is not important to you). Density may be important if you are
growing corals for transplant onto artificial reefs - accelerated extension
is usually associated with reduced density and strength - so buoyant weight
could be essential.

I am glad to see someone giving acroporids equal attention to the so-called
lab-rats in the Pocilloporidae. I suspect the physiological (and  growth)
responses to some environmental variables may be quite different between
these groups.

You may be able to obtain a copy of my thesis from Southern Cross
University that includes descriptions of some simple methods as well as a
discussion of extension and density relationships in acroporids. I am still
preparing papers from it at the moment, but two are now available.

Bucher, D. 2000 The effects of Experimentally Elevated Nutrient
Concentrations on Growth Rate, Skeletal Architecture and Soft Tissue
Morphology of Acroporid Corals (Scleractinia: Acroporidae).  Ph.D. thesis,
Southern Cross University, Lismore NSW, Australia.

Bucher, D., Harriott, V. and Roberts, L. 1998 Skeletal bulk density,
micro-density and porosity of acroporid corals. Journal of Experimental
Marine Biology and Ecology.  228(1)117-135.

Bucher, D.J. and Harrison, P.L. (2000). Growth response of the reef coral
Acropora longicyathus to elevated inorganic nutrients: do responses to
nutrients vary among coral taxa? Proc. 9th International Coral Reef
Symposium, Bali, 1: 443-448

Cheers, Danny

>Date: Sat, 27 Mar 2004 11:24:01 EST
>From: Cades83898 at cs.com
>Subject: [Coral-List] Measuring growth
> Hello,
>    I am doing research on accelerated coral growth for aquaculture at the
>University of Maine. I'm looking for some accurate but simple methods to
>the growth of Acropora and Stylophora nubbins. I am considering mounting them
>on tiles and measuring vertical growth with digital calipers. We don't have a
>scale we can alter for the buoyant weight technique. This is for a master's
>thesis so, it has to be a fairly sound method. Growth period is expected to
>last for 2 months so, I expect there to be fairly significant growth.
>Craig Zievis
>Cades83898 at cs.com

  Dr. Daniel Bucher
  Lecturer in Biology/Fisheries Biology/Marine Ecosystems
  Course Coordinator: Fisheries and Aquaculture Management
  Course Coordinator: Marine Science and Management
  School Diving Officer
       School of Environmental Science and Management
      P.O. Box 157, Lismore, N.S.W. Australia, 2480
        Phone: 02 6620 3665   Fax: 02 6621 2669

E-mail: dbucher at scu.edu.au
School web page at: http://www.scu.edu.au/schools/esm/


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