[Coral-List] density of coral skeletons
dbucher at scu.edu.au
Thu Feb 9 18:40:49 EST 2006
Try the following reference for a discussion of Archimedian methods
for determining density of bleached coral skeletons. The important
distinction is whether you want bulk density/porosity or the specific
gravity of the mineral matrix (microdensity). We recommended the use
of acetone to penetrate the small pore spaces as the surface tension
in water is too great to remove all gas bubbles. We accelerated the
process by using a vacuum pump and a bell-jar to lower the pressure.
Without the vacuum pump overnight soaking was not long enough - you
need several days at least for porous skeletons. The acetone-
saturated skeleton was then soaked in several changes of water.
Acetone has the added advantage of dissolving residual organic matter
(waxes, oils etc) left behind by the bleaching process. Buoyant weigh
the saturated skeleton, dry it, coat it with a thin layer of parafin
wax and buoyant weigh it again - if you accurately measure the
specific density of the water in the weighing apparatus you can
calculate the coral's total enclosed volume (matrix plus pore
spaces), its dry weight and the volume of the matrix alone.
It's not the most exciting thing you will ever do, but it worked for us.
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.
It's not the most exciting thing you will ever do, but it worked for
us. See my small contribution to the next reference for an
application of this method.
K. Koop, D. Booth, A. Broadbent, J. Brodie, D. Bucher, D. Capone, J.
Coll, W. Dennison, M. Erdmann, P. Harrison, O. Hoegh-Guldberg, P.
Hutchings, G.B. Jones, A.W.D. Larkum, J. O'Neil, A. Steven, E.
Tentori, S. Ward, J. Williamson, D. Yellowlees 2001 ENCORE: The
effect of nutrient enrichment on coral reefs: Synthesis of results
and conclusions. Marine Pollution Bulletin 42(2):91-120.
Dr Daniel Bucher
Lecturer, Marine Biology and Fisheries
School Director of Postgraduate Studies and Research
School of Environmental Science and Management
Southern Cross University
PO Box 157 Lismore, NSW 2480
Ph: 02 6620 3665
Fax: 02 6621 2669
Mobile: 0414 864085
>Date: Wed, 8 Feb 2006 12:10:53 -0500
>From: Marah Newman <mjnewman at ucsd.edu>
>Subject: [Coral-List] density of coral skeletons
>To: coral-list at coral.aoml.noaa.gov
>I have several bleached coral skeletons and I need to calculate
>skeleton density. I have looked at several papers that detail...snip
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