[Coral-List] Michael Risk - C. delitrix as measure of bioerosion

Dr. Stephen Jameson sjameson at coralseas.com
Tue Oct 17 12:42:02 EDT 2006

Dear Mike,

Thanks for the coral-list note regarding:

> Back to The Destroyer. Christine Ward-Paige and I devised a
> quick-and-dirty scheme for FMRI by which amounts of C. delitrix could
> be estimated. Nothing special, a diver simply swims a transect line
> with a quadrat frame (25x25cm divided into 5x5cm squares works well),
> estimating area of delitirix. This takes next to no time. The problem
> with converting these measures to estimates of framework destruction is
> that colonies of delitrix are not two-dimensional. It frequently drives
> straight into the heart of the coral. Rose and Risk gives some idea of
> the variance involved in estimating rates from areas-but areas are a
> start, and it?s easy. Delitrix does not occur in the Indo-Pacific.

In our bioindicator review paper in the "Internal Bioeroders" section
(which can be downloaded at <www.coralseas.com/press.html>:

Jameson SC, Erdmann MV, Gibson Jr GR, Potts KW (1998) Development of
biological criteria for coral reef ecosystem assessment.  Atoll Res Bull,
September 1998, No. 450, Smithsonian Institution, Washington, DC, 102 pp

we provide the following summary and recommendation regarding Cliona

Internal Bioeroders

Of the above mentioned eutrophication bioindicators, one group, internal
bioeroders, have been thoroughly investigated and have demonstrated a
consistent, graded response of increasing abundance with increasing
eutrophication on reefs (Rose and Risk 1985, Sammarco and Risk 1990, Risk et
al. 1995, Holmes 1997).  Holmes (1997) found that the proportion of dead
coral rubble invaded by clionid sponges, as well as the number of invasions
per rubble sample, increased dramatically with increasing eutrophication on
reefs of Barbados.  Rose and Risk (1985) found similar results with Cliona
infestations of live Montastrea cavernosa heads in the Grand Caymans, while
Sammarco and Risk (1990) and Risk et al. (1995) suggested that distinctive
cross-continental shelf patterns of bioerosion (by sponges and bivalves) in
Porites and Acropora on the Great Barrier Reef were explained primarily by
increasing organic input with proximity to the mainland.

Research recommendation:  Though this group has not yet been formally
proposed for inclusion in biomonitoring programs, results of the above
research suggest that internal bioeroders provide a sensitive assessment of
increasing eutrophication on reefs and that development of a rigorous
bioassay could be accomplished with minimal additional research.


Mike Questions:

1.  Have you given any thought as to what would be appropriate reference
conditions (concentrations in minimally impaired environments) for the
various Cliona species in their respective geographical locations throughout
the world?

2.  In minimally impaired conditions, does their concentration vary in
different coral reef zones?

Best regards,

Dr. Stephen C. Jameson, President
Coral Seas Inc. - Integrated Coastal Zone Management
4254 Hungry Run Road, The Plains, VA  20198-1715  USA
Office:  703-754-8690, Fax:  703-754-9139
Email:  sjameson at coralseas.com
Web Site:  http://www.coralseas.com


Research Collaborator
Smithsonian National Museum of Natural History
Washington, DC 20560

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