Are coral reefs doomed? // Land based sources of pollution

Katharina Fabricius k.fabricius at
Mon Oct 1 20:24:15 EDT 2001

Another, recently published study from the Indo-Pacific province, in which
we looked at the effects of increasing turbidity on biodiversity:

Fabricius KE & De'ath G (2001) Biodiversity on the Great Barrier Reef:
Large-scale patterns and turbidity-related local loss of soft coral taxa.
Pp 127 - 144 in: Wolanski E (ed) Oceanographic processes of coral reefs:
physical and biological links in the Great Barrier Reef. CRC Press, London.

The article is best to be read in the original book which contains a CD
with the colour images and animations of processes. In our chapter, we
present a spatial model of increasing turbidtiy (originating from a
single-point-discharge), related to decreasing biodiversity. However I'm
happy to send out free reprints in paper form (black & white print) or
electronically (colour).

Spatial patterns and abiotic controls of soft coral biodiversity were
determined from an extensive reef surveys on the Great Barrier Reef (GBR).
Taxonomic inventories of soft corals, and estimates of cover of the major
benthos forms and of the physical environment, were obtained from 161
reefs, spread relatively evenly along and across the whole GBR. Reefs on
the mid-shelf between latitude 13° and 16° represented the "hotspot" of
taxonomic richness in soft corals on the GBR. Overlapping distributions of
in-shore and off-shore taxa maximised richness on mid-shelf reefs.
Taxonomic richness decreased with increasing latitude, and was low and
relatively even across the shelf south of 21° lat. Soft coral richness was
strongly depressed in areas of high turbidity. It was also weakly
positively related to the amount of sediment deposited, and strongly
increased with depth. Total cover of hard corals and soft corals was poorly
explained by physical and spatial variables, however both varied with depth. 
The findings presented here have three major management implications: (1)
Turbidity and sedimentation affect the generic richness of soft corals.
Reefs with highest soft coral richness are < 20 km from the coast, well
within the range of terrestrial run-off, and hence a loss of biodiversity
could result if turbidity increases due to land use practices which
generate soil loss; (2) Taxonomic composition is more strongly related to
environmental conditions than total hard and soft coral cover. Taxonomic
inventories are thus better indicators of environmental conditions and
human impacts than are assessments of total cover. (3) Richness and cover
change more within a single site between 0 and 18 m depth, than between
reefs hundreds of kilometers apart along the shelf at the same depth.
Valuable additional information can be gained in a cost-efficient way if
monitoring and survey programs covered several depth zones rather than a
single depth.


Katharina Fabricius


Dr. Katharina Fabricius
Research Scientist
Australian Institute of Marine Science
PMB 3, Townsville Qld 4810, Australia

Fax    	+61 - 7 - 4772 5852
Phone 	+61 - 7 - 4753 4412  or 4758 1979
email k.fabricius at
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