Interpretation of benthic survey categories

[Tim Daw]

Greetings listers,
=20
We are using trained volunteers to conduct line intercept and line point =
surveys in northern Sabah. We try to keep our methodologies standard for =
the region and so I would be interested to hear from anybody who has =
views on the interpretation of some of the standard AIMS categories.=20

Looking at the data from past phases we found that the following codes =
raised queries or ambiguities. I have listed the problems that have =
arisen and detailed what solutions we have tried here. We would be very =
grateful for any suggestions or comments.
=20
Rubble - How big is a piece of unattached coral before it is classified =
as rock, DCA etc? We set 50cm as a maximum size in any dimension.
Silt - How deep does it have to be? Does a few cm laying on top of dead =
or live coral count as silt or should this be ignored? We have told our =
volunteers to record the underlying substrate and record the covering of =
silt separately.
DCA - English et. al. state "if the skeletal structure is visible". Does =
this mean corallites or just growth form? The corallites of Branching =
Porites for example are obscured by any layer of algae whereas they =
would be visible on Favites for much longer. Would standing dead coral =
with no corallites or detailed skeletal features visible be classed as =
DCA or rock? In the past we have interpreted DCA as having skeletal =
features intact and so set a new category to distinguish between old =
dead coral (lacking skeletal detail but lifeform is visible) and rock =
(amorphous limestone or bedrock).
=20
Another concern was that dead substrate colonised by algae was only =
categorised as algae. As most rubble, old coral and rock becomes =
colonised by coralline algae, recording "CA" gives no indication of the =
substrate. When looking at reef condition, the implications of rubble =
and dead standing coral in an area impacted by cyanide and blast fishing =
are quite different. In an attempt to overcome this we separated this =
into two fields "substrate" and "overgrowth". This allows us to record =
the underlying substrate without being thrown by all-encompassing CA or =
ephemeral macroalgae blooms. We are still able to combine the fields =
into the standard AIMS format for comparison with other programmes.

With thanks for any comments or suggestions,

Tim Daw

Chief Scientist
Greenforce Pulau Banggi Project for Coral Reef Biodiversity
C/O Sri Mahiruddin
PO Box 526
89508 Kudat
Sabah
E. Malaysia

tim_daw at yahoo.com


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