Land-Based Sources of Pollution

Michael Risk riskmj at
Fri Dec 20 16:49:32 EST 2002

Hello Brad (-list).

The direct effects of sewage on reefs are well-known, and can be
assessed via bioindicators and measured via a variety of isotopic

Some time ago, there was a meeting in the Florida Keys to evaluate the
various monitoring programs that were under way there. At that meeting,
there was some concern voiced about the lack of coverage of bioerosion:
bioerosion responds directly to nutrient loadings in sea water, and
accounts (on healthy reefs )for about 50% of the carbonate
budget-programs looking only at coral are missing the boat.

The FMRI monitoring program, an excellent one run by a troika of Jaap,
Porter and Wheaton, asked us if we could devise a rapid assessment
protocol they could fold into their program. This became the thesis
research of Christine Ward-Paige, and the rest is history.

We based the technique on results that date from the mid-1980's, notably
a paper by Rose and Risk on the effect of point-source fecal input
(turtle poop) on the reefs of Grand Cayman. That work showed that
amounts of Cliona delitrix, an aggressive, bright-orange boring sponge,
were related to % fecal bacteria in the water. As far as I am aware,
this is the only reef organism that has been shown to respond so
directly to sewage. (Why the reef community has been so slow to pick up
on the use of this bioindicator is yet another question.)

Christine's early results were presented this summer at the Victoria
ASLO meeting-the Abstract may be read on their website. By using
archival videos and recent surveys, she has shown that the amounts of C
delitrix have increased as the coral cover has dropped-most of the List
by now is probably aware that there is a regional mass extinction under
way in Florida. Analyses of 15-N ratios link the sponge nutrition to
terrestrial sources.

I also recommend the wonderful work Kate Holmes did in Barbados, which
she and Evan Edinger (and others) then applied in Indonesia. She found a
direct relationship between water quality and boring sponge abundance in
coral rubble. This is a field technique which can be taught to villagers
in about 2 hours.

As far as the broader question, the importance and assessment of
land-based sources: methods to asess sewage and sediment stress are
available, and in some cases have been known (but not generally applied)
for decades. The Toolbox paper in the Proc. Ft Lauderdale conf. outlines
some of the main techniques-also, in that same ASLO conference, I
present a way to assess the relative importance of sewage and sediment
stress on reefs.

The response of the coral reef research community to land-based threats
has not been salutory. I see resume-building at the expense of
ecosystem-saving; and I also see a near-fatal reluctance to adopt common
methodology, coupled with a lack of firm guidance from federal agencies.

It may not be too late. Some of the methods produce results in a few
days. What seems to be required are programs with firm political
backing, which are fundamentally interdisciplinary in scope and
composition. I recently was asked to evaluate reef proposals to an
un-named agency of an un-named nation, for an un-named but large amount
of money. I saw with amazement that, to some organisations, an
"interdisciplinary" team was 25 biologists-BUT all working in different
fields! Please. (I should point out here that I am a biologist, lest I
be accused of parochiality.) It is time to recognise that geochemistry
is capable of providing real answers.
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