Disease obs.

Mike Risk riskmj at mcmail.cis.mcmaster.ca
Fri Nov 2 17:44:31 EST 2001

I would agree with Osha, disease seems to be absent from the discussion to
date. What is more, the distribution and impact of disease vary markedly.

I began my reef work in the Caribbean (in the Late Holocene), but for the
past 15 or so years, most of my time was spent in the Indo-Pacific. When I
recently returned to Caribbean reef work, I was astounded and depressed by
the impact disease has had there.

I was one of the reviewers for the Smith, Harvel and Kim paper (Hi, Kiho-I
was the one who didn't know much about diseases). I don't recall exact
figures, but these authors compared soft corals in an "impacted" area and a
"relatively unimpacted" area. Their infection rates in the UNIMPACTED area
were something like 50%!

My impression is that this is a recent, Caribbean, phenomenon. If this is in
fact correct, and not due to the Observer Effect or my ignorance, then the
reasons bear investigation. This situation cannot be due to:

1. "global change." By definition, global change effects the globe. Any
change in the oceans (pH, temp, etc) post-dates the rise of disease as a
major factor.

2. population density/sewage input. Show me Miami, I will show you Jakarta.
There may very well be qualitative changes in what is entering the oceans,
but SE Asia has supported dense human populations longer than the Caribbean.

3. overfishing/grazing. See 2.

Although there have been several volumes produced to date comparing
Caribbean and Indo-Pacific reefs, these have been dominated primarily by
biologists-and we need more interdisciplinarity in reef work. I think we
need to look more closely at the history of
reefs in both provinces, in particular the ages of the coral fauna and the
inputs to which they may be expected to have been acclimated. There are
fundamental differences in sea level history, terrestrial inputs and coral
evolutionary history, and some of these may affect resistance to disease.
And here I have to say that African Dust may well be a factor. (I would like
African Dust a whole lot better if I didn't think most of you already
harbour Aspergillus in the backs of your fridges-I'm not really sure we need
Africa as an infection source.)

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