nutrient deficiency and bleaching

[christine.schoenberg]

Dear Debbie,

a compliment up front: I like the way you defend your idea. We always need
to ask new questions, sometimes daring ones. The most difficult paths to
follow are against well-trodden ones, i.e. the ones everybody believes in.
However, we need to test the merit of such new ideas. I have some thoughts
re your question whether bleaching could be caused by nutrient depletion,
however, I am afraid they take Ove's side.

How come that bleaching is usually more severe nearshore, where nutrients
are enhanced to levels, which in turn can become detrimental to many coral
reef organisms, which are highly adapted to exist in oligotrophic
conditions? Could that maybe relate to some patchiness, too: too much
'food' and maybe toxic substances?

You reason that corals may not think that the stuff we pour into the seas
are edible. But some species certainly benefit from our disposals (see eg.
KRN Anthony 1999. Coral suspension feeding on fine particulate matter.
JEMBE 232: 85-106 and KRN Anthony 1999. A tank system for studying benthic
aquartic organisms at predictable levels of turbidity and sedimentation:
case study examining coral growth. Limnol Oceanogr 44(6): 1415-1422.).

I have another angle to look at your question: a different organism group.
I work on bioeroding sponges, some of which also contain zooxanthellae.
Sponges have been shown to be great biomonitors for nutrient conditions and
some species just love human waste materials and especially the bacteria
growing on them. The bioeroding sponge I worked with bleached under
nutrient-rich conditions, but did very well in less rich environments.

Sorry to be a spoil-sport...

Cheers, Christine

Dr. Christine Schönberg, PhD
Dept. of Zoosystematics & Morphology
Fachbereich 7 - Biology, Geo- & Environmental Sciences
Carl von Ossietzky University Oldenburg
26111 OLDENBURG
GERMANY
ph +49-441-7983373
fax +49-441-7983162
email christine.schoenberg at mail.uni-oldenburg.de
internet http://www.uni-oldenburg.de/zoomorphology/Whoiswho.html


~~~~~~~
For directions on subscribing and unsubscribing to coral-list or the
digests, please visit www.coral.noaa.gov, click on Popular on the
menu bar, then click on Coral-List Listserver.