[Coral-List] Pipes hung in the sea ...

John McManus jmcmanus at rsmas.miami.edu
Wed Oct 10 12:07:07 EDT 2007

Iron is an essential part of the molecular system that nitrogen-fixing
cyanobacteria use to pull nitrogen from its otherwise biologically useless
state of N2 (as in air) into forms that can be used in biological
production. Where there is an excess of phosphorus relative to nitrogen
(nitrogen is thus 'limiting') as in some central tropical sea areas, adding
iron essentially results in more nitrogen in the food web and thus more

One problem with the large-scale iron addition experiments is that the focus
was on near-surface changes. There has been little concern for the impacts
of adding large amounts of the resulting biomass on the deep sea areas below
these areas, where ecosystems for thousands of years have been highly
adapted to responding to only very small and sporadic introductions of
biomass. These are areas wherein we have extremely limited knowledge.
However, ecological theory would lead us to expect impacts such as new,
large anaerobic pockets. 

Another concern, of course, is that these biomass-laden waters are likely to
impinge upon remote coral reefs, many of which have similarly been adapted
to surviving in areas of very low nutrient input. While there are some coral
communities that can survive in areas of moderately high nutrients, they are
greatly different than those of off-shore atolls and platform reefs, in
terms of both species composition and growth forms of the species they hold
in common. Sudden additions of nutrients to low-nutrient reefs is always a
major concern, particularly when fishing and disease have reduced the
herbivores that would otherwise channel those nutrients into high trophic
levels (reducing seaweed).



-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Joan Kleypas
Sent: Wednesday, October 10, 2007 7:49 AM
To: Melissa Keyes; coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Pipes hung in the sea ...

Dear Melissa:

Iron fertilization is quite a debated topic these days, given the 
uncertainty of its effectiveness at drawing down atmospheric CO2 and the 
fact that industry is capitalizing on its use in the carbon credits game.

A website about very recent and interesting conference organized by Ken 
Buesseler and others at Woods Hole Oceanogr. Inst. (see 
http://www.whoi.edu/page.do?pid=14617) has some nice resources and links 
about this topic.


Melissa Keyes wrote:
> Hello, Listers,
>   I have been reading articles about Global Warming for ? thirty years,
>   Does anyone remember an experiment using elemental Iron?  Seems the
Tropical Oceans are clear because the water is devoid of Iron, so algae
cannot grow.  A group had to try twice, but when they sifted powdered iron
into the South Pacific,(quite offshore near the Equator) using the ship's
propellers to mix it well, they created a huge green bloom from what little
algae was present.  They followed their creation until the algae couldn't
reproduce anymore without more Iron.  It died and sank.
>   The big surprise was something about how they didn't stay in one place,
they drifted more than 800 miles, 19,200 km.  I distinctly remember a
comment that a few shiploads of Iron so deployed could sop up huge amounts
of Carbon, sending it to the bottom of the ocean when the plants died and
sank.  An Ice Age could be precipitated if they used too much Iron, they
said.  An ecosystem didn't form to recycle the carbon because,(another
remembered quote) "The cows couldn't keep up with the pasture", meaning too
few herbivores amongst the blooming algae.
>   I'm sorry that I cannot provide names and dates, this was quite a while
ago.  A possible drop in the ocean of our problem of the Earth's warming?
>   Cheers,
>   Melissa E. Keyes
>   St. Croix, USVI
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