[Coral-List] Subject: Overfishing contributing to ocean acidification?

Tim Wijgerde t.wijgerde at coralscience.org
Thu Jan 22 12:45:23 EST 2009

Dear all,

this is an interesting paper!
The article by Catherine is optimistic in this part:

Because fish carbonate
production goes up with temperature, fish are likely to produce more carbonate - and be more effective
of ocean acidity
- as temperatures increase through global warming.

, but isn't something overlooked? 

Yes, higher T and higher oceanic CO2 levels will indeed increase
production by fish, but also H+ excretion (from the
HCO3 − ions secreted by intestinal cells
into the intestinal lumen of fish are derived largely from metabolic CO2
reacting with water [...] This reaction produces H+, which is exported
into the blood and ultimately excreted into the external seawater via
ion-transporting cells in the gills of fish.

So, the more
carbonates fish excrete into the water, the more H+ (acidic particles if
you will) are excreted at the same time! This negates the increase in
aragonate saturation state, as the H+ ions will decrease it at the same
time. I just quickly browsed through the paper (will read it better
later), but it seems that TA will increase in deeper waters, as more CaCO3
dissolves, but TA in shallow waters may decrease due to the H+ production.
Won't these two factors eventually cancel out one another?


Tim Wijgerde

Op Do, 22 januari,
2009 18:00, schreef coral-list-request at coral.aoml.noaa.gov:
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> Date: Thu, 22 Jan 2009 08:36:54
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> Message: 2
Date: Thu, 22 Jan 2009 08:56:43 -0500
> From: John Ware
<jware at erols.com>
> Subject: Re: [Coral-List] Over fishing
contributing to ocean
> 	acidification?
> To: Douglas
Fenner <dfenner at blueskynet.as>
> Cc:
coral-list at coral.aoml.noaa.gov, Gene Shinn
<eshinn at marine.usf.edu>
> Message-ID:
<49787B1B.4080609 at erols.com>
> Content-Type: text/plain;
charset=us-ascii; format=flowed
> Doug et al.

> In the far distant past (1992) a paper appeared in Coral
> describing the process by which the deposition of CaCO3 by
> increases pCO2 in the water and decreases pH (increases
> Ware, Smith, Reaka-Kudla:  Coral reefs:
sources or sinks of atmospheric
> CO2?  Coral Reefs 11:127-130.
> This was published at a time when some coral reef
scientists were
> claiming that coral reefs were SINKS of CO2 -
after all, look at all
> that CO3 stuff.  In fact, one reviewer, a
geologist, questioned the
> utility of the paper because
"everyone knows that the deposition of
> CaCO3 in water is a
source of atmospheric CO2".
> John
> Douglas Fenner wrote:
 I thought that the chemistry was that when corals secrete a skeleton,
>>they put more CO2 into solution in the water, which actually
makes the
>> water
>>more acid.  If fish solidify
calcium carbonate, the same chemistry would
>>have to apply,
wouldn't it??  Would reverse as the calcium carbonate
>>dissolved.  But I'm no chemist.  (and I'm not defending
>> Doug
>>----- Original Message -----
>>From: "Gene
Shinn" <eshinn at marine.usf.edu>
<coral-list at coral.aoml.noaa.gov>
>>Sent: Monday, January
19, 2009 4:48 AM
>>Subject: [Coral-List] Over fishing
contributing to ocean acidification?
>>>An interesting article about an
article published in Science. Gene
an ally against climate change
>>>    *
New Scientist 13:02 16 January 2009 by Catherine Brahic
>>>An unlikely ally may have been found in
the fight against the effects
>>>of climate change. Fish
excretions seem to play a key role in
>>>maintaining the
ocean's delicate pH balance, says a study that also
>>>reveals that there are 2 billion tonnes of fish in the
world's oceans.
>>>Bony fish excrete lumps
of calcium carbonate, known as "gut rocks"
>>>which are thought to dissolve in the upper layers of the
ocean. A
>>>team led by Rod Wilson of the University of
Exeter in the UK has now
>>>shown that the sheer amount of
gut rocks produced plays a key role in
>>>buffering the
carbon dioxide that acidifies seawater.
>>>"This study really is the first glimpse of the huge
impact fish have
>>>on our carbon cycle - and why we need
them in the ocean," says
>>>Wilson's colleague Villy
Christensen of the University of British
>>>Columbia in
>>>Protective role
>>>While marine biologists have known for
some time that fish produce
>>>gut rocks, until now no-one
had estimated just how much calcium
>>>carbonate is spewed
out into the ocean in this way.
>>>It was
widely believed that most marine carbonate is provided by the
>>>external skeletons of marine plankton. These microscopic
>>>are likely to be hard hit as climate change
increases the acidity of
>>>the oceans and their skeletons
literally dissolve away.
>>>The new study
reveals that fish play an important role in stopping
from happening.
>>>ferent models to estimate the amount of
fish biomass that is in the
>>>global oceans, and its
>>>By drinking salt water,
fish ingest a lot of calcium, and they
>>>excrete more or
less calcium carbonate depending on their size and
temperature of the water. "For a given total mass of fish,
>>>smaller fish produce more than bigger fish, and fish at
>>>temperatures produce more than fish at lower
temperatures," explains
>>>Surprise finding
>>>The team
then used data on how much carbonate fish produce on average
>>>to calculate how much the fish biomass represented in their
>>>models are likely to excrete.
>>>This revealed that between 3% and 15% of
all the calcium carbonate
>>>produced in the oceans comes
from fish. Wilson says this is a
>>>conservative estimate -
he and his team think the real figure could
>>>be three
times higher.
>>>"I expect it will be
a big surprise to most of the ocean scientists
>>>who study
the ocean carbon cycle," says Wilson. "Apart from a handful
>>>of fish biologists around the world, the scientific
community were
>>>previously unaware that fish produce of
any of this chalky mineral,
>>>let alone enough to be
significant on a global scale."
>>>Eric Achterberg of the National Oceanography Centre in
>>>UK, says the study offers an insight into an
underrepresented marine
>>>process. "Whether the fish
carbonate is really an important
>>>contribution to the
mid-water alkalinity is not certain yet and forms
excellent topic of research," he says.
>>>'Unrecognised allies'
>>>Wilson agrees that it is not yet certain whether the gut
rocks do
>>>indeed dissolve in the upper layers of the
ocean. Their chemical
>>>structure suggests that they are
very soluble in seawater and should
>>>readily dissolve. But
if future studies show this does not happen,
>>>this will
mean the gut rocks sink to the bottom of the ocean without
>>>dissolving and buffering the oceans.
>>>Because fish carbonate production goes up with temperature,
fish are
>>>likely to produce more carbonate - and be more
effective buffers of
>>>ocean acidity - as temperatures
increase through global warming.
>>>That's the good news.
The bad news is that overfishing may have an
downside: in addition to depleting food stocks, it could
>>>also deplete the precious carbonate buffer.
>>>Because of the complexity of ocean
chemistry, "we cannot really say
>>>much with any
confidence about how overfishing might affect ocean
>>>acidification says Wilson. "But we definitely need to
study this more
>>>to help make better predictions about
these future changes."
must buck the current trend of clear-cutting of the oceans and
>>>foster these unrecognised allies against climate
change," says
>>>Journal reference: Science (DOI: 10.1126/science.1157972)
>>>No Rocks, No Water, No Ecosystem (EAS)
>>>E. A. Shinn, Courtesy
>>>University of South Florida
>>>Marine Science Center (room 204)
Seventh Avenue South
>>>St. Petersburg, FL 33701
>>><eshinn at marine.usf.edu>
>>>Tel 727
>>>Coral-List mailing list
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> ------------------------------
Message: 3
> Date: Thu, 22 Jan 2009 18:18:22 +0400
> From:
"John Burt" <John.Burt at zu.ac.ae>
> Subject:
[Coral-List] COTs are not in Dubai, UAE
> To:
<coral-list at coral.aoml.noaa.gov>
> Message-ID:
<4978B860.CDD2.00C8.0 at zu.ac.ae>
> Content-Type: text/plain;
> Iain, Yusef, Kaveh,
> I have been diving approx. bi-weekly in Dubai since 2005
and have not
> observed a single COT on reefs in the area, nor on
coral encrusted
> breakwaters. I would imagine that the sizzling
summer temperatures or the
> salinity are keeping them out from
establishing in the area. They can
> undoubtedly get here via
ballast water or dispersal.
> John Burt
> ------------------------------
REGARDING Message: 4
> Date: Wed, 21 Jan 2009 04:42:35 -0800
> From: Kaveh Samimi <kaveh_s_n at yahoo.com>
Subject: Re: [Coral-List] COT current status
> To:
dr_iamacdonald at yahoo.co.uk, Coral-List at coral.aoml.noaa.gov
Message-ID: <168073.78690.qm at web53107.mail.re2.yahoo.com>
Content-Type: text/plain; charset=windows-1252
> Dear
> As far as I know this is the only?observation
of COT?at Iranian side of
> the Gulf.
> Price
ARG, Rezai H (1996) New echinoderm records for the Gulf including
> crown of thorns starfish, Acanthaster planci (Linnaeus) and
> biogeographical significance. Fauna of Saudi Arabia (15):
> Cheers,
> Kaveh

> Coral-List
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> End of Coral-List Digest, Vol 5, Issue 24

Wijgerde, M.Sc.
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