Biomass depletion in the big picture

Bob Buddemeier buddrw at
Mon May 28 23:06:45 EDT 2001


I will resume the discussion when you can come up with a testable hypothesis
that is based on:
1.  valid biogeochemical equations;
2.  valid mass-balance algebraic equations;
3.  supporting citations from the peer-reviewed scientific literature;
4.  data or well-formulated logical arguments refuting the published
findings you wish to ignore.

In the meantime, recommended reading:

Field, C.B., Behrenfeld, M.J., Randerson, J.T., and Falkowski, P., 1998,
Primary production of the biosphere: Integrating terrestrial and oceanic
components: Science, v. 281, p. 237-240.
--- Message -- Oceanic net primary production is approx 50  PgC/yr, (=5E16
g) phytoplankton turnover time is 2-6 days, so standing biomass averages
about 5E14gC.  Annual fisheries harvest is around 5E11 gC (as previously
discussed), or 0.1% of primary producer (not total) biomass.  Whether
expressed as C or N, this extraction is trivial compared to the overall
inventory, the measurement uncertainties, and both intra-annual and
interannual natural fluctuations.

Pahlow, M., and Riebesell, U., 2000, Temporal trends in deep ocean Redfield
ratios: Science, v. 287, p. 831-833.
--- Message -- Measurements of deepwater chemistry over time show a rising
N:P ratio in the N. Atlantic, and increased export production in the N.
Pacific (which incidentally, is identified as Fe- rather than N-limited).
Neither lends much support to the idea of productivity limitation by N

Keeling, C.D., Whorf, T.P., Wahlen, M., and van der Plicht, J., 1995,
Interannual extremes in the rate of rise of atmospheric carbon dioxide:
Nature, v. 375, p. 666-670.
--- Message -- Compare curves of atmospheric CO2 and fossil fuel emissions
(over nearly half a century).   Not only is there a correspondence that
defies classification as coincidence, but the anomalies show that biotic
effects have also been quite consistent , and rather minor in variability
(certainly with no evidence for a systematically increasing offset as
fisheries harvest increased).

Kleypas, J.A., Buddemeier, R.W., Archer, D., Gattuso, J.-P., Langdon, C.,
and Opdyke, B.N., 1999, Geochemical consequences of increased atmospheric
carbon dioxide on coral reefs: Science, v. 284, p. 118-120.
Ware, J.R., Smith, S.V., and Reaka-Kudla, M.L., 1992, Coral reefs: sources
or sinks of atmospheric CO2?: Coral Reefs, v. 11, p. 127-130.
--- Message -- Calcium carbonate production is a sink for carbon (extracted
from the marine DIC reservoir) but a source of atmospheric CO2.  And, for
obligate shallow-water calcifiers, carbonate ion may be or soon become a
limiting nutrient.

Moffat, A.S., 1998, Global nitrogen overload problem grows critical:
Science, v. 279, p. 988-989.
--- Message -- (with references)  Mobilization of fixed N to the ocean has
dramatically increased, particularly in coastal regions (which supply most
of the world fisheries harvest).

Bob Buddemeier

----- Original Message -----
From: Debbie MacKenzie <debimack at>
To: <buddrw at>
Cc: <coral-list at>
Sent: Monday, May 28, 2001 11:07
Subject: Re: Biomass depletion in the big picture

> Hi Bob,
> Thanks for your reply.
> At 05:34 PM 5/25/01 -0500, you wrote:
> >1.  Fossil fuel emissions:
> >"Since 1751 over 270 billion tons of carbon have been released to the
> >atmosphere from the consumption of fossil fuels and cement production.
> Half of
> >these emissions have occurred since the mid 1970s. The 1997 estimate for
> global
> >CO2 emissions, 6601 million metric tons of carbon, is
> >the highest fossil-fuel emission estimate ever."
> >(
> >
> Yes, very big numbers, which may or may not be accurate. Regardless, they
> are not particularly useful as long as the other half of the terrestrial
> carbon equation remains unknown. The capacity of terrestrial systems to
> as carbon sinks is just starting to be realized.
> And the very fact of the "missing sink" - approx. 30% of the carbon
> "airborne fraction" going "missing" - this reflects the crudeness of our
> understanding and probably our calculations. All of this obviously has a
> huge margin of error.
> Also, why was not "the highest fossil-fuel emission estimate ever"
> accompanied by the "highest jump in global CO2 ever?"  (And why did not
> "half of the CO2 rise" also occur since the mid 1970s, if that's the time
> period during which "half of these emissions" occurred? These observations
> weaken the direct cause and effect that is commonly believed: "rising
> emissions = rising CO2 levels")
> >2.  Global fishery production is cited by McGinn (1998) in Worldwatch
> Paper 142
> >as rising from 20 million tons in 1950 to about 120 million tons in the
> >1990s.  This is in tons of wet weight biomass, which is typically on the
> order
> >of 1% carbon.  Even with a generous estimate of 5% C/wet weight, annual
> fishery
> >removal from the sea is <0.1% of the annual fossil fuel input to the
> >atmosphere.
> >
> 120 million tons - that's including aquaculture production - for the farm
> fish that are fed fish meal are you counting the same wild fish twice? One
> when you caught him and then again after he was incorporated into the
> of the farm fish? Regardless, annual wild fishery yields rose for a long
> time but stabilized in the vicinity of 90 million tons about a decade ago.
> And the average trophic level of what makes up the 90 million tons is
> dropping...contrary to the expectations of "conventional wisdom" which
> that as the trophic level drops in the system, the overall biomass at
> levels should increase significantly. (Some thinking has it increasing by
> factor of 10 for each trophic level dropped.) Why has the yield not
> increased as the trophic level has dropped? It's because one key
> for building fish is in short supply - fixed Nitrogen.
> It's not clear to me why you would compare the carbon content of fishery
> removals with that in fossil fuel emissions. Carbon does not appear to be
> in short supply. It's the link between the carbon and nitrogen cycles that
> is most important in assessing the effect of fishing on CO2.
> And a simple calculation of tonnage is unlikely to tell the tale. As you
> know, fixed nitrogen is (most times) the limiting nutrient in marine
> ecosystems. (Actually another scientist did the math for me one time - dry
> weight of nitrogen removed by fisheries is only a small fraction of the
> nitrogen "put back" by humans via nutrient-enriched terrestrial runoff.
> However, the sea knows how to get rid of that - sedimentation,
> denitrification...and therefore very little becomes incorporated into the
> living web, since it's "given back" in inappropriate form, amount and
> location. Stunted growth of fish in an "overnourished" ocean presents a
> bizarre paradox, IMO.)
> Nitrogen is the limiting nutrient factor in marine food webs, therefore
> availability of nitrogen determines the strength of the biological pump.
> The "biological pump" contains two sections, each of which relies on the
> presence of nitrogen, but in slightly different ways. The "organic pump"
> delivers carbon to the deep water by sinking organic particles, and
> nitrogen is a necessary part of their makeup. Therefore, it's via the
> "limiting nutrient" route that nitrogen affects the strength of the
> pump.
> The other part of the biological pump, however, the "carbonate pump," may
> be the more significant side, since besides consigning carbon to the deep
> carbonate pool, it sequesters it in sediment, sand, limestone, skeletons
> coral reefs, seashells, etc. Nitrogen functions as a "catalyst" rather
> a key participating element in the carbonate pump. It allows the reaction
> to proceed without being consumed by the reaction itself.
> Visualize a scenario:
> phytoplankton uses ammonia from seawater as the critical N source for
> production/carbon fixation -> a shell-forming marine organism consumes the
> phytoplankton, incorporating 10% of the nitrogen into its flesh and
> excreting 90% back into the seawater in a form usable by the phytoplankton
> -> a small fish consumes the shell-former, the fish also keeps 10% and
> excretes 90% of the N (in two short steps, 99% of the N has therefore been
> returned to the phytoplankton), the fish excretes the carbonate shell
> it's nutrient content is too low and its indigestible (it's mineral, ends
> up making sand)...
> This cycle goes round and round, efficiently recycling the N but
> shunting more C into long-term storage in mineral and deep sea carbonate
> pools. Building the shells uses only minute amounts of N, but N is the
> "catalyst" for shell formation since the living shell-building organisms
> will not exist without it. No molluscs and corals -> no N ->
> molluscs and corals... Therefore, although N is not a catalyst in the
> chemical sense for the carbonate pump, it is so in the functional sense.
> So how could you calculate the effect on the carbon cycle of removing one
> mole of N from the marine ecosystem? From the "biological pump" point of
> view you've not only removed a building block, but an essential catalyst
> well. (The math will be very tough, a far cry from a linear
> >3.  If one assumes that most of the biomass extraction is at least two
> steps up
> >the food chain from the primary producers, the "factor of 10 per trophic
> level"
> >rule of thumb suggests that fisheries deplete total marine biomass by no
> >than 1%.  This is probably a significant overestimate.
> >
> As suggested above, that rule of thumb seems not to be working in the real
> world. "When theory conflicts with reality, reality always wins" - no?
> >4.  Human acceleration of nutrient cycles has led to major eutrophication
> >many coastal areas (which are disproportionately important to the total
> marine
> >productivity) -- this is production of EXCESS marine biomass at the most
> basic
> >and quantitatively dominant level.
> >
> Now this is a dangerous myth. EXCESS phytoplankton in polluted estuaries
> maybe, but this does not translate into EXCESS marine biomass. Ask any
> fisherman...or any fish. We've made some very crude adjustments to what
> once a finely balanced system...Polluting the water does not produce fish,
> it produces what you said, "major eutrophication." That means that the
> waterway is now functioning as a septic system, accelerated sedimentation
> and denitrification are the main things going on there.
> >5.  A review of the carbon cycle literature shows that the biggest
> >challenge is the identity of a "missing" carbon sink.  If fishery
> >were actually making an unrecognized contribution to the atmospheric CO2,
> this
> >would be a missing source, not a sink.
> >
> You've got it!
> >I hope that counterarguments will be put forward quantitatively, in terms
> >the extensive literature on global carbon inventories and dynamics.
> >
> OK, sure, so do I. BTW, did you read my article:
> , or did you just react to
> the abstract that I posted?
> Debbie MacKenzie
> ~~~~~~~
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