Biomass depletion in the big picture

Debbie MacKenzie debimack at
Wed May 30 13:45:06 EDT 2001


At 10:06 PM 5/28/01 -0500, you wrote:
>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.

Your third and fourth conditions are the ones that I thought that I had met
in my article: 

Have you taken the time to read it yet? 

What do you make of the concidental timing of the CO2 rise and the
progression of the fishing industry? And the theory that supports the
contention that a decrease in marine biota will cause an ocean-atmosphere
readjustment involving an increase in atmospheric CO2? (not my idea, backed
up by published, peer-reviewed references, if you read it.) Also, the key
question that the whole theory hinges on, is whether or not the total
marine biomass has been diminished over the course of the history of human
fishing. The references that you pointed me to do not address this
question, and this question is critical. To disprove my hypothesis, there
needs to be evidence somewhere that the overall marine productivity has NOT
been falling. I offered published evidence that it has been dropping, for
instance the record from the baleen of the bowhead whales. 

>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.

A quote from the article: "Our results based on time-averaged data are
likely to charcterize typical NPP from this time period but certainly miss
key anomalies such as ENSO, as well as progressive global changes."

Therefore no trend in NPP has been revealed in this work. Here are 2 more
quotes from that article: 

"In terrestrial ecosystems, it is relatively straightforward, in principle,
to determine NPP from incremental increases in biomass..."

"Because of the rapid turnover of oceanic plant biomass, even large
increases in ocean NPP will not result in substantial carbon storage
through changes in phytoplankton standing stock."

They measure accumulation of plant tissue (trunks, branches, roots) that
are not involved in photosynthesis, when trying to determine terrestrial
NPP. And this is considered a valid approach. Yet when assessing the marine
system, they only look at the phytoplankton segment/biomass, since that
represents "the plants." They are looking for phytoplankton to accomplish
"carbon storage" by amassing more phytoplankton. However, the phytoplankton
are analogous only to the leaves on the terrestrial trees (the actual
photosynthesizing units), the analogy to growth of trunks, roots, etc., in
the sea is the accumulation of standing stocks of fish. That's where the
photosynthesizing units in the sea store their opposed to the
treetrunks on land.

And I do not see where those authors tried to compare their NPP estimates
to a mass-balance with fisheries removals. And regarding your mass-balance
observation, what did you think of my comments to the effect that nitrogen
functions as building block and catalyst both for the organic pump?

>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

One key message from this work: "These findings imply that the biological
part of the marine carbon cycle currently is NOT in steady state."
(consistent with my points - no? Today's carbon cycle models assume the
opposite, that it IS in a steady state.)

Also, the possible reasons for the rising N:P ratio (without increasing
AOU, "apparent oxygen utilization," which would be expected if enhanced
N-fertilized primary productivity was the cause), in the North Atlantic
Ocean included "any process weakening export production, such as reduced
nutrient transport to the surface ocean due to declining vertical
mixing..." (the development of the open ocean N-shortage that I suspect,
would predictably "weaken export production") I can imagine that the N:P
ratio could rise as a result of fishing depletion since fishing removes
both N and P. The ocean has an active mechanism, albeit slow, to restore N
(nitrogen-fixation), but no means to actively restore P ... therefore
rising N:P ratio is quite plausibe and consistent with my ideas, it seems
to me.

This study did NOT report rising N-CONTENT in the deep ocean.

>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).

This requires a convoluted explanation to account for the fact that the
first 20 years of the data fit with the fossil fuel emission data in one
way (seemingly 55.9% of airborne CO2 fraction accumulated in the atmosphere
each year)..and the second 20 years did not. 

"Our double-deconvolution calculation suggests that the oceans typically
are a larger sink for atmospheric CO2 during El Nino event than
otherwise..."  This agrees with my statements that the atmosphere is
acutely sensitive to changes in ocean currents and accompanying
"outgassing" of CO2. Regarding the ocean becoming a "larger sink" during El
Nino...that's strange because it's rather well known that fish production
tends to drop at those times. Rather than becoming a "larger sink" the
ocean more likely becomes a "smaller source" during El Ninos.

"In summary, the slowing down of the rate of rise of atmospheric CO2 from
1989 to 1993, seen in our data and confirmed by other measurements, is
partially explained (about 30%) by the reduction in growth rate of
industrial CO2 emissions that occurred after 1979. We further propose that
warming of surface water in advance of this slowdown caused an anomalous
rise in atmospheric CO2, accentuating the subsequent slowdown, while the
terrestrial biosphere, perhaps by sequestering carbon in a delayed response
to the same warming, caused most of the slowdown itself."

This is what I mean by a "convoluted explanation." There are some large lag
times between cause and effect there, for example 10 years between reducing
the growth rate of emissions and slowing the rise rate of CO2. Also the
warming that caused a see-saw (first caused CO2 to go up, then a delayed
reaction by terr. plants brought it down) is a bit of a stretch. My take on
it: the rate of rise in atmospheric CO2 slowed down beginning in 1989 - the
same year that wild fishery yields peaked (and have stabilized thereafter)
- so the slowdown in rate of marine biomass removal nicely coincides with
the slowdown in rising atmospheric CO2 levels.

>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.

These concerns about the effects of rising CO2 on seawater pH, carbonate
saturation, and ease of calcification for marine organisms....I do not
dispute. This work still does not question the SOURCE of the rising CO2,
which is what I'm trying to get at. These scenarios would be the same
whether the CO2 came from terrestrial emissions or ocean-atmosphere carbon
imbalance, IMO.

>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).

A brief intro, really, to this work that Moffat recommends:

Human Alteration of the Global Nitrogen Cycle: Causes and Consequence. by
Peter M. Vitousek, Chair, John Aber, Robert W. Howarth, Gene E. Likens,
Pamela A. Matson,
David W. Schindler, William H. Schlesinger, and G. David Tilman
 online at:

>From Vitousek et al. "In large river basins, the majority of nitrogen that
arrives is probably broken down by denitrifying bacteria and released to
the atmosphere as nitrogen gas or nitrous oxide." (i.e. it doesn't
translate into more fish)

Also, this is another nice one: Oceanic Sources and Sinks
(Fred Mackenzie, Karen von Damm, Dave DeMaster, Tom Church, Billy Moore)

>From this article: "Water flux times the riverine composition cannot be
simply translated into net oceanic source terms without intimate knowledge
of biogeochemical and exchange reactions either at the transient saline
boundary of a river plume, or within the more permanent mixing zone of a
confined estuary and attendant sinks."  And this intimate knowledge is
seriously lacking. 

Another interesting observation from Fred Mackenzie et at. "The Atlantic
Ocean accumulates much more calcium carbonate than the Pacific because the
Atlantic deep waters have a higher pH (i.e. less corrosive to CaCO3) than
those in the Pacific..." (That helps to convince me that the cessation of
North Atlantic fishing during WWII allowed a partial recovery of the marine
biota, and consequently a significant global CO2 drawdown. Perhaps the
Atlantic marine biota represents a stronger "biological carbon pump" than
the Pacific?) 

Debbie MacKenzie

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