Challenging basic assumptions

Debbie MacKenzie debimack at
Sat May 25 08:27:29 EDT 2002

Dear Marine Scientists,

For the last several years I have been trying to draw your attention to the
possibility that marine productivity has been substantially lowered as the
result of centuries of fishing removals. The major objections that I have
received from many of you have been these: (1) Primary production rates are
determined by patterns of "physical forcing," (2) No changes have been
recorded in levels of dissolved nutrients in the ocean, and (3) Nutrient
overload is actually at the root of many problems in coastal waters.

What needs to be clarified, I believe, are these points:
(1) That "physical forcing" is not the only determinant of productivity in
temperate zones. In your analysis of nitrogen flux patterns you did not
include biological processes that counteract sinking, one of the largest
being the production by benthic organisms of floating spawn. "Tight
biological cycling" of nutrients in temperate coastal systems therefore
also occurs.
(2) Changes in the productivity rate of the ocean will not predictably be
reflected by declining levels of dissolved nutrients in seawater, because
the system has a strong natural tendency to stabilize these.
(3) The methods of diagnosing "eutrophication" need to be objectively
reviewed. You are finding too many "false positives" by relying on tests
with very low specificity.

I hope that my review of these topics may be helpful to you:

Debbie MacKenzie


Several years of research have been spent exploring the hypothesis that
generalized ‘starvation’ is at the root of today’s failing marine life, and
that total marine production has been steadily lowered, both developments
representing an unintended, and unrecognized, consequence of fishing. Prior
scientific investigation into this hypothesis appears to be lacking.
Mainstream scientific thinking on the hypothesis, however, has been to
firmly resist the idea because of the belief that marine production is
directly linked to, and determined by, patterns of "physical forcing."
(Berger et al, 1989, Carpenter and Capone, 1983, Parsons et al, 1984)

The physical forcing of dissolved nutrients from deeper waters to the
sunlit zone occurs as the result of seasonal weather patterns which are
essentially a constant. It was necessary therefore to demonstrate the point
of disconnection between physical forcing patterns and patterns of marine
primary productivity. This is best demonstrated by describing a nutrient
flux pattern that has not been accounted for, as such, in the literature.
‘Biological forcing’ of primary production is achieved in continental shelf
systems where assemblages of benthic invertebrates and fish release
prodigious numbers of floating pelagic spawn. Traditionally viewed only as
a "reproductive strategy" (Kasyanov, 2001, Steidinger and Walker, 1984),
this spawning behavior also represents an important, biologically forced,
nutrient flux that has not been quantified or considered in the standard
ecosystem models. Just as nitrates forced to the surface by weather
patterns will stimulate primary production, so will the physical raising of
eggs and larvae. The quality of the effect on phytoplankton productivity is
the same.

If biological forcing has therefore played an important role in all ocean
systems (and not only the tropical ones, where the idea was recognized
decades ago), then significant biomass removal by fishing has potentially
lowered system productivity. This potential, for net system productivity to
have been lowered as a consequence of fishing, has not been clearly
recognized in recent literature that has sought to discover the extent of
the ecosystem effects of fisheries. (Jackson et al, 2001, Kaiser and
deGroot, 2000, Goni, 2000)

A model of an individual starving marine population (Powell et al., 1995)
was used to predict which symptoms might emerge on a more general scale if
‘starvation,’ or bottom-up control, were increasingly exerted on the ocean
itself. The model revealed the likelihood of only a single early warning
signal, loss of the older members of the affected population, which could
easily be misinterpreted as a sign of overfishing. Differential diagnosis
at a systemic level relies on finding the signal in unfished, as well as
fished, populations.

In an attempt to find meaningful patterns in the larger picture of broad
changing trends in marine life today (the "down the web" shift, the failure
of Atlantic groundfish stocks to recover under moratorium, the widespread
decline in the age and size at maturity of fish, the increasing incidence
of harmful algae blooms, changes in seaweeds and intertidal invertebrates,
the starvation of marine mammals, etc…), I have drawn parallels between
what appear to be physiological homeostatic mechanisms at work in the
overall ocean system and similar biological processes that are known to act
to maintain a smaller living system - the human body. It was important to
demonstrate that long-term consistency in measurements of seawater nitrogen
(usually nitrate) concentration is unrelated to long-term changes that may
have occurred in rates of primary production.

With a background in an older biological scientific discipline, the study
of human medicine, I have taken the approach of using a medical diagnostic
model to assess both the state of the ocean’s health today and also the
value of the currently favored diagnostic tests used by marine scientists.
Many assessment tests used today, especially those for "eutrophication,"
are unacceptably prone to giving false positive results.

Signs of extreme stress due to nutrient loss emerge when the overall marine
ecosystem is assessed in this manner. And acute, and possibly abrupt,
downward shifts appear imminent as the biological system enters

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