20 December 1999
Page 4

of P fertilizers (which have increased statistically, longer record). Organic N loads were
probably high in the period of expansion of agriculture, then stabilized, then total N went
back up again with the advent of N fertilizer use (increase in the nitrate component, not
the organic component). The last part of the paragraph about model responses to N
teductions is accurate. The first part of the paragraph should be revised.

p. 33, 5. Approaches for Reducing Nutrient Loads. First two bullets are very good.

p. 35, comment about reductions in atmospheric nitrogen emissions... ptobably not
warranted, should be reconsidered. It appears that this conclusion is based on the amount
of deposition directly on the Gulf (1%) compared to the N flux from the river system.
Within the basin, however, atmospheric N contributes 16% of the load. Thus further
teductions in emissions within the basin appeat to be warranted.

p. 36, Table 5.1, footnotes 4 and 5 are missing from the copy J downloaded.

p. 37, paragraph before Figure 5.1, need a reference to “a current national goal is to
establish two million miles of conservation buffers...”

p. 38, Table 5.2, the potential nitrogen reduction from diverting rivers in coastal
Louisiana is probably an overestimate. The Jan 13-14 workshop will hopefully come to
tesolution on these values. This makes the unit cost for N removal ratio greatet than it
should be (Table 5.3).

p. 43, Monitoring Needs section. Need to emphasize that the river monitoring data needs
to be integrated with the offshore ecological data on appropriate time scales.

p. 48, Longer-term Priorities box, statement about atmospheric deposition contradicts
earlier statement concerning unwarranted remedial actions. Atmospheric in the
watershed is a component worth examining now and in the future. As human population
increases, the effects of atmospheric N will also increase (based on current predictions of
tiver N load based on population, atmospheric N, and fertilizer use).

J hope these comments are useful as you complete this document for submission
to CENR for its review. J there are any statements that need clarification, please do not
hesitate to contact me.

Sincerely,
Van P. balbelwa
Nancy N. Calais, PhD.

Professor



LOUISIANA UNIVERSITIES MARINE CONSORTIUM

DeFelice Marine Center, 8124 Highway 56
Chauvin, Louisiana 70344-2124

20 December 1999

Gulf of Mexico Hypoxia Working Group

C/o NOAA, National Centers for Coastal Ocean Science
1305 East-West Highway, Room 9127

Silver Spring, MD 20910

Re: Comments on Integrated Assessment (IA) of the Causes and Consequences of
Hypoxia in the Gulf of Mexico

These comments are offered from my perspective as a researcher on the issue,.a
lead author of one of the CENR reports, and a participant at many levels in the public
education and information exchange regarding the issue, and do not reflect the views of
my institution, Louisiana Universities Marine Consortium.

The [A has essentially accomplished the goal set forth, which is to consolidate
and synthesize the information in the six CENR technical reports and provide a concise
document that can be used by the Working Group to develop a Management Plan. The
document reads well and should convey an understandable message to a broad
readership.

As noted in the IA, the six technical reports and the literature and analyses in
them were used for the IA. All the detail of the six reports cannot be repeated here. Just
as all the detail of the six reports did not fit in their Executive Summaries. The essence is
in the IA. Additional detail can be obtained from the six reports, and should not
overburden the [A (i.e., the current status of text, fact, and references is adequate and on.
target).

Except where noted below, J agree with the statements made in the IA and feel
that they are clearly supported by the scientific evidence. Thus, I do not intend to doa
point-by-point “Lagree” or “I disagree” but rather point out where there might be a
chance for corrections or further information.

p. 7, Executive Summary, paragraph on economics of fishery should indicate that
adequate fisheries data or economic data are not available to determine changes due
entirely to. the presence of hypoxia.

Phone: (504) 851-2800 Fax: (504) 851-2874 http:/ /www.lumcon.edu
LUMCON is an Equal Opportunity and ADA Employer



20 December 1999
Page 2

p. 9, Executive Summary, currently the statements on reintroducing river water are
balanced. There may be additional information coming from the Jan. 13/14 workshop
that might be suitable for incorporation into the final draft of the IA.

p. 9-10, Executive Summary, the discussion of potential management strategies is very
well balanced.

p. 13, “1. The Problem,” 2m para, sentence that begins “Mobile organisms, leave, die...”
Should delete the words “die, or are eaten.” The mobile ones mostly escape; it is the
immobile ones that eventually die as the oxygen levels continue to decline.

p. 14 and figure 2.1, upwelled nutrients should be included only as a possibility, but
further statements are warranted that the contribution is unlikely given that this process is
limited to outer shelf and slope environments and that the physical mechanism is not
present to bring them to the continental shelf where hypoxia occurs.

p. 17, Box on “Factors Potentially Contributing...”, Organic Joading section is correct as
written, but can be strengthened based on the Hypoxia Science Meeting (Dec. 3, St.
Louis) results. Brian Eadie stands by his previous analysis (Eadie et al. 1994), and
indicates that the Gofii et al. (1998) article does not negate his and/or the work on stable
carbon isotopes in Turner and Rabalais (1994) and Rabalais et al. (1996).

p. 17, Box on “Factors Potentially Contributing...”, wetland loss is fine as written, but
the Spartina-based carbon isotope signatures are restricted to very close to shore and the
source of the carbon over the broad area affected by hypoxia is produced by marine
phytoplankton.

p. 17, Box on “Factors Potentially Contributing...”, again the soutce of upwelled
nutrients is possible (as are many factors), but unlikely for the reasons given above.

p. 18, “Trends in Indicators of Production, Low-Oxygen Stress, and River...” Suggest a
paragraph on historical evidence prior to the 1900 horizon of figure 2.2. This would be
the foraminiferan data of B. K. Sen Gupta (presented in Rabalais et al. 1996, and CENR.
#1) that shows prior to 1900, there is an indication that hypoxia was NOT a problem.
These and other data support the other data presented in the IA that oxygen stress has
worsened since the 1950s.

p. 19, “—Long term records — drainage basin changes.” These statements that put into
historical perspective the changes in landscape and nutrients is good.



20 December 1999
Page 3

p. 20, “—Shorter-term records.” The section on 1999 can probably be changed now that
Don Goolsby had updated flux calculations through Sep/Oct 99. Data he showed in St.
Louis indicated a higher streamflow than 1997, 1998, and a higher DIN flux. In fact, the
increase in DIN compared to the 2 previous years is a steeper increase than the
streamflow increase. The streamflow data were mirrored in the lower salinity signal
waters during the July 1999 sampling effort. The nutrient data for that period are not yet
available.

p. 21, “Sources, Loads, and Trends of River Nutrients.” This section can probably be
updated with further data analyses presented by Don Goolsby in St. Louis (Dec. 3).

p. 24-25, declining catch of penaeids with years of greatly increased hypoxia. This
“increase” is based on the 5-d estimate made in mid to late July. This is not really a
suitable comparison because the catch data span a much greater time period than the 5-d
mapping exercise. Better comparisons are likely available from the monthly data, but
these analyses have not yet been conducted. I think it is more accurate to state that
adequate data do not exist (or have not yet been analyzed) to determine relationships
between hypoxia (extent, severity, duration) and shrimp catch. The long-term trend
downward in catch since the late 1970s, however, is consistent with the sedimentary
indicators of worsening hypoxia stress. The next section (p. 25 on economics data
analysis) makes a much clearer statement concerning the limitations of the economic data
than the section about fisheries data.

p. 27, 4. Effects of Changing Nutrient Loads, “No Loading Change” Scenario. There was
a good sentence removed from a previous version that should be considered for re-
inclusion. Last paragraph before Figure 4.1 following “....between 1955 and 1980 (see
figure 4.1). If future nutrient increases are modest, the ecosystem might be expected to
remain stable, although the system will still be stressed.... However, even if...

p. 30, last paragraph in “Increased Loading Scenario” concerning harmful algal blooms.
Pseudo-nitzschia spp. is a group of ....sometimes.... toxic diatoms. Not all are toxic, but
toxic forms ARE found in the surface waters influenced by the Mississippi River, and
Pseudo-nitzschia, overall, has increased in the area as Mississippi River N flux has
increased.

p. 31, Effects if Reduction Measures Are Undertaken, Changes in the Gulf of Mexico.
Paragraph beginning with change in P flux. The data record for P is much shorter than
that of N. For this reason and the complications of sediment adsorption, there is not a
statistical relationship with time. The trend is up, however. To say that P loads over the
century have probably decreases is not supported by data. It is likely that P and N flux
were high during deforestation, clearing of land, and draining of soils. With soil erosion
measures, P may have gone down for a while, but then likely up again with the addition