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1. 14C Primary Productivity

No methods reported here

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2. Gross oxygen production

(Mary-Lynn Dickson: dickson@gsosun1.gso.uri.edu)

Gross oxygen production was measured by spiking seawater samples with 18-O labeled water and measuring the amount of 18-O labeled oxygen produced photosynthetically (Bender et al. 1987). This method measures gross primary production. The gross oxygen production measurements involved collecting 4 samples from each depth. Two samples per depth were extracted within an hour of collection for the initial del 18-O composition of the dissolved oxygen and 2 samples per depth were spiked with 18-O labeled water and incubated for 24 hours in deckboard incubators. The dissolved oxygen in each sample was extracted using the procedure of Emerson et al. (1991) and samples were analyzed on a Finnegan MAT 252 mass spectrometer.

3. Net oxygen production and respiration rates

(Mary-Lynn Dickson: dickson@gsosun1.gso.uri.edu)

Net oxygen production was measured from the change in the oxygen concentration in incubated bottles. Quadruplicate initial samples were fixed with Winkler reagents after being drawn from a Go-Flo bottle and quadruplicate samples were incubated for 24 hours in the same manner as the samples for the gross oxygen production measurements. Initial and final samples were titrated togethere using a high precision, automated titrator configured with a 5 ml burette. Net oxygen production was calculated as the difference in the oxygen concentration between final and initial samples.

Samples for community respiration rates were incubated in the dark for 24 hours in an environmental chamber that maintained the ambient seawater temperature. Decreases in the oxygen concentration between final and initial samples were used to calculate respiration rates.

4. Conversion from oxygen to carbon units:

(Mary-Lynn Dickson: dickson@gsosun1.gso.uri.edu)

In order to compare production rates based on oxygen-based measurements to 14C incorporation rates, it is necessary to apply a photosynthetic quotient to the oxygen data to convert it to carbon units. Gross and net oxygen production rates were converted to gross carbon and net carbon production rates using the equations:

Net C production = (Net O2 production/1.4)

Gross C production = [Net C prod. + (Gross O2 prod. - Net O2 prod.)/1.1]

A photosynthetic quotient (PQ) of 1.4, based on nitrate assimilation, was used to convert net oxygen production rates to net carbon rates. A PQ of 1.1 represents utilization of regenerated forms of nitrogen, primarily ammonium and urea. These relationships imply that under steady state conditions net community production and new production are equivalent and gross production is the sum of new and regenerated production, also known as total production (sensu Dugdale and Goering, 1967)

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5. New Production using 15N

No methods reported here

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6. New Production from "del-NO3"

(Bob Anderson: boba@ldeo.columbia.edu)

First, a brief description of the method:

Reported values represent the change (delta) integrated inventory of nitrate between time-zero and time-obs.

Integration is from 0 to 100m.

Time-sero is late winter conditions, as defined by Survey-I north of 62°S and the Site Survey between 62°S and 65°S.

By definition, "del NO3" equals zero for Survey-I, which we believe is not strictly true.

Delta inventories were computed at each degree of latitude, and all values falling within a latitude bin were averaged to produce the results reported here.

Delta inventories were computed for two observation periods: (1) Survey-II, using all data, and (2) Process-II southbound. I did not do calculations for Process-I, becasue of the more limited spatial coverage, or Process-II northbound because mixed layer deepening reduced the signal. These calculations could be done, if you wish, but not in the next couple of weeks, and the results may be less meaningful than the ones that are presented.

Delta inventories of C were estimated by multiplying delta inventories of NO3 by 6.6. Delta inventories were converted to rates (mmol/m2/day) assuming an average delta time of 90 days for Survey-II and 120 days for Process-II. Rates can be adjusted by changing delta time if necessary to adjust to a common schedule used by other investigators.

Survey-II 65-62S 62-60S 60-57S

(90 days)

Consumption Rate:

(mmol C/m2/d) 35.7 30.3 24.2

Integrated defecit:

(mmol C/m2) 3213 2728 2178

Process-II 65-62S 62-60S 60-57S

(southbound)

(120 days)

Consumption Rate:

(mmol C/m2/d) 21.8 20.4 20.5

Integrated defecit:

(mmol C/m2) 2615 2442 2457

We do not have winter data south of 65S, and data north of 57S are too sparse to use this method.

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New production and export based on changes in the TCO2 stock.

No methods reported here

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8. Export production based on changes in the POC stock

(Wilf Gardner: wgardner@ocean.tamu.edu)

Methods: POC was determined from the regression of Cp to POC. Values were summed in the upper 100 m for each cast. All casts within each specific zone (Polar Front) or each transect in the Ross Sea were averaged and differences were determined for the average in the zone or along the transect. Time differences were used as the mean for the stations occupied or the mean of the transect time in the Ross. All of these values are net changes averaged over days to months. They are not instantaneous measurements at the time of the profile.

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9. Fecal pellet flux

(Juanita Urban-Rich: jurban@lumcon.edu)

The values are integrated through the upper 200 m. These numbers are only from the largest of the mesozooplankton grazers so they do not represent the total potential fecal pellet flux from mesozooplankton. A very general and rough ball park estimate of the total potential fecal pellet flux would be to multiple these numbers by 3.

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10. Export flux derived from Thorium-234

(Ken Buesseler: kbuesseler@whoi.edu)

Measured inventories of total Thorium-234 and a 1-D scavenging model are used to predict the export of 234Th on sinking particles for a given station. Either Steady-State (Polar Front/Ross Sea) or Non-Steady State (Ross Sea only) models were used to calculate the 234Th flux. POC flux as reported here is derived from the 234Th flux multiplied by the site and time specific POC/234Th ratio on particles. In this Table, this ratio was obtained from material collected at 100m using in-situ pumps on a 142mm diameter teflon screen with a nominal pore size of 70 microns.

Details can be found in:

Buesseler, K. O., L. Ball, J. Andrews, C. Benitez-Nelson, R. Belastock, F. Chai and Y. Chao (1998). Upper Ocean Export of Particulate Organic Carbon in the Arabian Sea derived from Thorium-234. Deep-Sea Res. II, Arabian Sea Volume, 45 (10-11), 2461-2487

Buesseler, K.O. (1998). The de-coupling of production and particulate export in the surface ocean. Global Biogoechemical Cycles, 12 (2), 297-310.

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11. Sediment trap flux at 1000m

No methods reported here