2.1.

Micro-90 Cleaning solution is diluted to 2% solution using de-ionized water (DW).  Hydrochloric acid (HCl) Trace Metal Grade, Fisher Scientific, solution (1.2M) diluted with DW. Acid-washing of Teflon should be done with great care as Teflon is porous to HCl which can compromise dilute basic stock solutions of ¹⁴C -bicarbonate.

2.2.

250 ml polycarbonate incubation bottles are filled to capacity with 2% MICRO for 3 days with the cap on in an inverted position. Next, rinse all Micro away and then rinse down the walls with 20 -30mls 10%HCl and recap and shake  to acid rinse inside bottle.  This should be left overnight 12-16 hours. The acid is removed by rinsing the bottles three times with milliQ clean water before air drying.

2.3.

10 liter rosette sample bottles are cleaned with a 2% MICRO soak for 3 days, rinsed with de-ionized water and then dipped in 10% metals free HCl.  Caps, special coated springs and valve assemblies are also cleaned with a 2% MICRO soak for 3 days and then rinsed with de-ionized water and dried.

2.4.

All lab ware to be used is cleaned in this manner.

3.1.

To prevent contamination of self or solutions, work with the isotope stock is performed wearing vinyl gloves.

3.2.

A solution of 0.3 g of Na₂CO₃ anhydrous (ALDRICH 20,442-0, 99.995%) per liter Milli-Q filtered DW in a Micro cleaned 1 liter Teflon bottle to yield a concentration of 2.8 mM Na₂CO₃.   This solution is filtered through 0.2µM Nucleapore filter to remove particulate carbonate.

3.3.

Concentrated stock, 50ml of NaH-¹⁴CO₃ (~50-57 mCi mmole; MP Biomedicals LLC.) was diluted with 350 ml the 2.8mM Na₂CO₃ solution in productivity-cleaned 1 liter polycarbonate graduated cylinder.  It has become necessary to pH this up with an ultra clean 1N NaOH solution to raise the pH to ~10.

3.4.

Specific activity can be checked by diluting the above made solution to working concentrations, ie 50-200µl added to 250ml polycarbonate centrifuge bottle and measuring out triplicate 1ml portions into beta ethanolamine spiked (1.5%v/v) Ecolume scintillation cocktail.

3.5.

 To check for  ¹⁴C-organic carbon contamination another working aliquot of 200µl can be placed into a scintillation vial and acidified with 0.5ml 10% HCl and placed on a shaker overnight. This is done in the hood as it liberates ¹⁴C-CO₂. The acidified dpm should be <0.0001% of the total dpm of the ¹⁴C preparation.

4.1.

 Incubation apparatus consists of seawater-cooled, temperature monitored incubator tubes wrapped with neutral-density screens which simulate in situ light levels.

4.2.

Six incubation depths are selected, they represent 56, 30, 10, 3, 1  and ~0.3 % light level.  These values are estimated using a wand type PAR meter after cleaning tubes and screens covering them.  The near surface light level is reduced to 56% using common plastic screening to prevent a lense effect and subsequent cooking of the surface samples.

5.1.

Primary productivity samples are taken each day shortly before local apparent noon (LAN).  Light penetration was estimated from the Secchi depth (Using the definition that the 1% light level is three times the Secchi depth).  The depths with ambient light intensities corresponding to light levels simulated by near surface and the on-deck incubators were identified and sampled on the rosette up-cast.  Extra bottles were tripped in addition to the usual 20 levels sampled in the combined rosette-productivity cast in order to maintain the normal sampling depth resolution.

5.2.

5.3.

Using a dark sleeve to subdue the light, water samples are transferred to the incubation bottles (250 ml polycarbonate bottles) and stored in a dark box until inoculation.

Triplicate samples (two light and one dark control) were drawn from each productivity sample depth.

6.1.

Samples are inoculated with 50-200 µl of ¹⁴C as NaHCO3 stock solution of sodium carbonate (Fitzwater et al., 1982).

6.2.

Samples are incubated from LAN to civil twilight in a surface seawater-cooled incubators with neutral-density screens which simulate in situ light levels, corresponding to those from which samples were taken (see 4.2).

6.3.

At civil twilight the incubation is terminated and the time noted.  Sea state and safety is the only exception accepted to delay the end time.

7.1.

At the end of the incubation, all bottles have subsamples of 10mls removed for DO¹⁴C analysis. The LTER DOC filtrate apparatus consists of a plexi-glass filtration manifold to hold up to 18 scintillation vials over which syringe needles with 0.45um equivalent micro-syringe filters can be passed through stoppers with 25 ml syringe bodies serving as filter funnels.  The exception to this is dark bottles are only sampled for DO¹⁴C on two each high and low chlorophyll stations.

7.2.

Additionally, from dark bottles a 1ml sample is placed into beta mercapto-ethanol spiked (1.5%v/v) Ecolume scintillation cocktail  to determine the specific radioactivity in the samples.   These values are used to calculate an average cruise value after removing outliers.

7.3.

Finally the samples are filtered onto Millipore HA filters and placed in scintillation vials.  One half ml of 10% HCl was added to each sample.  The samples are then allowed to sit, without a cap, at room temperature for at least 3 hours (after Lean and Burnison, 1979).

8.1.

After addition of 10mls of Ecolume cocktail, vials are tightly capped and mixed before vials are counted for up to 10 minutes each for ¹⁴C  on a Beckman 6100LC liquid scintillation counter set to 1.0% counting precision.

8.2.

Data is captured to a flat file using Beckman data capture software for Windows in ASCII format.  This format is then used to integrate productivity depths into the CalCOFI data processing flow.