Dissolved Inorganic Nutrients on GLOBEC Cruises NBP0103 and NBP0104
The USF Nutrient Group (K. Fanning, Y. Serebrennikova, R. Masserini, H. Rutherford, and R. Conroy)

“Standard” Nutrient Methods (WOCE, mostly)
Nitrate & Nitrite: Sulfanilamide (SAN) + naphthyl-ethylaminediamine (NED)
Phosphate & Silica:  Ammonium Molybdate + reducing agents (hydrazine sulfate, stannous chloride)
Ammonia: alkaline phenol + sodium hypochlorite (bleach)

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Phosphate, nitrate, and silica : upper ocean increases between cruises suggesting remineralization
Change (µM)
Upper Phosphate        ~0.4 (or ~25% increase)
Deep Phosphate               ~0.0
Upper Nitrate               ~6.0 (or ~30% increase)
Deep Nitrate              ~0.0
Upper Silica                 ~10 (or ~20% increase)
Deep Silica                        ~0

But ammonia shows a different behavior between cruises.
Very high ammonia concentrations on 103 cruise: > 4 micromolar!
Ammonia concentrations decline in upper water column               Consumption?  Nitrification?
Deep ammonia concentrations remain at zero.
Ammonia decline demonstrated best by integrating ammonia profiles at each station down to depth of zero ammonia: standing stock of ammonia.

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Because nitrification converts ammonia to nitrate, a graph of nitrate vs ammonia was prepared for Cruise 103

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Nitrate, phosphate, and silica increased 20-40% in the upper water column between cruises.
Ammonia declined strongly (~60%) in the upper water column between cruises.
Very high standing stock of ammonia in Marguerite Bay
~500 µmol/m2
possibly drifted to southwest during cruise 103
declined ~3-fold between cruises
Nutrient remineralization (nitrification) possible but difficult to explain quantitatively
No attempt to correct for circulation effects