Bioavailability of Nitrogen Compounds

Uptake of various N compounds changes on short time scales (e.g., days) (Morse et al., in preparation MuUioUand et al., in preparation). 

Nitrate was thought to be the predominant source of new N to the euphoric zone and so its uptake has been more widely measured that any other N compound (Table 7.1). That said, NOs upweUed from the deep ocean is not new N in the context of oceanic N inventories in general (see discussion of N2 fixation below and Chapter 4 by Carpenter and Capone, this volume) 

Assimilation of NOs assimilation of NOs requires the synthesis of NOs and N02 reductases, associated active transport systems, and the turnover of cellular ATP and NADPH (Chapter 32 by Berges and Mulholland, this volume McCarthy, 1981 Syrett, 1981). Further, supply of NOs is limited by rates of nitrification and vertical 

Generally speaking, when N02 is abundant in the euphoric zone, N02 uptake can be significant (e.g., Glibert et al, 1991), however, N02 uptake is measured far less routinely than NOs and NH4+ uptake. N02 concentrations are generally low, but can at times accumulate throughout the entire euphoric zone (Al-Qutob et al, 2002 Lomas and Lipschultz, 2006) as well as at the base of the euphoric zone in what has been termed the primary N02 maximum (e.g., Rakestraw, 1936). Further, high N02 concentrations have been found in estuaries and coastal systems at least seasonally (Filippino et al, in revision Morse et al, in preparation Bronk, personal 

Date Location Depth (nmolNL h ) Method Reference 

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