Table 2. Comparison of nitrification rates reported for pelagic environments.

All rates were obtained by measuring the oxidation of ¹⁵N-labeled NH₄⁺.

Location	Type of system	Depth	NH4+ (μmol L-1)	Nitrification rate (nmol L-1 d-1)	Light condition	References
Lake Croche, Quebec	small oligotrophic lake	Bottom of the photic zone	0–3.36	0–333	In situ	This study
Lake Superior, US and Canada	large freshwater lake (oligotrophic)	2–150 m	0.09–1.11	0–83*	Dark	Small et al. (2013)
Taihu Lake, China	large and shallow freshwater lake	Surface (0.2 m) and near-bottom water (2 m)	0.26–131	2–3750*	In situ	Hampel et al 2018
Mono Lake, California	alkaline and saline lake	Surface to oxycline layer	0–20	4–480*	Dark	Carini and Joye (2008)
Scheldt estuary, Netherlands and Belgium	freshwater part of the estuary	2 m	≤ 150	3600–16800**	Dark	Andersson et al. (2006)
	marine part of the estuary		≤ 25	0–480**
Hood Canal, Washington	fjord	0–120 m	0–0.646	0–550*	Dark	Horak et al. (2013)
Saanich Inlet, British columbia	fjord	Between photic zone and the oxic-anoxic interface (~140 m)	0–3.5	0–120	Dark	Ward and Kilpatrick (1990)
Gulf of California	coastal waters	Upper water column (30–60 m)	0.01–0.05	0–93*	In situ	Beman et al. (2008)
Monterey Bay, California	coastal waters	Photic zone and 3 depths below	Undetectable	20–80	In situ	Ward (2005)
Central California Current	open ocean	Photic zone	0–1	2–210*	Dark	Santoro et al. (2010)
Arabian Sea	open ocean	60–0.1% Io	≤ 1	5–100	In situ	McCarthy et al. (1999)
Arabian Sea	open ocean	40–1500 m	undetectable	0–22	Dark	Newell et al. (2011)

Values with * correspond to rates that were calculated based on the accumulation of the ¹⁵N in both NO₂^- and NO₃^- pools, instead of NO₂^- pool. Values with ** correspond to rates that were calculated based on the accumulation of the ¹⁵N in the NO₃^- pool only. The type of system, the depth sampled, the range of ambient ammonium (NH₄⁺) concentrations and the light conditions during incubation are reported.