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Untangling the uncertainties about combined effects of temperature and concentration on nutrient uptake rates in the ocean
Author(s) -
Smith S. Lan
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl043617
Subject(s) - biogeochemical cycle , nutrient , environmental science , nitrate , atmospheric sciences , arrhenius equation , environmental chemistry , chemistry , kinetics , physics , ecology , biology , quantum mechanics
I show that assumptions about how uptake rates depend on concentration strongly impact the interpretation of field observations, specifically with respect to the combined effects of temperature, T , and nitrate concentration, [NO 3 ], on nitrate uptake. The standard assumption that maximum uptake rate, V max , is independent of ambient nutrient concentration, S a , contrasts with the prediction of the recently developed Optimal Uptake kinetics that V max should increase hyperbolically with S a . Assuming Arrhenius T dependence, I fit the respective equations to field observations of chlorophyll‐specific V max , T and [NO 3 ]. The inferred sensitivity to T differs by a factor of two. Considerable uncertainty therefore remains about the T dependence of uptake rates, and therefore about biological production and biogeochemical cycles. Given that both climate change and anthropogenic nutrient inputs are altering the relationship between T and nutrients in the ocean, these uncertainties limit our understanding of the direct effects and associated feedbacks.