Box-modelling of the impacts of atmospheric nitrogen deposition and benthic remineralisation on the nitrogen cycle of the eastern tropical South Pacific
نویسندگان
چکیده
Both atmospheric deposition and benthic remineralisation influence the marine nitrogen cycle, and hence ultimately also marine primary production. The biological and biogeochemical relations in the eastern tropical South Pacific (ETSP) among nitrogen deposition, benthic denitrification and phosphorus regeneration are analysed in a prognostic box model of the oxygen, nitrogen and phosphorus cycles in the ETSP. Atmospheric nitrogen deposition (≈ 1.5TgNyr−1 for the years 2000–2009) is offset by half in the model by reduced N2 fixation, with the other half transported out of the model domain. Modeland data-based benthic denitrification in our model domain are responsible for losses of 0.19 and 1.0 TgN yr−1, respectively, and both trigger nitrogen fixation, partly compensating for the NO−3 loss. Modeland data-based estimates of enhanced phosphate release via sedimentary phosphorus regeneration under suboxic conditions are 0.062 and 0.11 TgPyr−1, respectively. Since phosphate is the ultimate limiting nutrient in the model, even very small additional phosphate inputs stimulate primary production and subsequent export production and NO−3 loss in the oxygen minimum zone (OMZ). A sensitivity analysis of the local response to both atmospheric deposition and benthic remineralisation indicates dominant stabilising feedbacks in the ETSP, which tend to keep a balanced nitrogen inventory; i.e. nitrogen input by atmospheric deposition is counteracted by decreasing nitrogen fixation; NO−3 loss via benthic denitrification is partly compensated for by increased nitrogen fixation; enhanced nitrogen fixation stimulated by phosphate regeneration is partly counteracted by stronger water-column denitrification. Even though the water column in our model domain acts as a NO−3 source, the ETSP including benthic denitrification might be a NO−3 sink.
منابع مشابه
Box-modeling of the impacts of atmospheric nitrogen deposition and benthic remineralization on the nitrogen cycle of the eastern tropical South Pacific
متن کامل
Interactive comment on “Box-modeling of the impacts of atmospheric nitrogen deposition and benthic remineralization on the nitrogen cycle of the eastern tropical South Pacific” by B. Su et al
Based on a prognostic 5 box model of the OMZ region in the ETSP published earlier in 2015, the authors focus here on the effects and feedbacks between major sources and sinks in the marine N cycle. They consider in particular the atmospheric deposition and benthic remineralisation. I found this work rather interesting as it tends to show that those processes are important for N cycle in the stu...
متن کاملWhat prevents nitrogen depletion in the oxygen minimum zone of the eastern tropical South Pacific?
Local coupling between nitrogen fixation and denitrification in current biogeochemical models could result in runaway feedback in open-ocean oxygen minimum zones (OMZs), eventually stripping OMZ waters of all fixed nitrogen. This feedback does not seem to operate at full strength in the ocean, as nitrate does not generally become depleted in open-ocean OMZs. To explore in detail the possible me...
متن کاملNitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean
observations, to constrain the pattern of N2 fixation across the Pacific Ocean. N2 fixation introduces isotopically light atmospheric N2 from to the ocean (d N = 0‰) relative to the oceanic average near 5‰, which makes nitrogen isotopes suitable to infer patterns of N2 fixation. Including atmospheric iron limitation of diazotrophy in the model shifts the pattern of simulated N2 fixation from th...
متن کاملContrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones
We present new data for the stable isotope ratio of inorganic nitrogen species from the contrasting oxygen minimum zones (OMZs) of the Eastern Tropical North Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru. Differences in minimum oxygen concentration and corresponding N-cycle processes for the two OMZs are reflected in strongly contrasting δ15N distributions. Paci...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2016