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Feedbacks between oceanic redox states and marine productivity: A model perspective focused on benthic phosphorus cycling
Author(s) -
Wallmann K.
Publication year - 2003
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2002gb001968
Subject(s) - benthic zone , oceanography , environmental science , deep sea , anoxic waters , productivity , pelagic zone , eutrophication , continental shelf , phosphorus , biogeochemical cycle , nutrient , ocean chemistry , seawater , geology , environmental chemistry , chemistry , ecology , biology , organic chemistry , economics , macroeconomics
A new model for the marine cycles of particulate organic carbon (POC), oxygen, nitrate, and phosphorus has been developed and applied to explore the controls and constraints on marine productivity and nutrient inventories. The coupled benthic‐pelagic model uses a new approach for the simulation of the reactive phosphorus turnover (P reac corresponding to the sum of organic P, authigenic P, and adsorbed phosphate) in marine sediments. The simulated POC/P reac burial ratio in shelf, slope and rise, and deep‐sea sediments increases under strongly reducing conditions in agreement with field observation. The model runs revealed that the spread of anoxia in bottom waters may enhance the productivity of the global ocean by one order of magnitude if sufficient nitrate is provided by N 2 ‐fixation. Thus anoxic bottom waters promote eutrophic conditions and vice versa. Additional model runs showed that the productivity and nutrient inventory of the glacial ocean were probably enhanced due to the falling sea level. Marine regression induced a narrowing of the depositional areas on the continental shelves and thereby an increase in the fraction of POC exported to the deep ocean. The accelerated POC delivery, in turn, decreased the oxygen contents of the deep water and thus favored the release of phosphate from deep‐sea and rise sediments. Enhanced recycling of phosphate at the seafloor promoted further POC export in a positive feedback loop.