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Temporal variation and stoichiometric ratios of organic matter remineralization in bottom waters of the northern G ulf of M exico during late spring and summer
Author(s) -
Xue Jianhong,
Cai WeiJun,
Hu Xinping,
Huang WeiJen,
Lohrenz Steven E.,
Gundersen Kjell
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc011453
Subject(s) - redfield ratio , dissolved organic carbon , remineralisation , biogeochemical cycle , alkalinity , environmental chemistry , nitrate , oceanography , bottom water , organic matter , chemistry , salinity , nutrient , geology , phytoplankton , inorganic chemistry , organic chemistry , fluoride
An improved extended optimum multiparameter (eOMP) analysis was applied to hydrographic (temperature and salinity), and water chemistry data, including dissolved oxygen (O 2 ), nutrients (nitrate plus nitrite, phosphate, and silicate), dissolved inorganic carbon (DIC), and total alkalinity (TAlk) data collected during late spring and summer from 2006 to 2012 in bottom waters off the Louisiana coast, to explore the dynamics and stoichiometry of DIC production during the development and maintenance of summer hypoxia. Our analysis demonstrated that DIC in bottom water was relatively low from April to June, but increased significantly in July, peaked in August, and dropped slightly in September. Furthermore, DIC production resulted from both aerobic organic carbon (OC) respiration and denitrification, as well as substantial loss due to vertical mixing with surface water. The average summer gross OC respiration rate was estimated to be 0.19 g C m −2 d −1 , with the highest values occurring in late summer when hypoxic conditions dominated. We also found that C org /N/P/‐O 2 remineralization ratios for aerobic respiration were generally consistent with the classic Redfield ratio (106/16/1/138) except individual C/N and C/P ratios were slightly lower, indicating that marine OC was the major source of the DIC production in the bottom water. This study quantified the role of temporal bottom‐water microbial respiration to seasonal DIC dynamics and provided a means for studying the stoichiometry of biogeochemical processes in coastal waters.