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A one-dimensional water quality model, Gulf of Mexico Dissolved Oxygen Model (GoMDOM-1D), was developed to simulate phytoplankton, carbon, nitrogen and phosphorus in the northern Gulf of Mexico. The model was calibrated and corroborated against a comprehensive set of field observations and process measurements. Model results fit measured nutrients and phytoplankton concentrations well, but the model was unable to sustain dissolved organic carbon and water-column respiration at measured levels. The decline in modeled dissolved organic carbon (DOC) and respiration supports the notion that autochthonous production of DOC was insufficient to offset the respiratory demand from bacterial processes for the most of the Louisiana continental shelf. Transport of carbon from high production areas close to the Mississippi and Atchafalaya River plumes likely supplied a part of the respiratory demand of the water column. Modeling results showed that DOC in the study area on the Louisiana shelf was very labile with the highest lability during the month of June, and decreased lability in April. Primary production at the study sites was mainly nitrogen limited, although phosphorus limitation was found in the surface layers for the areas most impacted by the Mississippi River plume. The model also provided insights into the interplay between nutrients and light in regulating phytoplankton production, which is important when predicting the location and extent of hypoxia in the Gulf of Mexico. Published by Elsevier B.V.