Modeling the relative contributions of autotrophs and heterotrophs to carbon flow at a Lagrangian JGOFS station in the Northeast Atlantic: the importance of DOC. Limnol. Oceanogr

• Main Authors: Michael J. R. Fasham, Philip W. Boyd
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1999
• Subjects: Northeast Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.3248; http://www.aslo.org/lo/toc/vol_44/issue_1/0080.pdf

A size-structured ecosystem model was developed and fitted to an extensive set of observations of size-fractionated biomass, primary and heterotrophic bacterial production, respiration, particle flux, and zooplankton herbivory obtained on a cruise in the NE Atlantic during 20 days of the spring bloom. Rates of water-column-integrated primary production and heterotrophic bacterial production were used to force the model, and the model parameters were determined by optimizing the model to the remaining observations. A unique model solution was not possible in the absence of dissolved organic carbon (DOC) measurements. By setting a weak constraint on the DOC concentrations (that they should remain broadly constant), a solution was obtained that predicted a small DOC increase during the bloom period; this increase was similar in magnitude to observations in other areas and produced a good fit with the other data. Major conclusions: (1) gross primary production (GPP) was over twice the measured 14C production estimates; (2) phytoplankton exudation was a major source of DOC, and 35 % of the GPP flowed through the DOC and was utilized by the bacteria, with a low gross growth efficiency (17%); (3) 62 % of the community respiration came from organisms �5 �m in size; (4) the major source of food for microzooplankton was phytoplankton 1–5 �m in size, but the mesozooplankton ingested more microzooplankton than phytoplankton; and (5) only 8 % of the total net primary production was grazed by mesozooplankton. These results provide quantitative