We assembled a dataset of 14C-based productivity measurements to understand the critical variables required for accurate assessment of daily depth-integrated phytoplankton carbon fixation (PP,,) from measurements of sea surface pigment concentrations (C,,,). From this dataset, we developed a light-dependent, depth-resolved model for carbon fixation (VGPM) that partitions environmental factors a...

In this course we will, of course, cover the autotrophs or phytoplankton, which is responsible for the genesis of approximately 70% of the world’s atmospheric oxygen. For these organisms to inhabit the open water, it is pertinent that they remain in the upper waters that have the highest light intensity (euphotic zone). However, since the euphotic zone is prone to turbulence (induced by wind, t...

The use of several light-related variables, such as the Secchi disc depth, euphotic and in particular, diffuse attenuation coefficient (Kd), is deeply rooted phytoplankton research, but these are not most appropriate indicators amount light available for photosynthesis. We argue that variable interest mean intensity mixed layer (Im), which represents to cells exposed throughout their life cycle...

[1] The rate of oxygen utilization beneath the sunlit surface ocean provides a measure of the export rate of biologically produced carbon to the deep sea, and its variation with depth suggests where remineralization of that carbon occurs. The latter consideration is relevant to the efficiency of carbon sequestration in deep water. However, accurate characterization of this process, particularly...

A long time-series study was conducted over 15 yr (1989–2004) to measure particulate organic carbon (POC) flux as an estimate of food supply reaching .4,000-m depth in the northeast Pacific. Sequencing sediment traps were moored at 3,500-and 4,050-m depth, 600 and 50 m above the seafloor, respectively, to collect sinking particulate matter with 10-d resolution. POC fluxes were compared with thr...

We present the first measurements of nitrogen isotopic composition (δ15N) in suspended particulate matter (SPM) of the surface Bay of Bengal (BOB) at 24 different locations during pre(April–May 2003) and post(September– October 2002) monsoon seasons. The δ15N values of particulate organic nitrogen (PON) in surface suspended matter of coastal and northern open BOB show mixing between continental...

The input of new nitrogen into the euphotic zone constrains the export of organic carbon to the deep ocean and thereby the biologically mediated long-term CO2 exchange between the ocean and atmosphere. In low-latitude open-ocean regions, turbulence-driven nitrate diffusion from the ocean's interior and biological fixation of atmospheric N2 are the main sources of new nitrogen for phytoplankton ...

The magnitude of the flux of biogenic particulate organic carbon (POC) exported from the surface waters of the world ocean and remineralized at depth is critical to constraining models of the global carbon cycle, yet remains controversial. The use of upper ocean sediment traps is still one of the primary tools for determining this export flux, although trap fluxes have been shown to vary signif...