Regulation of phytoplankton carbon to chlorophyll ratio by light, nutrients and temperature in the Equatorial Pacific Ocean: a basin-scale model

Abstract

Abstract. The complex effects of light, nutrients and temperature lead to a variable carbon to chlorophyll (C:Chl) ratio in phytoplankton cells. Using field data collected in the Equatorial Pacific, we derived a new dynamic model with a non-steady C:Chl ratio as a function of irradiance, nitrate, iron, and temperature. The dynamic model is implemented into a basin-scale ocean circulation-biogeochemistry model and tested in the Equatorial Pacific Ocean. The model reproduces well the general features of phytoplankton dynamics in this region. For instance, the simulated deep chlorophyll maximum (DCM) is much deeper in the western warm pool (∼100 m) than in the Eastern Equatorial Pacific (∼50 m). The model also shows the ability to reproduce chlorophyll, including not only the zonal, meridional and vertical variations, but also the interannual variability. This modeling study demonstrates that combination of nitrate and iron regulates the spatial and temporal variations in the phytoplankton C:Chl ratio in the Equatorial Pacific. Sensitivity simulations suggest that nitrate is mainly responsible for the high C:Chl ratio in the western warm pool while iron is responsible for the frontal features in the C:Chl ratio between the warm pool and the upwelling region. In addition, iron plays a dominant role in regulating the spatial and temporal variations of the C:Chl ratio in the Central and Eastern Equatorial Pacific. While temperature has a relatively small effect on the C:Chl ratio, light is primarily responsible for the vertical decrease of phytoplankton C:Chl ratio in the euphotic zone.

The Impact of Atmospheric Dry Deposition Associated Microbes on the Southeastern Mediterranean Sea Surface Water following an Intense Dust Storm

“…Thus, assuming a C to chl-a ratio of ∼80 (e.g., Behrenfeld et al, 2005;Wang et al, 2009) and a 106:1 C:P ratio (Redfield, 1934), the addition of the dust-derived P could explain a chl-a enhancement of ∼0.05 mg m −3 above the ambient levels. The chl-a enhancement calculated based on the added P is lower than the overall chl-a change measured following the dust examined here (∼0.08 mg m −3 , Figure S1 and see Discussion below).…”

Description and basic evaluation of Beijing Normal University Earth System Model (BNU-ESM) version 1

“…The soilcarbon scheme will be further improved to simulate the large carbon accumulations in organic peat soils, the stocks and dynamics of organic matter in permafrost. A dynamic marine ecosystem scheme will replace the current iBGC module, the new marine ecosystem scheme has improved parameterizations of dissolved organic materials and detritus , a phytoplankton dynamic module that produces a variable of carbon to chlorophyll ratio (Wang et al, 2009a), and refined nitrogen regeneration pathways (Wang et al, 2009b). Additionally, a three-dimensional canopy radiative transfer model (Yuan et al, 2014) will be adopted to replace the traditional one-dimensional two-stream approximation scheme in the land component to calculate terrestrial canopy radiation more realistically.…”

Seasonal to decadal variations of sea surface pCO2 and sea‐air CO2 flux in the equatorial oceans over 1984–2013: A basin‐scale comparison of the Pacific and Atlantic Oceans

“…We have used observational data sets (e.g., phytoplankton carbon, and chlorophyll) to calibrate the DMEC model for both the equatorial Pacific [Wang et al, 2009] and Atlantic Oceans [Wang et al, 2013], which yield different values for some biological parameters for the two basins (Table 1). The rest of the biological parameters were reported by Wang et al [2008].…”

“…In this study, a basin-scale, fully coupled physical-biogeochemical model that has a carbon chemistry submodel [Wang et al, 2006] is employed to simulate the carbon cycle in the tropical Pacific and Atlantic Oceans. The model faithfully reproduces the general features of phytoplankton dynamics in the equatorial surface waters of these two oceans [Wang et al, 2009[Wang et al, , 2013. This study consists of model validations of sea surface pCO 2 and air-sea CO 2 flux, using available data, including the latest Surface Ocean CO 2 Atlas (SOCAT) [Pfeil et al, 2013].…”