Investigating phytoplankton-grazer dynamics at the deep chlorophyll maximum: A model-data comparison
Abstract
Biogeochemical models are primarily validated against sea surface chlorophyll. However, the vertical structure of phytoplankton biomass and production is important for determining the depth at which sinking particles are produced in the ocean and the regions where respiration begins to exceed photosynthesis. The vertical structure of phytoplankton is also crucial for predicting prey availability for many taxa that live at discrete depths in the pelagic ocean. In most plankton functional group (PFG) models, the deep chlorophyll maximum (DCM) is too shallow in oligotrophic regions. Even models that correctly simulate the depth of the DCM, incorrectly identify DCM dynamics. Models maintain phytoplankton biomass at the DCM through a combination of low C:Chl ratios and high phytoplankton growth rates. However, in situ growth and grazing rate measurements from diverse regions suggest that growth rates at the DCM are substantially lower than in the mixed layer. High phytoplankton biomass is maintained because grazing (i.e. mortality) rates are depressed in the DCM. In this project we investigate DCM dynamics in the Gulf of Mexico using a combination of 1) in situ depth-stratified growth and grazing rate measurements and 2) a biological-physical coupled simulation of the Gulf of Mexico using a modified NEMURO model.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B51F2003S
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0434 Data sets;
- BIOGEOSCIENCESDE: 1635 Oceans;
- GLOBAL CHANGEDE: 4806 Carbon cycling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL