Abstract. Biogeochemical models that simulate realistic lower-trophic-level
dynamics, including the representation of main phytoplankton and
zooplankton functional groups, are valuable tools for improving our
understanding of natural and anthropogenic disturbances in marine ecosystems.
Previous three-dimensional biogeochemical modeling studies in the northern
and deep Gulf of Mexico (GoM) have used only one phytoplankton and one
zooplankton type. To advance our modeling capability of the GoM ecosystem and
to investigate the dominant spatial and seasonal patterns of phytoplankton
biomass, we configured a 13-component biogeochemical model that explicitly
represents nanophytoplankton, diatoms, micro-, and mesozooplankton. Our model
outputs compare reasonably well with observed patterns in chlorophyll,
primary production, and nutrients over the Louisiana–Texas shelf and deep GoM
region. Our model suggests silica limitation of diatom growth in the deep GoM
during winter and near the Mississippi delta during spring. Model
nanophytoplankton growth is weakly nutrient limited in the Mississippi delta
year-round and strongly nutrient limited in the deep GoM during summer. Our
examination of primary production and net phytoplankton growth from the model
indicates that the biomass losses, mainly due to zooplankton grazing, play an
important role in modulating the simulated seasonal biomass patterns of
nanophytoplankton and diatoms. Our analysis further shows that the dominant
physical process influencing the local rate of change of model phytoplankton
is horizontal advection in the northern shelf and vertical mixing in the
deep GoM. This study highlights the need for an integrated analysis of
biologically and physically driven biomass fluxes to better understand
phytoplankton biomass phenologies in the GoM.
Characteristics of Phytoplankton Biomass, Primary Production and Community Structure in the Modaomen Channel, Pearl River Estuary, with Special Reference to the Influence of Saltwater Intrusion during Neap and Spring Tides
