Modeling microzooplankton and macrozooplankton dynamics within a coastal upwelling system

A simple nutrient-phytoplankton-zooplankton (NPZ) pelagic ecosystem model coupled to a two-dimensional primitive equation circulation model with explicit mixed-layer physics is config- ured in a coastal setting to study the biological response to idealized wind-driven upwelling conditions. Conventional ecosystem model parameterization, which assumes macrozooplankton as the target grazers, leads to upwelling-induced phytoplankton blooms that exhaust available nutrient supply and whose zonal scale increases with wind duration. Offshore zooplankton maxima result from upwelled water with greater total nitrogen concentrations than initial ambient surface water. Substantial vertical mixing in the surface boundary layer sets the vertical scale of the productivity. Phytoplankton sinking contributes to a nearshore accumulation of total nitrogen, and enhances the magnitude and duration of the phytoplankton bloom. The system responds differently when the zooplankton are parameterized to represent microzooplankton. The phytoplankton and zooplankton maxima have more limited zonal extent, are more independent of the duration of wind forcing, and near-surface nutrient levels remain high over most of the domain. When winds are relaxed, the diminished offshore transport reveals the underlying biological oscillations in the microzooplankton-parameterized ecosystem, and reduced vertical mixing decouples surface from subsurface dynamics. In contrast, the macrozooplankton system relaxes to a steady state supporting limited phytoplankton and large zooplankton levels in the upwelling region.

[1]  P. Franks,et al.  Phytoplankton patches at fronts : A model of formation and response to wind events , 1997 .

[2]  D. Straile.  Gross growth efficiencies of protozoan and metazoan zooplankton and their dependence on food concentration, predator‐prey weight ratio, and taxonomic group , 1997 .

[3]  W. Large,et al.  Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization , 1994 .

[4]  D. Menzies,et al.  Patterns of primary productivity and biomass in a coastal upwelling region , 1981 .

[5]  S. Neuer,et al.  Protist herbivory in the Oregon upwelling system , 1994 .

[6]  H. Ducklow,et al.  A nitrogen-based model of plankton dynamics in the oceanic mixed layer , 1990 .

[7]  S. Strom,et al.  Comparative growth rates and yields of ciliates and heterotrophic dinoflagellates , 1998 .

[8]  J. Steele.  The Structure of Marine Ecosystems , 1974 .

[9]  John Moisan,et al.  Modeling Nutrient and Plankton Processes in the California Coastal Transition Zone , 1994 .

[10]  J. Steele,et al.  The role of predation in plankton models , 1992 .

[11]  P. A. Newberger,et al.  Downwelling Circulation on the Oregon Continental Shelf. Part I: Response to Idealized Forcing , 1995 .

[12]  P. Franks.  New models for the exploration of biological processes at fronts , 1997 .

[13]  G. Mellor,et al.  Development of a turbulence closure model for geophysical fluid problems , 1982 .

[14]  J. G. Field,et al.  The size-based dynamics of plankton food webs. I. A simulation model of carbon and nitrogen flows , 1991 .

[15]  P. Delecluse,et al.  Comment [on “Net diffusivity in ocean general circulation models with nonuniform grids” by F. L. Yin and I. Y. Fung] , 1992 .

[16]  A. Huyer,et al.  Phytoplankton and photosynthetic light response in the Coastal Transition Zone off northern California in June 1987 , 1991 .

[17]  Glenn R. Flierl,et al.  Behavior of a simple plankton model with food-level acclimation by herbivores , 1986 .

[18]  D. Halpern.  Structure of a coastal upwelling event observed off Oregon during July 1973 , 1976 .

[19]  E. Hofmann,et al.  Plankton dynamics on the outer southeastern U.S. continental shelf. Part II: A time-dependent biological model , 1988 .

[20]  K. Denman,et al.  Time scales of pattern evolution from cross‐spectrum analysis of advanced very high resolution radiometer and coastal zone color scanner imagery , 1994 .

[21]  Steven H. Strogatz,et al.  Nonlinear Dynamics and Chaos , 2024 .

[22]  The stability of an NPZ model subject to realistic levels of vertical mixing , 2000 .

[23]  F. Chavez,et al.  Horizontal transport and the distribution of nutrients in the coastal transition zone off Northern California: effects on primary production, phytoplankton biomass and species composition , 1991 .

[24]  John H. Steele,et al.  The Structure of Plankton Communities , 1977 .

[25]  J. Wroblewski,et al.  A model of phytoplankton plume formation during variable Oregon upwelling , 1977 .

[26]  David M. Glover,et al.  A new coupled, one-dimensional biological-physical model for the upper ocean: Applications to the JGOFS Bermuda Atlantic Time-series Study (BATS) site , 1996 .

[27]  M. Carr.  A numerical study of the effect of periodic nutrient supply on pathways of carbon in a coastal upwelling regime , 1998 .

[28]  K. Denman,et al.  A coupled 1-D biological/physical model of the northeast subarctic Pacific Ocean with iron limitation , 1999 .

[29]  I. Fung,et al.  Net diffusivity in ocean general circulation models with nonuniform grids , 1991 .

[30]  J. R. Nelson,et al.  Grazing, growth and mortality of microzooplankton during the 1989 North Atlantic spring bloom at 47°N, 18°W , 1993 .

[31]  Graeme C. Wake,et al.  The dynamics of a model of a plankton-nutrient interaction , 1990 .

[32]  K. Banse.  Grazing, Temporal Changes of Phytoplankton Concentrations, and the Microbial Loop in the Open Sea , 1992 .

[33]  V. A. Ryabchenko,et al.  What causes short-term oscillations in ecosystem models of the ocean mixed layer? , 1997 .

[34]  Glenn R. Flierl,et al.  An Ocean Basin Scale Model of plankton dynamics in the North Atlantic: 1. Solutions For the climatological oceanographic conditions in May , 1988 .

[35]  Adriana Huyer,et al.  The nature of the cold filaments in the California Current system , 1991 .

[36]  Geneviève Lacroix,et al.  Influence of meteorological variability on primary production dynamics in the Ligurian Sea (NW Mediterranean Sea) with a 1D hydrodynamic/biological model , 1998 .

[37]  D. Gifford.  Impact of grazing by microzooplankton in the Northwest Arm of Halifax Harbour, Nova Scotia , 1988 .

[38]  Ricardo M. Letelier,et al.  Decorrelation scales of chlorophyll as observed from bio-optical drifters in the California Current , 1998 .

[39]  E. Hofmann,et al.  Modeling nutrient and plankton processes in the California coastal transition zone. 1. A time- and depth-dependent model , 1996 .

[40]  M. Landry.  The structure of Marine Ecosystems: An alternative , 1976 .