Simulation study of biological responses to environmental changes associated with coastal upwelling off NW-Africa
A two dimensional model of upwelling and its effects on nutrient and phytoplankton fields has been developed. In it, a phytoplankton population is defined by a set of variables for cell numbers and particulate carbon, nitrogen, chlorophyll, and silica. Phytoplankton growth rate is simulated as a function of concentrations of nitrate, ammonium, and silicate and intensity of photosynthetically active radiation. Grazing losses occur to one species of herbivorous fish and two size classes of zooplankton. Several simulation experiments have been run to study the effects of upwelling in the northwest African coastal ecosystem. Time varying habitat characteristics are defined by independent submodels for physical circulation and solar radiation. Comparisons of simulated results with measurements made during the JOINT-I expedition during 1974 suggest that some observed characteristics may occur as consequences of interactions expressed in the model. Simulations show a flux of nutrient rich water into the euphotic zone supporting high rates of primary production seaward of a turbid nearshore region. High ammonium concentrations, occurring in the nearshore region, are shown in the simulations to be sensitive to physical circulation processes and phytoplankton uptake rates. Given comparable environmental conditions, simulated and observed intrinsic rates of phytoplankton growth are approximately equal. However, rates of primary production during simulated upwelling exceed significantly the losses attributed in the model to phytoplankton physiological mortality and ingestion by herbivores. An underestimate of the significance of grazing related to the vertical distribution and feeding behavior of the zooplankton is tentatively identified as the factor responsible for the discrepancy between observed and simulated conditions.
- Research Organization:
- Brookhaven National Lab., Upton, N.Y. (USA)
- DOE Contract Number:
- EY-76-C-02-0016
- OSTI ID:
- 7028111
- Report Number(s):
- BNL-24204; CONF-780448-2
- Resource Relation:
- Conference: International council for the exploration of the sea, Las Palmas, Spain, 14 Apr 1978
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
AFRICA
COASTAL WATERS
AQUATIC ECOSYSTEMS
DISTURBANCES
PHYTOPLANKTON
UPWELLING
POPULATION DYNAMICS
ENVIRONMENTAL EFFECTS
MATHEMATICAL MODELS
AMMONIUM COMPOUNDS
CARBON
CHLOROPHYLL
FORECASTING
NITRATES
NITROGEN
NUTRIENTS
SILICA
SILICATES
SIMULATION
SOLAR RADIATION
AQUATIC ORGANISMS
CARBOXYLIC ACIDS
CHALCOGENIDES
CRYOGENIC FLUIDS
ECOSYSTEMS
ELEMENTS
FLUIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MINERALS
NITROGEN COMPOUNDS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYTOCHROMES
PIGMENTS
PLANKTON
PORPHYRINS
RADIATIONS
SILICON COMPOUNDS
SILICON OXIDES
SURFACE WATERS
520100* - Environment
Aquatic- Basic Studies- (-1989)
580500 - Oceanography- (1980-1989)