One aim of the physical sciences has been to give an exact picture of the material world. One achievement of physics in the twentieth century has been to prove that that aim is unattainable . . . . There is no absolute knowledge. And those who claim it, whether they are scientists or dogmatists, open the door to tragedy. All information is imperfect. We have to treat it with humility. Bronowski (1973) The Ascent of Man It seems particularly appropriate to us to begin this book with Jacob Bronowski's passionate message firmly in mind. Those who set out to construct numerical models, especially ones that are mechanistic and essentially deterministic, must work always with this awareness as a backdrop for their efforts. But this is also true for the most meticulous physiologist or observant naturalist. We are all dealing with simplifications and abstractions, all trying to figure out how nature works. Unfortunately, this common pursuit does not always lead to mutual understanding, and we have become increasingly aware over the past six years that many ecologists feel a certain hostility or at least distrust toward numerical modeling. In a number of cases the reasons for such feelings are personal and very understandable-hard­ gotten data skimmed off by someone with little appreciation for the difficulties involved in obtaining reliable measurements, grandiose claims of predictability, the tendency for some model builders to treat other scientists as number-getters whose research can be directed in response to the needs of the model, etc.

Inhalt

1. Perspectives.- 1.1 The Evolution of Ecosystem Models.- 1.2 The Modeling Process.- 1.3 Narragansett Bay.- 1.3.1 Physical Setting.- 1.3.2 Biology.- 2. The Narragansett Bay Model.- 2.1 General Formulation Strategy.- 2.2 A Conceptual Overview.- Theoretical Formulations.- 3. Physical Forcing Functions.- 3.1 Temperature.- 3.2 Solar Radiation.- 3.3 Tidal Circulation.- 3.4 Exchange with Rhode Island Sound.- 3.5 River Flow.- 4. Phytoplankton.- 4.1 Temperature-Growth Relationship.- 4.2 Effects of Nutrients.- 4.3 Effects of Light.- 4.3.1 Theoretical Background.- 4.3.2 Time and Depth Integration of the Steele Equation.- 4.3.3 Light Acclimation and the Selection of Iopt.- 4.3.4 Self-Shading and Extinction Coefficient.- 4.3.5 Sinking Rate.- 4.4 Two Phytoplankton Species Groups.- 5. Zooplankton.- 5.1 General Background.- 5.2 Ingestion.- 5.2.1 Ration, Filtering Rate, and Experimental Observations.- 5.2.2 The Maximum Ration.- 5.2.3 Reducing the Maximum Ration.- 5.2.4 Cannibalism.- 5.3 Assimilation.- 5.4 Respiration.- 5.5 Excretion.- 5.6 Reproduction.- 5.7 Egg Hatching Time.- 5.8 Juvenile Development.- 5.8.1 Growth Rate of Juveniles.- 5.8.2 Development Time.- 5.8.3 Food Limitation.- 6. Additional Compartments.- 6.1 Carnivorous Zooplankton.- 6.2 Adult Fish and Higher Trophic Levels.- 6.3 The Benthos.- 6.3.1 Grazing by Clams.- 6.3.2 Nutrient Regeneration.- 6.4 Nutrients.- Simulation and Analysis.- 7. Mathematical Considerations and the Computer Program.- 7.1 Instantaneous Rates, Finite-Interval Rates, and Integration.- 7.2 Developing the Computer Program.- 7.2.1 General Comments.- 7.2.2 Digital Computer Simulation.- 7.2.3 The Narragansett Bay Computer Program.- 8. The Tidal Mixing Model.- 9. The Standard Run.- 9.1 Selection of Parameters.- 9.2 Zooplankton.- 9.3 Phytoplankton.- 9.4 General Description.- 9.5 Rates and Mechanisms.- 9.6 Relative Role of Nutrients and Grazing in Phytoplankton Control.- 9.7 Zooplankton Excretion and Benthic Fluxes.- 9.8 Metabolic Carbon Budgets for Zooplankton.- 9.9 Annual Integrals.- 10. The Role of Biological Detail.- 10.1 Light Optima and Acclimation.- 10.2 The "Most Limiting" Nutrient.- 10.3 Two Species Groups and Luxury Nutrient Kinetics.- 10.4 Juvenile Zooplankton and Cannibalism.- 10.5 The Role of Carnivores.- 11. Sensitivity and Stability.- 11.1 Sensitivity Analysis.- 11.1.1 Initial Conditions.- 11.1.2 Hydrodynamic Characteristics.- 11.1.3 Extinction Coefficient.- 11.1.4 Phytoplankton.- 11.1.5 Zooplankton.- 11.1.6 Seasonal Cycles.- 11.1.7 General Implications and the Role of Sensitivity Analysis.- 11.1.8 A Note on Numerical Stability.- 12. Applications and Limitations.- 12.1 Ecosystem Modeling and Environmental Management.- 12.2 Holism and Reductionism.- References.- Author and Subject Index.