18 Primitive Equation Modelling of
Plankton Ecosystems
JOHNWOODS
Imperial College, London
18.1 Introduction
We start with a technical problem that hindered progress in biological
oceanography throughout the 20 th century, and show how it will be circumvented
in the 21 st century. Because of inadequate sampling, very little of our knowledge of
population dynamics in the plankton ecosystem is derived from hypothesis-free
analysis of observations. On the contrary, most of our knowledge comes from
mathematical simulation. But here comes Catch 22: the same sampling problems
make it very difficult to collect data that can effectively test the models used to
make those simulations. So their credibility depends mainly on the equations used
in the models. Equations used in 20 th century models did not have secure scientific
foundations of the kind that made modem physics work. They were not based on
reproducible laboratory experiments.
18.1.1 Biological Primitive Equations
This lecture will show how using primitive equations in ecosystem models can
bring biological oceanography up to the standards by which we address complex
physical phenomena like the weather. It starts by considering whether there are any
primitive equations for biology, of the kind that have been so effective in physics.
This question was first considered by Descartes (1664). Today we answer that they
do not exist for higher animals, because we cannot perform reproducible experiments to describe how animals change their minds when responding to events in
their ambient environment. However, it is possible to establish biological primitive
equations for micro-organisms, which do not have minds to change.
Most plankton are mindless organisms, whose physiology and behaviour are
govemed by rules fixed throughout their lives. These genetically-controlled rules
can be discovered by reproducible laboratory experiments. They are described by
Biological Primitive Equations (BPEs), which are as trustworthy as the primitive
equations ofphysics and chemistry. An ecosystem model, which is based on physical, chemical and biological primitive equations, has sound scientific foundations.
Simulations ofthe plankton ecosystem based on BPE models have credibility, even
when formal verification is skimpy. That is the fundamental message of my lecture.
Plankton Ecosystems
JOHNWOODS
Imperial College, London
18.1 Introduction
We start with a technical problem that hindered progress in biological
oceanography throughout the 20 th century, and show how it will be circumvented
in the 21 st century. Because of inadequate sampling, very little of our knowledge of
population dynamics in the plankton ecosystem is derived from hypothesis-free
analysis of observations. On the contrary, most of our knowledge comes from
mathematical simulation. But here comes Catch 22: the same sampling problems
make it very difficult to collect data that can effectively test the models used to
make those simulations. So their credibility depends mainly on the equations used
in the models. Equations used in 20 th century models did not have secure scientific
foundations of the kind that made modem physics work. They were not based on
reproducible laboratory experiments.
18.1.1 Biological Primitive Equations
This lecture will show how using primitive equations in ecosystem models can
bring biological oceanography up to the standards by which we address complex
physical phenomena like the weather. It starts by considering whether there are any
primitive equations for biology, of the kind that have been so effective in physics.
This question was first considered by Descartes (1664). Today we answer that they
do not exist for higher animals, because we cannot perform reproducible experiments to describe how animals change their minds when responding to events in
their ambient environment. However, it is possible to establish biological primitive
equations for micro-organisms, which do not have minds to change.
Most plankton are mindless organisms, whose physiology and behaviour are
govemed by rules fixed throughout their lives. These genetically-controlled rules
can be discovered by reproducible laboratory experiments. They are described by
Biological Primitive Equations (BPEs), which are as trustworthy as the primitive
equations ofphysics and chemistry. An ecosystem model, which is based on physical, chemical and biological primitive equations, has sound scientific foundations.
Simulations ofthe plankton ecosystem based on BPE models have credibility, even
when formal verification is skimpy. That is the fundamental message of my lecture.