Primitive Equation Modelling ofPlankton Ecosystems
395
used effectively to "tune" models of the kind developed by plankton ecologists
(Hassell, Lawton and May 1976). 1 shall discuss such tuning later (18.15).
However, there is more to say about the differences between modelling practice
in marine and terrestrial ecology. 1 have emphasized the need to divide ecosystems
into complex non-adaptive ecosystems and complex adaptive ecosystems (18.3).
The former are concemed with micro-organism which can be modelled with biological primitive equations. The latter are concemed with larger organisms, which
can change their minds in unpredictable ways; we cannot devise reproducible
experiments to establish primitive equations for that process. Plankton ecology
falls into the first category; and so does a significant fraction of terrestrial ecology.
The techniques of primitive equation modelling that 1 present in this lecture are
equally applicable to both marine and terrestrial modelling of the population ecology of micro-organisms.
Steele's dilemma need not arise if we limited ourselves to comparing concepts
applicable to plankton and terrestrial microbes, because they are both examples of
complex non-adaptive ecosystems. However, the population ecology of larger
organisms, whether on land (e.g. ants or deer) or in the ocean (e.g. fish or seals),
cannot be addressed usefully by primitive equation modelling. They both fall into
the category of complex adaptive ecosystems. The theoretical ecologist's response
to that difficulty has been to adopt either empirical models fitted to data describing
the animal populations, or idealized population-based models tuned to the data
(Solow 1995). The extensive literature on theoretical population ecology is based
on one or other of those two approaches. The literature on the population ecology
of fish and sea mammals is different from that on terrestrial animals, because the
respective databases are different. The marine databases do not support the kind of
sophisticated modelling that can be achieved with terrestrial databases. That is fons
et origo ofSteele's dilemma.
However, if we restrict ourselves to micro-organisms, we have the much more
powerful option of primitive equation modelling. Biological oceanographers are
motivated to pursue that approach for two reasons. Firstly, it replaces difficult-tocollect data from observations at sea by data acquired from reproducible experiments in the laboratory. And, secondly, it deals with most ofthe biomass in the sea,
which provides the food for fish and mammals. Lacking such motivation, theoretical ecologists concemed with terrestrial micro-organisms have tended to adapt the
methods developed for complex adaptive ecosystems, rather than to develop primitive equation modelling. So Steele's dilemma persists in micro-ecology for historical rather than scientific reasons.
Having introduced theoretical population ecology, 1 shall now describe how it is
practised in primitive equation modelling of the plankton ecosystem.
18.8.2 Demographic time series
Demographic time series are the raw material of population ecology. The demographic variables are birth rate, death rate for each cause of death (starvation, being
eaten, fatal disease, old age or after reproduction), and life expectancy. In classical
395
used effectively to "tune" models of the kind developed by plankton ecologists
(Hassell, Lawton and May 1976). 1 shall discuss such tuning later (18.15).
However, there is more to say about the differences between modelling practice
in marine and terrestrial ecology. 1 have emphasized the need to divide ecosystems
into complex non-adaptive ecosystems and complex adaptive ecosystems (18.3).
The former are concemed with micro-organism which can be modelled with biological primitive equations. The latter are concemed with larger organisms, which
can change their minds in unpredictable ways; we cannot devise reproducible
experiments to establish primitive equations for that process. Plankton ecology
falls into the first category; and so does a significant fraction of terrestrial ecology.
The techniques of primitive equation modelling that 1 present in this lecture are
equally applicable to both marine and terrestrial modelling of the population ecology of micro-organisms.
Steele's dilemma need not arise if we limited ourselves to comparing concepts
applicable to plankton and terrestrial microbes, because they are both examples of
complex non-adaptive ecosystems. However, the population ecology of larger
organisms, whether on land (e.g. ants or deer) or in the ocean (e.g. fish or seals),
cannot be addressed usefully by primitive equation modelling. They both fall into
the category of complex adaptive ecosystems. The theoretical ecologist's response
to that difficulty has been to adopt either empirical models fitted to data describing
the animal populations, or idealized population-based models tuned to the data
(Solow 1995). The extensive literature on theoretical population ecology is based
on one or other of those two approaches. The literature on the population ecology
of fish and sea mammals is different from that on terrestrial animals, because the
respective databases are different. The marine databases do not support the kind of
sophisticated modelling that can be achieved with terrestrial databases. That is fons
et origo ofSteele's dilemma.
However, if we restrict ourselves to micro-organisms, we have the much more
powerful option of primitive equation modelling. Biological oceanographers are
motivated to pursue that approach for two reasons. Firstly, it replaces difficult-tocollect data from observations at sea by data acquired from reproducible experiments in the laboratory. And, secondly, it deals with most ofthe biomass in the sea,
which provides the food for fish and mammals. Lacking such motivation, theoretical ecologists concemed with terrestrial micro-organisms have tended to adapt the
methods developed for complex adaptive ecosystems, rather than to develop primitive equation modelling. So Steele's dilemma persists in micro-ecology for historical rather than scientific reasons.
Having introduced theoretical population ecology, 1 shall now describe how it is
practised in primitive equation modelling of the plankton ecosystem.
18.8.2 Demographic time series
Demographic time series are the raw material of population ecology. The demographic variables are birth rate, death rate for each cause of death (starvation, being
eaten, fatal disease, old age or after reproduction), and life expectancy. In classical