A Dynamic State of Closed Ecosystem and Generation of the Earth's Environment

Shigeru Moriyama, Mitsuko Takahara and Gakuji Nomoto*

College of Industrial Technology, Nihon University, Narashino, Chiba 275

*Department of Agriculture, Tokyo University, Tokyo 113


The earth forms a living-system and is one of huge closed ecosystems (CES). We are performing various experiments to study the living-system and the nature of microcosmic type CES. In this paper, we show some interesting experimental results of behaviors of CES mainly at a changeover process from a semi-open state to a perfectly closed state. And we report very noteworthy phenomena on instability of CES which may be included inherently in CES. From the above experiments, we suggest that CES possesses some important properties to elucidate the nature of the actual earth as a living-system, and that climatic changes, such as oceanic anoxia events and the accompanying changes emerged on the ancient earth, could be brought, not by any substantial and special cause but by a slight disturbance to CES.

1. Introduction

The earth forms one of huge closed ecosystems. Closed ecosystem (CES) is characterized by materially closed but energetically open system. CES is categorized into two kinds of type in their characteristics. One is CES of a space station type, and another is of microcosmic type. The actual earth is never the CES of a space station type which is controlled and supported for the human survival, by man, mechanical and electric powers. The actual earth's ecosystem has been developing in autonomous and holistic order. So, CES of microcosmic type is quite suitable for a model of the earth.

Until now we have made three experimental apparatus of microcosmic type CES named CES#1-#3. Each container with about 40 - 60 cm diameter is filled halfway with water, and the upper part in the container has an atmosphere. In the container, at first there were water plants, aquatic and semi-aquatic animals such as beeshrimps and snails, and pebbles. The container is placed within a water-bath to maintain a constant temperature of 25C. The system is lighted with an artificial sun-light: the study given in this paper was made by 24 hours-lightening. Various measuring tools are connected to the apparatus. We are measuring in real time O2 and CO2 concentrations in the atmosphere and dissolved O2 concentration in the hydrosphere. ATP measurements are made to obtain the numbers of living and dead bacteria in water, and chemical measurements are also performed to research water qualities.

We have performed various experiments for a few years, using the above three apparatus of the microcosmic type CES developed by us (CES#1 is not running now, and CES#3 is operating to collect data in the state of the 'open'). In this paper, we will show interesting results of behaviors of CES#2 mainly in a switchover process from a 'open' system to a 'closed' system. Here, the word 'open' means a state of CES which has been exposed to the open air by opening the top part of the container in about 5 cm-width.

At first, we have carried out some experiments with CES#2 about one year by using the 'open' system. Waiting for a suitable time, then we have closed the container perfectly to make 'closed' state. We compare the behaviors of these two systems and investigate dynamic states of these systems.

2. Characteristics of CES

Intuition seems to tell us that CES is pretty polluted since green algae (Rhizoclonium sp.) are surpassing other water plants and grow thickly. But it is wrong. Regardless of 'closed' or 'open', water qualities in these ecosystems are rather pure than not. The numbers of living and dead bacteria in CES, for instance, are nearly equal to those in the water collected from natural spring water to drink. The reason why the numbers of bacteria in CES fall below expectations is brought about from the fact that lives in CES are not free to display all of their abilities, because lives are trying to live together in mutual prosperity by holding down demonstration of their abilities.

The pH of the hydrosphere in CES is high. In general the value is over 8.5, regardless of 'closed' or 'open'. And CES in the state of perfectly 'closed' has the value over 9.0 of pH. These high values of pH are due to the release of ammonia ejected finally from animals in case of decomposition of protein. Although nitrifying bacteria oxidize ammonia aerobically into nitrite(by nitrite bacteria) and nitrate(by nitrate bacteria), the closed and narrow space in CES would contribute to rise the value of pH up.

But the value of pH seems to keep near constant as long as the ecosystem is lasting. The data of concentrations of NH3(`0 mg/l), NO2 (0.005 mg/l) and NO3 (`0 mg/l) ions in the hydrosphere of CES definitely indicate activation of the nitrifying bacteria in CES. Purifying the hydrosphere in CES by oxidizing ammonia, they act to retain a stable state of the system. This is the reason CES sustains near constancy of pH against release of harmful ammonia into the hydrosphere, and is one of regulations of 'living system'.

3. About 'open' system

Input to 'open' system is light and CO2 for photosynthesis from the open air. Since the 'open' system is exposed to the infinite amount of air, it is possible in theory for organic bodies to propagate as much as they like. But, a high increase in organism is a characteristic only in the developing stage seen at the early stages of the system, and in the period of maturity a constant amount of organisms is maintained to sustain the ecosystem stably. Supported by infinite amount of resources, the 'open' system works stably consuming the resources moderately.

The numbers of living and dead bacteria are comparable at the early stages of the system, and they had repeated to increase and to decrease out of phase each other. This is a regulating behavior to stabilize the young system. In the developing stage, the number of bacteria is 10 times or more larger than that in the maturity period. In the period of maturity, regardless of 'open' or 'closed'(CES#"), the number of living bacteria is always much larger than that of dead ones except the times of some changes. These are phenomena common to CES#2 and #3.

In summary, 'open' system is working photosynthesis by consumption of CO2 from an open air which has an infinite amount of resources, and, keeping more amount of organism than in 'closed' system, it is ejecting waste matter largely. A chain of these processes is continuing stably in case of 'open' system.

And the systems of, for instance, rumen and hyponica also fall under the category of this 'open' system.

4. Behavior in transition from 'open' to 'closed' system

The behavior of CES just after perfectly closing is very stimulative.

First, dissolved O2 concentration in the hydrosphere had dropped abruptly. Near the bottom of the container (30 cm in depth from the water surface) it decreased rapidly from 12 ppm to 0 - 0.8 ppm in only 4 days. And it restored the concentration at a slower speed and became 10 ppm in a month. Here, it should be noted that an anoxic state can be made comparatively easily in the hydrosphere of CES by some disturbance.

Second, O2 gas concentration in the atmosphere of CES also decreased sharply in about 1 %, but got back again in 3 days. CO2 gas concentration in the atmosphere decreased rapidly, together with decrease in O2 concentration, from 0.02 % to near 0 % (lower limit of the measuring instrument). This shows that all the CO2 released into closed space is used immediately for photosynthesis and thus circulating.

The regulating behavior to the abrupt disturbance is also recorded clearly in variations of oscillating periods of atmospheric O2 and CO2 concentration. The most prominent oscillation period in 'open' system was 0.5 - 1.5 days. After closing, it shifted quickly to shorter periods of 6 - 7 hours and of 1.5 hours.

These are regulating responses of the system to a disturbance of an abrupt closing of CES.

5. Instability of CES

It deserves special mention that the CES we are observing might actually possess instability. The following two cases (a) and (b) support the suggestion.

(a): We had supposed that the temporary opening of the 'closed' system could not damage the system so much, because the 'closed' system had been maintaining a near constant status for 46 days after the closing and especially keeping the atmospheric O2 concentration near constancy of 21% which is almost the same condition as an open air. So, even if a temporary opening is imposed upon the system, the circumstances around the CES are supposed to be unchanged as long as no other disturbances are assigned to the system. In fact, we imposed no other disturbances than a temporary opening of the top of the container.

But, no sooner had we opened the CES#2 temporarily for only one hour than the O2 concentrations both in the atmosphere and dissolved in the hydrosphere began to drop down suddenly. The O2 concentration in the atmosphere dropped down from around 21% to about 15% in 40 days. Photosynthetic mechanism of the system seems to have been out of order as a whole; although at the present we cannot give a detailed explanation on the mechanism, it would not be so simple. The green algae which covered vigorously with the water surface decreased sharply. This is thought to induce the sharp drop of the atmospheric O2 concentration of the CES.

The dissolved O2 in the hydrosphere of the CES showed a little different behavior from one of the atmospheric O2. Although, showing ups and downs, the dissolved O2 concentration also decreased rapidly from around 10 ppm to about 6.5 ppm in only 10 days, it had restored again toward 9 ppm in two weeks after the temporary opening. Green algae became again very fresh in the hydrosphere except at the surface, covering the bottom of the container with vigor, and thus reformation of the damaged system is likely to be made persistently.

(b): Another abrupt unexpected changes of the state of the CES#2 had happened after three months of the case (a), when a light was turned off for one days. The stable state of the system of long standing had been destroyed in an almost instant. O2 concentration in the atmosphere had decreased from about 19% to 12% in 10 days, and on the contrary CO2 concentration had increased from about 0% to 1.7% in 12 days. Furthermore, more shocking movement was observed at the dissolved O2 concentration in the hydrosphere; in almost one day, it had dropped sharply in only one day from some 25% toward mere 4% (Fig.1). The green algae which had been covering vividly with the hydrosphere (and also snails) were damaged badly, remaining some small patches of green algae in the bottom of the hydrosphere. The number of living bacteria have become ten times as large as that before the destruction, while the number of dead ones remains unchanged. The value of pH had also shown a dramatic change from 9.5 to 7.5.

The result of (b) demonstrates that influence of the photosynthetic living things has been waning abruptly by the darkening, and as a result the nature of the system had transferred to another one. We think that the leading figures supporting the system had been rearranged completely; both methane bacteria and methane-oxidizing bacteria may have become influential and emit CO2, decomposing organic matters.

And furthermore, the result of (b) gives one important suggestion for mechanism of climatic changes: (i) first of all, a change of anoxia event would break out suddenly in the hydrosphere and then it will appear slowly in the atmosphere; (ii) the system without photosynthetic living things would have an environment enriched with CO2 gas as proposed by the Lovelock's gaia theory.

The fact that similar phenomena, as in (a) and (b), had happened twice in CES deserves attention and would suggest universality of this phenomenon. The events happened in (a) and (b) tell us that CES which looks like stable at a glance might actually be very unstable, and even by a slight disturbance it would be transferred toward another unexpected state. However, on the other hand, as shown in (a) CES certainly has a latent regulating ability against damages. Thus, CES has the same characteristics as 'chaos', while, different from chaos, CES has an autonomous latent ability to regulate persistently.

AS also indicated above, this nature peculiar to CES seems to be very important to the mechanism of climatic changes of the earth. By a slight disturbance, the earth which is composed of a huge CES could change its state drastically, as our experiments showed. For instance, the anoxic state in the ocean could be emerged easily not by an external forcing but by the inherent nature of CES-itself. Historical oceanic anoxia events which had emerged on the earth, e.g., 250 million years ago, have been explained until now by changes of oceanic currents and of biotic activities linked with super continental formation. These proposed mechanisms, however, request further problem to solve; that is, why then had the changes of oceanic currents or super continental formation happened? All of these explanations are based upon the point at issue on mechanical responses of the earth system for the given external and powerful perturbations; namely, these theories need a substantial and special cause for emergence of oceanic anoxia events.

But, the earth as a CES may not need such an external, special and mechanical cause, e.g., changes of ocean currents, for an appearance of anoxic ocean, because CES can induce an anoxic state easily in the hydrosphere by the inherent instability of CES-itself. As our experiments indicate, only a slight and any disturbance for the earth as a CES may be enough to bring an anoxic event into the ocean and then large impact into the atmosphere.

The above matters need further study. We are now planning further confirmation of these very interesting phenomena by using CES#3.

6. Concluding remarks

Concerning the characteristics of CES, the following are noteworthy:

i) CES takes dynamic action for creation and regulation of the circumstance and the system-itself. This means that life and its environment in the earth which is a huge CES construct a cooperative system, and they are never separated from each other.

ii) CES is operating with its own oscillation. This is very important to the mechanism on appearance of climatic variation on the earth in the point that, without any external forcing, the earth as a living-system can vary its state.

iii) CES has a possibility for a sudden turn of state of the system by a slight perturbation, but on the other hand it has a persistently restoring ability. Abrupt anoxia events occurring in the hydrosphere should be noted most. This indicates that there exists instability in CES despite of a stable state in appearance, and gives an important suggestion different from the current theories for the mechanism of climatic changes.

We think that it is very important to investigate behaviors of CES, as a living system, in order to grasp the nature of the actual earth system which most obviously is a huge CES.