**5. Conclusion**

It is now becoming clear that the movement away from thermodynamic equilibrium, and the subsequent increase in organization during ecosystem growth and development, is a result of system components and configurations that maximize the flux of useful energy and the amount of stored exergy. Both empirical data, as well as theoretical models, support these conclusions. Exergy is widely used in ecology to analyze theoretical problems and to solve applied tasks. The most perspective use of exergy parameters in recent ecology is the use of them as ecosystem health indicators.

Some Applications of Thermodynamics for Ecological Systems 337

**0 10 20 30 40 50 60**

**0 10 20 30 40 50 60**

Fig. 8. Dynamics of system (26) without external perturbations.

Fig. 7. Dynamics of system (25) at income of pesticide, causing death of 10 % of phytoplankton, together with nutrients (10% of ecosystem strorage). Y-axis – biomass (kJ m-2), X-

**x1 x2 x3**

> х11 х21 x3 x12 x22

**0**

axis – years.

**0**

**2**

**4**

**6**

**8**

**10**

**12**

**14**

**5**

**10**

**15**

**20**

**25**

**30 35**

**40**

**45**

Exergy, and, especially structural exergy, is shown to be a good health indicator for ecosystems in many model, experimental, field and complex case studies.

The application of exergy calculations to long-term dynamics of the lake Baikal plankton demonstrates the steady state of plankton community structural exergy and well observed increase of its total exergy.

Presented model of two competing hypercycles shows: 1) simultaneous coexistence of two ecologically equivalent phytoplankton species obtaining nutrients from the one source; 2) auto-oscillations of all the components included in model in constant environmental conditions, similar to those observed in real ecosystems.

Fig. 6. Idealized scheme of an ecosystem as system of coupled hypercycles.

Exergy, and, especially structural exergy, is shown to be a good health indicator for

The application of exergy calculations to long-term dynamics of the lake Baikal plankton demonstrates the steady state of plankton community structural exergy and well observed

Presented model of two competing hypercycles shows: 1) simultaneous coexistence of two ecologically equivalent phytoplankton species obtaining nutrients from the one source; 2) auto-oscillations of all the components included in model in constant environmental

Bacteria

Alga1

Zoo1

ecosystems in many model, experimental, field and complex case studies.

Fig. 6. Idealized scheme of an ecosystem as system of coupled hypercycles.

conditions, similar to those observed in real ecosystems.

increase of its total exergy.

Alga2

Zoo2

Fig. 7. Dynamics of system (25) at income of pesticide, causing death of 10 % of phytoplankton, together with nutrients (10% of ecosystem strorage). Y-axis – biomass (kJ m-2), Xaxis – years.

Fig. 8. Dynamics of system (26) without external perturbations.

Some Applications of Thermodynamics for Ecological Systems 339

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