Table

Steps in Developing a Living Model of an Ecosystem

1. Set up physical environmental parameters which provide the framework for the model.

2. Account for chemical and biological effects of adjacent ecosystems as imports and exports with either attached functioning models or simulations.

3. Add first biological elements which provide structure to the model. Typically these are plants or animals in reef structures (oysters or corals).

4. Begin biological additions in community blocks which are manageable units of soil or mud.

5. Repeat biological "injections" to enhance species diversity.

6. Add the larger, more mobile animals, particularly predators or large herbivores last, after plant production and food chains have developed.

7. The human operator takes over functions left out of the model, such as cropping top predators.

Source: Adapted from Adey, W. H. and K. Loveland. 1998. Dynamic Aquaria, 2nd ed. Academic

Press, San Diego, CA.

et al., 1980; Petersen et al., 1998). The study by Nixon et al. (1980) is particularly interesting in describing the incorporation of turbulent mixing in the MERL tanks as a design challenge with many comparisons of measurements of turbulence both within the microcosms and in Narragansett Bay. Their plunger rotated in an elliptical fashion with a variable number of revolutions per minute. Thus, there was considerable engineering required to design, manufacture, operate, and maintain the plunger apparatus. Finally, Sanford (1997) provides a complete review of the issue with great attention to physical processes and assessments of alternative design options. He notes that no existing designs match microcosm turbulence within the real world but some options are better than others.

Walter Adey has developed an approach to building aquatic microcosms that includes matching forcing functions between a model (i.e., the microcosm) and the natural analog. His approach probably derives from his field work, especially on coral reef ecology, where he has shown the importance of "synergistic effects" of different external influences on ecosystems (Adey and Steneck, 1985). This attention to matching forcing functions is included in Adey's stepwise instructions for building effective model ecosystems, as shown in Table 4.2. An example of this approach is the Everglades mesocosm built in Washington, DC near the Smithsonian Institution's National Museum of Natural History where Adey works. This was a greenhouse scale model that was built as a prototype for one of the ecosystems in Biosphere 2. Like the real Everglades it included a gradient of subsystem habitats ranging from freshwater to full seawater (Figure 4.15). The model was successfully operated for more than a decade (Adey et al., 1996), which is a major accomplishment for a system of this size and complexity. The success of the mesocosm was partly due to a matching of forcing functions between the Washington, DC, greenhouse and the Florida Everglades. Figure 4.16 shows an example of this matching for annual temperature patterns. Temperature inside the greenhouse matched closely with data from southwest Florida while temperatures outside the greenhouse in Washington,

Gulf of Mexico Mangrove forest

FIGURE 4.15 Floor plan of the Smithsonian Institution's Everglades mesocosm in Washington, DC. Note: Lengths are in meters. (Adapted from Adey, W. H. and K. Loveland. 1998. Dynamic Aquaria, 2nd ed. Academic Press, San Diego, CA.)

Gulf of Mexico Mangrove forest

FIGURE 4.15 Floor plan of the Smithsonian Institution's Everglades mesocosm in Washington, DC. Note: Lengths are in meters. (Adapted from Adey, W. H. and K. Loveland. 1998. Dynamic Aquaria, 2nd ed. Academic Press, San Diego, CA.)

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