Inlet Filter Holder 



Acrylic Plastic 



Outlet 



Filter 



Holder 



Plywood 



Figure 3. The microagroecosystem of Nash and Beall^ is a large (2 x 1 .5 x 0.5 m) 

 monoculture of crop or grass without added fauna. Trapping of material at 

 outlet contributes to mass balance studies. 



• Microcosms can be adapted to specific situations involving a chemical, site, 

 crop, or impacted species/community, without loss of the basic character of 

 the ecosystem; 



• Microcosms can be structured by not only the physical system but also by the 

 use of "expert judgment" to frame research questions in an optimal manner; 



• Multimedia interactions and disposition are evident particularly for bio- 

 accumulation and intermedia transfer rates; 



• The systems provide greater realism, both objectively to the scientists and 

 subjectively to the lay person, than do laboratory tests and are therefore more 

 persuasive regarding the relative hazard or safety apparent from the data. 



At the same time it was necessary to point out several problems: 



• Microcosms are not self-sustaining. 



• Criteria do not presently exist to determine what factors of scale in time and 

 space are significant for a particular kind of information. 



• Criteria have not been established for the accuracy of microcosm data with 

 respect to real ecosystems. Can they be generalized or do they simply represent 

 only some special system (if that)? 



• Requirements for radioactive chemicals in fate studies, for special material and 

 operating controls, and for skilled technical personnel at all levels limit how 

 and by whom these systems might be used. 



• Except for one system, none of the microcosms has been defined in the explicit 

 terms of a mathematical model which can provide extrapolation to other 

 situations. 



• Ecological theory and research have not defined processes adequately, so that 

 their study application in microcosms is generally restricted. 



• Serious questions remain about such matters whether or not larger organisms 

 (e.g., the field mouse, fish or crab) can be included in these systems. 



158 



