• Primary Productivity — loss of energy-trapping ability to an ecosystem. 



• 



Growth — loss or severe alteration of material-sequestering ability among the 

 trophic levels and their constituents. 



• Reproduction and Development — extreme fluctuations of populations and 

 age-class distributions. 



• Decomposition — interruption in nutrient cycling, mineralization, and mobili- 

 zation. 



• Key Species — loss of species critical to or characteristic of ecosystem function 

 (in contrast to economic or aesthetic values). 



• Structural Diversity — extreme simplification or greatly altered species diver- 

 sity ("richness," relative abundance), either as a result of pollution and a factor 

 in reduced resistance resilience to environmental insult. 



• Endangered Species and Habitats — loss of certain species and or their 

 habitats as a primary legal consideration. 



Ecological studies over the past three decades, notably by the Odum brothers and 

 their co-workers and by the staffs of such laboratories as Oak Ridge and Argonne 

 National Laboratories, have established the interrelationship of these functions of 

 ecosystems. Although the interrelatedness is not fully understood, we have begun to 

 describe the connection between processes and components quantitatively. 



Part of this process information is learned in the field; part comes from the 

 laboratory. These processes are assembled into descriptive statements which, with 

 proper assumptions, became interpretable as mathematical statements or models. As 

 attempts are made to obtain parameters for these models, it has become necessary to 

 perform experiments under the reproducible and controlled conditions of the lab. 

 Moreover, there are a great number of processes about which very little is known. It is 

 therefore desirable to study them as closely at hand as possible. 



Single species assay tests for acute and chronic toxicity and the specific 

 physiochemical measurements characterizing chemical processes in the abiotic 

 environment were developed for screening pollutant problems. Dr. Robert Metcalf 

 and his students and associates at the University of Illinois brought these approaches 

 together (Figure 1) into a chemical test system mimicking some of the features of a 

 "farm pond.'"* Several dozen chemicals have been tested in this system on behalf of 

 the Federal Government, Food and Agriculture Organization (FAO). World Health 

 Organization (WHO), and various companies (Table I). The system is based on 

 application of the chemical to sorghum grow n in sand or soil. The plants are eaten by 

 caterpillars which, along with any grass and debris, fall into the water or decompose 

 on the sand. The aquatic phase then has short, constructed food chains of algae and 

 other pond organisms leading to snails or a mosquitofish. By following the chemical 

 and its transformation products to the terminal repositories, Metcalfe/ al. were able 

 to set forth certain indices suggestive of problematic chemicals. Using the Ecological 

 Magnification (EM) index — the ratio of parent chemical in the selected organism to 

 that of the media, either soil or water — they have shown that the persistent and 

 pervasive chemicals found in the field, such as DDT and other organochlorines, have 

 very high EM values (greater than 3,000). Similarly, these same chemicals show very 

 low Biodegradation Indices (BI) — the ratio of degradation products to residual 

 parent compound — usually less than 0.03. Conversely, easily degraded and poorly 

 accumulated chemicals have BI of over I and EM less than 1. 



At the same time, one could make observations about the lethality or other toxic 

 action of the chemicals. Even if quantitative statements could not be made, a "flag" 

 might be raised for more specific determinations in side experiments. Therefore, 

 organisms were selected for which the principles of the single species assay were 

 generally established: easy rearing, known responses, and representativeness of 

 various phyla to cover a spectrum of sensitivities and possible selective response. The 

 physical environment was kept simple to minimize need for elaborate controls of 

 complex situations which were not understood. 



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