surveys of other flora and fauna (species diversity) that would probably be 

 applicable to that time and place only. Also, field studies are somewhat 

 limited to effects evaluation after contamination has occurred and can pro- 

 vide only limited predictability (Brungs and Mount 1978). 



One of the main objectives of recent research has been to establish the 

 necessary measurements essential to predicting pesticide and other contami- 

 nant effects on lentic ecosystems (Boyle 1979a, b). In experimental ponds 

 exposed to herbicides (2,4-D DMA, dichlobenil, and fenac), one to seven 

 characteristics were sufficient to explain 80-90 percent of the differences 

 observed. The seven characteristics found to be most important were pH, 

 alkalinity, turbidity, total dissolved nitrogen, total phosphorus, chloro- 

 phyll a, and zooplankton density. 



Biochemical Characteristics of Ecosystem Stress 



The onset of environmental change in aquatic systems due to stress im- 

 posed by man is often difficult to discern. Even after severe ecological 

 damage has occurred, substantiation requires the collection and evaluation 

 of voluminous amounts of data. Train (1972) has pointed to the need for 

 usable indicators of environmental quality. Indicators of ecological stress 

 would be especially useful if they could be applied at the beginning of 

 ecological disasters, rather than proof that extensive ecosystem change has 

 already occurred. Although there is no well developed literature on this 

 subject, several studies indicate the possibility of using chemical and bio- 

 chemical characteristicss as indicators of ecological stress. Woodwell 

 (1972) cites three qualities of stressed ecosystems, (1) simplification of 

 structure; (2) shifts in the ratio of production to respiration; and (3) 

 loss of inorganic nutrients. Some marine studie-^ have linked specific bio- 

 chemical characteristics with ecological change (Jefferies 1972; Jefferies 

 and Alzara 1970), but similar references are not apparent in the literature 

 in freshwater. The changes in some chemical variables, such as concentra- 

 tion and location of inorganic nutrients, total organic matter and bio- 

 chemical diversity, seem to offer an opportunity to construct a set of 

 symptoms for early detection of ecological contamination. Interpretation of 

 the significance of field-measured changes, however, requires realistic 

 physiological and biochemical studies under experimental conditions. It 

 also requires development and adaptation of chemical methods for measurement 

 of contaminants in biota, sediment, and water. 



RESIDUE DYNAMICS AND BIOCONCENTRATION 



Factors that control the flow of contaminants through an ecosystem have 

 been classified into four major areas: (1) Physical transport and spatial 

 distribution; (2) Interfacial processes; (3) All noninterfacial chemical 

 transformations exogenous to the biota; and (4) Biotransformations (Pavlou 

 et al. 1977). 



The physical transport and spatial dispersion are ecosystem specific and 

 depend on the circulation and flow dynamics associated with the dispersive 



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