Ground water contamination is of increasing concern in the United States because about 50 percent of our drinking water comes from well water. The causes of contamination stem from both point sources and nonpoint sources. Since ground water moves slowly, the contaminant may affect only a small portion of an aquifer for a considerable period of time. Deleterious effects on human health have resulted from pathogenic organisms in ground water and from its toxic chemical composition. It is difficult to estimate the extent of contamination on a national basis as the frequency of instances of contamination is very variable. Remedial actions to clean up aquifers are difficult, expensive, and sometimes not feasible. Many of the laws and regulations that control ground water contamination are designed with other main objectives.

INTRODUCTIONA considerable amount of data now exists on the relationship between metabolism and body size in a wide range of organisms from bacteria and protozoans through to large mammals. Much of this information has been reviewed by Kleiber (1932, 1947), Brody and Procter (1932), Brody (1945), Zeuthen (1947, 1953), Hemmingsen (1950, i960) and Bertalanffy (1957). In general the metabolism has been shown to be proportional to a fractional power of the body weight thus eggs, the larger metazoan poikilotherms and even homoiotherms is proportional to a constant power of the body weight. This factor has been shown to be 0.751 ± 0.015 by Hemmingsen (i960). Superimposed upon this general relationship are variations according to the weight range of the organisms concerned. Thus both Zeuthen (1953) and Hemmingsen (i960) have shown that the value of the constant b for unicellular organisms is approximately 0.7 (Zeuthen, 1953) or 0.751 (Hemmingsen, 1960), whilst that for small metazoans is 0.95 (Zeuthen, 1953) or 1.0 (Hemmingsen, 1960). Finally, the slope of the line relating the metabolism to body size in larger metazoans is 075 (Zeuthen, 1953) or 0.751 (Hemmingsen, 1960). That is, the value for b — 1 in equation (2) is likely to be between -0.3 and -0.249 in unicellular organisms; 0 and -0.05 in small metazoans and approximately -0.249 in larger metazoans.Despite this apparently fundamental relationship between metabolism and body size, there are many instances where for a particular species the relationship may not apply. Indeed in some species the metabolism may vary in its relationship to body weight according to conditions such as salinity, shore level, experimental temperature and acclimation temperature.

The winkle Littorina littorea (L.) feeds mainly when moistened by the tide and is quiescent when exposed to the drying effects of the wind and sun. Upper shore winkles thus experience a reduced feeding time compared with individuals living lower in the intertidal zone, but are able to completely compensate by an increased rate of radular activity when immersed. The rate of radular activity is influenced by the body size of winkles, by experimental temperature and by acclimation temperature, but is mainly modified by the duration of exposure to air which directly controls the rate of radnlar activity on immersion.