In such tests one may examine histological changes in gills, liver, and 

 pancreas; physiological changes in respiration rates; or enzymatic 

 changes. For example, Hinton, et al . (1973) have found that DDT inhibits 

 the formation of ATP--that is, adenosine triphosphatase. Other enzymes 

 often studied as to the effects of a given waste are d-hydrogenase, acid 

 phosphatase, and carbonic anhydrase. 



In such long-term or chronic tests one often measures the build-up or 

 accumulation of materials within the cells such as heavy metals, radio- 

 active materials, or some of the chlorinated hydrocarbons. Behavioral 

 tests are often used in these long-term chronic tests. For example, Cairns 

 and Scheier (1964) found the dieldrin will interfere with the sight of 

 certain fish at extremely low concentrations, thus they are not able to see 

 their food as well nor, in the case of schooling fish, are they able to 

 school. One also is concerned about the effect upon the fecundity of 

 organisms. Shifts in temperature or chemicals that alter the food species 

 may affect the fecundity of the female and success of offspring. If the 

 fecundity of a species is changed very much it may alter the whole food web. 



Recent work of Patrick et al . (1975) has shown that minute amounts of 

 heavy metals such as nickel, vanadium, and chromium may alter the species 

 composition of the algae in a community and thus greatly change the plant 

 food source of the food web. If such changes occur and the primary produc- 

 tion is carried out by species of low food value, the productivity of the 

 rest of the food chain will be greatly reduced. 



Monitoring may be concerned with changes in individual species in the 

 waters in which they live or with changes in communities. If one is 

 studying one or a few species, such studies are usually carried out by 

 isolating the species under study either in the field or in semi natural 

 conditions. For example, oysters or clams are often sorted as to size and 

 age class and placed into large trays with each oyster or clam being 

 marked; thus over time one can study growth, the attack by disease, and the 

 condition of the oyster or clam in question by sacrificing the individual 

 organism (Figures 1,2). One can also determine the accumulation of heavy 

 metals, or radioactive materials, or of chlorinated or polycyclic hydro- 

 carbons. Thus such studies are valuable not only to monitor the potential 

 of the commercial crop in the area but also to monitor whether or not cer- 

 tain toxicants have passed through the estuary. 



Fish in aquaria are sometimes used to monitor the effect of a given 

 waste as it is being discharged. Cairns et al. (1973) have described such 

 a methodology. Fish can be sacrificed from time to time to discover 

 histological and physiological changes as well as the observations from day 

 to day of death. In such studies of fish or oysters the same organisms may 

 be studied over time and thus the monitoring is continual, although observa- 

 tion may not be continual. More recently, Dr. Burton of the Academy labora- 

 tories has developed methods of inserting probes into crabs and thus being 

 able to continually monitor the heartbeat and various kinds of biochemical 

 changes within the crab. 



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