Bayne and his colleagues argue that physiological responses that may be inte- 

 grated into the ability of the organism to grow have been shown to be effective 

 indices in both field and laboratory studies. This study of "scope for growth" seeks 

 measurements of the changes in feeding rate, absorption efficiency, excretion, and 

 respiration rates and introduces them into a balanced energy equation. A decline in 

 growth potential is a clear sign of a stress. Any statistically valid evidence of a 

 decrease might constitute an endpoint. 



Metals in excessive amounts are known to interfere with enzyme systems. For 

 example, cadmium and mercury can displace copper or zinc from metalloenzymes 

 such that the enzyme is rendered inactive. However, in many organisms detoxifi- 

 cation activity is a response to metal stresses. This mechanism involves the binding of 

 the metal to the low molecular weight protein, metallothionen. The amounts of the 

 metals bound to metallothionen will increase with increasing exposure levels to a 

 saturation state. At this point, the metals will spill over into the higher molecular 

 proteins in the enzyme pool. When the binding capacity of metallothionen is sur- 

 passed, measurable toxic effects occur such as a decreased growth rate. The spillover 

 point then corresponds to the endpoint. M ussels are known to detoxify heavy metals 

 with metallothionen. 



The partitioning of metals into lysosomes in kidney, digestive gland, gut, gill, and 

 blood cells is presented as a detoxifying mechanism for mussels (Lowe and Moore, 

 1979). As the levels of metals in the lysosomes increase in mussels, the lysosomal 

 latency decreases. As a result, hydrolytic enzymes are released into the cytoplasm. 

 Further, as the storage capacity of the lysosome for metals is exceeded, it appears 

 that the metals arealso released into the cytoplasm. Thus, studies on the composition 

 of the cytoplasm can be revealing of stress resulting from collectives of polluting 

 metals. 



Some empirical measurements seem to reflect the stress syndrome. For example, 

 Jeffries ( 1972) indicates that clams reflect pollutant exposures through their taurine 

 to glycine ratios. Acute stresses are indicated when the molar ratio is greater than 5. 

 Normal values are 3 or less, while chronic stresses may be described when the ratio 

 varies between 3 and 5. The theoretical basis for this phenomenon has yet to be 

 discovered. 



Histopathological techniques show great promise in establishing the relative 

 health of animals (Bayne et al., 1980). Recent investigations with mussels from both 

 polluted and nonpolluted environments have revealed a variety of conditions that in 

 general can be identified by different investigators studying the same samples: 

 ( I) hyaline degeneration of the connective tissue of the gills; (2) parasite burdens; 

 (3) increases in the number of mucous secretory cells; (4) gonadal neoplasms; (5) 

 hemopoietic neoplasms; (6) granulocytomas; (7) hemocytic infiltration of tissues; 

 and (8) loss of synchrony in digestive tissues. 



Other avenues might be taken to reveal general stress conditions that so far have 

 been only modestly investigated. Such genetic indices as the breakage of chromo- 

 somes or chromatids might be useful. So far studies with' marine organisms have 

 been carried out with pollutant levels that are generally higher than those ever 

 observed in the environment. Still, such effects might be useful in assessing impacts 

 upon organisms exposed to increased levels of pollution. 



THE FUTURE NEEDS 



Past activities in marine pollution provide a substantial basis for the consideration 

 of waste disposal in the oceans. Clearly, for any given material awaiting disposal, 

 three options are possible: disposal to the atmosphere, to the oceans, or to land. Each 

 has its advantages and disadvantages based on scientific, social, and economic 

 considerations. For example, the burning at sea of toxic halogenated hydrocarbons 

 and the discharge of the resultant water, carbon dioxide, and hydrochloric acid to 

 the atmosphere appears to be a rational option. The storage of high-level radioactive 



14 



