phosphorites have not been deposited for the last 100,000 years, and so 

 this mechansism for the removal of calcium and fluoride is not active 

 at the present time. 



Sulfate reduction by bacteria and the formation of pyrite, particularly 

 in deltaic sediments, is apparently the major life process that significantly 

 changes sulfate concentrations in the sea over long time periods (Berner, 

 1971). Further studies of this important "sink" are necessary for a 

 total understanding of the impact of life processes on the major con- 

 stituents. 



In considering the impact of life process on the major constituents, 

 the inverse relationship, that is, the effect of the major constituents on 

 life processes, should not be neglected. Questions remain concerning 

 the changes in the chemical composition of the ocean with time, whether 

 or not life processes had a part in changing the concentrations of the 

 major constituents, and changes in inputs and sinks for the major con- 

 stituents. These are all chemical oceanographic research areas requiring 

 further investigation. 



IMPACT OF LIFE PROCESSES ON HEAVY METALS 



Heavy metals, important trace components of the ocean, may func- 

 tion in both the regulation and stimulation of biological processes. 

 Seven metals (Mn, Cu, Zn, Mo, Co, Mg, and Fe) have known biological 

 functions and are required in varying concentrations for growth and 

 metabolism of all organisms. Of this group, copper and zinc have been 

 found in toxic concentrations in the marine environment. Other heavy 

 metals (including Sb, As, Pb, Cd, Cr, Hg, Ni, Ag, Sn, Se, and V) are 

 found in organisms in concentrations that are high in comparison to 

 the surrounding medium (Brooks and Rumsby, 1965). Many of these 

 elements are highly toxic; lead, chromium, mercury, selenium, silver, 

 and antimony have been identified as agents of the greatest environ- 

 mental concern. Perturbations to the natural flux of trace elements 

 into geochemical cycles are imposed by man's activities, and these are 

 important to ecosystem functions. Natural control of ecosystems may 

 well depend upon synergism and antagonism of heavy metal interactions, 

 and relatively small perturbations caused by man may overload normal 

 cycles and temporarily drive the system in a nonequilibrium direction. 

 Uncontrolled stresses may drive the system beyond its ability to recover 

 and could result in long-term or permanent damage. 



Contemporary State of Knowledge 



Our knowledge of the distribution, chemical forms, and fate of the 

 trace metals in the oceans is inadequate to relate their chemistry to 



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