for much of the complexing of metals in seawater is biologically derived. 

 The organic moiety involved in complexing is not generally known; 

 however, zinc has been found associated with a fulvinic acid type of 

 residue in seawater (Hood, 1967), and part of the copper in some waters 

 is extractable in organic solvents (Slowey et al., 1967). Variable frac- 

 tions of copper, manganese, and zinc occur in nondialyzable forms 

 implying organic complexation (Slowey et al., 1971). 



Modeling 



Modeling of the distribution of heavy metals in the ocean has had 

 limited success because the basic knowledge indicated above is lacking 

 (also see pp. 27). The construction of models should be encouraged — 

 but only after our understanding of their interactions with the biota 

 is improved. 



Future Efforts 



The most clearly identified problem in relating biological systems to 

 the chemistry of heavy metals in the ocean is that of chemical speciation 

 and the effects of these species in controlling or stimulating biological 

 activity. Not until we are aware of the chemical form in which heavy 

 metals interact with biological membranes and are involved in vital 

 life processes, can we obtain useful working models of the manner in 

 which biological processes are controlled by heavy metals or provide 

 detoxification systems against their deleterious effects. 



The complexation of heavy metals with organic molecules has been 

 urmed. The source and structures of the organic portion, the stability 

 of such complexes, and the availability of these complexes to biological 

 systems need careful investigation. The attack must be coupled with 

 biological experimentation that is sensitive to ultrasmall quantities of 

 added trace elements, but this approach must await development of 

 suitable techniques for it to be successful. 



Studies of the spatial and temporal distributions of heavy metals in 

 the ocean are needed, particularly near coasts. These studies should 

 identify the chemical species, ratios of dissolved to particulate matter, 

 association with sediments, and (where possible) the rate of movement 

 between phases. The hypothesis should be carefully tested that sediment 

 removal controls heavy-metal concentrations in the water column at 

 the coastline. 



IMPACT OF ORGANISMS ON MARINE ORGANIC CHEMISTRY 



The organic chemistry of the marine environment is extremely com- 

 plex. The ocean presumably contains most, if not all, of the compounds 



52 



