262 EISLER 



Total mercury levels in soft tissues from bivalves or fish axial 

 musculature should not exceed 500 /Lig/kg wet weight (0.5 ppm). 

 This is the current limit in comestibles set by the Food and Drug 

 Administration. Until additional evidence becomes available it is also 

 suggested that expectant mothers limit to 200 g/week their dietary 

 intake of seafood items containing total mercury concentrations in 

 the 0.3- to 0.5-ppm range. 



6. Conduct research. One of the highest priorities should be 

 assigned to refining the current analytical chemistry methods for 

 detecting mercury. Specifically, procedures must be developed for 

 accurate, precise, and inexpensive determination of mercury at 

 concentrations as low as 0.02 ^ig/liter. 



An equally high priority could be assigned to laboratory studies 

 on lethal, sublethal, and latent effects of mercurials on selected 

 marine indicator species during lifetime exposure. These data do not 

 exist at present. Tests must be conducted in flowing seawater and 

 should, at a minimum, accurately assess mercury effects on survival, 

 growth, behavior, reproduction, accumulation, and histopathology. 

 Results of these studies would provide a basis for a more reasonable 

 assessment of safe levels of mercury in water and would probably 

 result in some modification of the proposed 0.0392 //g/liter value 

 recommended here. 



Field and laboratory investigations of interaction effects of 

 mercury with other constituents in the environment should be 

 conducted. The significance of the apparent protective effect of 

 selenium in marine mammals is a case in point. At present, data on 

 field studies of mercury cycling and effects of mixed wastes 

 containing mercury on community structure are scarce or absent. 

 These studies should be conducted, with a major effort being 

 assigned to roles played by aquatic mammals, fish-eating birds, 

 predatory fishes, higher plants, and mercury-resistant strains of 

 bacteria. Establishment of a nation-wide monitoring program on 

 mercury levels in coastal sediments appears to be a necessary 

 prerequisite for identifying heavily contaminated cireas and selecting 

 appropriate sites for field investigations. 



One of the most important research needs is to develop an early 

 warning system in selected indicator organisms that will forecast 

 generalized stress among marine communities, with emphasis on 

 response parameters peculiar to mercury-induced stress. Within the 

 past decade, multiparametric approaches have been used extensively 

 by industrial toxicologists and others who work with poisonous 

 substances; however, application of these approaches to marine 

 communities is rare and difficult. Typically, mercury-induced stress 



