248 EISLER 



1972). Mercury also inhibits zoospore activity and subsequent 

 development of sporangia in marine fungi (Schneider, 1972). 



Mercury interferes w^ith enzyme production or activity in marine 

 teleosts, including brain cholinesterase (Abou-Donia and Menzel, 

 1967), blood transaminases and dehydrogenases (Christensen, 1971), 

 hemopoietic Na—K—ATPase activities (Renfro et al., 1974), and liver 

 aminolevulinate dehydrases and other enzymes (Jackim, 1973; 

 Jackim, Hamlin, and Sonis, 1970). Low levels, 5.0 Mg Hg/liter, 

 increased allantoise formation in marine annelids, but higher levels 

 prevent formation (May and Brown, 1973). Enzyme activities may 

 have potential as an early warning system of mercury -induced stress. 

 For example, a concentration of 0.17 fig Hg/liter, one-tenth the level 

 causing growth inhibition of marine hydroids, inhibited the lyso- 

 somal hydrolase staining reaction in that group (Moore and Stebbing, 

 1976). 



Histopathological damage was observed among marine teleosts 

 subjected to 500 [ig Hg/liter; damage was most severe in olfactory 

 organs and in the lateral line system (Gardner, 1975). An observed 

 dose-related increase in mantle tentacle epithelial cells of mercury- 

 treated clams (Fowler, Wolfe, and Hettler, 1975) suggests that 

 histological studies might also make it possible to predict impending 

 mercury stress. 



Mercury affects oxygen consumption and ventilation rates of 

 aquatic animals. Increased respiration of the mollusc Congeria 

 leucophaeta was observed during immersion in 10.0 /ig Hg/liter for 

 48 hr (Dom, 1974). Concentrations of 3.0 /ig Hg/liter caused a 

 significant increase in "cough frequency" of trout, and this may 

 alter oxygen consumption in that species (Drummond, Olson, and 

 Batterman, 1974). Larvae of the fiddler crab Uca pugilator exposed 

 to 1.8 fig Hg/liter for 24 hr showed a marked reduction in swimming 

 ability and reduction in general metabolic processes, including 

 oxygen consumption (DeCoursey and Vernberg, 1972). Marine 

 teleosts exposed for 60 days to 10.0 /ug Hg/liter exhibited elevated 

 respiration rates, and, at 5.0 jug/liter, there were increases in plasma 

 proteins and decreases in plasma osmolality (Calabrese et al., 1975). 



Studies with antifouling compounds suggest that mercury is 

 relatively ineffective in preventing metamorphosis of barnacles 

 attached to glass plates (Clarke, 1947). Some mariculture studies 

 have indicated that low concentrations of mercury salts for short 

 periods have either no measurable effect or beneficial, therapeutic, or 

 prophylactic applications (Green et al., 1976; Rodgers et al., 1951; 

 Rucker and Amend, 1969). The preponderance of studies, however, 

 seems to demonstrate that mercury adversely affects several vital life 



