252 EISLER 



Skeletal muscle of teleosts appears to function as a reservoir for 

 methyl mercury (Giblin and Massaro, 1973; Johnels et al., 1967; 

 MacLeod and Pessah, 1973; Middaugh and Rose, 1974; Pentreath, 

 1976b; Weisbart, 1973). Maximum concentration factors of radio- 

 mercury were reached in skeletal muscle, brain, and lens after 34, 56, 

 and >90 days, respectively; maximum values were reached in most 

 other tissues and organs in about 7 days (Giblin and Massaro, 1973). 

 One pathway by which anadromous fishes accumulate mercury from 

 a medium is through the gills; up to 90% of the mercury taken up on 

 the gills is subsequently bound to erythrocytes within 40 min (Olson, 

 Bergman, and Fromm, 1973; Olson and Fromm, 1973). 



The retention time of mercury in marine organisms depends on 

 several factors. Weisbart (1973) found that the gill, heart, and 

 swim-bladder tissues of fish lost mercury at rates faster than the 

 whole organism, but some tissues, including brain, liver, muscle, and 

 kidney, showed no significant decrease with time. In clams radio- 

 mercury seems to have a biological half-life of 10 days if accumu- 

 lated via the food chain but only 5 days if taken up from the water 

 (Unlu, Heyraud, and Keckes, 1972). Retention times of ^°^Hg in 

 most marine species were comparatively lengthy, ranging from 267 

 days for the fish Serranus scriba to 1000 days for mussels, Mytilus 

 galloprouincialis (Miettinen, Heyraud, and Keckes, 1972; Miettinen 

 etal., 1969; 1972). Miettinen and coworkers found that phylogenet- 

 ically related species follow a similar pattern of methyl mercury 

 excretion, with biological half-life depending on water temperature 

 and mode of entry into organisms; it is longer after intramuscular 

 injection than after peroral administration. There is some evidence 

 that mercury excretion rates follow a biphasic or polyphasic pattern 

 (Burrows and Krenkel, 1973; Giblin and Massaro, 1973; Tillander, 

 Miettinen, and Koivisto, 1972; Weisbart, 1973). Tillander, Miettinen, 

 and Koivisto found that, in seals, Pusa hispada, the fastest excreted 

 component took 20 days for 50% elimination and the slowest 

 excreted mercury fraction, which comprised 45% of all mercury, 500 

 days for 50% elimination. 



Field Investigations 



Residues in Water and Sediments 



Mercury levels in coastal seawater from various locations ranged 

 from 0.021 to 0.078 Mg/liter (Dehlinger et al., 1973); concentrations 

 were lower in continental slope water, ranging from 0.010 to 

 0.041 jug/liter. Mercury levels in water were several orders of 



