is upset, causing accumulation to take place. 



Raymont and Shields (1964), in studies with 

 the small prawn, Leander squilla, found a thresh- 

 old level of a litde less than 5 mg/1 Cr. Thus, at 

 chromium concentrations ranging from 10 to 80 

 mg/1 Cr, 100-percent mortality occurred in 1 

 week; at 5 mg/1 Cr no deaths occurred in 1 week 

 although a few animals died over the subsequent 

 21 days. Larger prawns of the same species ap- 

 peared to be considerably more resistant to chro- 

 mium poisoning. The threshold was about 10 mg/1 

 Cr. Raymont and Shields in additional experiments 

 on the toxicity of chromium to crustaceans (the 

 shore crab, Carcinus maenas), indicated that chro- 

 mium concentrations above 50 mg/1 (NaoCrOi) 

 were definitely toxic for a period of exposure of 

 12 days. At 60 mg/1 Cr, 50-percent mortality oc- 

 curred after 12 days. At 40 mg/1 Cr, 9 percent 

 died within 1 2 days, while at 20 mg/1, an 8-percent 

 mortality was observed. In studies on the marine 

 polychaete worm, Nereis virens, these same inves- 

 tigators working in the range of 2 to 10 mg/1 Cr 

 found that there was heavy mortality with all solu- 

 tions in 2 to 3 weeks. The threchold of toxicity ap- 

 pears to be at about 1.0 mg/1 Cr level. 



Pringle (in press), in experiments using a well- 

 controlled, flow-through system and chromium 

 concentrations of 0.1 and 0.2 mg/1 (NajCroO,), 

 showed the average weekly mortality to be ap- 

 proximately 1 percent over a 20-week period. This 

 was about the same as that for the sea water 

 controls. 



Copper. — Copper is found in seawater at a level 

 of 0.003 mg/1. It is found in marine plants at 

 about 1 1 mg/1, while marine animals are found to 

 contain 4 to 50 mg/1. It is accumulated by some 

 sponges and is essential for the respiratory pig- 

 ment in the blood of certain annelids, Crustacea, 

 and mollusks. In excess, it is highly toxic to algae, 

 seed plants, and to invertebrates and moderately 

 toxic to mammals. Copper is not considered to be 

 a cumulative systemic poison like lead or mercury. 



The toxicity of copper to aquatic organisms 

 varies significantly not only with the species but 

 also with the physical and chemical characteristics 

 of the water. Copper acts synergistically with zinc, 

 cadmium, and mercury, yet there is a sparing 

 action with calcium. 



Barnacles and related marine fouling organisms 

 were killed in 2 hours by 10 to 30 mg/1 copper. 

 Clarke (1947) showed that the mussel, Mytilus 

 edulis, was killed in 12 hours by 0.55 mg/1. Lob- 

 sters transferred to tanks lined with copper after 

 living in aluminum, stainless steel, and iron tanks 

 for 2 months, died within 1 day. Copper is concen- 

 trated by plankton from surrounding water in 



ratios of 1,000 to 5,000 or more (Krumholz and 

 Foster, 1957). 



Concentrations of copper above 0.1 to 0.5 

 mg/1 were found to be toxic to oysters by Galtsoff 

 (1932). The 96-hour TLn, for oysters was esti- 

 mated at 1.9 mg/1 (Fujiya, 1960). Oysters cul- 

 tured in waters containing 0.13 to 0.5 mg/1 ac- 

 cumulated copper in their tissues and became unfit 

 as a food substance. Pringle (in press) found the 

 soft clam, Mya arenaria, extremely sensitive to 

 copper. At a concentration of 0.5 mg/1, 100-per- 

 cent mortality took place in 3 days. Using a 0.2 

 mg/1 concentration at 10 and 20 C, all clams died 

 within 23 days at the lower temperature, while at 

 the higher temperature all succumbed in 6 to 8 

 days. When 0.1 mg/1 Cu at 20 C was used, all 

 animals died in 10 to 12 days. Raymont and 

 Shields (1964) in studies with the marine poly- 

 chaete worm Nereis, showed that a concentration 

 of 1.5 mg/1 Cu was lethal in 2 to 3 days, and con- 

 centrations exceeding 0.05 mg/1 Cu were lethal in 

 approximately 4 days. 



Clendenning and North (1958, 1960) and 

 North and Clendenning (1958, 1959) evaluated 

 the effect of copper (from the chloride and sulfate 

 salts) on the rate of photosynthesis of the giant 

 kelp, Macrocystis pyrijera. With 0.1 mg/1 of cop- 

 per, net photosynthesis was inhibited by 50 percent 

 in 2 to 5 days and 70 percent in 7 to 9 days. Visi- 

 ble injury appeared in 10 days. Copper was 

 slightly less toxic than mercury but more so than 

 nickel, chromium, lead, or zinc. Marvin, Lansford, 

 and Wheeler (1961) found 0.05 mg/1 Cu toxic to 

 Gymnodinium breve (red tide organism). 



Mercury. — Mercury is found in seawater at a 

 level of 0.00003 mg/1. It is found in marine plants 

 at approximately 0.03 mg/1. 



Irukayama (1966) reported on a mercurial pol- 

 lution incident in Japan, which was first recognized 

 in 1953. A severe neurological disorder resulted in 

 the area^of Minamata Bay as a result of eating fish 

 and shellfish from these waters. Many species of 

 animals including waterfowl were succumbing to 

 the "disease" called Minamata disease. Clinical 

 features were cerebellar ataxia, constriction of vis- 

 ual fields, and dysarithia. Pathological findings 

 were regressive changes in the cerebellum and 

 cerebral cortices. Investigation through 1965 sug- 

 gested that the main cause was the spent factory 

 waste of the Kanose Factory upstream from the 

 Minamata Bay area. Methyl mercury compounds, 

 waste byproducts from the acetaldehyde synthesis 

 process, were being discharged and concentrated 

 especially in shellfish. 



Ukeles (1962) made a study of pure cultures of 



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