mg/1 copper as copper sulfate produces the fol- 

 lowing percents of death in algae: 



57 percent in 17 species of blue-green algae. 

 35 percent in 17 species of green algae. 

 100 percent in 6 species of diatoms. 



Fitzgerald, Gerloff, and Borg (1952) report that 

 0.2 mg/1 of copper (as copper sulfate) produces 

 a 100-percent kill of Microcystis aeruginosa. 

 Crance (1963) found 0.05 mg/1 kills Microcystis. 

 Hassall (1962), working with Chlorella vulgaris 

 found that 25 g/1 of copper sulfate did not in- 

 hibit respiration if cultures were shaken. If shaking 

 stopped, concentrations greater than 250 mg/1 

 were toxic. Preliminary experiments indicate that 

 lack of air increases toxicity of copper. Hale 

 (1937) — according to Jordan, Day, and Hendrix- 

 son (1962) — reported that the following concen- 

 trations were necessary to control the indicated 



0.5 mg/1 — Cladophora. 

 0. 1 mg/1 — Hydrodictyon. 

 0.12 mg/1 — Spirogyra. 

 0.20 mg/l—Ulothrix. 



Calcium and magnesium concentrations are usu- 

 ally not given for algal tests, but it would seem 

 that the concentrations deemed safe for fish 

 would also be acceptable for plankton. 



Recommendation: The maximum copper (expressed 

 as Cu) concentration (not including copper attached 

 to silt particles or in stable organic combination) at 

 any time or place should not be greater than Ho the 

 96-hour TLm value, nor should any 24-hour average 

 concentration exceed '/^o of the 96-hour TLm value. 



Cadmium: Few studies have been made of the 

 toxicity of cadmium in the aquatic environment. 

 Mammalian studies have shown it to have sub- 

 stantial cumulative effects. Permissible levels in 

 drinking water are 0.01 mg/1 (USDHEW, 

 1962b), and concentrations of a few /^g/g in 

 food (McKee and Wolf, 1963) have caused 

 sickness in human beings. Mount (1967) found 

 accumulations in living bluegills as high as 100 

 ixg/g (dry weight) and in the gills of dead catfish 

 up to 1000 yu-g/g. Little accumulation was found 

 in the muscle. Consideration should be given to 

 acceptable residue levels in fish when establishing 

 cadmium criteria. 



Daphnia appears to be very sensitive to cadmium 

 (Anderson, 1950). Bringmann and Kuhn (1959a) 

 indicate Scenedesmus, and Escherichia coli are 

 about equally sensitive. Data as yet unpublished 

 (Pickering, in press) reveal that following pro- 

 longed exposure there is a large accumulation of 

 cadmium m fish. Even though very little data are 



available yet, the evidence warrants a more re- 

 strictive requirement for cadmium than specified 

 under the general bioassay section. 



Recommendation: The concentration of cadmium 

 must not exceed V^o of the 96-hour TLm concentration 

 at any time or place and the maximum 24-hour average 

 concentration should not exceed %oo of the 96-hour 

 TLm concentration. 



Hexavalent Chromium: The chronic toxicity 

 of hexavalent chromium to fish has been studied 

 by Olson (1958) and Olson and Foster (1956, 

 1957). Their data demonstrate a pronounced 

 cumulative toxicity of chromium to trout and sal- 

 mon. Mr. P. A. Olson (personal communication) 

 of Battelle Memorial Institute advises that some 

 recent comparisons of 48 and 96-hour TL^ con- 

 centrations with concentrations not adversely af- 

 fecting the same species indicate that the applica- 

 tion factor for hexavalent chromium is ^^oo.ooo 

 for salmon and ^oo.ooo for rainbow trout. He 

 also feels however, that such factors are not valid 

 for carp. Doudoroff and Katz (1953) found that 

 bluegills tolerated a 45 mg/1 level for 20 days in 

 hard water. Cairns (1956), using chromic oxide 

 (CrOa), found that a concentration of 104 mg/1 

 was toxic in 6 to 84 hours. Daphnia and Micro- 

 regma exhibit threshold effects at hexavalent 

 chromium levels of 0.016 to 0.7 mg/1. 



Some data are available concerning the toxicity 

 of chromium to algae. The concentrations of chro- 

 mium that inhibit growth (Hervey, 1949) for the 

 test organisms are as follows: Chlorococcales, 3.2 

 to 6.4 mg/1; Euglenoids, 0.32 to 1.6 mg/1; and 

 diatoms, 0.032 to 0.32, mg/1. Chromium at sub- 

 lethal doses sometimes stimulates algae. Patrick 

 (unpublished data) has studied the effects of tem- 

 perature on the toxicity of chromium to certain 

 algae. Her findings on the concentrations which re- 

 duce population growth by 50 percent are as fol- 

 lows: 



Nitzschia linearis. — 50 percent reduction in 

 growth of population as compared with control 

 (soft water 44 mg/1 Ca-Mg as CaCOa) 



22 C— 0.208 mg/1 Cr 



28 C— 0.261 mg/1 Cr 



30 C— 0.272 mg/1 Cr 

 Navicula seminulum var. hustedtii (hard water 

 170 mg/1 Ca-Mg as CaCOg) 



22 C— 0.254 mg/1 Cr 



28 C--0.343 mg/1 Cr 



30 C— 0.433 mg/1 Cr 



Recommendation : Data are too incomplete to do more 

 than urge caution in the discharge of chromium. Con- 

 centrations of 0.02 mg/1 in soft water have been found 

 safe for salmonid fishes. 



61 



