TABLE 19. DETERMINATION OF A CONCENTRATION OF TIN WHICH 
WOULD SELECT FOR TIN-RESISTANT MICROORGANISMS 
Type of 
Sample 
Tin added 
(ppmSn, as 
SnCl 4 ) 
Viable count 
(mean 
+ standard 
Water 
0 
8.7 
X 
10 2 
+ 
1.8 
X 
10 2 a 
50 
5.4 
X 
10 2 
+ 
6.8 
X 
ioi b 
Sediment 
0 
8.1 
X 
10 5 
+ 
2.6 
X 
10 4 a 
50 
9.4 
X 
10 4 
+ 
8.5 
X 
10 3 b 
100 
4.0 
X 
10 4 
+ 
3.9 
X 
10 3 c 
150 
2.6 
X 
10 4 
+ 
7.1 
X 
10 3 c 
200 
1.7 
X 
10 4 
+ 
3.4 
X 
10 3 c 
* 
Means with the same superscript are not significantly different 
at the 5 percent level as determined by a one-way analysis of 
variance (ANOVA). 
of volatile tin compounds were included in each experiment. 
Each experiment also included positive controls in which the 
medium contained 75 ppm tin as dimethyltin chloride. The use of 
a solid medium containing a suspension of tin renders this method 
qualitative, not quantitative. 
ii) Hungate tubes . Each tube (Hungate 1969) , containing 
5.0 ml of liquid Nelson's medium (Nelson's medium minus agar), 
was inoculated with 1.0 ml of sediment suspended in estuarine 
salts. Sterile controls and positive controls were included in 
each experiment. Tubes were incubated for 16 days at 27 + 2 C 
on a rotary shaker operating at 80 rpm; each tube was then sam¬ 
pled for the presence of organotin compounds. 
For each water or sediment sample, one set of bioflasks and 
Hungate tubes was inoculated from a sample which had received 
500 pg of sodium azide per ml. This additional set of controls 
was used as a demonstration that effects observed in cultures 
were due to biological activity. 
Analyses of Tin 
Inorganic tin— 
For sediment samples, 1.0 g (wet weight) was transferred to 
an acid-cleaned, screw-capped tube. Then, 2.0 ml of a solution 
containing 50 percent (vol/vol) HC1 and 50 percent (vol/vol) 
concentrated HNO 3 were added. The tube was shaken vigorously 
for 1 hr. It was then centrifuged and 1.0 ml of the supernatant 
89 
