Statistical Analyses 
Data for bacterial enumerations, and data for tin levels were 
analyzed using a one-way analysis of variance (ANOVA). Sample 
means were compared using the studentized (SNK) multiple range 
test. 
Correlation coefficiencts (r) were analyzed for significance 
of association between tin concentration and counts of tin-re¬ 
sistant microorganisms; and for significance of association 
between tin concentration and percent of the microbial popula¬ 
tion resistant to tin. All associations were tested at the 
5 percent level of significance. No significant positive or 
negative correlations were noted. Thus, the data available do 
not suggest that tin (organic and/or inorganic) selects for a 
population of tin-resistant microorganisms. 
General Discussion 
The data indicate that surface sediments from oyster bars in 
the Chester River contain significantly more tin than is con¬ 
tained in sediments from a site near Tilghman Island, but they 
contain significantly less tin than sediment from Baltimore 
Harbor. The three freshwater sites examined--the Tenneco plant, 
the Campbell factory and the Chestertown sewage treatment plant-- 
all contribute tin to the Chester River ecosystem at an undeter¬ 
mined rate. There may be other contributors. It is clear that 
microorganisms capable of converting inorganic tin to more toxic 
organotin compounds are ubiquitous in the Chesapeake ecosystem 
(Table 24) . 
Zuckerman et al. (1978) reviewed the known toxic effects of 
organotin compounds on a variety of living organisms. Relative¬ 
ly little is known of effects on estuarine organisms, but the 
following toxic levels have been reported for organisms relevant 
to the present study: guppies, less than 1 ppm of bis(tributyl- 
tin) oxide and 0.1 ppm triphenltin hydroxide; molluscs, 1.0 ppm 
of several trialkyltin and 0.05 - 0.10 bis(tributyltin)oxide; 
algae, barnacles, shrimp and tubeworms, 0.1 to 1.0 ppm of tri¬ 
butyl and triphenyltin compounds. Very little is known of the 
levels of organotin compounds in estuarine systems. But sedi¬ 
ments in the Chester River ecosystem contain between 3 and 
8 ppm of tin (Table 25). Data from the present study do not in¬ 
dicate the chemical speciation of the tin compound(s) detected. 
Although the chemical species of tin compound (s) was not estab- 
lised, if even one-third of the tin is present as organotin 
compounds, the estuarine biota could be at risk, particularly 
if stress from toxic tin(s) is coupled with other stresses such 
as low dissolved oxygen. 
99 
