Treatment Weight Loss (%) 
Control 22) 75 2Q.6, 23.9 
Cu,0 5 2803 
TBTO and Cu,0 230 
TBTO 22025 QP 
TBTO/ creosote 79 
In Figure 7, the results from those treatments which were duplicated are 
averaged. 
None of the cylinders prepared with nails placed at the center and 
1 cm from the surface showed signs of cracking or spalling after 445 
days. These cylinders were exposed so that the bottom one-third was 
immersed in continually flowing seawater, while the top two-thirds of 
the cylinder was in air to simulate the hull of a concrete vessel. 
Biotoxicity 
Two experiments were performed to evaluate biotoxicity; the first 
using fertilized eggs of the red abalone H. rufescens, and the second 
using larvae of the same organism. 
In the initial part of the first experiment, it was found that an 
untreated control specimen caused cessation of development and death of 
fertilized eggs, so specimens were leached in flowing seawater for 102 
days and the test repeated. Concrete cylinders prepared using TBTO, 
TBTO/creosote, TBTO/Cu,0, Cu,0, and an untreated control were evaluated. 
Approximately 5,000 fertilized eggs were placed in 17 liters of 
seawater in a polyethylene bucket, into which a test cylinder was then 
placed. After 18 hours, the development of the eggs was observed micro- 
scopically. All eggs in buckets with a treated specimen had ceased 
development, while eggs in seawater with a control specimen were developing 
normally. Some differences were observed in the stages to which devel- 
opment progressed before death and in the morphology of the organism, 
depending on the toxicant present (Ref 13), but all the toxicants did 
cause cessation of development at some stage. 
The second experiment used the larvae of H. rufescens as the test 
organism. In this test three toxicant systems were evaluated at three 
different concentrations. Cylinders prepared using TBTO alone, a 
TBTO/creosote mixture, and a methoxychlor/TPTH/Cu,0 mixture were exposed 
to seawater in polyethylene pails containing 4.3 [Titers of seawater for 
2, 20, and 200 minutes. They were previously leached for 12 days in 
flowing seawater to establish a steady-state diffusion rate. An untreated 
control was similarly employed. Approximately 1,000 larvae were added 
to each pail, and the progress of development was observed periodically 
through a microscope. Table 5 shows the effect of the various toxicants 
at each concentration as a function of time. Differences in the 
morphology of the larvae exposed to the different toxicants were again 
observed. It is interesting to note that methoxychlor, a DDT analog, 
produced effects on the larvae more slowly than did other toxicants. 
