１７５

Impact of Antifouling Biocide on
Marine Environment
Noritaka Tsunemasa
Environment Conservation Division of the Environment Bureau, City of Hiroshima
730-8586, Hiroshima, Japan Tel: +81-82-504-2188 Fax: +81-504-2229
E-mail: tunemasa-n@city.hiroshima.lg.jp
Introduction
Organotin (Ot) compounds had been used for many years on ships, marine structures and fishery nets until
detection of toxicity and accumulation characteristics. Ot compounds were subsequently prohibited on the 17th ofSeptember, 2008. Alternative compounds began to be used for ships with the thought that Ot alternativeantifoulants would not accumulate in seawater and sediment as much as Ot compounds, due to the faster
resolution speed. However, Ot alternative antifoulants have been detected at higher levels than initially expectedwhich has caused concern about the possible affects on marine organisms.
In this research, sea water samples from the northern part of Hiroshima Bay were used to evaluate the toxicity ofDiuron, Sea-Nine 211, TPBP, TPBOA and Irgarol 1051 on oysters. These chemicals were chosen due to their
popular use in Japan following the prohibition in 1997 of paints that used TBT. For comparative reasons, TBT
and TPT were also investigated. Oysters were chosen because of their high sensitivity to chemical compounds
and the fact that they can be found worldwide.
The research sought to not only analyze the chemical compounds in survey points but also to measure the effectof antifouling biocides on fertilized oyster egg’s development. Finally, the environmental risk was evaluated.

Results

Fig. 1 Map of the survey
pointsResidual antifouling biocides in environmental samples
In this study, Sea-Nine 211, Diuron, Irgarol 1051 and the latter’s degradation product M1 were detected inseawater from Hiroshima Bay whereas TPBP was not detected. Analysis results over the research period areshown in Table 1.
Effects of antifouling biocide on oyster embryo development
In this report, the survival rate of the eggs and the occurrence of deformity in D-shaped embryos wereinvestigated. In the report by His et al., four types of deformity were shown: convex hinge, indented shell margin,
incomplete shell, and protruding mantle. In our experiments, only protruding-mantle deformities were observed.
The LC10 and LC50 values of each compound were calculated from the survival rate of the fertilized oyster eggs
after an exposure time of 2 and 24 h using the Ecotox-Statics software package. The results are shown in Table 2.

Discussion
In the evaluation of the environmental impact of these chemicals, a risk factor that used
the predicted environmental concentration (PEC) divided by predicted no-effectconcentration (PNEC) was used. When this value exceeded a risk factor of 1.0, it wasdecided the chemical had an influence on the environment. The PNEC on the aquaticorganism was calculated from the examination result of the acute or chronic effect in theorganism species divided by assessment factor. In this research, the chemicals that wereresolved in the toxicity experiment had their PNEC evaluated, so the assessment factor
was set at 10.
In this research period, Sea-Nine 211 was detected at values that exceeded Sea-Nine
211’s PNEC in almost all survey points. This means that Sea-nine 211 is present in theconcentration that effect oyster embryo’s development in the northern part of Hiroshima
Bay. If the effects that were observed in the laboratory took place in nature, at least 10%of oyster embryos would exhibit a deformity. It is reasonable to say that oyster embryos
which show signs of deformity are unlikely to develop into adult oysters.
In recent times, the indication of delayed development of oysters in Hiroshima Bay has
become more noticeable. If this trend continues, oyster numbers will decrease. If theoyster’s numbers decrease, there are a number of influences that could be possible.
Oysters play an important role as natural filters for the marine environment so a decline
in numbers could see an adverse affect on the water quality of Hiroshima Bay. Also,
various marine life (e.g. Acanthopagrus schlegelii, Takifugu poecilonotus) in Hiroshima
Bay use oysters as a food source so any change in oyster numbers could affect not only
the organisms which feed off them but also the alternative food sources. It is clear fromthe aforementioned examples that any decline in oyster numbers would have a negative
impact on the northern part of Hiroshima Bay’s ecosystem.

Table 1: Minimum-Maximum concentration of antifoulingbiocides in seawater from Hiroshima BaySurvey
pointＡＢＣＤＥＦＧＨＩ

Irgarol 1051

M1Diuron

Sea-Nine 211

ND
ND
ND
ND
ND
ND
ND
ND - 0.092
ND

ND - 1.1
ND - 1.3
ND - 1.1
ND - 0.17
ND - 0.10
ND - 0.10
ND
ND - 0.12
ND - 0.060

ND - 0.43
ND - 0.73
ND - 0.21
ND - 0.17
ND - 0.24
ND - 0.10
ND - 0.14
ND - 0.18
ND - 0.17
ND: not detected

ND - 0.10
ND - 0.10
ND - 0.097
ND
ND - 0.067
ND - 0.035
ND - 0.085
ND - 0.069
ND - 0.052(µg/L)

Table 2: Lethal effects of antifouling compounds to oyster embryo
2hLC102.6 (2.5-2.7)
TBT
2.4 (2.3-2.5)TPT
7.4 (6.8-7.7)
Sea-Nine 211
1.1 (1.0-1.1)
TPBP
2.7 (2.6-2.8)
TPBOA
>1000
Diuron>1000
Irgarol 1051
Degradation product>1000
DPB>1000
MPB>1000
Biphenyl>1000
Phenol
>1000
Pyridine>1000
BenzeneBoric acid>1000
LC50 : 50% lethal concentration (µg/l)
LC10 : 10% lethal concentration (µg/l)

24h
LC50
16 (14-18)
14 (12-15)
28 (26-31)
7.5 (6.7-8.5)
23 (20-26)>1000>1000

LC100.36 (0.31-0.39)
0.52 (0.48-0.54)
0.90 (0.89-0.91)
0.58 (0.55-0.60)
2.2 (2.1-2.8)>1000>1000>1000>1000>1000>1000>1000>1000>1000(LC50
3.9 (3.3-4.5)
3.7 (3.2-4.2)
17 (14-21)
6.3 (5.4-7.4)
10 (9.5-12)>1000>1000>1000>1000>1000>1000>1000>1000>1000) : 95% confidence interval>1000>1000>1000>1000>1000>1000>1000Conclusions･Although Sea-Nine 211 is present in lower concentration than the other chemical substances, it is the most harmful
on oyster embryos in investigated compounds because Sea-Nine 211 should be changed another compound.
･Chemical substances bring negative impacts to the northern part of Hiroshima Bay’s ecosystem.
･Antifouling biocides should show a high toxicity around the hull, but quickly resolve in the sea water.