THESIS
2016
xxiv, 282 pages : illustrations (some color) ; 30 cm
Abstract
A good antifouling compound not only needs to be efficacious against the
settlement of fouling organisms, but also is required to be environmentally friendly.
Because of the high toxicity and pollution in marine environment, the antifouling
booster biocides currently in use are not the optimum solutions to biofouling problem.
It is recognized that natural products isolated from living organisms will provide a
plentiful resource for the development of environmentally friendly antifoulants.
Therefore, in order to compare the relative applicability of antifouling booster biocides
and natural products, this thesis work employed three representative antifoulants,
SeaNine 211 of booster biocide together with butenolide and 3,3'-diindolylmethane
(DIM) of natural product, and investiga...[
Read more ]
A good antifouling compound not only needs to be efficacious against the
settlement of fouling organisms, but also is required to be environmentally friendly.
Because of the high toxicity and pollution in marine environment, the antifouling
booster biocides currently in use are not the optimum solutions to biofouling problem.
It is recognized that natural products isolated from living organisms will provide a
plentiful resource for the development of environmentally friendly antifoulants.
Therefore, in order to compare the relative applicability of antifouling booster biocides
and natural products, this thesis work employed three representative antifoulants,
SeaNine 211 of booster biocide together with butenolide and 3,3'-diindolylmethane
(DIM) of natural product, and investigated their comparative degradation kinetics in
marine environment and chronic toxicity using marine medaka (Oryzias melastigma),
an increasingly-used model for marine toxicology. The results showed that butenolide
could be degraded rapidly in natural seawater with half-life at 13.0 h while 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), the active ingredient of SeaNine 211, and
DIM had no obvious degradation after 96-h incubation. Furthermore, no toxic
byproducts would be generated by the degradation of butenolide, as inferred from the
decreasing toxicity along with degradation. Bacterial effects should be the major
contributor to the biodegradation of butenolide. In addition, the degradation kinetics of
antifoulants were found to depend on temperature heavily, indicating the seasonal
variation of the applicability of antifouling agents.
Chronic exposure of adult medaka to antifouling compounds revealed that
butenolide was relatively safer compared with DCOIT and DIM in terms of oxidative
stress, neurotoxicity, endocrine disruption and reproductive impairment. Proteomic
profiling indicated that the activated detoxification system in liver may account for the
biosafety of butenolide. DCOIT was determined to be a moderate disruptor of endocrine
homeostasis. It showed estrogenic activity mainly in male fish at environmentally
realistic concentrations. Transgenerational toxicity of DCOIT was also reflected on the
decreased viability of medaka larvae, such as delayed hatching and lethargic swimming.
Compared with butenolide and DCOIT, DIM was very potent on endocrine disruption.
It behaved estrogenic in males but anti-estrogenic in females along with the
hypothalamus-pituitary-gonadal-liver (HPGL) axis. There were significantly decreased
levels of vitellogenin (VTG) and choriogenin, proteins for the yolk and egg envelop of
medaka eggs, in females but increased levels in males. The deficiency in VTG and
choriogenin speculatively resulted in the decreased fecundity and impaired viability of
offspring. Genomic profiling of gonads at the transcript and protein levels further
identified a series of biochemical processes that plotted an Adverse Outcome Pathway
(AOP) from bottom up, which linked the molecular initiating events with the apical
adverse outcomes including egg production and swimming behavior.
In summary, after taking the degradation, toxicity and activity into combined
consideration, we can generally conclude that butenolide is a promising antifouling
compound in view of its fast degradation, biosafety and efficacious antifouling activity.
More work are thus warranted to obtain a clear understanding of the properties of
butenolide to facilitate its future registration and commercialization. For DCOIT, it is
arguing for systematic investigation of its ecological risks in certain area because it can
not be degraded rapidly in the waters of Hong Kong and shows endocrine disruptive
effects. However, with regard to the chemical stability and strong toxicity on endocrine
homeostasis and reproductive performance, DIM is not suitable for antifouling usage.
Post a Comment