THESIS
2018
xi, 70 pages : illustrations, 1 map ; 30 cm
Abstract
We analyzed both the total mercury (THg) and methylmercury (MeHg) concentrations in
nine species of commercial fish from two marine-cage farms in Southern China.
13C and
15N
stable isotopes were concurrently analyzed to identify the artificial feed sources and the
trophic levels of farmed fish. Mercury concentrations of all species were much lower than the
human health screening values and safety limits established by different countries. Mercury
levels in artificial pellets were the main determinants of Hg accumulation in fish between two
sites, while somatic growth dilution and size also played an important role. Among the
different fish tissues, muscle was a major sink for Hg and contained the highest ratio of
MeHg/THg, and liver was the second important organ for Hg accumula...[
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We analyzed both the total mercury (THg) and methylmercury (MeHg) concentrations in
nine species of commercial fish from two marine-cage farms in Southern China.
13C and
15N
stable isotopes were concurrently analyzed to identify the artificial feed sources and the
trophic levels of farmed fish. Mercury concentrations of all species were much lower than the
human health screening values and safety limits established by different countries. Mercury
levels in artificial pellets were the main determinants of Hg accumulation in fish between two
sites, while somatic growth dilution and size also played an important role. Among the
different fish tissues, muscle was a major sink for Hg and contained the highest ratio of
MeHg/THg, and liver was the second important organ for Hg accumulation in most fish
species. Intestine was a critical organ for Hg biotransformation with its %MeHg differing
greatly among different fish species. δ
15N analysis could not be used to determine the trophic
levels in culturing systems where artificial practices were involved. Based on the δ
13C
signatures, five species of fish were identified to solely feed on the artificial pellets, yet the
Hg bioaccumulation differed significantly among these species. We therefore concluded that
Hg bioaccumulation in different fish species may be dependent on their internal Hg
biotransformation as well as their biokinetics. An in-vivo bioavailability test based on a mice
model was also conducted to look in to the fraction of Hg that can be absorbed after digestion,
as well as four in-vitro bioaccessibility methodologies for comparison. But the results vary
too much from different methods that it could not be used to predict the released fraction of
Hg in gastrointestinal tract.
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