THESIS
2017
xii, 74 pages : illustrations, 1 map ; 30 cm
Abstract
Despite salinity has been well documented for its significant effects on the bioaccumulation
of trace elements in marine bivalves, we identified a species whose metal burden was less
influenced by salinity – black mussel Septifer virgatus. According to the biokinetics modeling,
the weak salinity effects on the tissue concentration of Ni and Zn can be explained by the
synchronized variations of waterborne uptake and elimination under the influence of salinity,
since both their rates of uptake and efflux were negatively correlated with salinity. In contrast,
salinity can significantly influence the metal accumulation of oyster Crassostrea hongkongensis,
suggesting potential interference for biomonitoring. For the first time, we established a novel
method to calibrate biomonitoring...[
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Despite salinity has been well documented for its significant effects on the bioaccumulation
of trace elements in marine bivalves, we identified a species whose metal burden was less
influenced by salinity – black mussel Septifer virgatus. According to the biokinetics modeling,
the weak salinity effects on the tissue concentration of Ni and Zn can be explained by the
synchronized variations of waterborne uptake and elimination under the influence of salinity,
since both their rates of uptake and efflux were negatively correlated with salinity. In contrast,
salinity can significantly influence the metal accumulation of oyster Crassostrea hongkongensis,
suggesting potential interference for biomonitoring. For the first time, we established a novel
method to calibrate biomonitoring data against salinity. Relationships between tissue metal
concentration and biological proxy for salinity (tissue Na) are required in field calibration, which
were quantified based on laboratory exposure experiment. The method was applied to the
biomonitoring of Pearl River Estuary, and verified to be feasible and effectively reduces the
influence of salinity. The behavior of Ni in oyster C. hongkongensis is different from other
metals that have been studied. A 4-week waterborne exposure at 3 different concentrations
demonstrated that Ni in oysters reached steady-state rapidly. The efflux rate constant (k
e)
determined through a 30-day depuration was positively correlated with tissue concentration, with
the highest k
e reaching 0.155 d
-1. Pre-exposure to Ni significantly reduced the dissolved uptake,
probably accompanied with depressed filtration activity. Ni in oysters was predominantly in
detoxified fractions, among which metallothionein-like protein (MTLP) was the most important
one for binding. The high proportion of Ni in MTLP was further presumed to contribute to the
rapid elimination. Overall, Ni in oysters can be regulated by enhanced efflux, suppressed uptake,
and sequestration of most Ni into detoxified pool.
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