Biokinetics and toxicological response of valve daily rhythms in the freshwater clam Corbicula fluminea following exposure to arsenic
Date Issued
2008
Date
2008
Author(s)
Jau, Sheng-Feng
Abstract
The purpose of this thesis is to assess the biokinetics and toxicological response of valve daily rhythms in the freshwater clam Corbicula fluminea following exposure to waterborne arsenic. We carried out a laboratory 14-day exposure experiment to obtain biokinetic parameters of bioconcentration factor (BCF) and depuration rate constant (k2). A one-compartment first-order model was used to fit the exposure data to estimate BCF and k2 values. The three acute toxicity models, critical body residue (CBR) model, critical area under the curve (CAUC) model and damage assessment model (DAM) were verified with time-dependent external median lethal concentration (LC50) data obtained from a 7-day acute arsenic toxicity bioassay. We develop an inductance-based valvometry technique to characterize the valve daily rhythms in C. fluminea in response to arsenic, and use a three-parameter Hill model to estimate intergration time-specific median effect concentration (EC50) values. The resulting values of BCF, k2 and 96-h LC50 of C. fluminea exposure to arsenic were 4.38 mL g-1, 0.39 d-1 and 20.74 mg L-1, respectively. We fitted valve opening daily rhythm in the absence of arsenic as the form of by 4-parameter sine function, linking Hill response function to predict valve daily rhythm dynamics in response to arsenic. The time-varying EC50s are estimated to be 4.65, 3.48, 1.38, 0.60, 0.38 and 0.35 mg L-1, respectively, at integration times of 10, 15, 30, 60, 120 and 300 min. The simulation results show that in the valve opening hours from 03:00 – 08:00 h the predicted daily rhythm changes in valve opening in response to different arsenic exposure concentrations ranging from 0.3 to 10 mg L-1 are notably agreed well with the observations justified by the root mean squared errors (RMSE) ranging from 4 – 10%. Moreover, we also kinetically linked a DAM model and a Hill sigmoid model to reconstruct an internal effect concentration based time-mortality model assessing the effect of soft tissue arsenic burden on the C. fluminea mortality. Our study indicates that C. fluminea exposed to arsenic will cause behavioral changes and mortality, suggesting that our results can provide the knowledge to establish the arsenic water quality criteria to clam farm.
Subjects
Freshwater clam
Corbicula fluminea
Arsenic
Bioaccumulation
Acute toxicity
Dose-response
Valve movement
Biomonitor
Type
thesis
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