Asiatic clam (Corbicula fluminea)–based dynamic biosensor for real-time in situ monitoring waterborne metals
Date Issued
2007
Date
2007
Author(s)
Jou, Li-John
DOI
en-US
Abstract
The goal of this dissertation is to develop a novel freshwater clam Corbicula fluminea-based on-line bimonitoring system as a bioassay tool to offer a real-time and cost-effective method to measure copper (Cu) and cadminm (Cd) concentrations in natural water resources. The proposed system used sublethal changes in the daily valve closing activites of C. fluminea as a biological endpoint and built upon the basic principles of biological early warning system (BEWS) model in three phases. In the first phase, a probabilistic-based approach describing the valve closure behavior of C. fluminea in response to Cu and Cd was developed. The valve closure response data from published literature was reanalyzed to reconstruct the response time-dependent dose-response profiles based on an empirical three-parameter Hill equation model. The reconstructed dose-response profiles and EC50-time relationships associated with the fitted daily valve opening/closing rhythm characterized by a three-parameter lognormal function were integrated to successfully predict the time-varying bivalve closure rhythm in response to waterborne Cu/Cd. A probabilistic-based methodology associated with the time-varying dose-response relationships of valve closing behavior is incorporated into the mechanisms of a dynamic clam compiled by a LabVIEW graphic control program language in a personal computer (PC). It allows the parsimony estimation of the time-varying waterborne Cu/Cd concentrations for on-line providing the performances of the toxicity detection technique.
Secondly, the biotic ligand model (BLM) describing the bioavailability was employed to link between acute Cu toxicity and its effect on valve closure behavior of freshwater clam C. fluminea based on the published experimental data of C. fluminea closure daily rhythm and dose-response profiles. The results show that a BLM-based Hill model best describes the free Cu2+-activity−valve closure response relationships. The proposed Cu-BLM-Corbicula model shows that the free ionic form of waterborne Cu bind specifically to a biotic ligand (i.e., clam gills) and impair normal valve closure behavior, indicating that a fixed-level of metal accumulation at a biotic ligand is required to elicit specific biological effects. The site-specific EC50(t) and valve closure rhythm at any integrated time was demonstrated to obtain a good prediction, indicating that the proposed model has the potential to develop a biomonitoring system as a bioassay tool to on-line measure waterborne Cu levels in aquatic systems.
In the third phase, the principles of water chemistry were integrated into the modified BLM-based pH-specific concentration-time-response model. Through the combination of the Hill model-based dose-time-response function and the fitted daily rhythm function of valve closure, the constructed Cu-BLM-Corbicula-based programmatic mechanism can be used to simulate the valve closure rhythm exposed to copper in various time-varying scenarios. The compensatory mechanism under temperature-specific and pH-specific aquatic environmental conditions was incorporated into the constructed Cu-BLM-Corbicula model-based dynamic Cu detection mechanism to precisely and completely reflect the suitability for practical environmental statuses. The performance for a system testing in a dynamic clam synthesis was also demonstrated by employing a LabVIEW software in a PC. The simulation results reveal that the developed Cu-BLM-Corbicula-based programmatic mechanism can be used to indirectly estimate the time-varying waterborne Cu ion activity under the influence of water temperature and pH to further evaluate the local-specific waterborne Cu concentration.
In the present study, an important system function for adjusting the time response and threshold concentration was added to improve the real-time metal toxicity detection technique. The virtual instrumentation techniques to design and simulate a C. fluminea-based biomonitoring system based on a valvometric conversion technique were adopted to greatly reduce the costs, development time and errors in implementing procedures. This proposed Cu-BLM-Corbicula model-based dynamic clam synthesis has been completed to provide a better understanding to quantify on-line measurement of Cu toxic effect on bivalve health to technically assist in developing a defensible site-specific BEWS for the protection of aquatic ecosystems, and may foster applications in clam farm management strategies.
Subjects
亞洲蜆
生物預警系統
金屬毒性
生物監測
貝殼活動行為
生物配體模式
生物可獲取率
Asiatic clam
Biological early warning system
Metal toxicity
Biomonitor
Valve movement
Corbicula fluminea
Biotic ligand model
Bioavailability
SDGs
Type
thesis
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