A biologically based damage assessment model to enhance aquacultural water quality management

The lethal concentration for 50% of aquacultural animals (LC50)-based tests determines the external effect concentration (EEC) following certain statistical models, revealing that no biologically based mechanistic information and only statistical interpretations of its model parameters could be made. The purpose of this paper is to determine the survival risk of waterborne metals toward farmed species with respect to lethality based on biologically based mechanistic models. Here we study a biologically based mechanistic damage assessment model (DAM) compared with a pharmacodynamic (PD)-based critical area under the curve (CAUC) model to demonstrate the ability of predicting the internal effect concentration (IEC) and survival rate of farmed species. We tested the proposed models using published acute toxicity and accumulation data for two farmed species, tilapia (Orechromis mossambicus) exposed to arsenic (As) and abalone (Haliotis diversicolor supertexta) exposed to zinc (Zn), to compare observed and predicted LC50 and IEC and, subsequently, to predict the survival rate. Our analyses demonstrate that the DAM- and PD-based survival models performed well and proved its usefulness as a tool in the quantification of risk assessment in aquacultural ecosystems. The study also supports the suggestion that replacing exposure-based EECs by IECs is a first step toward a measure for inherent toxicity and can be used to improve the construction of future environmental quality criteria programs aimed at protecting and restoring the rapidly degrading aquacultural ecosystems.