Interpreting copper bioaccumulation dynamics in tilapia using systems-level explorations of pulsed acute/chronic exposures.

To understand how environmental variability could impose aquatic organisms in response to altered disturbance regimes and temporal patterns of waterborne toxicants is challenging. Few studies have reported in an organ/tissue specific basis, and most studies have been restricted to steady-state conditions. For interpreting systematically copper (Cu) bioaccumulation in tilapia (Oreochromis mossambicus) in a pulse scheme, we combined mechanistic and statistical as well as model-based data analyses of exposure data that cover short-term mortality to long-term organ/tissue growth bioassay. Our present pulsed Cu-tilapia physiologically-based pharmacokinetic model was capable of elucidating the Cu accumulation dynamics in tissues of tilapia under different pulsed exposure scenarios. Under acute and chronic pulsed exposures, our study found that (i) stomach and kidney had the highest uptake and elimination capacities, (ii) liver was prone to a highest BCF and was more sensitive than the other tissues, and (iii) Cu accumulations in most of organs and other tissues were strongly dependent on the exposure pulse characteristics such as frequency and duration and not on concentration (i.e., amplitude). We showed that interactions across multiple pulsed or fluctuating Cu exposures were involved in accumulation changes that could also be achieved by controlling pulse timing and duration. The analytical approach we described provides an opportunity to examine and quantify metal accumulation dynamics for fish in response to environmental variability-induced non-uniform metal exposures on an organ/tissue-dependent scale and to integrate qualitative information with toxicokinetic and physiological data. We hope that our systems-level tools for mathematical analyses and modeling will facilitate future large-scale and dynamic systems biology studies in other model fish.