The effect of zinc on aquatic microbial ecosystems and the degradation of dissolved organic matter

We developed a simple aquatic microbial ecosystem model in order to examine potential effects of zinc on microorganisms and the related degradation of dissolved organic matter (DOM). The model is a combination of both a traditional food chain and a microbial loop. The traditional food chain is mainly composed of phytoplankton and zooplankton, whilst the microbial loop is composed of DOM, bacteria and bacterivorous protozoa. We incorporated the suppressive effect of zinc on the bacterial uptake of DOM and assessed the steady state responses of the model for various zinc concentrations. The analytical and numerical results of the model implied that either zooplankton or bacterivorous protozoa might be the most vulnerable group to excessive zinc load than bacteria, depending on the grazing preference of zooplankton between phytoplankton and bacterivorous protozoa. The sensitivity analyses supported that the microbial loop solely is more sensitive to zinc than the coupled system combining both the traditional food chain and the microbial loop. (C) 2012 Elsevier Ltd. All rights reserved.