Exposure and Effect Modelling

Abstract

This study investigates the importance of water and food as exposure sources of three model contaminants with different physico-chemical properties and modes of action to zebrafish. It is explored to what extend uptake via water or food results in different responses and toxic effects. The responses and effects are studied at molecular, cellular and organismal level using genomics, proteomics and physiological approaches. The project aims to provide a in depth understanding of how different substances interact with a model system taking into account key factors such as developmental stage, exposure route and exposure time. The results of the genomics and proteomics analysis should considerable enlarge our understanding of the molecular mechanisms of toxicity and defense.

Over the years, our environment became polluted by various hazardous substances, such as heavy metals. Contamination by heavy metals may have severe effects on every level of biological organisation, i.e. from cell to ecosystem. An important problem that frequently occurs in ecotoxicological metal studies is that a clear relationship between exposure, accumulation and effects of heavy metals in an organism is often not found under natural conditions. There are two possible explanations. First, in many papers the absolute concentration of heavy metals in the soil and in the food are quantified while a large fraction of these metals are not bioavailable for the organism. Second, acclimatisation and/or adaptation to heavy metal contamination can result in a reduced uptake and accumulation of the bioavailable fraction of heavy metals and an altered sensitivity or tolerance. However, it is still unclear how and to what extent organisms can adapt and/or acclimatise to heavy metal contamination. Possible ways are: (1) a reduced absorption of heavy metals, (2) an increased excretion of heavy metals, (3) a different organ and tissue distribution and (3) a more efficient induction of detoxifying mechanisms like metallothionein (MT).

This study investigates the importance of water and food as exposure sources of copper to zebrafish. (Danio rerio) It is explored to what extend uptake via water or food results in different responses and toxic effects.

Field studies on terrestrial mammals that integrate exposure, (biochemical) effects as well as data on the individual and population level, are scarce. Furthermore, wildlife toxicology traditionally involves sacrificed animals. However, increasing ethical concerns - especially for mammalian species - gave rise to the need for non-destructive methods. Non-destructive methods involve minimal stress to populations and permit successive biomonitoring of the same populations and individuals. Moreover, they are suited to investigate pollution in endangered species or threatened populations. While non-destructive methods are regularly used in marine mammals, there is no such trend in terrestrial mammalian ecotoxicology.

Aquatic vertebrates like fish can accumulate metals through different uptake routes. Each route leads to a typical tissue distribution pattern of the metal and thus to different toxicological effects. To make an ecological founded risk assessment it is therefore essential to know to which extent each uptake route contributes to the total metal accumulation. Also for marine species data are rather scarce when compared to freshwater fish.