Environmental Physiology and Biochemistry

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.

Although cadmium toxicity is a well studied theme in the field of aquatic toxicology, still little is known concerning the molecular mechanisms of its toxic action. Moreover most laboratory studies only consider waterborne cadmium exposure, whereas dietary exposure can also contribute to the accumulation and effects of cadmium in fish. For a better understanding of the toxic responses leading to adverse effects there is an increasing need for more sensitive tools to determine early reactions on cadmium exposure and accumulation.

In collaboration with the Molecular Laboratory of the Royal Institute of Natural Sciences.

In Flanders (Belgium), many fish species are declining at an alarming rate, several species have gone extinct in the last few decades, and many more risk the same fate. Water pollution and river management practices have reduced and extensively altered aquatic habitats. For many species, the number of populations as well as the number of individuals per population have decreased dramatically. Moreover, it seems very difficult for individuals to develop genetic adaptations to their polluted habitats, since adaptation through natural selection is a relatively slow process. Surprisingly, previous studies reveal that various species are capable of developing adaptations to changing environments at fast rates. Studying the occurence of genetic adaptations in natural fish populations inhabiting polluted streams can therefore be of great value to evaluate the consequences of human activities on aquatic ecosystems. This is of vital importance for setting up conservation strategies.