Strand, J., Bossi, R., Dahllöf, I., Jensen, C.A., Simonsen, V., Tairova, Z. & Tomkiewicz, J. 2009: Dioxin og biologisk effektmonitering i ålekvabbe i kystnære danske farvande. Danmarks Miljøundersøgelser, Aarhus Universitet. 66 s. - Faglig rapport fra DMU nr. 743.
Indications of disturbances on reproductive success in eelpout (Zoarces viviparus), also called Viviparous blenny, from Danish marine areas have been observed in recent years in connection with the yearly monitoring programme, called NOVANA. Prime suspects thought to have caused these disturbances have been contaminants, especially in relation to malformed larvae. If this is the case, then there can also be undesirable effects on reproduction for other marine organisms due to contaminants.
The aim of this study was to investigate whether additional new biomarkers could reveal more information on both pressures of contaminants as well as the effects in eelpout.
The project consisted of several parts focussing on dioxin-like compounds and PAHs and their potential effects in eelpout collected at 6-7 different sites in November 2007 and May to June 2008. Population genetics based on isozymes was also included in the study to verify that the eelpout had stationary populations and can be used in monitoring activities to assess the status of different marine areas.
The overall results showed that the populations differ with respect to the degree of contamination effects, but the picture is somewhat unclear as there are no direct link between the magnitude of dioxin and PAH contamination and the magnitude or type of effects seen. This suggests, however, that it is not only these compounds that are the causes for effects, but rather the complex mixtures of contaminants that occur in marine coastal areas. Furthermore, the magnitude or types of deformities cannot be directly correlated to the compounds in focus, or the other effects, but it has to be kept in mind that the effects occur at different time-scales, and that also other compounds or environmental factors can be involved.
The chemical analyses showed that all the eelpout populations were contaminated with dioxin-like compounds and PAHs. The differences in contamination levels between sites were most pronounced in the expression of CYP1A enzymes, and to a lesser degree by the activity of this enzyme system, as the enzymes also can be inhibited at higher contamination. CYP1A is important for the organism as it represents a pathway for biotransformation and excretion of contaminants like PAHs and dioxin-like compounds.
There are also indications that the Danish eelpout populations are effected by hormone disrupting compounds as a large fraction of the males (8-36%) developed intersex, seen as early stages of oocytes in their testicular tissue.
Overall for all studied parameters Aarhus Bight has in this study the most affected eelpout population, followed by Randers Fjord, Karrebæk Fjord, Roskilde Fjord and Vejle Fjord. The population from Agersø is in comparison only affected to a smaller extent.
Considering that the populations are stationary and that they are affected by contaminants that result in reduced reproductive success, including hormone disruptions, most likely some of the populations are more vulnerable, which can result in severe population declines.
It can finally be concluded that future monitoring activities of eelpout should be supported by both chemical analyses and complementary biomarkers like PAH-metabolites and intersex, in order to better understand what causes the undesirable effects seen today.
Full report in Danish i PDF-format (5.7 MB).
