Since 2000, a surprisingly high number of macroscopical gonad alterations has been
reported in whitefish (Coregonus spp.) from Lake Thun, Switzerland. This unique phenomenon
is still unexplained and has received much public attention. As one possible trigger
for these effects, the presence of persistent, bioaccumulative and toxic compounds
acting as endocrine disruptors in the lake has been discussed. In this study, concentrations
of selected persistent organic pollutants were examined in two morphs of whitefish
from Lake Thun and their link to the observed abnormalities was investigated. Analyzed
compound classes included polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins
and dibenzofurans, polychlorinated naphthalenes, polybrominated diphenyl ethers and
hexabromocyclododecanes. The target substances were identified in all samples and
concentrations of the analyzed compounds were highly correlated among each other.
These correlations show that the analyzed substances have the same distribution pattern
throughout the lake and that uptake, accumulation and elimination processes are similar.
Significant differences in contaminant levels within the samples existed between the
two analyzed morphs of whitefish, most likely due to different age, food patterns
and growth rate. No difference in contaminant levels was observed between fish with
abnormal gonads and fish with normal gonads, suggesting no causal link between the
investigated lipophilic organohalogen compounds present in fish and the observed gonad
abnormalities in whitefish from Lake Thun. A comparison to existing data shows that
concentrations in Lake Thun whitefish are at the lower bound of contaminant levels
in whitefish from Swiss lakes or from European waters.