Ultrastructural biomarkers as tools to characterize the health status of fish in contaminated streams

Abstract

Ultrastructural biomarkers in gill, liver, and kidney of brown trout (Salmo trutta f. fario) and stone loach (Barbatula barbatula) were investigated over a five year period. The cellular damage of the organs was assessed semiquantitatively based on a three-step classification of ultrastructural responses. Data obtained for fish exposed under semi-field conditions in two differently polluted test streams and in the laboratory demonstrated that the ultrastructure of the organs can be correlated with different pollutant exposure conditions. Cellular damage was generally more severe in fish exposed to a complexly polluted stream than in those exposed to a moderately polluted stream or to tap water in the laboratory. Histopathological effects in liver and gill of trout were more pronounced in feral fish than in transplanted fish, whereas responses in the kidney in both species, and in liver and gill of loach, were similar for introduced and feral fish. In a laboratory experiment where trout were exposed to different mixtures of pollutants including pesticides, PAH, and ammonia, only the ultrastructure of kidney and liver showed significant differences between the three experimental set-ups. In a recovery experiment, where trout were transferred from the semi-field condition back to the laboratory, ultrastructural investigations showed a differential capacity of the respective organs to recover from stress under field conditions. Kidney and liver fully recovered after three months under control condition whereas gills demonstrated only partial recovery.