Microscopic anatomy and histopathological observations in Antarctic rock cod (Trematomus bernacchii) collected from uncontaminated and contaminated sites

The circumpolar Antarctic rock cod ( Trematomus bernacchii ) is an important bioindicator species for marine Antarctic coastal waters. Histopathological alterations of key organs in this species provide an indicator of anthropogenic impacts and overall ecological condition. As a long-lived benthic species with a small home range, assessments of histopathology and health status of Trematomus bernacchii are ideal for identifying spatial and temporal changes and impacts resulting from exposure to contaminants in their environment. A collection of microscopic anatomy and histopathological observations of representative normal compared to abnormal histology of key organs including gill, liver, spleen, kidney and gonad was compiled from fish near Davis station, East Antarctica. Fish were collected within 300 m of the wastewater outfall, and at reference sites up to 9 km away from any obvious signs of anthropogenic input or impacts. Sub-lethal histological alterations identified across multiple organs indicates impaired health in fish near the outfall, providing strong evidence of response to contamination. Familiarity with ‘normal’ baseline and common pathologies improves ability to detect changes due to contamination, and reduces the chance of subjective observations and misidentification of alteration. Having a standard microscopic anatomy and histological observation for comparative assessment of tissue samples reduces error associated with subjectivity and differing levels of experience of examiners, and enables direct comparisons between populations in coastal areas around the whole of Antarctica, across temporal and spatial scales. The value of histopathology as a key component in multiple-lines-of-evidence ecological risk assessments, is further strengthened when combined with a numeric histological health index (HHI) which quantifies overall site-specific severity of impact in the environment.