Embryo aberrations in the amphipod Monoporeia affinis as indicators of toxic pollutants in sediments : A field evaluation

Reproduction in the amphipod Monoporeia affinis is sensitive to contaminant exposure, and embryo aberrations are used in the Swedish National Monitoring Program to indicate biological effects of contaminants. However, empirical support for a causal relationship between contaminant load and frequency of aberrations is largely based on experimental studies. A field evaluation of aberration frequency in relation to contaminant exposure is required, if we are to use reproductive disorders as indicators of contaminant effects in risk assessment. In this study, we evaluated occurrence of females carrying malformed embryos and frequency of specific embryo aberrations in broods of M. affinis in relation to concentrations of various pollutants in sediments. Gravid M. affinis and surface sediment were sampled at ten sites in the Gulf of Bothnia located at varying proximity to historical and current polluting point sources. At each site, concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and trace and heavy metals in surface sediments were determined. Amphipod fecundity and embryo development status were assayed with regard to morphologically recognizable aberrations (malformed embryos, membrane-damaged embryos, embryos with arrested development and females with dead brood). Our key finding is that different types of embryo aberrations were significantly associated with specific contaminant groups in the sediment. In particular, occurrence of females with embryo malformations was strongly related to elevated concentrations of Cd and PCBs, while females with membrane-damaged embryos occurred at high PAH concentrations. Also, frequency of embryos with arrested development was linked to elevated concentrations of PAHs and metals. Finally, frequency of females carrying dead broods, which was earlier considered to be a hypoxia-induced pathology, was significantly positively related to PAH concentrations. Thus, these reproductive aberrations in M. affinis can serve as contaminant-specific indicators of PCB, PAH and heavy metal exposure in biological effect monitoring.