Biomarkers and bioindicators of hypoxia and sediment toxicity in Monoporeia affinis

Abstract: Two of the most pressing environmental problems in the Baltic Sea are pollution and oxygen deficiency. The aim of this doctoral thesis was to evaluate a set of biomarkers and reproductive variables in the amphipod Monoporeia affinis to test their suitability as indicators of exposure to contaminants and hypoxia. In Paper I and Paper II, field-sampled M. affinis were exposed to varying oxygen conditions in combination with contaminated or reference sediment. Paper I showed that the combined effect of hypoxia and contaminants induced larger increases in antioxidant enzyme activities and higher levels of damaged lipids, resulting from oxidative stress, than single-stress treatments. The biomarkers AChE and GST responded only to the contaminant exposure. Paper II demonstrated that M. affinis can prepare against oxidative stress that facilitates recovery after a hypoxic episode, but that exposure to contaminants altered this response and resulted in higher baselines of antioxidants during hypoxia and no response upon reoxygenation. Paper III linked the occurrence of different embryo aberrations in M. affinis to concentrations of PAHs, PCBs and metals in sediments in the field. A key finding is that different types of embryo aberrations were associated with specific contaminant groups in the sediment. Paper IV addressed the link between biomarkers and bioindicators in M. affinis and found positive associations between increased antioxidant capacity in females and higher occurrence and frequencies of malformed and membrane-damaged embryos. AChE inhibition was linked to frequency of membrane-damaged embryos. Links between biomarker response and fecundity and embryo developmental stage were also established. Further, a large part of the variation in female antioxidant capacity and AChE activity could be explained by variation in concentrations of different metals, PAHs and PCB congeners, in combination with the environmental variables salinity, depth and sediment TOC.