| Summary: | Marine ecosystems are essential to life on Earth, but they constantly face the consequences of human activities. International conventions such as the Convention for the Protection of the Marine Environment of the North-East Atlantic and directives such as the Marine Strategy Framework Directive urge countries to improve monitoring and conservation of ocean health. Bioindicator species can help us assess the health status of ecosystems, and while there are many good candidates among the hundreds of extant shark species, the blue shark (Prionace glauca) stands out as one of the most widely distributed and socioeconomically important shark species in the world. This work highlighted the importance of blue shark in the Portuguese elasmobranch fisheries and the need for better management strategies. Sixty sharks were sampled in the Northeast Atlantic and the results evidenced high contaminant body burdens, with two thirds of the sharks presenting concentrations of Hg and/or Pb in their muscle above safety thresholds for human consumers. Location was the main factor influencing contaminants accumulation, with sharks captured closer to the continental shore presenting higher contamination when compared with sharks from more oceanic locations. A similar pattern was observed in biomarker responses, with the sharks from areas closer to the continental shore (i.e., more contaminated) exhibiting more pronounced responses. Additionally, the amount of damaged DNA in the liver and protective alterations in the gills correlated strongly and positively with contaminants in sharks from the more contaminated area (i.e., As, PCBs, and PBDEs). Ultimately, this thesis validated the potential of blue shark as a bioindicator of pollution in the Atlantic, and the specific biomarkers with potential in marine biomonitoring surveys, whilst contributing useful data for better management and conservation.
|
|---|