Assessing the genotoxicity of heavy metals and organic pollutants in Burrunan dolphins

Bioaccumulation ©MMF

Assessing the genotoxicity of heavy metals and organic pollutants in Burrunan dolphins

We aim to assess the health of the dolphins, trace the level of bioaccumulation of toxicants through the food-web and investigate the diet source.

Pollutants within an ecosystem biomagnify up the food chain and accumulate within the tissues of top order predators such as marine mammals. As such, dolphins are some of the best indicators of the bioavailability of pollutants and thus can be used as indicators for the health of an ecosystem. We know there are resident populations of Burrunan dolphins in Victoria which live almost exclusively within Port Phillip Bay or Gippsland Lakes. The levels of toxicants which may have accumulated in these resident dolphins is a direct bioaccumulation of the toxicants in these ecosystems and can therefore give us an indication of the overall health of these water ways.

PCBs and PAHs as well as mercury have been suggested to be related to mass mortality and population decline of some cetacean species, as a result of impaired reproductive success and immune defence (Taddei et al., 2001). The Burrunan dolphin has been found to contain some of the highest recorded mercury levels among all cetaceans worldwide (Monk et al., 2014), with beach-cast deceased individuals recording levels three times higher than those in the live population (Monk et al., 2014). Newer technologies now exist to assess, in real-time, the genotoxicity and stress impacts of heavy metal and organic toxicants on the Burrunan dolphins. However, to date there has been no analysis taken on the health of the animals, and therefore we cannot draw conclusions of the high but sub-lethal concentrations. Additionally, there is a need for a comprehensive food web study in order to calculate the amount of heavy metals and organic pollutants the Burrunan dolphin is consuming and trace the route of accumulation.

Recent advances in research and technology have allowed for improved methods for collecting and analysing biological samples of live animals in a less-invasive manner. Using remotely acquired biopsy samples, Comet Assays and MICA protein expression can be preformed to assess genotoxicity and stress respectively from the aforementioned toxicants. Biopsy sampling protocols are in accordance with current animal ethics and scientific permit conditions. One biopsy sample collected from free-swimming dolphins will allow genetic analyses (using the skin portion of the sample) and diet and/or toxicological analyses (from the blubber/skin portion). This small but important sample from living populations, coupled with fin identification, uses a multi-disciplinary approach encompassing studies on population & conservation genetics, and assesses health of the Burrunan dolphins. All animals will be identified prior to a biopsy, and since the scientists at MMF are familiar with each marked individual, there will be no risk of the same animal being biopsied more than once.

Aims

  • Assess health of the Burrunan dolphins by investigating the genotoxicity of heavy metals and organic pollutants (using COMET assays), and stress from pollutants (via MICA protein expression) in Burrunan dolphins.
  • Investigate the diet of the Burrunan dolphins, to establish the route of bioaccumulation of toxicants within the animals.

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