Summary
Antarctic krill (Euphausia superba) is a keystone species of the Southern Ocean, vastly abundant and an essential food source of some of the Southern Ocean's most charismatic predators, including penguins, seals, and baleen whales. Antarctic krill are also targeted by a krill fishery, which is sustainably managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Krill abundance estimates, to date mainly calculated from acoustic surveys and trawls, inform CCAMLR to set catch limits. Our aim was to develop Antarctic krill specific eDNA markers for quantification of krill eDNA in open ocean surveys. We developed a range of potential markers targeting unique sequences of the MT 16S rRNA gene and tested them on DNA from a range of Southern Ocean krill species to ascertain species specificity. We determined DNA decay rates for three markers with diverse amplicon lengths under experimental conditions in the Australian Antarctic Division's Marine Research Aquarium, to establish whether an eDNA age signal could be estimated from contrasting decay rates. We also quantified krill eDNA from open ocean samples collected between Hobart, Tasmania and Australian Antarctic Davis station, and compared results to data obtained from euphausiid specific and broad range metazoan metabarcoding makers. This study helps to determine whether quantitative Antarctic krill eDNA surveys can contribute to krill abundance estimates in the Southern Ocean, and help inform CCAMLR to set sustainable catch limits for the krill fishery.
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