Project description:Antarctic toothfish are a commercially exploited upper-level predator in the Southern Ocean. As many of its prey, the ectothermic, water-breathing Antarctic toothfish is specifically adapted to the temperature and oxygen conditions present in the high-latitude Southern Ocean. Additionally, the life cycle of Antarctic toothfish depends on sea-ice dynamics and the transport of individuals by currents between regions with different prey. To assess the impact of 21st-century climate change on potential interactions of Antarctic toothfish and its prey, we here employ the extended aerobic growth index (AGI), which quantifies the effect of ocean temperature and oxygen levels on the habitat viability of individual species. We quantify changes in predator-prey interactions by a change in viable habitat overlap as obtained with the AGI. As environmental data, we use future projections for four emission scenarios from the model FESOM-REcoM, which is specifically designed for applications on and near the Antarctic continental shelf. For the two highest-emission scenarios, we find that warming and deoxygenation in response to climate change cause a subsurface decline of up to 40% in viable habitat overlap of Antarctic toothfish with important prey species, such as Antarctic silverfish and icefish. Acknowledging regional differences, our results demonstrate that warming and deoxygenation alone can significantly perturb predator-prey habitat overlap in the Southern Ocean. Our findings highlight the need for a better quantitative understanding of climate change impacts on Antarctic species to better constrain future ecosystem impacts of climate change.
Project description:Stomach contents of the Antarctic toothfish, Dissostichus mawsoni, collected from subareas 58.4 and 88.3, were analyzed using next generation sequencing (NGS) technology. After processing the raw reads generated by the MiSeq platform, a total of 131,233 contigs (130 operational taxonomic units [OTUs]) were obtained from 163 individuals in subarea 58.4, and 75,961 contigs (105 OTUs) from 164 fish in subarea 88.3. At 98% sequence identity, species names were assigned to most OTUs in this study, indicating the quality of the DNA barcode database for the Antarctic Ocean was sufficient for molecular analysis, especially for fish species. A total of 19 species was identified from the stomach of D. mawsoni in this study, which included 14 fish species and five mollusks. More than 90% of contigs belonged to fish species, supporting the postulate that the major prey of D. mawsoni are fish. Two fish species, Macrourus whitsoni and Chionobathyscus dewitti, were the most important prey items (a finding similar to that of previous studies). We also obtained genotypes of prey items by NGS analysis, identifying an additional 17 representative haplotypes in this study. Comparison with three previous morphological studies and the NGS-based molecular identification in this study extended our knowledge regarding the prey of D. mawsoni, which previously was not possible. These results suggested that NGS-based diet studies are possible, if several current technical limitations, including the quality of the barcode database or the development of precise molecular quantification techniques to link them with morphological values, are overcome. To achieve this, additional studies should be conducted on various marine organisms.