This data features stable carbon and nitrogen isotopes of co-occurring Southern Ocean pteropods in order to estimate and compare their Bayesian isotopic niches. Other data includes station number, latitude and longitude, species names and sample ID. Details for each column are as follows: A: "species" - Species analysed including, "clio" = Clio pyramidata f. sulcata; "clione" = Clione limacina antarctica; "spongio" = Spongiobranchaea australis; "Large-fraction POM" = large-fraction particulate organic matter; "Small-fraction POM" = small-fraction particulate organic matter B: "speciesID" - Sample ID = unique identifier from Central Science Laboratory, University of Tasmania C: "station" = CTD number (KAxis research voyage) D: "date" = Date of sample (RMT-8 net trawl, KAxis research voyage) E: "lat" = Latitude (degS) F: "long" = Longitude (degE) G: "%C" = percent carbon (no unit) H: "%N" = percent nitrogen (no unit) I: "C:N (bulk)" = uncorrected (raw) carbon-to-nitrogen ratio (no unit) J: "delta 13C (bulk)" = uncorrected (raw) stable carbon isotope values (‰) H: "delta 15N (bulk)" = uncorrected (raw) stable nitrogen isotope values (‰) L: "notes" = samples may be duplicated or triplicated M: "atomic C:N" = C:N (bulk) x 14/12 (no unit) N: "atomic L" = 93/(1+ (1/((0.246 x atomic C:N) - 0.775))) O: "L" = 93/(1+(1/((0.246 x C:N (bulk) - 0.775))) P: "delta 13C (Kiljunen)" = delta 13C (bulk) corrected using formula by Kiljunen et al. 2006 Q: "delta 13C (atomic Kiljunen)" = delta 13C (bulk) corrected using formula by Kiljunen et al. 2006 and atomic L value (column N) R: "delta 13C (Post)" = delta 13C (bulk) corrected using formula by Post et al. 2007 S: "delta 13C (Weldrick)" = delta 13C (bulk) corrected using formula by Weldrick et al. 2019 T: "delta 13C (atomic Smyntek)" = delta 13C (bulk) corrected using formula by Smyntek et al. 2007 and atomic L value (column N) U: "delta 13C (Smyntek)" = delta 13C (bulk) corrected using formula by Smyntek et al. 2007 V: "delta 13C (Logan)" = delta 13C (bulk) corrected using formula by Logan et al. 2008 W: "delta 13C (Syvaranta)" = delta 13C (bulk) corrected using formula by Syvaranta and Rautio 2010 The analysis is featured within a recently accepted paper titled "Trophodynamics of Southern Ocean pteropods on the southern Kerguelen Plateau" peer-reviewed for Ecology and Evolution (2019). It is based on samples collected during the KAxis research voyage, 2015/16.

Mesopelagic fish bulk stable isotope data from the Kerguelen Axis ecosystem study (AAS_4344): These data are based on samples collected as part of the Kerguelen Axis marine ecosystem study (AAS_4344), chief scientist Andrew Constable. This research was supported by the Australian government under the (i) Cooperative Research Centre Program through the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), (ii) Australian Antarctic Science Program (Projects 4343, 4344, 4347 and 4366), and (iii) Australian Research Council’s Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). The preferred citation is: Woods, B., Walters, A., Hindell, M.A., Trebilco, R. (2019) Isotopic insights into mesopelagic niche space and energy pathways on the southern Kerguelen Plateau. Deep Sea Research Part II: Topical Studies in Oceanography Samples for stable isotope analysis were collected on board the R.S.V Aurora Australis during the austral summer of 2016 (22 January – 17 February) as part of the Kerguelen Axis marine ecosystem study (AAS_4344). Samples were collected from 15 sampling stations along two transects from the Antarctic continental shelf to the BANZARE Bank over the Kerguelen Plateau and in an east to west direction across the Kerguelen Plateau. Mesopelagic fish were sampled from the surface to 1000 m depth using an IYGPT (International Young Gadoid Pelagic Trawl) net equipped with a MIDOC (Mid-water Open Close) multiple cod-end device. Analyses focused on an assemblage including genera from the family Myctophidae (Electrona, Gymnoscopelus, Krefftichthys and Protomyctophum), and the genus Bathylagus from the family Bathylagidae, as these are dominant genera in the Southern Ocean (Pusch et al., 2004; Hulley and Duhamel, 2011; Collins et al., 2012). Muscle tissue from each fish was analysed for δ15N and δ13C. Collins, M. A., Stowasser, G., Fielding, S., Shreeve, R., Xavier, J. C., Venables, H. J., . . . Van de Putte, A. (2012). Latitudinal and bathymetric patterns in the distribution and abundance of mesopelagic fish in the Scotia Sea. Deep-Sea Research Part Ii-Topical Studies in Oceanography, 59, 189-198. doi:10.1016/j.dsr2.2011.07.003 Hulley, P. A., and Duhamel, G. (2011). Aspects of lanternfish distribution in the Kerguelen Plateau region. The Kerguelen Plateau: marine ecosystems and fisheies. G. Duhamel and DC Welsford, Editors, 183-195. Pusch, C., Hulley, P. A., and Kock, K. H. (2004). Community structure and feeding ecology of mesopelagic fishes in the slope waters of King George Island (South Shetland Islands, Antarctica). Deep-Sea Research Part I-Oceanographic Research Papers, 51(11), 1685-1708. doi:10.1016/j.dsr.2004.06.008