Water samples were collected from the seawater line on the Aurora Australis during the K-Axis voyage. They were filtered so that two fractions of each sample were collected: a fraction that was between 1.2 and 210 um and a fraction that was between 210 and 1000 um. A 47 mm diameter 1000 um mesh was placed upstream of all samples, and this prevented larger particles (e.g. zooplankton) from entering the samples. The underway water was taken from the pCO2 rig at 1.4 to 1.5 atmospheres. All samples were collected on 25 mm diameter 1.2um Sterlitech silver membrane filters. The greater than 210 samples were collected on mesh and refiltered onto silver filters. The filters were stored frozen until they were processed in Hobart. Subsamples of the filters were analysed at the Central Science Laboratories, University of Tasmania to determine elemental N and C. The remainder of the filters were analysed by ANSTO (NSW) to determine delta15N and delta13C. Volumes are in litres, and the values for the nitrogen isotopes are presented as ratios.

High-throughput DNA-sequencing data for mesopelagic fish stomach contents sampled during the Kerguelen Axis voyage (January-Februay 2016). Mesopelagic fish form an important link between zooplankton and higher trophic levels in Southern Ocean food webs, however their diets are poorly known. Most of the dietary information available comes from morphological analysis of stomach contents and to a lesser extent fatty acid and stable isotopes. DNA sequencing could substantially improve our knowledge of mesopelagic fish diets, but has not previously been applied. We used high-throughput DNA sequencing (HTS) of the 18S ribosomal DNA and mitochondrial cytochrome oxidase I (COI) to characterise stomach contents of four myctophid and one bathylagid species collected at the southern extension of the Kerguelen Plateau (southern Kerguelen Axis), one of the most productive regions in the Indian sector of the Southern Ocean. Diets of the four myctophid species were dominated by amphipods, euphausiids and copepods, whereas radiolarians and siphonophores contributed a much greater proportion of HTS reads for Bathylagus sp. Analysis of mitochondrial COI showed that all species preyed on Thysanoessa macrura, but Euphausia superba was only detected in the stomach contents of myctophids. Size-based shifts in diet were apparent, with larger individuals of both bathylagid and myctophid species more likely to consume euphausiids, but we found little evidence for regional differences in diet composition for each species over the survey area. The presence of DNA from coelenterates and other gelatinous prey in the stomach contents of all five species suggests the importance of these taxa in the diet of Southern Ocean mesopelagics has been underestimated to date. Our study demonstrates the use of DNA-based diet assessment to determine the role of mesopelagic fish and their trophic position in the Southern Ocean and inform the development of ecosystem models. For more detail, see Clarke LJ, Trebilco R, Walters A, Polanowski AM, Deagle BE (2018). DNA-based diet analysis of mesopelagic fish from the southern Kerguelen Axis. Deep Sea Research Part II: Topical Studies in Oceanography. DOI: 10.1016/j.dsr2.2018.09.001.

Midwater fish nitrogen 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: Walters et al. Food sources and trophic structure of deep sea midwater (fish) food webs in the Southern Ocean as inferred from nitrogen isotopic compositions. Midwater fish samples 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 9 sampling stations along one transect from the Antarctic continental shelf to the BANZARE Bank over the Kerguelen Plateau. Midwater 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 mesopelagic and bathypelagic fish taxa. The nitrogen isotopic composition of individual amino acids was measured in muscle tissue from each fish. As of 2022-09-30, these data were still being worked up for publication.

Sampling Samples were collected on board the RSV Aurora Australis between 22 January and 17 February 2016. The cruise surveyed the region south of the Kerguelen Plateau including the Princess Elizabeth Trough and BANZARE Bank in a series of eight transects covering 8165 km. Plankton communities were collected at 45 conductivity temperature depth (CTD) stations and seven additional underway stations, with biological replicates collected at two stations (52 independent sites). Surface water was sampled from 4 plus or minus 2 m depth using the uncontaminated seawater line. Deep Chlorophyll Maximum (DCM, 10-74 m) water samples were obtained using 10 L Niskin bottles mounted on a Seabird 911+ CTD. Plankton communities were size-fractionated by sequentially filtering 10 L seawater through 25 mm 20 micron (nylon) and 5 micron filters (PVDF), and 0.45 micron Sterivex filters (PVDF). Filters were stored frozen at -80 °C. DNA extraction and high-throughput sequencing DNA was extracted from half of each filter using the MoBio PowerSoil DNA Isolation kit at the Australian Genome Research Facility (AGRF, Adelaide, Australia; http://www.agrf.org.au). The V4 region of the 18S rDNA (approximately 380 bp excluding primers) was PCR-amplified using universal eukaryotic primers from all extracts and sequenced on an Illumina MiSeq v2 (2 x 250 bp paired-end) following the Ocean Sampling Day protocol (Piredda et al. 2017). Amplicon library preparation and high-throughput sequencing were carried out at the Ramaciotti Centre for Genomics (Sydney, Australia). Sequence analysis, OTU picking and assignment followed the Biomes of Australian Soil Environments (BASE) workflow (Bissett et al. 2016). Taxonomy was assigned to OTUs based on the PR2 database using the ‘classify.seqs’ command in mothur version 1.31.2 with default settings and a bootstrap cut-off of 60%. OTUs representing any terrestrial contaminants (e.g. human) and samples with low sequencing coverage (less than 7000 reads) were removed from the dataset. The date of sea ice melt for each station was estimated from daily SSM/I-derived sea-ice spatial concentration from the National Snow and Ice Data Centre (NSIDC) at 25 x 25 km resolution. Days since melt was considered to be the number of days between the date on which sea ice concentration first fell below 15% and the date of sampling. Other environmental variables included are in situ chlorophyll a, as an indicator of biological production, and near-surface salinity (mean over the upper 10 m) as an indicator for recent sea ice melt. Both environmental measurements were taken from the associated CTD seawater samples. The surface chlorophyll a in seawater (1-2 L) collected in Niskin bottles was analysed by high performance liquid chromatography (HPLC, provided by Karen Westwood and Imojen Pearce, Australian Antarctic Division, doi:10.4225/15/5a94c701b98a8). Sampling times are given in UTC.

Mesopelagic fish gut content 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: Riaz, J., Walters, A., Trebilco, R., Bestley, S., Lea, M-A. (2019) Stomach content analysis of mesopelagic fish from the southern Kerguelen Axis. Deep Sea Research Part II: Topical Studies in Oceanography. Samples for gut content analysis were collected on board the R.S.V Aurora Australis during the austral summer of 2016 (22 January-17 February) during the Kerguelen Axis marine ecosystem survey (AAS_4344). Analyses focused on four of the most common and widespread Southern Ocean mesopelagic fish species: three myctophids (Electrona antarctica, Gymnoscopelus braueri, Krefftichthys anderssoni), and one bathylagid (Bathylagus antarcticus). Species were sampled across a broad range of size classes to investigate the influence of predator size on predator and prey size relationships. Fish were collected from six sampling stations along the major south-to-north transect of the Kerguelen Axis. Three sampling sites were located in subpolar waters south of the Southern Boundary (SB) of the Antarctic Circumpolar Current (ACC) over the Princess Elizabeth Trough. The other three sampling sites were located north of the Southern Antarctic Circumpolar Circulation Front (SACCF) over the Banzare Bank on the southern Kerguelen Plateau.The contribution and relative importance of prey taxa to stomach contents was quantified with four traditional metrics of dietary composition (Hyslop 1980). These were calculated for each fish species separately at northern and southern sampling stations, and across species within all stations. Hyslop, E. J. (1980) Stomach contents analysis-a review of methods and their application. Journal of Fish Biology 17:411.

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

This entry contains: Locations for sampling sites for ASAC project 2596 on voyage 3 of the Aurora Australis in the 2004/5 season, collected between December and February of 2004/5; CTD bottle-derived seawater viscosity data and CTD bottle-derived in vivo fluorescence data. Note: ASAC project 2596 operates in direct collaboration with ASAC project 2382 (Impact of viscosity on the morphology and swimming behaviour of motile bacterioplankton, phytoplankton and protozooplankton). There are four spreadsheet files in this entry. Each spreadsheet file contains several worksheets. 1) Transect 1 (CLIVAR I9 = 'I9') station and sampling details: CTD stations, CTD profiles, Surface samples. 2) Transect 2 (Kerguelen Plateau and Princess Elizabeth Trough = 'PET') station and sampling details: CTD stations, CTD profiles. 3) 10 x 10 Flow Cytometry (FCM) data, derived from a two-dimensional microscale sampling device. 4) FluoroMAP profiles. These files contain the following data: Count Date Time Pressure (milliVolts)/Depth Chlo Depth - is the pressure in milli-Volts (mV) which is can be converted to depth in meters using the manufacturers calibration, Where, depth (m) = 0.00149 * (depth (mV)) -7.5 Chlo= is short for chlorophyll fluorescence and has arbitrary units (a.u.) For all files -999 entry = missing data A word document details the sampling protocols for FCM, 10 x 10 samples and FluoroMAP profiles. See the link below for public details on this project.

During the K-Axis marine voyage from mid Jan-late Feb 2016, a diverse range of sampling techniques were employed to collect specimens and data. Each sampling event was recorded by scientists and technical support staff in a logbook that was kept in the operations room on board the Aurora Australis. This is a PDF of the scanned original document, compiled on paper during the voyage. event_number: A unique event identifier in the log, in the order that the events were written down (usually but not always chronologically) event_type: The code defined and used by each research project to identify the types of equipment deployed or samples collected for an event. event_type_prefix: A non-mandatory prefix field used by some research projects to identify the type of an event event_type_number: A sequential number or alphanumeric-number combination defined and used by each research project to identify unique equipment deployment or sample collection events station_number: A universal (voyage-wide) station number used across all projects to identify a nominal lat/lon position defined during voyage planning leg: A nominally straight-line section of the voyage track defined during voyage planning. The voyage track was planned as a series of roughly N-S and E-W transects that intersected in some locations. Legs start at a station and continue through more stations to a vertex-station which is the start of the next leg. Legs are numbered consecutively. waypoint: A GPS waypoint used by Aurora Australis crew, AAD science technical support and researchers to identify target lat/lon positions in the voyage. Some waypoints correspond with station numbers. start_date_utc: The start date of the event in UTC start_time_utc: The start time of the event in UTC start_lat_deg: The latitude (whole degrees) of the vessel at the beginning of the event start_lat_min: The latitude (minutes) of the vessel at the beginning of the event start_lat_dec_deg: The latitude (decimal degrees) of the vessel at the beginning of the event start_lon_deg: The longitude (whole degrees) of the vessel at the beginning of the event start_lon_min: The longitude (minutes) of the vessel at the beginning of the event start_lon_dec_deg: The longitude (decimal degrees) of the vessel at the beginning of the event end_date_utc: The end date of the event in UTC end_time_utc: The end time of the event in UTC end_lat_deg: The latitude (whole degrees) of the vessel at the end of the event end_lat_min: The latitude (minutes) of the vessel at the end of the event end_lat_dec_deg: The latitude (decimal degrees) of the vessel at the end of the event end_lon_deg: The longitude (whole degrees) of the vessel at the end of the event end_lon_min: The longitude (minutes) of the vessel at the end of the event end_lon_dec_deg: The longitude (decimal degrees) of the vessel at the end of the event remarks: Comments/remarks written by researchers when completing the paper log

During the K-Axis marine voyage from mid Jan-late Feb 2016, a diverse range of sampling techniques were employed to collect specimens and data. Each sampling event was recorded by scientists and technical support staff in a logbook that was kept in the operations room on board the Aurora Australis. This is a direct digital copy/transcription of the paper logbook. event_number: A unique event identifier in the log, in the order that the events were written down (usually but not always chronologically) event_type: The code defined and used by each research project to identify the types of equipment deployed or samples collected for an event. event_type_prefix: A non-mandatory prefix field used by some research projects to identify the type of an event event_type_number: A sequential number or alphanumeric-number combination defined and used by each research project to identify unique equipment deployment or sample collection events station_number: A universal (voyage-wide) station number used across all projects to identify a nominal lat/lon position defined during voyage planning leg: A nominally straight-line section of the voyage track defined during voyage planning. The voyage track was planned as a series of roughly N-S and E-W transects that intersected in some locations. Legs start at a station and continue through more stations to a vertex-station which is the start of the next leg. Legs are numbered consecutively. waypoint: A GPS waypoint used by Aurora Australis crew, AAD science technical support and researchers to identify target lat/lon positions in the voyage. Some waypoints correspond with station numbers. start_date_utc: The start date of the event in UTC start_time_utc: The start time of the event in UTC start_lat_deg: The latitude (whole degrees) of the vessel at the beginning of the event start_lat_min: The latitude (minutes) of the vessel at the beginning of the event start_lat_dec_deg: The latitude (decimal degrees) of the vessel at the beginning of the event start_lon_deg: The longitude (whole degrees) of the vessel at the beginning of the event start_lon_min: The longitude (minutes) of the vessel at the beginning of the event start_lon_dec_deg: The longitude (decimal degrees) of the vessel at the beginning of the event end_date_utc: The end date of the event in UTC end_time_utc: The end time of the event in UTC end_lat_deg: The latitude (whole degrees) of the vessel at the end of the event end_lat_min: The latitude (minutes) of the vessel at the end of the event end_lat_dec_deg: The latitude (decimal degrees) of the vessel at the end of the event end_lon_deg: The longitude (whole degrees) of the vessel at the end of the event end_lon_min: The longitude (minutes) of the vessel at the end of the event end_lon_dec_deg: The longitude (decimal degrees) of the vessel at the end of the event remarks: Comments/remarks written by researchers when completing the paper log transcribe_comments: Comments/remarks made by the transcriber when the log was digitised

During the K-Axis marine voyage from mid Jan-late Feb 2016, a diverse range of sampling techniques were employed to collect specimens and data. Each sampling event was recorded by scientists and technical support staff in a logbook that was kept in the operations room on board the Aurora Australis. This is a direct digital transcription of the paper logbook with interpolated lat/lon from underway data to supplement start times as recorded in the log. The method used to obtain the supplementary position is described in the associated eventlog_matchup.html file. event_number: A unique event identifier in the log, in the order that the events were written down (usually but not always chronologically) event_type: The code defined and used by each research project to identify the types of equipment deployed or samples collected for an event. event_type_prefix: A non-mandatory prefix field used by some research projects to identify the type of an event event_type_number: A sequential number or alphanumeric-number combination defined and used by each research project to identify unique equipment deployment or sample collection events station_number: A universal (voyage-wide) station number used across all projects to identify a nominal lat/lon position defined during voyage planning leg: A nominally straight-line section of the voyage track defined during voyage planning. The voyage track was planned as a series of roughly N-S and E-W transects that intersected in some locations. Legs start at a station and continue through more stations to a vertex-station which is the start of the next leg. Legs are numbered consecutively. waypoint: A GPS waypoint used by Aurora Australis crew, AAD science technical support and researchers to identify target lat/lon positions in the voyage. Some waypoints correspond with station numbers. start_date_utc: The start date of the event in UTC start_time_utc: The start time of the event in UTC start_lat_deg: The latitude (whole degrees) of the vessel at the beginning of the event start_lat_min: The latitude (minutes) of the vessel at the beginning of the event start_lat_dec_deg: The latitude (decimal degrees) of the vessel at the beginning of the event start_lon_deg: The longitude (whole degrees) of the vessel at the beginning of the event start_lon_min: The longitude (minutes) of the vessel at the beginning of the event start_lon_dec_deg: The longitude (decimal degrees) of the vessel at the beginning of the event end_date_utc: The end date of the event in UTC end_time_utc: The end time of the event in UTC end_lat_deg: The latitude (whole degrees) of the vessel at the end of the event end_lat_min: The latitude (minutes) of the vessel at the end of the event end_lat_dec_deg: The latitude (decimal degrees) of the vessel at the end of the event end_lon_deg: The longitude (whole degrees) of the vessel at the end of the event end_lon_min: The longitude (minutes) of the vessel at the end of the event end_lon_dec_deg: The longitude (decimal degrees) of the vessel at the end of the event remarks: Comments/remarks written by researchers when completing the paper log transcribe_comments: Comments/remarks made by the transcriber when the log was digitised utc: The start date and time of the event in UTC start_lon_dec_deg_interp: The latitude (decimal degrees) of the vessel at the beginning of the event interpolated from the vessel underway data start_lat_dec_deg_interp: The longitude (decimal degrees) of the vessel at the beginning of the event interpolated from the vessel underway data