This record describes multibeam echosounder data collected on RV Investigator voyage IN2019_V03, 2nd Indian Ocean Expedition Line which departed Fremantle on the 14/05/2019 and returned to Fremantle on the 14/06/2019. The Kongsberg EM710 MKII multibeam echosounder was used to acquire seafloor bathymetry and backscatter information watercolumn backscatter in the area of the Indian Ocean, 110° E. The EM710 MKII provides a 0.5° by 1° transmit and receive angular resolution respectively. The echosounder's nominal frequency range is from 40 to 100 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 825 files totalling 94.8 GB of raw data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. Tide corrections were not applied to the processed data. Processed data has had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

Samples were obtained from the RV Investigator from 14 May - June 5, 2019 as part of the 2nd Indian Ocean Expedition (IIOE-2). A total of 20 stations (90 nautical miles apart) from 39.5 deg south to 11.5 deg S along the 110 ?E meridian was sampled during both day and night. The samples were obtained by means of hauls using a EZ multi-net with a 1 m2 mouth area and eight operating nets (500 µm mesh). It was sent down to 500 m depth and oblique hauls discriminating the following depth strata of the water column were taken as the net was retrieved: 500-400, 400-300, 300-200, 200-150, 150-100, 100-50, 50 - 5 m. Each stratum was sampled for about 10 min and the volume of water filtered was obtained via use of an electronically recording flowmeter (mean volume: 486.5 m3). In summary, 273 discrete stratum hauls, covering the upper 500 m of the water column, were made along the 110 deg E transect in the Indian Ocean. After sorting and identification of fish specimens on board, samples were preserved in 10% buffered formalin with borax for later inspection in the laboratory.

The aim of this study, as part of a large number of related studies, was to examine the occurrence of cetaceans and seabirds along the 110◦E meridian from temperate to tropical waters (39.5–11.5◦S). Cetaceans and seabirds were actively scanned for across a four-week period spanning austral autumn to winter. Acoustic recordings of vocalising cetaceans weremade using directional and omnidirectional sonobuoys (n = 87 deployments). In total, seven cetacean sightings (six baleen whale, one toothed whale), 186 seabird sightings and 225 cetacean acoustic detections were recorded. A total of 22 seabird species were sighted, including, petrels, albatrosses, tropicbirds, terns, shearwaters, boobies, frigatebirds, gannets, gulls, skuas and prions.

This record describes gravity data collected on RV Investigator voyage IN2019_V03, 2nd Indian Ocean Expedition Line which departed Fremantle on the 14/05/2019 and returned to Fremantle on the 14/06/2019. The gravity meter instrument is a MicroG Lacoste Air-Sea II. Data are stored in .ENV and .DAT data files at CSIRO. There are 66 files totalling 520 MB of raw data in this dataset. Wharf ties were undertaken at Fremantle (before departure) and Fremantle (upon arrival) using a Scintrex Autograv CG-5. Wharf tie data can be found in in2019_v03_Gravity_Tie_Fremantle.TXT, which is stored with the raw data. No processing has been conducted on this data. Additional information regarding this dataset is contained in the GSM data acquisition and processing report.

This record describes sub bottom profiler data collected on RV Investigator voyage IN2019_V03, 2nd Indian Ocean Expedition Line which departed Fremantle on the 14/05/2019 and returned to Fremantle on the 14/06/2019. The Kongsberg SBP120 (sub bottom profiler) was used to acquire data containing the specular reflections at different sediment interfaces below the seafloor. The SBP120 provides a 3° by 3° angular resolution. The echosounder's frequency sweep range is from 2.5 to 7 kHz. The SBP120 was logged sporadically for the extent of the voyage. The SBP120 pinging and logging was suspended when holding station (ie not underway) Data are stored in *.raw (458 files 8.6 GB) raw and *.seg (458 files 8.7 GB) segy formats at CSIRO. The segy format data had a real time processing stream applied, which applies gain, a gain correction, matched filter with replica shaping, an attribute calculation for instantaneous amplitude and time variable gain. Additional information regarding this dataset is contained in the GSM data acquisition and processing report. Additional data products may be available on request

This record describes scientific split-beam echosounder data collected on the RV Investigator voyage IN2019_V03, 2nd Indian Ocean Expedition Line which departed Fremantle on the 14/05/2019 and returned to Fremantle on the 14/06/2019. The Simrad EK60 split beam echosounders 18, 38, 70 120, 200 and 333 kHz were used to acquire acoustic backscatter data to a range of 1500 m in the area of the Indian Ocean, 110° E. All frequencies were logged continuously for the extent of the voyage. The frequencies were set to passive for the whole of the voyage. Data are stored in *.raw, *.bot and *.idx format at CSIRO. There are 2626 files totalling 73.4 GB of raw data in this dataset. No processing has been conducted on this data. Additional information regarding this dataset is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2019_V03, 2nd Indian Ocean Expedition Line which departed Fremantle on the 14/05/2019 and returned to Fremantle on the 14/06/2019. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter in the area of the Indian Ocean, 110° E. The EM122 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 1190 files totalling 60.8 GB of raw data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. Tide corrections were not applied to the processed data. Processed data had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes the Acoustic Doppler Current Profiler (ADCP) data collected from the Marine National Facility RV Investigator voyage IN2019_V03, titled: "A coupled bio-physical, ecosystem-scale, examination of Australia’s International Indian Ocean Expedition line." The voyage took place between May 14 and June 14, 2019 departing from Fremantle (WA) and arriving in Fremantle. Data was collected during in2019_v03 for the duration of the voyage. Data was collected using UHDAS and post-processed using CODAS. Both the RDI Ocean Surveyor 150kHz ADCP and the RDI Ocean Surveyor 75kHz ADCP were run in narrowband. Internal triggering was used. The drop keel was at 2m below the waterline for the duration of the voyage. See the voyage computing and electronics report for more details regarding data acquisition. This dataset was processed and then archived within the CSIRO Oceans and Atmosphere (O&A) Information and Data Centre (IDC) in Hobart.

This record describes Hydrology (HYD) data collected from the Marine National Facility (MNF) RV Investigator voyage IN2019_V03, titled: "A coupled bio-physical, ecosystem-scale, examination of Australia’s International Indian Ocean Expedition line 110E." The voyage took place from Fremantle (WA) to Fremantle between May 14 and June 14, 2019. Hydrology samples were collected from Niskin bottles sampled at various depths during Conductivity-Temperature-Depth (CTD) deployments. Parameters analysed were salinity, dissolved oxygen, phosphate, silicate, nitrate plus nitrite and ammonium. This dataset has been archived at the CSIRO O&A Information and Data Centre (IDC) in Hobart. Additional information regarding this dataset is contained in the Voyage Report and Data Processing Report.

This record describes the data (CTD, Dissolved Oxygen, Transmissometer, PAR, ECO Triplet, Nitrate, Fluorescence and LOPC) collected using the towed TRIAXUS platform on Investigator voyage IN2019_V03, titled: "A coupled bio-physical, ecosystem-scale, examination of Australia’s International Indian Ocean Expedition line." The voyage took place between May 14 and June 14, 2019 departing from Fremantle (WA) and arriving in Fremantle. Data for 3 Triaxus deployments were acquired using seabirds SeaSave acquisition software with Seabird SBE911+ CTD #23. Sea-Bird and O&A Calibration lab supplied calibration factors were used to compute the pressure, preliminary conductivity, oxygen and temperature values. The data was subjected to automated QC to remove spikes and out-of-range values. Dissolved oxygen sensors, Photosynthetically Active Radiation (PAR) sensors were also installed on the auxiliary A/D channels of the CTD. In addition to the auxiliary channels an ECO Triplet and LOPC were mounted on the Triaxus as attached payloads. The standard data product (1 decibar/10 second binned averaged) was produced using data from the primary and seconday sensors to produce an along-track time-series dataset for each data scan file. These files were grouped into sections/legs containing the Triaxus deployment. Moreover, for each section, vertical casts were created with interpolated values from the along-track time-series binned dataset with a maximum interpolation distance of 1 cast. These generated the along-track and vertical cast section data products for each Triaxus deployment. Throughout the voyage there were some issues with the Triaxus deployments. As a result, the standard data products could not be made for every deployment. See the Processing Report for further details. The collected data were subsequently archived within the CSIRO Oceans and Atmosphere (O&A) Information and Data Centre (IDC) in Hobart. Additional information regarding this dataset may be contained in the Voyage Summary and the Data Processing Report.