This record describes multibeam echosounder data collected on RV Investigator voyage IN2025_V04, titled "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. The Kongsberg EM712 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter between Hobart and Eden. The EM712 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 *.kmall raw format for bathymetry and backscatter and *.kmwcd format for watercolumn backscatter at CSIRO. There are 1188 files totalling 255 GB of raw data and 1183 files totalling 1.32 TB of watercolumn data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.kmall format are corrected for motion and position. GPS tide was computed using the EGM2008 model and applied to the processed data. Processed data has had outliers removed. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report.

This record describes sub bottom profiler data collected on RV Investigator voyage IN2025_V04, ['Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV'] which departed Hobart on 27/05/2025 and returned to Hobart on 28/06/2025. The Kongsberg SBP29 (sub bottom profiler) was used to acquire data containing the specular reflections at different sediment interfaces below the seafloor. The SBP29 provides a 3° by 3° angular resolution. The echosounder's frequency sweep range is from 2 to 9 kHz. The SBP29 was logged continuously on the shelf for the extent of the voyage. Data are stored in *.raw (1,111 files 26.7 GB) raw and *.seg (1,094 files 26.3 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 multibeam echosounder data collected on RV Investigator voyage IN2025_V04, titled "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. The EM124 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz. Data are stored in *.kmall raw format for bathymetry and backscatter and *.kmwcd format for watercolumn backscatter at CSIRO. There are 20 files totalling 1.85 GB of raw data and 20 files totalling 4.0 GB of watercolumn data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.kmall format are corrected for motion and position. GPS tide was computed using the EGM2008 model and applied to the processed data. Processed data has had outliers removed. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report.

This data set contains the imagery collected on the Marine National Facility (MNF) RV Investigator voyage IN2025_V04, titled ‘Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV (SEA-MES Voyage 4)’. The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart, collecting imagery of benthic habitats together with oceanographic data. Instrument(s) used to collect this data: MNF Deep Towed camera (DTC) Datasets include: Video (oblique forward view) Stereo stills (oblique forward view) Navigational data

This record describes ME 70 scientific multibeam fisheries echosounder data collected on the Marine National Facility (MNF) RV Investigator voyage IN2025_V04, titled "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. The Simrad ME70 scientific multibeam echosounder acquired acoustic backscatter data through the water column up to 500 m (maximum). The echosounder's frequency range is from 70 kHz to 120 kHz. The ME70 logged sporadically only for specific trawling operations for the extent of the voyage. Data are stored in Simrad *.all raw format at CSIRO. There are 519 files totalling 60.2 GB of raw data in this dataset. No processing has been conducted on this data. Additional information regarding this dataset, including the settings used, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes gravity data collected on the Marine National Facility (MNF) RV Investigator voyage IN2025_V04, titled "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. The gravity meter instrument is a MicroG Lacoste Air-Sea II. Data are stored in .ENV and .DAT data files at CSIRO. There are 33 files totalling 541 MB of raw data in this dataset. A wharf tie was undertaken at the end of the voyage at the Hobart Princes Wharf using a Scintrex Autograv CG-5. Wharf tie data can be found in GravityTie_in2025_v04_Hobart_20250627.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 scientific split-beam echosounder data collected on the RV Investigator voyage IN2025_V04, titled "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. The Simrad EK80 split beam echosounders for 18, 38, 70 120, and 200 kHz were used to acquire acoustic backscatter data to a range of up to1500 m, between Hobart and Eden. Logging range was changed throughout the voyage based on depth. The 18, 38, 70 120, and 200 kHz frequencies were logged continuously for the extent of the voyage. The 333 kHz was set to passive for the duration of the voyage due to a known issue with the transducer. Data are stored in *.raw, *.bot and *.idx format at CSIRO. There are 1,164 files totalling 112 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 dataset comprises the Multi-net plankton sampling collected during the SEA-MES program across four RV Investigator voyages (IN2023_V05, IN2024_V03, IN2024_V05, IN2025_V04). A total of 173 Multi-net operations were conducted, using 100 µm and 500 µm mesh nets to collect depth-stratified samples through the water column, capturing both day and night to assess diel vertical migration. The dataset includes 560 samples from 100 µm nets and 140 samples from 500 µm nets, providing information on zooplankton composition, biomass, and community structure, including 58,246 individuals from 105 genera and 70 families identified to date. These data provide a detailed view of pelagic biodiversity across the south-eastern continental shelf and upper slope of Australia.

This record describes the CTD data collected on Investigator voyage IN2025_V04, titled: "Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV (SEA-MES Voyage 4)." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. Data for 61 CTD deployments were acquired using the Sea-Bird SBE911 CTD unit #22, fitted with 36 twelve-litre bottles on the rosette sampler. Sea-Bird-supplied calibration factors were used to compute the pressures and preliminary conductivity values. CSIRO-supplied calibrations were applied to the temperature data. The data were subjected to automated QC to remove spikes and out-of-range values. Majority of casts were bottom approaches to 10m off bottom, some casts did not approach the bottom due to the operators deciding that conditions were too risky to attempt a bottom approach. The test cast was not attempted due to strong winds, hence cast #01 was a scientific cast. Cast #61 no SUNA data is available for this cast. Between cast #35 and #36 the pumped sensors were cleaned with freshwater. This did not affect the conductivity sensor but did the oxygen sensor, hence the final calibrations were based on a single deployment group for conductivity and multiple deployment groupings for oxygen. The final conductivity calibration from the secondary sensor had a standard deviation (SD) of 0.0030364 PSU, outside our target of ‘better than 0.002 PSU’. The standard product of 1-decibar binned averages were produced using data from the secondary sensors. The dissolved oxygen data calibration fit had a SD of 0.68397μM (#01-#35) and 0.79591μM (#36-#61). The agreement between the CTD and bottle data was good. PAR, CDOM, Transmissometer, Chlorophyll-a and Scattering sensors were also installed on the auxiliary A/D channels of the CTD. The collected data were processed (quality-controlled), and subsequently archived by the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC). Additional information regarding this dataset may be contained in the Voyage Summary and the Data Processing Report.

This record describes Hydrology (HYD) data collected from the Marine National Facility (MNF) RV Investigator voyage IN2025_V04, titled:"Untangling the causes of change over 25 years in the southeast marine ecosystem - Voyage IV ." The voyage took place between May 27, 2025 and June 28, 2025 (AEST), departing from Hobart and returning to Hobart. Water samples collected during CTD deployments were processed in the ship’s hydrochemistry laboratory and analysed for key parameters, including nutrients, dissolved oxygen, and salinity. Dissolved inorganic carbon and total alkalinity samples were also collected at selected stations to continue the time series established during previous voyages, with these samples to be analysed on shore by the CSIRO carbon team. Additionally, Thermosalinograph (TSG) samples were continuously collected throughout the voyage, with on-board measurements of their salinity used to calibrate the ship's underway system. Please cite the following manuscript when reporting or publishing data for silicate, phosphate, nitrate+nitrite (NOx) and nitrite: Rees, C., L. Pender, K. Sherrin, C. Schwanger, P. Hughes, S. Tibben, A. Marouchos, and M. Rayner. (2018) “Methods for reproducible shipboard SFA nutrient measurement using RMNS and automated data processing.” Limnol. Oceanogr: Methods, 17(1): pp. 25-41. doi:10.1002/Iom3.10294 If publishing ammonium data, please cite the following: Rees, C., Janssens, J., Sherrin, K., Hughes, P., Tibben, S., McMahon, M., McDonald, J., Camac, A., Schwanger, C. and Marouchos, A., (2021) “Method for Reproducible Shipboard Segmented Flow Analysis Ammonium Measurement Using an In-House Reference Material for Quality Control.” Frontiers in Marine Science, 8. doi:10.3389/fmars.2021.581901 This dataset has been processed (quality-controlled), and archived at the CSIRO National Collections and Marine Infrastructure (NCMI) Information and Data Centre (IDC) in Hobart. Additional information regarding this dataset is contained in the Voyage Report and Data Processing Report.