Ongoing data collection for Mooring for Epipelagic Echosounding of Krill (MEEK) deployments

Published: 2025-11-25

This dataset contains all data collected from Mooring for Epipelagic Echo-sounding of Krill (MEEK) platforms. MEEK moorings are tethered by a mooring string in deep water, with the top float at approximately 400m depth. The minimum depth of a mooring is 350m to avoid collision with icebergs and the maximum depth is 1500m. Moorings are typically deployed in summer months from vessels and are left to collect data for one year (at least). Active acoustic (ADCP and echosounder) data, passive acoustic data, CTD data and video camera footage are available from various instruments installed on the moorings. Active acoustic deployment files, compass calibrations and echosounder calibration files are included. Echosounders were calibrated in a 10,000L tank of temperature-controlled seawater at the Australian Antarctic Division in Kingston, using a 23mm tungsten carbide sphere and a paired Simrad EK80 333kHz echosounder to map the beam. Calibration raw data and code is included to produce Nortek SONAR equation CalibrationOffsetSv for each frequency. Calibration is only available for narrowband frequencies. Data collection began in 2024 and is ongoing. The MEEK moorings are long-line oceanographic moorings designed for year-round observation of krill and associated ecosystem processes in the Antarctic epipelagic zone. Each mooring carries an upward-looking echosounder and ADCP mounted on a top float at ~400 m to monitor krill biomass, vertical migration, and water-column dynamics. A sediment trap positioned below the acoustic package collects sinking particulate material to quantify carbon flux and link pelagic processes with export production. MEEK moorings provide high-resolution, multi-season records that support studies of krill ecology, biogeochemical cycling, and Southern Ocean change. The time series is ongoing and data will be continuously added upon platform retrieval. 2026-05-12 update (to add Hydrophone data for 2024-2025): This dataset contains long-term passive acoustic data (i.e. underwater sound recordings) collected from the first deployment of Mooring for Epipelagic Echo-sounding of Krill (MEEK 001) — a long string mooring platform deployed at the Mawson shelf break (-66.7451°S, 63.4403°E) at a seafloor depth of 734 m. MEEK 001 was deployed from RSV Nuyina on 13 March 2024 and recovered on 23 January 2025, yielding 7548 hours of continuous underwater recording across all three instruments. Three models of autonomous moored acoustic recorder were deployed simultaneously on MEEK 001 as part of a trial to determine the viability and quality of each instrument: an AAD Moored Acoustic Recorder (MAR), a Jasco AMAR G4 Ultradeep, and a Develogic Sono.Vault Submares. The three recorders were co-located in series near the bottom of the mooring, approximately 50 m above the seafloor. All three instruments recorded successfully for the entirety of the underwater deployment, and all underwater recordings from all three instruments are included in this dataset. Recordings made above water prior to deployment and following recovery have been excluded. The AAD-MAR contained a factory-calibrated HTI hydrophone and AAD-calibrated electronics, and recorded continuously producing hour-long WAV files at 12 kHz sample rate and 16-bit depth. The Jasco AMAR G4 Ultradeep recorded at 64 kHz sample rate and 24-bit depth; its hydrophone was individually calibrated with a certificate of calibration per channel provided by the manufacturer. The Develogic Sono.Vault Submares recorded at 64 kHz sample rate and 24-bit depth; its hydrophone sensitivity was derived from a batch calibration of the production run rather than individual calibration of the specific unit. The start date and time of each recording is embedded in the file name of each WAV file (i.e. yyyy-mm-dd_HH-MM-SS). All instruments were calibrated using manufacturer-provided component calibration factors; none were field-calibrated prior to deployment. Passive acoustic recorders recorded low and mid-frequency sounds that may be used for investigation of the physical environment (e.g. ice, wind, waves), biological environment (e.g. animal vocalisations including Antarctic blue whale, fin whale, minke whale, and leopard seal calls), and anthropogenic noise (e.g. sounds produced by ships and other human activities). Note: acoustic performance findings in the included report are preliminary, pending further calibration analysis.