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EARTH SCIENCE | OCEANS | OCEAN CHEMISTRY | OXYGEN

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    These data are from a piggy back voyage to IN2018_V05, October-November 2018. The Chief Scientists were Helen Phillips and Nathan Bindoff. Nic Pittman and Clara Vives collected biogeochemical data on the voyage, and Xiang Yang used these data in his Hons thesis 2020-2021. The purpose of the study was to investigate biogeochemical variability in the region of the Polar Front meander south of Tasmania. Data include CTD nutrients, chlorophyll and oxygen as well as underway phytoplankton physiology and pCO2. Some data are duplicated but not in exactly the same format on the CSIRO Data Trawler.

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    These data are from a voyage (IN2019_V01) on RV Investigator with the Australian Antarctic Division (AAD), that took place during January-March 2019. The Chief Scientist was Mike Double from the AAD. Clara R. Vives collected biogeochemical data on the voyage, and performed a series of incubation experiments for her PhD. The purpose of the study was to investigate the effects of iron and light on phytoplankton growth off East Antarcitca. Data include CTD nutrients, chlorophyll and oxygen as well as underway phytoplankton physiology (measured as the photochemical efficiency) and pCO2. Some data are duplicated but not in exactly the same format on the CSIRO Data Trawler.

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    This dataset consist of dissolved oxygen (DO) and temperature data collected using HOBO Dissolved Oxygen loggers (U26-001) under FRDC project 2016-067. Loggers are deployed on strings in two locations in Macquarie Harbour, Tasmania.

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    This dataset consists of data collected by the real-time dissolved oxygen (DO) monitoring system in Macquarie Harbour, Tasmania, originally established under the Sense-T program, continued under FRDC project 2016-067 and deployed and maintained by IMAS. The system consists of 3 strings of acoustically telemetered, optical fluorescence DO, temperature and depth sensors (VEMCO, Bedford, Canada) which measure DO in % saturation, temperature in °C and depth in meters. The dataset spanning the time period from the 1st of January 2017 to the 19th of April 2017 consists of data collected using the first generation of sensors as described above. Subsequent quarterly updates from the 3rd of June 2017 onwards consist of data collected using the new generation of tags which contain a tilt instead of a depth sensor.

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    Antarctic krill is a key component of Southern Ocean ecosystems and there is significant interest in identifying regions acting as sources for the krill population. We develop a mechanistic model combining thermal and food requirements for krill egg production, with predation pressure post-spawning, to predict regions that could support high larval production (spawning habitat). We optimise our model on regional data using a maximum likelihood approach and then generate circumpolar predictions of spawning habitat quality. The uploaded datasets represent model predictions of seasonal circumpolar spawning habitat quality of Antarctic krill as well as composite data of the circumpolar mean annual number of weeks in which modelled spawning habitat quality is higher than the summer 80th percentile.

  • -- Layton et al. Chemical microenvironments within macroalgal assemblages: implications for the inhibition of kelp recruitment by turf algae. Limnology & Oceanography. DOI:10.1002/lno.11138 -- Kelp forests around the world are under increasing pressure from anthropogenic stressors. A widespread consequence is that in many places, complex and highly productive kelp habitats have been replaced by structurally simple and less productive turf algae habitats. Turf algae habitats resist re-establishment of kelp via recruitment inhibition; however little is known about the specific mechanisms involved. One potential factor is the chemical environment within the turf algae and into which kelp propagules settle and develop. Using laboratory trials, we illustrate that the chemical microenvironment (O2 concentration and pH) 0.0–50 mm above the benthos within four multispecies macroalgal assemblages (including a turf-sediment assemblage and an Ecklonia radiata kelp-dominated assemblage) are characterised by elevated O2 and pH relative to the surrounding seawater. Notably however, O2 and pH were significantly higher within turf-sediment assemblages than in kelp-dominated assemblages, and at levels that have previously been demonstrated to impair the photosynthetic or physiological capacity of kelp propagules. Field observations of the experimental assemblages confirmed that recruitment of kelp was significantly lower into treatments with dense turf algae than in the kelp-dominated assemblages. We demonstrate differences between the chemical microenvironments of kelp and turf algae assemblages that correlate with differences in kelp recruitment, highlighting how degradation of kelp habitats might result in the persistence of turf algae habitats and the localised absence of kelp.

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    The dataset was collected on the research voyage (IN2018_V05 on RV Investigator) and from satellite observations. The dataset includes in-situ data and satellite data collected at the Polar Front (PF) south of Tasmania in a region where the Antarctic Circumpolar Current (ACC) has a permanent meander upstream of the Macquarie Ridge. This study characterises the upwelling of Circumpolar Deep Water (CDW) in a standing meander of the ACC in the PF south of Tasmania and investigates the submesoscale processes associated with upwelling.