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Project details

Title: Aus-India Bio-Argo Float deployments
Id: 2526
Investigator(s): Tom Trull
CSIRO Oceans & Atmosphere - Hobart [details]

Description: Two bio-optical floats will be deployed along the early portion of the transit in the vicinity of the Subtropical front. In conjunction with a CTD/LADCP to 2000 m, a bio-optical sensor cast, and a TRIAXUS tow.
Years: 2016

List of surveys that this project was on.

Use [details] link to view survey details (map, reports, metadata etc) including links to download data.

Survey InvestigatorDescription

M. Coffin (IMAS, UTAS) HEOBI Heard Earth-Ocean-Biosphere Interactions RV Investigator voyage IN2016_v01. Voyage objectives: [1] Seafloor and subseafloor mapping/geophysical characterisation. Continuous mapping will be carried out using the multibeam systems, multi-frequency split-beam echosounders, sub-bottom profiler, gravimeter, and (on long transits between ports and the study area) magnetometer to characterise bathymetric features and identify those most likely to include volcanic or hydrothermal activity. XBT or CTD data will be acquired at standard intervals for sound velocity corrections to the multibeam data. The data will be initially processed at sea to inform site selection for volcanic and hydrothermal sampling. [2] Nature of submarine volcanoes and hydrothermal systems. We will characterise the spatial distribution, morphology, and geology of active submarine volcanoes and hydrothermal systems. [Extract only] [3] Detecting hydrothermal inputs to the ocean, and vertical water movements that deliver them to surface waters. full-depth CTD/LADCP/TMR transects will be performed to capture cross-shore gradients in water. [Extract only] [4] Detecting impacts on surface phytoplankton production. During the underway mapping we will continuously operate sensors to measure biological activity (fluorescence for phytoplankton abundance, fast-repetition-rate fluorescence for phytoplankton photosynthetic competence, transmission for total carbon biomass, and O2/Ar ratio mass spectrometry for net community production). The sensors will be augmented by underway sampling for phytoplankton pigments, particulate organic and inorganic carbon, biogenic silica, heterotrophic bacterial responses, and microscopic phytoplankton identification to characterise community structures, and 15N measurements to identify the extent of nitrate versus ammonium metabolism - a key indicator of ecosystem Fe stimulation capable of additional carbon sequestration. Above and downstream of active hydrothermal systems, we will obtain samples for further analyses ashore. We also intend to carry out deckboard micro-nutrient enrichment incubation experiments to ascertain the biological response of hydrothermal iron to surface phytoplankton communities. Deployment of a bio-optical sensor package after each CTD deployment will provide measurements to link these communities to satellite images. [5] Ocean circulation around Heard Island and across the eastern Indian Ocean sector of the Southern Ocean. The shipboard ADCP and all available underway systems (thermosalinograph, meteorology, and biogeochemical systems) will be run at all times. We will seek contributions of autonomous instruments to deploy on the voyage to provide more detailed sampling of the circulation. We have contacted the Global Surface Drifter Program run by NOAA, and the Australian office of the International Argo Program. The lowered ADCP will be used at every CTD station to measure full water column velocity. New processing methods also allow the detection of internal waves and mixing using a shear-strain parameterisation, even in shallow waters. [Extract only] [6] Microbial response and bacterial processes What is the response of the microbial community to iron and organic carbon availability in different zones of the Southern Ocean, with focus on the possible impact of hydrothermal activity. More specific question: How does iron and carbon limitation affect heterotrophic bacterial respiration and growth efficiency, and its diversity? This text is an extract ONLY from the voyage plan. Please see in2016_v01 plan for full details.
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