IMAS Metadata Catalogue
SILICATE
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The CANYONS voyage on RV Investigator aimed to investigate past and present processes governing the flow pathways, formation and geochemical signatures of Antarctic Bottom Water (AABW) off Cape Darnley, East Antarctica. The proposed survey area was focussed on the Wild and Daly canyons and the adjacent sediment drifts - the Daly and ‘Armand’ drifts. The survey aimed to collect systematic multibeam bathymetry and sub-bottom profiles across the region to support collection of long sediment cores (up to 24 m), Kasten cores and multicores, CTDs (conductivity- temperature-depth instruments) and deep towed camera transects This dataset reports analyses of samples collected from the surface uncontaminated "underway" seawater supply on R/V Investigator. The samples were collected while the ship transited from Perth to Cape Darnley. A suite of samples were collected in order to characterise surface ocean particles across the oceanographic gradients that characterise the Southern Ocean. these data were generated by IMAS Honour student Veda Surapaneni, and were included in her honours thesis.
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The CANYONS voyage on RV Investigator aimed to investigate past and present processes governing the flow pathways, formation and geochemical signatures of Antarctic Bottom Water (AABW) off Cape Darnley, East Antarctica. The proposed survey area was focussed on the Wild and Daly canyons and the adjacent sediment drifts - the Daly and ‘Armand’ drifts. The survey aimed to collect systematic multibeam bathymetry and sub-bottom profiles across the region to support collection of long sediment cores (up to 24 m), Kasten cores and multicores, CTDs (conductivity- temperature-depth instruments) and deep towed camera transects. This dataset reports analyses of particulate organic carbon and biogenic silica from two CTD casts conducted in the Cape Darnley region. The voyage was terminated after a medical evacuation so only two CTD stations were occupied. These data were generated by IMAS Honour student Veda Surapaneni, and were included in her honours thesis. The dataset also includes hydrochemistry, DIC, Alkalinity and pigment data generated by CSIRO, although these data are published in other national repositories and reproduced here for completeness and convenience only.
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Ocean alkalinity enhancement (OAE) is an emerging carbon dioxide removal (CDR) strategy that leverages the natural processes of weathering and acid neutralisation to durably store atmospheric CO2 in seawater. OAE can be achieved with a variety of methods, all of which have different environmental implications. One widely considered method utilizes electrochemistry to remove strong acid from seawater, leaving sodium hydroxide (NaOH) behind. This study evaluates the impacts of OAE via NaOH (NaOH-OAE) on a coastal plankton bloom, with particular focus on how macronutrient regeneration in the aftermath of the bloom responds to the perturbation. To investigate this, we enclosed a natural coastal phytoplankton community, including coccolithophores, in nine microcosms. The microcosms were divided into three groups: control, unequilibrated (512.1 ± 2.5 µmol kg-1 alkalinity increase) and equilibrated (499.3 ±5.65 µmol kg-1 alkalinity increase). Light was provided for 11 days to stimulate a bloom (light phase) and lights were turned off thereafter to investigate alkalinity and nutrient changes for 21 days (dark phase). We found no detectable effect of equilibrated NaOH-OAE on phytoplankton community and bacteria abundances determined with flow cytometry but observed a small yet detectable restructuring of phytoplankton communities under unequilibrated conditions. NaOH-OAE had no significant effect on alkalinity, NOx- and phosphate regeneration, but increased silicate regeneration by 64% over 21 days under darkness in the unequilibrated treatments where seawater pH was highest (8.65 relative to 7.92 in the control). Additional dissolution experiments with two diatom species supported this outcome on silicate regeneration for one of the two species, thereby suggesting that the effect is species specific. Our results point towards the potential of NaOH-OAE to influence regeneration of silicate in the surface ocean and thus the growth of diatoms, at least under the very extreme NaOH-OAE conditions simulated here.
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These files contain the data recorded from a mesocosm experiment conducted in Bergen, Norway 2022 which assessed the effect of simualted mineral-based (silicate or calcium) ocean alkalinity enhancement (OAE) on diatom silicification. Ten mesocosms were used in total, divided into two groups either the silicate- or calcium based group and alkalinity was increased by either 0, 150, 300, 450 or 600 µmol L-1 above natrually occuring levels. The PDMPO-fluorescence (an appropriate proxy for silicification) of diatoms was recorded on eight seperate days during the experiment. Accompanying data includes measured; macronutrients (nitrate, nitrite, phophate, silicate), total alkalinity, biogenic silica in the water column and sediment trap.
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Biologically relevant macronutrients, nitrate + nitrite, silicate, phosphate and ammonia, were measured at all sites throughout the study. Nitrate + nitrite values (NOx) at the surface showed clear seasonal trends, peaking over winter and drawing down to near zero in summer and autumn. Phosphate concentrations also reached a peak in winter, which was associated with Southern Ocean influence. Median ammonium concentrations at all sites were generally <0.5 μM, with no clear peaks in any season or month. Overall, the lowest values were measured in August and other months showed reasonable spread around the median. Median silicate concentrations were consistently highest at sites 1 and 9, followed by site 5. Water from the River Derwent flows through site 1, then tracks east towards site 9 then site 5. Seasonally, silicate was generally highest in winter when the River Derwent outflow is also greatest.