Antarctic diatom silicification diminishes under ocean acidification
This data set was collected during an ocean acidification mesocosm experiment performed at Davis Station, Antarctica during the 2014/15 summer season. It includes:
- description of methods for all data collection and analyses.
- diatom cell volume
- bulk silicification
- species specific silicification via fluorescence microscopy
- bulk community Fv/Fm on day 12
- single-cell PAM fluorometry data (maximum quantum yield of PSII: Fv/Fm)
A natural community of Antarctic marine microbes from Prydz Bay, East Antarctica were exposed to a range of CO2 concentrations in 650 L minicosms to simulate possible future ocean conditions up to the year ~2200. Diatom silica precipitation rates were examined at CO2 concentrations between 343 to 1641 micro atm, measuring both the total diatom community response and that of individual species, to determine whether ocean acidification may influence future diatom ballast and therefore alter carbon and silica fluxes in the Southern Ocean.
Described and analysed in:
Antarctic diatom silicification diminishes under ocean acidification (submitted for review)
Methods described in:
Antarctic diatom silicification diminishes under ocean acidification (submitted for review)
Location: Prydz bay, Davis Station, Antarctica (68 degrees 35'S, 77 degrees 58' E)
Date: Summer 2014/2015
Worksheet descriptions:
Bulk silicification - raw data
Measured total and incorporated biogenic silica using spectrophotometer for all tanks on day 12 after 24 h incubation with PDMPO - raw data
Bulk Fv/Fm - dark-adapted maximum quantum efficiency of PSII (Fv/Fm) on whole community - raw data
Measured Fv/Fm of individual cells from 3 mesocosm tanks.
Single-cell silicificiation, Fluorescence microscopy - raw data
Measured autofluorescence and PDMPO fluorescence of individual diatoms from 6 mesocosm tanks
Single-cell PAM, dark-adapted maximum quantum efficiency of PSII (Fv/Fm) - raw data
Measured Fv/Fm of individual cells from 3 mesocosm tanks.
Cell volume
Calculated cell volume (um3) of 7 species from minicosm tanks 1 and 6 - raw data
Abbreviations:
Fv/Fm Maximum quantum yield of PSII
PDMPO 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole
Tant Thalassiosira antarctica
DiscLg Large Discoid centric diatoms
Stella Stellarima microtrias
Chaeto Chaetoceros spp.
Prob Proboscia truncata
Pseu Pseudonitzschia turgiduloides
FragLg Fragilariopsis cylindrus / curta
Centric Large Discoid centric diatoms
LargeThalassiosira Large Discoid centric diatoms
Phytoplankton Distribution in Surface Samples and Cores from Prydz Bay and Long Fjord and its Relationship to Sea Level and Climatic Change
Metadata record for data from ASAC Project 492 See the link below for public details on this project.
From the abstracts of the referenced papers:
Diatom assemblages in two Holocene sediment cores (GC1 and GC2) from the Mac. Robertson Shelf, East Antarctica, are compared with modern sedimentary diatom assemblages from the same area. Open marine deposition commenced in Iceberg Alley (GC1), on the outer continental shelf, greater than 10.7 adj. 14C kyr BP. Chaetoceros resting spores, which may indicate water-column stabilsation from melting glacial and/or sea ice or the maximum summer sea-ice retreat, dominate the diatom assemblage. Approximately 7.5 adj. 14C kyr BP, a sea-ice diatom assemblage was deposited. This assemblage is similar to that being deposited in the surface sediments of the Mac. Robertson Shelf today and suggests that perennial sea ice has persisted in the vicinity of Iceberg Alley since that time. Interbedded within the sea-ice assemblage, however, are Corethron-rich sediment layers that suggest mid- to late-Holocene high-productivity events associated with a climatic optimum. The diatom record from Nielsen Basin (GC2), on the inner continental shelf, is relatively uniform compared to that in GC1. Glacial ice was present over the region c. greater than 5.6 adj. 14C kyr BP and a dissolution diatom assemblage was deposited beneath it. following ice retreat, an ice-edge diatom assemblage was deposited briefly before sea-ice conditions similar to that on the continental shelf today developed. There is no evidence in GC2 for the mid- to late-Holocene high-productivity events identified in GC1.
Four diatom assemblages are identified from the surface sediments of Prydz Bay and the Mac. Robertson Shelf using multivariate analysis. A coastal assemblage is characterised by the sea-ice diatoms Fragilariopsis curta, F. angulata, F. cylindrus and Pseudonitzschia turgiduloides. A continental shelf assemblage is characterised by the open-water diatoms Fragilariopsis kerguelensis, Thalassiosira lenuginosa, T. gracilis var. expecta and Trichotoxin reinboldii. The Cape Darnley assemblage contains both sea-ice and open-water diatoms, but all are characteristically large and heavily silicified. Multiple regression has been used to identify the relationships between the diatom assemblages and known environmental variables. There are strong correlations between the coastal, shelf and oceanic assemblages and ecological conditions, including latitude, sea-ice distribution and ocean currents. The Cape Darnley assemblage is thought to represent an assemblage from which the smaller and more lightly silicified species have been removed by current winnowing.
The palaeo-depositional environment of inner Prydz Bay, East Antarctica, has been reconstructed for the past 21,320 14C yr B.P., using diatom assemblages and sediment facies from a short, 352 cm long gravity core. Between 21,320 and 11,650 14C yr B.P., compact tillite and diamicton are present in the core, and diatom frustules are rare to absent. These data suggest that an ice sheet grounded over the site during the last glacial maximum. Following glacial retreat, siliceous muddy ooze was deposited, from 11,650 to 2600 14C yr B.P., in an open marine setting. During this stage, diatom frustules are abundant and well preserved, and Thalassiosira antarctica resting spores and Fragilariopsis curta dominate the assemblage. This assemblage suggests open marine deposition in an environment where the spatial and temporal distribution of sea ice is less than today. Since 2600 14C yr B.P., sea-ice and ice-edge diatom species have become more abundant, and neoglacial cooling is inferred. The assemblage is similar to that forming currently in Prydz Bay, where sea-ice is absent (less than 10% cover) for 2-3 months of the year and permanent ice edge and/or multiyear sea ice remains in close proximity to the site.