Sea ice primary production off eastern Antarctica

Brief description

Sea ice covers up to 20 million km2 of the Southern Ocean. When present it supports a vigorous ecosystem that provides energy and food for all other marine organisms. Using the latest micro sensor technology, we are examining the factors that effect the productivity of this vital link in the Antarctic marine food web.

New data were added to this metadata record in January 2011. These data included FRRF data collected on the CEAMARC, CASO, SIPEX and SAZ-SENSE voyages. A word document in the download file provides details about these datasets, plus those collected on Voyage 1 2009-2010, and voyage 2 2008-2009.

The download file also contains a folder labelled "Older data". This data is described below:

An explanation of the excel spreadsheet in the download file is as follows:

Worksheet 1 is the chlorophyll data
Worksheet 3 is the location data

CHLOROPHYLL DATA
Column A is sample name, the first letter refers to the location data in worksheet 3, the second to the ice flow number and the third to the replicate number Section refers to depth in ice core, measured from the bottom
Ignore C
Column D is the total volume of melted ice
Column E is the volume of D that was filtered
Column G is the Fluorometer reading before the addition dilute HCl
Column H is the fluorometer reading after the addition of acid
Column I is the calculation of chlorophyl concentration in the sample
Column K is areal chlorophyll estimate
Column L is the mean for the core
Column N is the mean for the site
Column O is the standard deviation

LOCATION DATA
Lat, longs and times of each sampling. The first set (B-G) refers to the time sampling started, the second (H-M) to when it finished

Project objectives:
- Determine the net photosynthesis and primary productivity of the phytoplankton and major sea ice algal communities of the Eastern Antarctic Sea Ice Zone (SIZ). Estimate seasonal and annual algal production and inter annual variability

- Obtain data on biomass distribution and variability to establish regional relationships between ice thickness, snow cover, and biomass

- Determine the effects of

a) Light
b) Nutrients (principally nitrate and iron)
c) Temperature

on photosynthesis and primary production

- Determine whether the biomass and productivity of the phytoplankton and sea ice algae in winter and spring limits the biomass or growth of krill

- Estimate the effects of climate change on Sea ice Zone primary production

Taken from the 2008-2009 Progress Report:
Progress against objectives:
This project used V2, a spring voyage, to collect underway data to determine surface biomass and primary production. Biomass samples (chlorophyll a) were taken every 3 hours. Productivity estimates by PAM were also made every 3 hours. Productivity measurements by FRRF were made every 1 minute. Nutrient samples were taken at the same time as the biomass samples.
Analysis of the biomass samples is complete. Preliminary analysis of the productivity data has commenced. This data is being used for a Masters project (Rob Johnson, IASOS).
An iron addition experiment accompanied this monitoring. Iron was added to samples taken every 3 hours and the change in photosynthesis (maximum quantum yield) measured with a PAM. The rate of recovery from iron stress was the principal focus.
Most of this data has been submitted as metadata.
Using The PAM and FRRF simultaneously also enabled a comparison to be made between these different ways of measuring photosynthesis.

Progress was also made on the analysis of FRRF productivity and biomass data collected over several years on the L'Astrolabe transect. Analysis involves quantitative manipulation of FRRF data and correlation with chlorophyll, nutrients, temperature and other biological parameters. A publication arising from this work will be submitted this year.

Taken from the 2009-2010 Progress Report:
Progress against objectives:
We participated in V1 of the Aurora Australis, spring 2009. The objective of this project was to measure surface primary production off East Antarctica. Photosynthetic parameters of phytoplankton under actinic light (L) as well as in darkness (D) were measured using a fast repetition rate fluorometer (FRRF). The parameters included the maximum photochemical efficiency (Fv/FmL,D), the functional absorption cross section of photosystem II (sPSII,L,D) and a turnover time of electron transfer (tL,D). Chlorophyll a concentration was measured by using Turner fluorometer. The photosynthetic parameters, irradiance and chlorophyll a concentration will then be used to estimate primary production of phytoplankton.

This field program particularly focussed on the first of the listed objectives, ie 'Determine the net photosynthesis and primary productivity of the phytoplankton and major sea ice algal communities of the Eastern Antarctic Sea Ice Zone (SIZ). Estimate seasonal and annual algal production and inter annual variability'. We have been collecting FRRF-based primary production data from each season and the 2009 data provides the late spring data to supplement data from autumn, winter and summer, collected in previous seasons. We have now built up a comprehensive assessment of season variability which will enable a reliable estimate of annual primary production. These analyses will also provide a detailed snap shot of primary production with which to compare future changes.

Preliminary analysis shows clear patterns of variation in Fv/Fm, a parameter that is particularly sensitive to low iron concentration. This data is shown on an accompanying diagram. Productivity analysis is still underway. Much of the work for this project forms part of the PhD project of Cheah Wee.Wee is expected to finish his PhD by December 2010 and it is anticipated that all data analysis for the project will have been completed and the finished manuscripts submitted for publication. He has already had one manuscript form this project accepted (Cheah et al, 2010).