Use of regularly migrating non-biological platforms as vehicles for spatio-temporal sampling of Southern Ocean systems Simon Wright, Brian Griffiths, Bronte Tilbrook, Steve Rintoul, Alain Poisson

25 Jan Feb Feb 2003

How to model microbial populations? Recognize different types of communities Key species and associations When and where do they occur? Time of season Oceanographic conditions MLD, nutrients, ice, etc Parameterize the community properties Primary production, respiration Aggregation Sedimentation Size distribution

What would a Southern Ocean Observing System look like?

Regularly Migrating Non-Biological Platforms Seagoing Hydro-Investigative Platforms (SHIPs) (RMNBPs)

Aurora Australis LAstrolabe

Programmable Ecological Observing Package (Live Elements) (PEOPLE)

Three pronged approach Monitoring on repeat transects lAstrolabe Intensive oceanographic surveys Aurora Australis Process studies in minicosms Coupled with laboratory experiments

Aurora Australis

ASF Tmin Pycnocline

ASF Tmin Pycnocline

Disadvantage of Aurora Australis erratic migratory route

Three pronged approach Monitoring on repeat transects lAstrolabe Intensive oceanographic surveys Aurora Australis Process studies in minicosms Coupled with laboratory experiments

Sokolov & Rintoul 2002 Regular monitoring of Hobart - Dumont dUrville 3 – 4 repeat transects per season

Astrolabe lab in hold

Astrolabe lab interior

lAstrolabe repeat transects –Oceanography: XBT sections, nutrients: Steve Rintoul, CSIRO alkalinity –Alain Poisson IPEV, Paris –Phytoplankton: Chlorophyll fluorometry, FRRF –Brian Griffiths, CSIRO HPLC pigments, Species ID and counts (whole and net), coccolithophorid counts –Australian Antarctic Division –Carbon dioxide: pCO 2 Bronte Tilbrook, CSIRO

CO2 drawdown Chlorophyll a Astrolabe 2002/03

CO2 drawdown Chlorophyll a Astrolabe 2002/03

Oct | Nov | Dec | Jan | Feb | Mar

Date of bloom at mid latitude (53- 60ºS) SeasonBloom peak Dec Dec Jan Jan Jan Feb Jan Dec

Oct | Nov | Dec | Jan | Feb | Mar

Bloom dynamics at mid latitude (53- 60ºS) Bloom in Feb about 1 ug Chl a/ L Dominant species – F. kerguelensis, Phaeocystis, Trichotoxon, Thalassiothrix, Pseudonitzschia 2003 – 2004, 2004 – 2005 (Typical) Bloom in Dec - Jan about ug Chl a/ L Dominant species F. kerguelensis, Pseudonitzschia, Trichotoxon, Chaetoceros dichaeta

Oct | Nov | Dec | Jan | Feb | Mar

Bloom dynamics at mid latitude (53- 60ºS) The late bloom in was associated with relatively warm, very low salinity water This water had low nutrient concentrations. A bloom developed only after nutrient concentrations increased

Conclusions Regular sampling of Southern Ocean from lAstrolabe identified seasonal patterns in microbial populations –relationship to carbon dioxide uptake –Relationship to nutrient drawdown Substantial interannual differences in bloom dynamics appeared to be driven by seawater chemistry An anomalous late bloom developed only after nutrient concentrations increased in a large area of warm low salinity water. A small subset of total data: made possible by repeated sampling of many parameters in a collaborative program

lAstrolabe repeat transects –Organization: –Alain Poisson IPEV, Paris –Bronte Tilbrook, CSIRO –Acknowledgements –Captain and crew S.V. lAstrolabe –Many volunteer samplers

What should a SOOS look like? –Regular transects along the same transect

What should a SOOS look like? –Oceanography: Thermosalinograph XBT sections, nutrients Alkalinity Carbon dioxide: pCO 2 –Atmospheric Carbon dioxide, oxygen, DMS Dust –Environment Temperature, radiation, wind speed, wave height, ice –Plankton: Chlorophyll fluorometry, FRRF HPLC pigments, Species ID and counts (whole and net) Continuous plankton recorder