CS29 Phytoplankton & Primary Production
Date: Monday, June 10, 2002
Time: 2:45:00 PM
Location: Oak Bay
 
ThompsonPA, CSIRO, Hobart, Australia, peter.a.thompson@csiro.au
Hanson, C, , University of Western Australia, Perth, Australia, hanson@cwr.uwa.edu.au
Waite, A, , University of Western Australia, Perth, Australia, waite@cwr.uwa.edu.au
 
THE DEEP CHLOROPHYLL MAXIMUM OFF THE WEST COAST OF AUSTRALIA.
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A synopsis is presented of the multi-disciplinary oceanographic cruise from 21 to 28S and 111 to 114E (west coast of Australia) during the austral summer of 2000. This cruise assessed currents and the spatial patterns of nutrient concentrations, hydrographic conditions, phytoplankton biomass and composition, nutrient uptake rates and primary production. ADCP indicated physical domination by the poleward-flowing Leeuwin Current with a more localized complex current pattern and unique TS regions. In spite of this physical complexity a very widespread and consistent feature of the study area was a deep chlorophyll maximum (DCM). The DCM was directly above the nutricline and showed net photosynthesis at depths of between 60-120 m. As assessed by pigments and cell counts the phytoplankton community composition was similar throughout the study area. Overall stations the pigment data indicated vertically uniform distributions of cyanophytes while there was preferential accumulation of cryptophytes and coccolithophorids at the DCM. The spatial variation of the phytoplankton community in response to the large-scale current patterns and other physical and chemical forcing factors is discussed.