Evidence of an upwelling centre on the western shelf of Tasmania

Satellite-derived chlorophyll-a data using standard ocean-colour algorithms (OC3 and OC4) are strongly biased by coloured dissolved organic matter and suspended sediment of river discharges, which is a particular problem for... [ view full abstract ]

Satellite-derived chlorophyll-a data using standard ocean-colour algorithms (OC3 and OC4) are strongly biased by coloured dissolved organic matter and suspended sediment of river discharges, which is a particular problem for the western Tasmanian shelf. This work reconstructs phytoplankton blooms in the study region using a quadratic regression between ocean-colour data and chlorophyll fluorescence based on the fluorescence line height (FLH) data. This regression is derived from satellite data of the nearby Bonney upwelling region, which is devoid of river influences. To this end, analyses of 10 years of MODIS-aqua satellite data reveal the existence of a highly productive ecosystem on the western Tasmanian shelf. The region normally experiences
two phytoplankton blooms per annum. The first bloom occurs during late austral summer months as a consequence of upwelling-favourable coastal winds. Hence, the western Tasmanian shelf forms another, previously unknown upwelling centre of the regional upwelling system, known as Great South Australian Coastal Upwelling System. The second phytoplankton bloom is a classical spring bloom also developing in the adjacent Tasman Sea. The author postulates that this region forms another important biological "hot spot" for the regional marine ecosystem.