Articles | Volume 11, issue 1
Research article
05 Jan 2015
Research article |  | 05 Jan 2015

Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem

J. Kämpf

Abstract. Satellite-derived chlorophyll a data using the standard NASA-OC3 (ocean colour) algorithm 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 OC3 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 a 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.

Short summary
This paper describes the discovery of a previously unknown coastal upwelling centre on the western coast of Tasmania, Australia. This region forms part of the Great South Australian Coastal Upwelling System, which turns out one of the largest seasonal coastal upwelling systems on Earth. Upwelling events fuel phytoplankton blooms in last austral summer months and associated coastal jets are presumably an important nutrient source for the adjacent Bass Strait.