Variation in silicate concentration at Port Hacking station, Sydney, in relation to phytoplankton growth.

Abstract

Data are presented to show the variation in silicate concentrations in surface waters at a station in the Western Tasman sea, over two annual cycles. The area is characterized by low silicate concentrations in the surface (0-20 m) waters over the whole year with a maximum of 40 µg/litre occurring at very brief intervals in mid-winter. In spring and summer values frequently fall below detectable limits. The subsurface waters (20-60 m) are also usually low in silicate, but show a series of periodic intrusions in which concentrations go as high as 120 µg/l. These variations in silicate concentration are discussed in relation to the known variations in phytoplankton populations and the hydrology of the area.