Wednesday, September 7, 2011

Phosphate and Dissolved Silicon

Figure 5 - Silicon concentration depth profiles at each offshore stationFigure 4 - Phosphate concentration depth profiles at each offshore station
Both these nutrients are depleted in surface waters due to their utilisation by phytoplankton, with phosphate concentrations being zero at Stations 3 and 4, and silicon values being approximately 1μM at Stations 1, 3 and 4. The thermocline prevents replenishment of these nutrients by exchange between the surface and lower layers. Below the thermocline the nutrient concentrations increase more rapidly (Figures 4 and 5), which is likely to be due to the recycling of phosphate and silicon by bacterial decomposition, as well as the inability of phytoplankton to access these nutrients.

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