Abstract
This study investigates the variability of dissolved silica levels within the natural water systems of the Otago region. It examines three rivers in the area: the Clutha, Taieri, and Leith, the Otago Harbour, the Southland Current and the Blueskin Bay Counter Current System. It considers seasonal variations, comparing and contrasting temperature, levels, salinity levels, river flows, rainfall, and draws these factors together to give an interpretation leading to concrete conclusions. That there is a linked system of silica flux in the rivers and marine waters, and that biological activity is the major sink for the highly conservative dissolved silica. This is particularly true in the period of the spring bloom. However biological activity is not appreciable in winter months.
Sampling took place at two weekly intervals in the harbour at 25 set sampling points, in the rivers weekly and in the sea monthly within the counter current system at 7 sites at mile intervals offshore. Sampling equipment included plastic bottles , glass salinity bottles, a Conductivity, Temperature and Depth probe ( CTD) and NIO (National Institute of Oceanography) deep sea sample bottles. Sampling
platforms varied from river bridges, to a runabout in the harbour, to the R. V. Munida a 14m ocean going vessel in the offshore regions.