Circulation and Sedimentation of suspended particulate matter in New Zealand fjords Technical Report
- Author
- Pickrill, R.A.
- Year
- 1987
- Journal / Source
- Marine Geology
- Publisher / Organisation
- Elsevier
- Volume
- 74
- Number
- 1-2
- Month
- January
- Pages
- 21-39
- Keywords
- Circulation, New Zealand, fjords, estuarine, brackish layer, suspended particulate matter, SPM, phytoplankton, agglomeration, faecal pelletization, flocculation
- Summary
- Circulation in the New Zealand fjords is estuarine, with a seaward-flowing brackish layer overflowing saline water. Despite an extremely high rainfall (>6000 mm yr-1), terrestrial dediment input is low and concentrations of suspended particulate matter (SPM) rarely exceed 1 mg 1-1. The terrestrial influence is barely detectable anywhere in the fjords; SPM in near-surface waters is dominated by phytoplankton. In surface waters, SPM components remain separate, as they settle they are clustered into larger groups by agglomeration, faecal pelletization and flocculation. Phytoplankton produce a secondary SPM maximum at the top of the deep zone. Deep waters are barren of living plankton with clustered SPM and broken phytoplankton settling from above. The low terrestrial SPM input and high organic/biogenic concentrations are reflected in low sedimentation rates and high organic carbon content of bottom sediments. The estuarine stratification is broken up in the fjord entrances by ocean waves which also resuspend sediment off the entrance sills thereby increasing SPM concentrations in bottom waters. High SPM concentrations are found in basins cut off from the main fjord by shallow sills which inhibit deep-water renewal.
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