Clifton sediment monitoring

New River Estuary is a large (4,100ha) tidal lagoon estuary located near Invercargill that has a range of high value habitats including saltmarsh, seagrass, sandy tidal flats, herbfields and native marginal forest. 

This report summarises the results of the third year of baseline estuary sediment monitoring as required by the Invercargill City Council as a condition of its resource consent to discharge treated wastewater to the New River Estuary.

Sediment monitoring results:

  • All sites were dominated by sand. Since 2000, mud content has declined.
  • Mud, organic enrichment and freshwater tolerant invertebrates dominate the infauna community.
  • Sediment nitrogen and organic carbon concentrations have declined since 2000.
  • Sediment redox potential discontinuity has deepened (ie more oxygenated)
  • Heavy metals, semi-volatile organic compounds and total petroleum hydrocarbons were well below the ANZECC (2000) ISQG-Low trigger values (ie low toxicity).