Clifton sediment monitoring
This report summarises the results of the second year of baseline estuary sediment monitoring as required by the Invercargill City Council’s (ICC) consent to discharge treated wastewater to the New River Estuary.
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 second year of baseline estuary sediment monitoring as required by the Invercargill City Council’s (ICC) consent to discharge treated wastewater to the New River Estuary. Results are reported for the nine intertidal sites situated adjacent to the treated wastewater discharge channel within the estuary.
Sediment monitoring results:
- All sites were dominated by sand. Since 2000, mud content has declined.
- Mud and freshwater tolerant invertebrates dominate the infauna community.
- Sediment nitrogen and organic carbon concentrations have declined since 2000.
- RPD (redox potential discontinuity) has deepened (i.e. more oxygenated).
- Invertebrate community showed moderate dominance by organic enrichment tolerant species.
- Heavy metals, semi volatile organic compounds (SVOCs) and total petroleum hydrocarbons (TPHs) were well below the ANZECC (2000) ISQG-Low trigger values (ie low toxicity).