Mill Bay
Mill Bay is located on the Manukau Harbour’s northern coastline, at the eastern end of Cornwallis Beach. The site is situated approximately 300 meters from shore, with a surrounding catchment comprising primarily of native vegetation. To date, Mill Bay has been sampled three times in 2010, 2015 and 2021.
This mostly sandy site has patches of seagrass interspersed throughout, and currently has relatively low levels of metal contamination.
Monitored site results
This dashboard shows information on the data collected by the regional councils and unitary authorities for the Estuary health scientific indicators, click the tiles for more information:
Estuary Health Indicator
Estuary Macrofauna Score information
What do the grades mean?
The Estuary Macrofauna Score is based on the composition of the macrofaunal community and tells us how impacted the monitored site is by mud (via a Mud Benthic Health Model). The calculated scores are continuous and represent a gradient of impact. Low scores indicate low impacts from mud (good health), whereas high scores indicate high impact (poor health). Scores are converted into one of five categories for visualisation and to easily compare sites, however the thresholds between categories do not necessarily reflect breakpoints in ecological condition. See the Estuary macrofauna factsheet for more information.
- Very low impacts
- Low impacts
- Moderate impacts
- High impacts
- Very high impacts
Estuary stressor
Mud content information
What do the grades mean?
Mud content refers to the amount of fine silt and clay particles (collectively called ‘mud’) that are present in the estuary sandflats. This figure shows (mean) annual mud content measured at the monitoring site. The annual values are assessed against custom, national guidelines that indicate increasingly negative impacts on the macrofaunal community.
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≤3%
Ecology is not negatively impacted.
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3-10%
The diversity of the macrofauna community is slightly reduced.
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10-30%
The diversity of the macrofauna community is reduced and less resilient to disturbance.
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30-60%
The macrofauna community is unbalanced and dominated by a small number of tolerant species.
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>60%
The macrofauna community is degraded.
Zinc information
View results alongside National guidelines:
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What do the grades mean?
This figure shows the (mean) annual contaminant concentration measured in the sediments of the monitored site. The annual values are assessed against the ANZG 2018 guidelines by default, and you can choose to view them assessed against several additional, more conservative guidelines. All of the guidelines show how likely it is that the contaminant is having negative ecological impacts. See the Contaminants factsheet for more information.
- Ecological impacts unlikely
- Ecological impacts possible
- Ecological impacts probable
Copper information
View results alongside National guidelines:
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What do the grades mean?
This figure shows the (mean) annual contaminant concentration measured in the sediments of the monitored site. The annual values are assessed against the ANZG 2018 guidelines by default, and you can choose to view them assessed against several additional, more conservative guidelines. All of the guidelines show how likely it is that the contaminant is having negative ecological impacts. See the Contaminants factsheet for more information.
- Ecological impacts unlikely
- Ecological impacts possible
- Ecological impacts probable
Lead information
View results alongside National guidelines:
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What do the grades mean?
This figure shows the (mean) annual contaminant concentration measured in the sediments of the monitored site. The annual values are assessed against the ANZG 2018 guidelines by default, and you can choose to view them assessed against several additional, more conservative guidelines. All of the guidelines show how likely it is that the contaminant is having negative ecological impacts. See the Contaminants factsheet for more information.
- Ecological impacts unlikely
- Ecological impacts possible
- Ecological impacts probable
Arsenic information
View results alongside National guidelines:
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What do the grades mean?
This figure shows the (mean) annual contaminant concentration measured in the sediments of the monitored site. The annual values are assessed against the ANZG 2018 guidelines by default, and you can choose to view them assessed against several additional, more conservative guidelines. All of the guidelines show how likely it is that the contaminant is having negative ecological impacts. See the Contaminants factsheet for more information.
- Ecological impacts unlikely
- Ecological impacts possible
- Ecological impacts probable
Mercury information
View results alongside National guidelines:
View results alongside alternative guidelines:
What do the grades mean?
This figure shows the (mean) annual contaminant concentration measured in the sediments of the monitored site. The annual values are assessed against the ANZG 2018 guidelines by default, and you can choose to view them assessed against several additional, more conservative guidelines. All of the guidelines show how likely it is that the contaminant is having negative ecological impacts. See the Contaminants factsheet for more information.
- Ecological impacts unlikely
- Ecological impacts possible
- Ecological impacts probable