Big Muddy
Big Muddy is located in Symonds Bay on the northern coast of the Manukau Harbour. This site is close to the outflow of the Williams Stream, which drains out below the Lower Nihotupu Reservoir. As the name suggests, this site is muddy, comprising around 80% of the site’s sediment. First monitored in 1998, this site has been sampled nine times at various intervals, most recently in 2021.
Big Muddy currently has low levels of metal contamination and marginal ecological health.
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
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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
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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
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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
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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:
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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