Monitoring background and interpretation
To measure the health of our marine waters, a comprehensive range of parameters including nutrients, turbidity, salinity, pH (and more) are measured. Results are classified according to the Water Quality Index, which was developed by the Canadian Council of Ministers of the Environment in 2001 and adapted by Auckland Council. Scores are based on the averages over the last three years and exclude ‘bathing beach water quality’. Check out report TR2013/031.
Contaminants in sediment:
Auckland Council tests for zinc, copper and lead every two to five years. Other contaminants such as PAHs (polycyclic aromatic hydrocarbons, by-products of burning fuels) and arsenic are also monitored. Environmental Response Criteria (ERC) are used: green indicates low levels of contaminants, amber indicates some elevation and red indicates relatively high levels (as outlined in Blueprint for monitoring urban receiving environment, ARC TP 168, 2004 and ANZECC guidelines). Check out report TR2012/041.
At harbour and estuarine sites, seabed-dwelling (benthic) species are counted and contaminants in sediments and sediment grain size are measured every two to five years, with the most contaminated sites sampled most frequently. Results are classified according to a five-point health index outlined in Health of estuarine soft-sediment habitats: continued testing and refinement of state of the environment indicators, Auckland Council technical report, TR2012/012, which ranges from ‘extremely good’ to ‘unhealthy with low resilience’. Ecology is also monitored more frequently at selected sites, every two to three months for soft sediment sites and annually for subtidal rocky reefs. There is currently no reporting indicator for reef ecology. Check out report TR2013/027.
Bathing beach water quality:
Tests for microbiological (enterococci) contamination are carried out in summer as part of the Safeswim programme and are in line with Ministry for the Environment guidelines. These results are reported as a ‘Quickfact’ and are calculated from all tests carried out at all monitored beaches in the Harbour. ‘Bathing beach water quality’ has not been included in the overall score as it relates to human health and is based on a different method of assessment (number of alerts). Individual results for monitored beaches are provided on the Safeswim section of the Auckland Council website.
These State of the Environment indicators DO NOT measure or indicate food quality or safety; refer to foodsafety.govt.nz for more information.
Marine water quality monitoring began in 1992. The water quality of the Tāmaki Estuary has been ranked as ‘poor’. Two sites are monitored, one site was ranked as ‘poor’ while the second had ‘fair’ water quality. These water quality grades remain the same as last year.
Contaminants in sediment:
Sediment quality sampling began in 1998. The Tāmaki Estuary has high levels of contaminants (particularly zinc) in its older, densely urbanised and industrialised headwater zones (e.g. Middlemore, Pakuranga, Ōtāhuhu and Panmure). Contaminants lessen with distance from the headwaters and consequently the estuary mouth has lower levels of contaminants.
All four sites sampled for PAHs fell into the green ERC category. Of the 10 sites regularly monitored for metals their ERC status is as follows:
» Copper: 30% of sites are green, 70% are amber and none are red
» Lead: 50% of sites are green, 50% are amber and none are red
» Zinc: 20% are green, 10% are amber and 70% are red.
The overall ecological health grade for the Tāmaki estuary comprises of eight monitoring sites mainly located in the upper reaches of the estuary where ecological health is ranked as ‘unhealthy’. Two additional sites used in this year’s overall health grade from Pakuranga creek have a ‘poor’ grading. The mid estuary site near Benghazi Road has the highest grade of ‘moderate’. Other sites nearer the mouth of the estuary are not monitored but are likely to have better ecological health.