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 sampling began in 2009. The water quality of Tāmaki Strait has been ranked as ‘fair’. Of the two monitored sites, one site had ‘good’ water quality while the second site had ‘poor’ water quality. These water quality grades are the same as last year.
Contaminants in sediment:
Sediment quality sampling in Tāmaki Strait estuaries was mostly carried out in 2010. These estuaries had very low concentrations of contaminants. All three sites sampled in each of the predominantly rural Turanga, Waikopua and Mangemangeroa estuaries fell into the ERC green category for copper, lead, zinc and PAHs. Te Matuku Bay on Waihekē Island is a rural reference site with very little urban activity and a catchment dominated by regenerating bush and pasture. Te Matuku Bay has been sampled since 1998, most recently in 2013, and also falls into the ERC green category for all contaminants monitored.
The overall ecological health grade for the Tāmaki Strait reporting area remains the same as last year. It is important to note that the ecology grade for this area is derived only from the monitored estuarine sites and may not represent the wider associated coastal environment. Of the 22 sites included in this score, ecological health is generally ranked as ‘good’ near the mouth of the estuary, declining to ‘moderate’ and ‘poor’ further up the estuary. Some sites had lower grades than last year, while others showed an improved grade. There was no overall consistent pattern of change and individual site changes likely reflect natural variability.