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Auckland Council

Marine report card, Central Waitematā reporting area 2016

Area grade: C

What makes up this grade?

The overall environmental health grade from A to F is based on the average of the scores for water quality, contaminants in sediment and ecology. Bathing Beach scores are not included in this grade. Note that from 2016 the ‘contaminants in sediment’ and ‘water quality’ scores have been assessed using an updated method which may result in a change to the scores unrelated to a change in quality. See the back page for monitoring results and interpretation. These grades represent a summary of averaged results from individual sites and are not designed to track trends. Individual site results will vary and localised issues may not be represented by the overall grades. More detailed analyses are presented in technical reports.

Quick facts

  • Of the eleven bathing beaches tested during summer 2015/16 96% passed recreational bacteria guidelines
  • Several sites within the Waitemata Harbour provide significant habitat for coastal bird species including wrybill, dotterel and North Island fernbird
  • The harbour’s deep navigable channels and sheltered bays helped to determine the choice of a site for New Zealand’s capital in 1840
  • A large number of  introduced species have been recorded in Waitemata Harbour
  • Change in grade: The improvement in the overall grade from a ‘D’ to a ‘C’ is a combination of a change in the method used to calculate the ‘contaminants in sediment’ and ‘water quality’ scores.

Monitoring background and interpretation

Water quality:

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 with the scores being converted into four water quality categories (excellent, good, fair and poor). The calculation of the water quality index has changed this year with the addition of a site from both the Kaipara and Manukau harbours into the list of ‘reference sites’. This may cause changes in the grades which are due to the adjustment within the water quality index rather than real changes in the environment. The most recent results can be found in technical report TR2016/021

Contaminants in sediment:

Auckland Council tests for zinc, copper and lead every two to five years. Environmental Response Criteria (ERC) are used: green indicates low levels of contaminants, amber indicates some elevation and red indicates relatively high levels. Note that from 2016 a nationally consistent but less conservative scoring system has been applied and may result in an apparent improvement in the score for contaminants and the overall grade. The most recent results can be found in technical report TR2016/020.

Ecology:

At selected harbour and estuarine sites, species living in or on intertidal sand flats are counted. Results are classified according to a five-point health index (TR2012/012), which ranges from‘extremely good’ to ‘unhealthy with low resilience’. Ecology is also monitored more frequently at sentinel sites, every two to three months for soft sediment sites.

Bathing beach water quality:

Tests for microbiological (enterococci) contamination are carried out in summer as part of the Safeswim programme 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.

Warning:

These State of the Environment indicators DO NOT measure or indicate food quality or safety; refer to foodsafety.govt.nz for more information.

Monitoring results

Water Quality

Marine water quality is sampled at three sites and began in 1991. The water quality of the Central Waitematā Harbour has been ranked as ‘good’ which is an improvement from the ‘fair’ ranking the Central Waitematā received in 2014. This ‘good’ ranking is made up of ‘fair’ water quality at Henderson, ‘good’ water quality at Whau River/Pollen Island and ‘excellent’ water quality at Chelsea. We have observed improvements in the water quality grades at Chelsea due to a change in the method used to calculate the water quality index.

Contaminants in sediment    

Sediment quality sampling began in 1998. The Central Waitematā Harbour is widely contaminated. The highest concentrations of metals are present at muddy estuarine sites along the southern shores of Central Waitematā Harbour which receive runoff from older urban and industrial catchments. Note that the metals scores have changed from the 2014 scores due to a change in analysis approach and the removal of five sites no longer monitored. If the new approach is applied to the previous data and sites then there has been no significant change in scores. Of the 21 sites regularly monitored for metals their ERC status is as follows:

  • Copper: 62% of sites are green, 33% are amber and 5% are red
  • Lead: 62% of sites are green, 24% are amber and 14% are red
  • Zinc: 57% of sites are green, 14% are amber and 29% are red

Ecological Health  

There was very little change in individual site scores from the 2014 report card. Ecological health varies greatly across the harbour with some sites ranked as ‘good’. However, the majority of sites are ‘moderate’, ‘poor’ or ‘unhealthy’. Ongoing, detailed monitoring of ecological communities has shown most sites exhibit moderate variability relating to natural cyclic patterns in abundance. Monitoring at Meola Reef shows there to be little difference in the number and abundance of species overall, however some slow changes are associated with noted increases in the kelp Ecklonia radiata cover. Other changes include the presence of invasive species including the algae Undaria pinnatifida, the sea squirt Styella clava, and the Mediterranean fanworm Sabella spallanzanii.