Beach water quality, the ecology of rocky reefs and estuaries, any impact on the coast from our rivers, and consent compliance for activities such as consented discharges.
Measuring ecological diversity is a useful indicator of coastal water quality. Our long-term rocky shore ecological monitoring programme has been in operation for over 20 years.
Within the programme we survey the biological community in the low tide zone of rocky reef habitats. A number of grid areas are surveyed at each site with the mean number and abundance of species reflecting the ecological diversity at the site.
We also compare the biological community at sites near coastal discharges with control sites, to check that the discharges are complying with consent conditions.
We use the results of all our ecological monitoring to analyse regional trends in marine water quality for overall state of the environment reporting.
Some species of shellfish, such as mussels, feed by filtering particles out of the sea water. In doing so, they can accumulate contaminants in their tissues, even when background concentrations are relatively low. We monitor shellfish flesh collected from kaimoana reefs, effectively using them as ‘bio-monitors’ to assess the presence of contaminants at particular sites.
We also monitor mussel flesh for norovirus contamination at coastal sites near wastewater treatment plant discharges. Comparing the flesh of shellfish from sites that have potential to be affected with unaffected control sites gives us a good indication of water quality.
All shellfish monitoring data is used to determine if consent holders are complying with conditions set our for activities such as treated municipal sewage discharge , oil and gas exploration, dairy and other industrial processing.
Beach bathing water quality
Every spring and summer, we keep a check on coastal water quality at popular swimming beaches to ensure our beaches are suitable for bathing and other recreation. Results are available to the public live on our website.
What we find is that water quality of the region’s bathing beaches is generally high, with around 95% of samples meeting New Zealand health guidelines for recreational use.
Occasionally water quality can be affected. This is particularly evident after heavy rain when a large volume of river water is discharged to the sea, carrying contaminants such as bird faeces, sediment, urban stormwater, agricultural run-off and so on. In some circumstances district council’s will issue public health warnings based on national guides and advice from the Medical officer of Health, the warning will remain until further testing shows water is suitable for swimming.