How good is the water quality in Ulva Island-Te Wharawhara Marine Reserve and how is it changing?

Status: superior

The water in Paterson Inlet/Whaka a Te Wera is cold (annual average is 11.4 °C), with good visibility. Water from the Pacific Ocean moves in and out of the inlet, driven by wind and tides. The level of sedimentation in the inlet is comparable with levels that would have been found in many parts of New Zealand in pre-human times. 

Freshwater River, the largest freshwater source entering the inlet, is in pristine condition. It contains very low levels of sediment and contaminants because of its natural native forest catchment. This fresh water is acidic (pH 4–5), stained dark brown with tannins and contains soluble iron (approximately 0.8 mg/L). After heavy rain, the discoloured stream water can reduce light penetration in the inlet for several days. 

Marine farms operate in Big Glory Bay, a southern arm of Paterson Inlet. 38 mussel licences and 2 salmon licences were current for this bay in 2016. Marine farms are situated about 3.5 km from the marine reserve. 

Trend: stable

No significant changes in water quality have been reported in the last five years.


No regular water quality monitoring is undertaken in the marine reserve. Environment Southland has a biomonitoring site on Mill Creek in the town of Oban and two coastal contact recreation sites in Halfmoon Bay, but does not currently carry out regular monitoring. 

Water quality monitoring is carried out in Big Glory Bay under the New Zealand Food Safety Authority’s Animal Products (Specifications for Bivalve Molluscan Shellfish) Notice 2006 (PDF, 330K) as a requirement for marine farming in the area. This food safety standard states the frequency and limits for a range of possible contaminants and is used here as a measure of ecosystem health. 

Testing for faecal coliforms and the bacterium E.coli is carried out monthly, sampling for biotoxins (the cause of algal blooms) is carried out weekly and the levels of heavy metals are surveyed every three years. Levels of these contaminants in Big Glory Bay are consistently below the upper limits of the standard. 

Ulva Island marine farms map.
The distance from the marine farms in Big Glory Bay in Paterson Inlet to the closest boundary to the marine reserve (3.1 km and 3.6 km)


See also research and monitoring.

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