Coastal water quality data

Council has two coastal water quality monitoring buoys which are deployed every quarter.  Deployments last for 30 days and the buoys collect data about water temperature, salinity, dissolved oxygen, turbidity and chlorophyll a every fifteen minutes.  One buoy is located in the Waitangi Estuary in the Bay of Islands and the other at the Hātea River in Whangārei Harbour. Data from the buoys provides council with information about water quality at the two sites and helps us to understand how water quality varies over diurnal and tidal cycles and how big rain events affect water quality.  The data can also help us to identify environmental issues.

Go to more information about what the different parameters tell us

Real time data from the buoys

Disclaimer: Data provided on this website is provided in good faith, but has been automatically generated by Council’s monitoring systems and has yet to be checked by staff.  Accordingly, data users should carefully consider the provisional nature of this information before using it for decisions involving personal or public safety, or the conduct of business that involves monetary or operational consequences.

What does the data mean?

Water temperature

Temperature affects many chemical and biological processes so human activities that alter the water temperature can therefore have adverse effects on marine organisms.  Large discharges can affect water temperature (for example cooling water from a power station) but in Northland human activities are unlikely to affect coastal water temperature in a meaningful way.


Salinity is a measure of all the salts dissolved in water.  The salinity of the ocean is 35 while river water is less than 0.5.  Salinity will be affected by the volume of freshwater inflow near a site, which is in turn affected by rainfall.  Human activities can also affect salinity if there are large freshwater discharges into the coast (for example a power station).   In Northland human activities are unlikely to affect coastal water temperature in a meaningful way.

Dissolved oxygen

Dissolved oxygen is a measure of the quantity of oxygen in the water column. Oxygen is required by marine plants and animals to live and grow and reduced oxygen levels have been shown to cause lethal and sub-lethal effects in a variety of marine organisms. Significant decreases in dissolved oxygen levels can occur when there is an excess of organic material in the system, for example, sewage effluent or dead plant material. Dissolved oxygen concentrations are typically between 80% -100% and 7 mg/l – 9mg/l.  If dissolved oxygen levels fall below 4.6 mg/l for prolonged periods there are likely to be adverse effects on the environment

Chlorophyll a

Chlorophyll a is a green pigment found in plants that is used to absorb sunlight during photosynthesis. Chlorophyll a concentrations are therefore an indicator of phytoplankton abundance and biomass in coastal waters. This is in turn an indicator of trophic status (how nutrient enriched the water is). Chlorophyll a itself can also have negative ecological impacts. For example, elevated chlorophyll a concentrations can reduce the light available for sea grass and other submerged aquatic vegetation. 


Turbidity is a measure of the degree to which light is scattered in water by particles, such as sediment and algae.  It is a measure of water clarity.  Water clarity can be important for the healthy functioning of marine ecosystems. Increased suspended solid loads that reduce water clarity can affect the amount of photosynthesis (primary production) of aquatic plants. Reduced water clarity can also affect the feeding efficiency of visual predators like fish and sea birds.  Turbidity is typically between 2 and 8 NTU at both sites.  A value over 10 NTU indicates there has been a rain event affecting water clarity.