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  • An industrial purple dye spill devastated the Oruarangi Stream ecosystem in 2013. It’s hard to believe such an event could have a positive outcome, but it was the inspiration behind a Participatory Science Platform project involving students from Aorere College, Makaurau Marae, Wai Care, NIWA and Ngā Pae o te Māramatanga.Together, they are working to restore mauri to the local awa (stream).

    The project is a mix of science and local history and has become the stepping stone for further citizen science projects in the South Auckland community.

    Rights: Eel image © Auckland Council and Stream image © Te Warena Taua

    Dye affects the Oruarangi Stream

    The banks and water of the Oruarangi Stream were adversely affected when over 1,000 litres of methyl violet dye leaked from an industrial storage tank. Freshwater and marine life died as a result of a dye spill.

    Oruarangi Stream – an awa of local significance

    Oruarangi Stream holds special significance to local iwi. Their papakāinga is Auckland’s oldest settlement. The stream was an important link to the Manukau Harbour – providing both food and navigation. The Mangere Wastewater Treatment Plant disrupted the stream’s flow for 40 years. Upgrades to the treatment plant in 1998 once again connected the stream to the harbour, and Makaurau Marae members worked to clean up and restore the stream. (Read about the history of this area in the article Ihumātao – past and present.)

    In 2013, more than 1,000 litres of methyl violet dye spilled into a local catchment pit and was carried through the Oruarangi Stream. The effect on freshwater and sea life was devastating. But there is a silver lining to this tragedy.

    Restoring mauri to Oruarangi Stream

    In 2015, year 9 students from Aorere College teamed up with youth and elders from Makaurau Marae. They learned about the local history and stories associated with the stream. Armed with a better understanding of the link between people and place, the group worked to learn about and help restore the stream’s ecosystems. Science experts from Wai Care and NIWA guided students as they investigated water-quality testing, species diversity and ecosystems and what they can do to improve them.

    Water-quality monitoring protocols

    A range of standard water-quality indicators are measured on site. Physical factors include water clarity, pH, temperature and streambed type. Biological factors include micro and macroinvertebrates, plants and larger animals. Water and streambed substrate samples are often collected for off-site analysis.

    Water clarity

    Water clarity is an important indicator of stream health. Just like plants growing on land, aquatic plants need sunlight to grow. Aquatic plants provide food and protection for other species. Plants also produce oxygen. Stream water can become cloudy (turbid) with sediments from erosion, run-off or algae. Turbidity blocks sunlight and limits plant growth and the oxygen that plants produce. Sediments in the water also absorb heat, raising the water temperature and reducing dissolved oxygen supplies. Sediment can block the gills of aquatic animals.

    Rights: Victoria Metcalf, Participatory Science Platform

    Testing water clarity

    Water clarity is assessed with a 1 m long acrylic tube.


    pH measures the acidity or alkalinity of the water. A pH of 7.0 is considered neutral. The optimal pH for many aquatic species is between 7.0 and 9.0.

    Vegetation and geology can influence stream pH. Accidental spills or run-off alter pH. For example, higher than usual alkaline readings indicate an excess of lime fertiliser or detergents, both of which may cause unwanted plant growth.

    Rights: Sarah Morgan, Comet Auckland

    Testing water for pH

    pH is a water quality indicator. Chemical spills and run-off can change stream pH, making it difficult for aquatic life to thrive.


    Water temperature is mostly determined by weather, but there are land-use practices that influence temperature. Macroinvertebrates – an important part of aquatic food webs – tend to prefer cool, fast-running water. Streamside vegetation provides shade and helps to keep water cool. Removing vegetation and damming waterways, which slows or reduces water flows, can cause water to warm.


    The streambed substrate (soft or hard bottom) influences the types of organisms that live in a stream. Soft-bottomed, muddy streams often have a slower flow and more plants. Stony, gravelly, hard bottoms usually have faster flows and support a more varied invertebrate community. Changes to a stream’s substrate will affect the ecosystem it supports.

    Rights: Sarah Morgan, Comet Auckland

    Muddy bottom

    This small tributary to the Oruarangi Stream has a muddy base. This will influence the types of aquatic life that live in the stream.

    Biological monitoring

    Macroinvertebrates are used to assess water quality. They are easily collected in most aquatic environments. Some species, like mayflies and caddisflies, are sensitive to physical and chemical changes to their habitat. They are called indicator species because their presence or absence is an indicator of water quality. These species like cold, rushing water so they are harder to find in slow-moving streams in warmer areas, even if the water quality is considered to be good. Macroinvertebrates are affected by decreases in oxygen levels as well as by pH, temperature and substrate changes.

    Macroinvertebrates are part of aquatic food webs that include larger species like eels, fish and birds.

    Rights: Sarah Morgan, Comet Auckland

    Species count at city stream

    Students involved in a citizen science project in Auckland identify and count the number of species they collected in a water sample at a local stream. A diverse species count can be an indication of good water quality.

    Any work to restore a stream must begin with a stock-take of what species are present and what issues are likely affecting the stream.

    Community outcomes

    The project established more than just baseline data from which to judge water quality in the Oruarangi Stream. The students learned scientific protocols in a relevant and meaningful context. Strong personal links developed between students, the marae community and science professionals. The timeline River investigations and the nature of science documents many of these moments.

    River investigations and the nature of science

    This interactive timeline highlights how students investigating the Oruarangi Stream engaged with the nature of science.

    Makaurau Marae hopes to continue with the project, bringing in new students each year to collect and compare data, monitor changes to water quality and species diversity and continue with the restoration of mauri to their awa.

    Mauri is an integral part of being Māori. Dr Kepa Morgan established a 'mauri model' in order to aid environmental workers and iwi in their work to determine environmental impacts and solutions in situations like water contamination.

    Nature of science

    Science is more than the collection and interpretation of data. Science has a social side – as demonstrated by the strong personal links created and fostered by this project. Scientific investigations bring people from a range of experiences together for a shared purpose.

    Related content

    Restoring Te Auaunga – Oakley Creek looks at the history of this Auckland awa and how its restoration benefits both ecosystems and communities.

    Activity idea

    Te mana o te wai explores the concept of mauri – the health and wellbeing of a waterway.

    Useful links

    NIWA has an online Stream Health Monitoring and Assessment Kit that enables non-scientists to collect consistent, scientifically valid information from small rural streams.

    Manaaki Whenua – Landcare Research has an online Freshwater invertebrates guide to assist community groups with monitoring freshwater invertebrates in New Zealand.


    Students from Aorere College and Makaurau Marae have teamed up to restore the mauri of the Oruarangi Stream. The project has received funding from the South Auckland pilot of the Participatory Science Platform (PSP) – a programme that is part of the Curious Minds initiative and funded by the Ministry of Business, Innovation and Employment. The PSP is currently being implemented as a pilot in three areas: South Auckland, Taranaki and Otago.

    The South Auckland pilot of the PSP is managed by COMET Auckland (Community Education Trust Auckland). COMET is a council controlled organisation of Auckland Council and an independent charitable trust. Its role is to advance education in Auckland by supporting education and skills across the region. COMET Auckland hosts the Auckland STEM Alliance which is leading the pilot in South Auckland. The Auckland STEM Alliance brings together businesses, educators and government.

    The Government’s national strategic plan for Science in Society, A Nation of Curious Minds – He Whenua Hihiri i te Mahara, is a Government initiative jointly led by the Ministry of Business, Innovation and Employment, Ministry of Education and the Office of the Prime Minister’s Chief Science Advisor.

      Published 29 September 2016 Referencing Hub articles
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