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  • Rights: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council
    Published 17 March 2020 Referencing Hub media

    A nutrient is a chemical that organisms need to live and grow. Nutrients such as nitrogen and phosphorus are naturally occurring, but urban and rural land use practices can add more of these nutrients to waterways. Excess nutrients lead to unwanted plant growth, which affects habitat and recreational uses.

    Dr Eloise Ryan explains why Waikato Regional Council assesses total nitrogen and total phosphorus as water quality indicators.

    The following resources provide information on how nutrients enter waterways, the impacts they can have and ways of managing or preventing them from entering.






    There’s lots of different types of nutrients – mainly we’re talking about the forms of nitrogen and phosphorus. And there’s different forms of nitrogen such as ammonia or nitrates, and with phosphorus, we talk about total phosphorus and phosphates. So all these different forms of nutrients can affect aquatic life differently.

    The more nitrogen and phosphorus that end up in our streams, the more algae will grow. Algae is naturally occurring in our lakes and streams and rivers. However, there’s a few factors that can make them grow more, and one of those factors are nutrients. And nutrients can be from things like fertilisers, so we’ve got to be very careful not to overuse fertilisers so we stimulate algal blooms.

    The other thing is algae are plants, and they grow with light and temperature. So if our waterways are heating up with global climate change, then we will see algal blooms grow more and more into the future.


    Dr Eloise Ryan
    Waikato Regional Council
    Footage of algae mats in river, Cawthron Institute
    Top-dressing footage, McDonald’s Lime


    This video has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.

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