Scientists partner with locals to restore heavily polluted East Coast lake
Friday, 22 April 2022
It is well known that excess nutrients (nitrates and phosphates) in freshwater result in rampant growth of algae and cyanobacteria, starving other underwater creatures of oxygen and causing all sorts of problems.
There is a little known lake near Wairoa – Lake Whakakī – which is suffering badly from these effects. The toxins produced by cyanobacteria are contaminating the highly valued tuna (eels). These cyanotoxins, such as nodularins, promote liver cancer and can cause death if very high levels are eaten.
Wild foods are important culturally and are a key food source (mahinga kai) for the community in this remote area.
A top science team from Massey University and the Cawthron Institute, under the auspices of the NZ Food Safety Science and Research Centre, has set themselves the task of working with the Whakakī Lake Trust, local hapu – Ngāti Hinepua, Ngāti Hine, Ngai Te Ipu and the Whakakī community to measure and manage the problem at Whakakī.
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Together, they have been successful in bidding for $227,000 from MBIE’s Vision Mātauranga Capability Fund, which stipulates collaboration and mutual learning. It’s a partnership approach that also brings in Hawke’s Bay Regional Council.
Accordingly, a programme has begun to measure cyanobacteria and toxin levels, and to swap information and observations with the locals. They are set to become experts in cyanobacteria biology and the techniques of water monitoring.
Levels of the cyanotoxin, and therefore risk of consuming the tuna, fluctuate over the year, so monitoring is essential.
The locals, including Trevor Waikawa, Pani Hook and other Whakakī Lake trustees, will be increasingly involved with measurement and management, empowering them to make decisions on the safety of their mahinga kai more independently in future.
Whakakī Lake and duneland system is regionally, nationally and internationally important. Traditionally, Whakakī Lake was well known as a major source of eels of special flavour.
Tangata whenua have seen a dramatic decline in tuna numbers over the past 40 years. It is estimated that the population is now about a quarter of what it was in the 1950s. Drainage, deforestation and commercial fishing have all impacted the eel fishery.
Meanwhile, a legacy load of nutrients and sediment has accumulated in the lake. Its maximum depth is about 1 metre, which means silt remains suspended in the water and nutrients are easily available for algal growth.
The vision of the hapu is to develop the lake property into a wetland park for the benefit of the environment and future generations, with a focus on helping the water recover and making the tuna fit for consumption. The Whakakī property has already been fenced and stock have been removed. The trust has planted over 45,000 native trees and flax.
Applying for government funding is a time-consuming and exacting business that many scientists complain about. The high opportunity cost is set against the low chance of success when there is a small amount of money and competition from many high quality applications.
The stiff competition has not deterred the manager of the lead agency, the NZ Food Safety Science & Research Centre, Wendy Newport-Smith, who, in successive roles, has been instrumental in winning more than one large tranche of money to support East Coast restoration.
Professor Phil Bremer is director of the Food Safety Science & Research Centre and Glenda Lewis is a science writer.