Partnership to restore polluted East Coast lake
It is well known that excess nutrients (nitrates and phosphates) in fresh water result in rampant growth of algae and cyanobacteria, starving other underwater creatures of oxygen and causing all sorts of problems.
A little known lake near Wairoa – Lake Whakakı¯ – 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, is working with the Whakakı¯ Lake Trust, local hapu – Ngāti Hinepua, Ngāti Hine, Ngai
Te Ipu and the Whakakı¯ community to measure and manage the problem at Whakakı¯.
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 Whakakı¯ 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.
Whakakı¯ Lake and duneland system is regionally, nationally and internationally important. Traditionally, Whakakı¯ 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 Whakakı¯ property has already been fenced and stock have been removed. The trust has planted more than 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.
Drainage, deforestation and commercial fishing have all impacted the eel fishery.