Omapere problem continues
Conservation group Forest and Bird are calling for the Northland Regional Council to do more following a significant algal bloom at Lake Omapere.
The lake - Northland’s largest - and the Utakura River which flows out of it started to produce froth, a pungent smell and turned a ‘‘duck egg blue’’ around February 16. A number of dead eels have also been reported from residents.
Forest and Bird freshwater advocate Annabeth Cohen says with longfin eels threatened with extinction and shortfin eels also in a declining state, any reports of dead fish are a concern.
She says low levels of oxygen in the water are likely to have caused the eels to suffocate.
‘‘Of high level concern is the amount of pollution entering the lake.
‘‘Algal blooms happen when you have high temperatures and nutrients in excess, so I am very sure pollution is the problem.’’
Cohen says the pollution is likely from nitrates and phosphates found in animal effluent and fertilisers.
’’We can’t blame algal blooms on high temperatures so we have to take responsibility for the nutrients going into the water.
‘‘NRC aren’t doing enough to control pollution entering the lake.’’
NRC said on February 23 water testing had not detected any cyanotoxins, which can pose health risks to people.
However, the tests showed the cyanobacteria that can produce those toxins were present at ‘‘very high levels’’.
Council spokesman Colin Dall said despite the fact no cyanotoxins had been found, people should not swim in the water or use it for household or stock supply.
‘‘The regional council will continue to sample and monitor the lake and Utakura River until the algal bloom recedes, which could still be some time away.’’
Dall said Omapere, at just 1.8 metres at its deepest point, was one of Northland’s shallowest lakes and has naturally high fertility.
This makes it more prone to algal blooms, and it has suffered a number since the early 1980s, he says.