Toxic al­gae warn­ings reis­sued

Wairarapa News - - FRONT PAGE - ILLYA MCLEL­LAN

Fluc­tu­a­tions in toxic al­gae lev­els in Master­ton’s Waipoua River have made it dan­ger­ous for swim­mers and dogs in re­cent weeks.

In late De­cem­ber it was de­clared un­safe, though the lat­est read­ing on Jan­uary 5 has seen the warn­ing down­graded to ‘‘low risk’’.

Greater Welling­ton Re­gional Coun­cil en­vi­ron­men­tal sci­en­tist Mark Heath said that, de­spite some re­cent rain, the wa­ter flow in the Waipoua was dropping and tem­per­a­tures were ris­ing, pro­vid­ing ideal con­di­tions for al­gal growth.

The river has been deemed a haz­ard again thanks to an or­gan­ism that was orig­i­nally cru­cial to the oxy­gena­tion of the Earth.

‘‘The or­gan­ism that causes the al­gae is a cyanobac­te­ria and this fam­ily of bac­te­ria has been around since the be­gin­ning of life on Earth.

‘‘There is con­fu­sion around the toxic al­gae, many peo­ple ask us if it is new or in­va­sive. It is ac­tu­ally over 3 bil­lion years old, but some things we are do­ing in terms of land use seem to be cre­at­ing con­di­tions it can thrive in.’’

Mon­i­tor­ing of the Waipoua River at Colombo Rd by the re­gional coun­cil shows that the amount of black or brown toxic al­gal mats grow­ing on the river bed has reached dan­ger­ous lev­els.

Records show toxic al­gal blooms in the Waipoua have been a com­mon oc­cur­rence over the past decade. This sum­mer’s blooms are sim­i­lar to what had been ob­served in pre­vi­ous years, Heath said.

The Waipoua has many char­ac­ter­is­tics which make it rather sus­cep­ti­ble to toxic al­gal blooms in­clud­ing sta­ble river flows, warm wa­ter tem­per­a­ture, high sun­shine hours, and el­e­vated ni­tro­gen con­cen­tra­tions.

It is a slower flow­ing river that comes out of the hills and flows through a lot of agri­cul­tural land, as well as sub­ur­ban and ur­ban ar­eas.

‘‘We will be un­der­tak­ing a tar­geted in­ves­ti­ga­tion this sum­mer to learn more about what is caus­ing the toxic al­gal blooms in the Waipoua.’’

Ngati Kahun­gungu ki Wairarapa gen­eral man­ager PJ Devon­shire said the iwi’s en­vi­ron­men­tal staff were work­ing with the coun­cil and other or­gan­i­sa­tions to try to in­crease the health of Wairarapa rivers.

‘‘We will con­tinue to fight for the health of our rivers. We do not want to get to a point where it is con­sid­ered nor­mal for peo­ple to not be able to swim.’’

If peo­ple are con­cerned about river safety they are ad­vised to check theGWRC ‘‘Is it safe to swim?’’ web­page.

PHOTO: PIERS FULLER

Waipoua River is show­ing fluc­tu­at­ing lev­els of toxic al­gae.

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