Red bloom invades Wellington Harbour

05:28, Sep 04 2012
An aerial view of the bloom in Wellington harbour, with Matiu/Somes Island visible.

Last Friday's fine weather brought a red bloom to Wellington Harbour, near Matiu/Somes Island.

A NIWA microalgae specialist said he suspects the bloom is not algae, but in fact millions of single-celled animals.

Dr Hoe Chang said the distinct burgundy-red colour is the clue - algal blooms, like one seen in Evans Bay two weeks ago, are normally slightly more orange or pink at this time of year.

However, he did not have a sample to test, so could not make a conclusive finding, but said neither the single-celled species or the algae were toxic to humans or animals.

Dr Chang said blooms like these were common in the early days of spring.

High winds and choppy waters in winter brought lots of nutrients to the surface.


Then, in the first days of spring sunshine, algae and other micro-organisms took advantage of these nutrients, plus warmer water and high light levels, and bloomed.

Dr Chang said yesterday's wind and rain is likely to have broken up the bloom, but the red waters may return.

''Chances are we'll see it again.

''In Wellington Harbour, every spring, we're bound to see one or two blooms.''

The Dominion Post