Algal bloom discolours Lyttelton Harbour
An apparent oil spill in Lyttelton Harbour is an outbreak of algal bloom.
Environment Canterbury said it had received several calls from people concerned about a large oil spill.
However, ECan's Jim Dilley said it had been investigated, and samples taken showed the discolouration was from an algal bloom.
"The algal bloom looks just like an oil spill when viewed from a distance, but once you get closer you can see that the coloured particles are under the surface of the water rather on the top where oil would float," he said.
ECan senior water-quality scientist Lesley Bolton-Ritchie said the algal bloom was caused by the organism Mesodinium rubrum.
"The discolouration of the water, which looks like oil, is because of the large amount of bloom that can change the seawater colour to brick red, brown or rusty red, which it is known for."
She said the outbreak could be caused by a combination of sunny days and the water warming up, mixed with recent rainfall causing nutrients, such as nitrogen, from rivers and streams to run into the harbour.
The freshwater streams always had nutrients, such as nitrogen, in them, but when heavy rain moved them around they could feed the organism that caused the algal blooms, she said.
"They are a bit like bacteria and they just keep dividing ... You can get millions."
The non-toxic bloom would naturally break up in rougher water, she said.
"You can get them anywhere any time, but it tends to be during spring and summer. They are just natural events," she said.
- © Fairfax NZ News
Which do you think is the quote of the year?Related story: Best quotes? Cats, sweat and Aaron Gilmore