The red seaweed washed up at the Ruakākā Estuary this week. Photo / Karen Sawford
The red seaweed washed up at the Ruakākā Estuary this week. Photo / Karen Sawford
The reoccurring crimson seaweed that's been plaguing Waipū has arrived 20km upstream at Ruakākā.
The Northern Advocate was notified of the red algal bloom's presence by Ruakākā Estuary resident Karen Sawford who first noticed it on Tuesday.
"We have not seen it this bad in 25 years of living here.It smells terrible. It is slowly washing away but hasn't been seen like this before."
Northland Regional Council (NRC) resource scientist Richard Griffiths said they were unaware of the Ruakākā deposit but staff had observed mats of red algae in similar quantities in that area of the Ruakākā Estuary before.
The red algal bloom has been known to wash up at the Ruakākā Estuary before. Photo / Karen Sawford
"From the photographs provided, it appears to be the same species that has been found in similar occurrences in Waipū, Bream Bay and Ruakākā Estuary. Algae is an important component of coastal ecosystems and from the photographs, this appears to be a natural phenomenon."
He said NRC regularly monitor water quality at Ruakākā Estuary.
"Given that we are aware that red algae has been observed in the estuary before in similar quantities by our staff, without adverse environmental consequences, we do not consider that further investigation is necessary at this stage. Nevertheless, we do keep a record of all these reports to see if the frequency of these events is changing over time.
"At this stage, we do not think that the red algae will cause a similar situation to what happened recently in Waipū Estuary. This section of the Ruakākā Estuary is very well flushed and we are aware that similar quantities of red algae have been found in the estuary before without having any wide-scale adverse effects."
The red algal bloom washed up at Waipū Cove last week. Photo / Michael Cunningham
The east coast beach of Waipū Cove, around 20km south of Ruakākā, was earlier this month a mass of the red seaweed, believed to be called Spyridia filamentosa, after increasingly being plagued by its presence over the past decade. It is particularly prominent after storms. As the tide recedes, it becomes trapped, stagnates, rots then smells in the sun.
Earlier this year, the algal bloom became trapped in the nearby estuary, depleting oxygen levels, which led to hundreds of thousands of marine life deaths, threatening a wildlife refuge within. The ensuing putrid stench, described as rotten eggs and dead bodies, drove nearby residents from their homes.
NRC coastal and water quality field operations manager Ricky Eyre said numerous samples had been sent to Niwa for identification and only native species had been identified with none of them found to be toxic or harmful. The estuary has since flushed out and replenished itself, but the recent layer blanketing Waipū Cove was almost half a metre deep in places.
"Though we have previously engaged Niwa to investigate the causes of the nuisance algae events at Waipū, we are still not fully clear on the full range and/or combination of conditions to cause the algae to get washed up in nuisance. It's likely a combination of tide and winds."
