Alarm at algae in springs
Call for action after conservation group’s ‘unacceptable’ discovery
The discovery of green algae on the clear waters of Te Waikoropupu¯ Springs has sparked alarm in Golden Bay.
Long-time resident Andrew Yuill, who regularly collects water samples for community conservation group Friends of Golden Bay, said he first noticed a patch of algae in Dancing Sands Spring about September 19.
‘‘I just saw it out of the corner of my eye and I thought, ‘It’s not right’,’’ Yuill said, adding that it was the first time he had seen such algal mats since he started taking water samples in early 2016.
He estimated that the initial patch of algae had since doubled in size. That patch and other algal mats were visible this week in Dancing Sands Spring and Main Spring when The Nelson Mail visited.
Save Our Springs co-ordinator Kevin Moran said he was concerned that the presence of algae might be a symptom of rising nitrate levels in the waters of Te Waikoropupu¯ , and he was worried about the potential effects of those nitrates on the Arthur Marble Aquifer, which feeds the springs.
‘‘The danger is that nitrate levels will kill the little creatures [stygofauna] in the aquifer, and if that happens, we’ve got pea soup at Te Waikoropupu¯ . . . we’ll lose the clarity,’’ Moran on Tuesday told the Golden Bay Community Board as he urged action by the Tasman District Council over the nitrate levels.
Moran told the board his major fear was that the springs could get lost in ‘‘the paper chase’’ over changes to freshwater policy signalled by the Government.
‘‘We’d like the assurance that Te Waikoropupu¯ – this national treasure – will be at the top of the list.’’
Yuill told the board that data collected by Friends of Golden Bay showed that the nitratenitrogen level in Main Spring had risen from 0.40mg per litre in 2016 to 0.51-0.52mg for six successive results over September, October and into November.
‘‘This is unacceptable, obviously,’’ he said. ‘‘We’re starting to see weed mats growing there on the springs.’’
Council environmental information manager Rob Smith said that while algae could respond to nitrate, they could also appear in spring and summer as a result of increased light and/or temperature.
However, while he understood that it was ‘‘not unique’’ to find some algae in the backwater areas, ‘‘this is the first time we have heard reports of algae present there like this’’ in the springs, Smith said.
‘‘We will certainly inquire further.’’
Smith said a sample of the algae would be taken to determine its species. It might have already been present but only become noticeable recently because of its spread.
That reproduction could be sparked by rain washing nutrients into the waterway, Smith said. Birds or wind could also carry algae to different locations where it could build up if it had warmth, food and shelter. ‘‘Anywhere there’s habitat, there’s algae.’’
Niwa freshwater ecologist and algae expert Dr Cathy Kilroy backed the call for a sample to be taken. She said proliferation of algae in rivers and ponds was ‘‘not that unusual’’, especially in
‘‘It’s not right . . . We’re starting to see weed mats growing there.’’ Andrew Yuill, Friends of Golden Bay
spring, when light increased, though it would be ‘‘really nice to keep a watching eye on it’’ at Te Waikoropupu¯ Springs.
The filamentous green algae Spirogyra was already present in the springs, Kilroy said.
Yuill and Nga¯ti Tama Ki Te Waipounamu Trust are joint applicants for a Water Conservation Order to protect the springs, the aquifer and associated water bodies. A hearing before a Special Tribunal closed in August 2018, and its recommendation report is awaited.
Council environment and planning manager Dennis BushKing told the community board the council was ‘‘in a bit of a state of limbo’’ regarding recommendations from the Takaka Freshwater and Land Advisory Group – including protection for Te Waikoropupu¯ Springs – until the results of that Water Conservation Order application were released.
‘‘We are legally obliged to give effect to the results of that order.’’