FRIDAY, MAY 31, 2019
Come jump in a lake with NIWA
Visitors to NIWA’s stand at this year’s Fieldays are invited to go diving with into the Rotorua lakes -without having to
NIWA is providing a window beneath the surface of New Zealand’s streams and lakes at Fieldays for people to learn more
about our freshwater systems and what keeps them healthy. Through the magic of virtual reality, visitors will take the
plunge with NIWA’s specialist divers and swim alongside them as they undertake a survey of underwater plants.
NIWA freshwater ecologist and specialist diver Tracey Burton conducts an underwater survey of plants in Lake Rotomā that
gives her an indication of the lake's ecological health. Picture: Rod Budd
The survey is known as LakeSPI (Submerged Plant Indicator) and uses the underwater plants as an indicator of a lake’s
LakeSPI surveys have been carried out on 12 Rotorua (Ōkāreka, Ōkaro, Ōkataina, Rerewhakaaitu, Rotoehu, Rotokākahi,
Rotomā, Rotomāhana, Rotoiti, Rotorua, Tarawera, and Tikitapu) lakes since 2005 and NIWA freshwater ecologist Tracey
Burton says she has seen positive and negative changes.
“Many of the negative changes are attributable to the spread of alien invasive weed species such as hornwort, egeria and
lagarosiphon which have had a devastating impact on the some of the lakes. But increased awareness around lake issues
and new management initiatives have seen some lakes improve.”
Only two of the 12 Rotorua Te Arawa lakes remain free of major weeds and constant vigilance is needed to prevent the
spread of weeds throughout New Zealand’s waterways. This is especially relevant for Lake Rotomā, currently one of the
highest ranked lakes in the region.
LakeSPI indicates Rotoma has remained stable with little change for more than 20 years. However just one kilometre to
the east is Lake Rotoehu, classified in poor condition, with a heavy infestation of hornwort and water quality issues.
“A piece of weed the size of your thumbnail would be all that it takes for hornwort to be transferred to Rotomā,” Ms
“Once in, it would displace the native vegetation in the lake – we’ve already seen this happen in Lake Tarawera and
areas of Lake Taupo,” says Burton. “That’s why the ‘check, clean, dry’ message is so important.”
The divers’ observations feed into the national LakeSPI database and build a picture of lake condition and change over
the years. The submerged plant indicators help measure two major influences on lake ecology and condition: increased
sediments and nutrients and the impact of invasive weeds on native vegetation.
LakeSPI has been used to assess the condition of 305 of New Zealand’s 3,800 lakes, with the data used by the Ministry
for the Environment to help describe the state of our freshwater, and it links directly to the Land And Water Aotearoa
The NIWA Fieldays stand will also house two aquariums – one showing native fish and plants in a good quality environment
and the other pest fish and plants in a degraded environment. Scientists will be on hand to discuss to how the health of
freshwater environments affects people’s lives.
NIWA ‘s team of weather forecasters will also be at the stand in the main pavilion to answer any questions on the rural