Restoration planting of an at-risk native species has resumed on Lake Wairarapa’s foreshore after the health threat posed by toxic algae receded in April.
More Karaihe sedges grown at the nearby He Kōtare nursery are being planted along the waterline this winter. It’s a programme for reviving this vitally important endemic species and also for supporting long-term improvement in the water quality of Wairarapa Moana.
He Kōtare’s Ellen Rodda said seed has been collected from patches of karaihe found growing at the moana and propagated at the nursery over the past three years.
“We are now returning to plant them in their natural habitat along the waterline,” Ellen said. “These are amazingly resilient plants that survive and thrive despite constant changes in the lake level and severe weather events.
If you’re visiting the moana, look out for clusters of red grass-like plants growing happily along the shoreline.”
He Kōtare is the Kaupapa Māori based native plant nursery under the umbrella of Pae Tū Mōkai o Tauira, a community rōpū (group) based in Featherston.
All its plants are from eco-sourced seed from older vegetation around the lake and within wetland areas which are all part of Wairarapa Moana. The nursery has a full range of healthy and particularly resilient sedges, grasses, flaxes, shrubs and trees for supply to farmers, gardeners, community groups and local authorities.
Ecologists have long classed Lake Wairarapa as “super trophic” because of high nutrient run-off levels from farms and urban activities, decades of sediment build-up and, at certain times, high bacterial counts.
Alarm bells went off in late summer when water testing and analysis by Greater Wellington regional council (GW) revealed high levels of toxic algae (technically known as cyanobacteria) in some lake water. GW issued public warnings from 14 March for people to avoid direct contact with the water and to look out for any bright green algal scum collecting on the lake edge.
Testing continued and over several weeks, the algae blooms were found to have dissipated such that the public warnings could be lifted on 11 April.
GW senior adviser Penny Fairbrother told The Star any resurgence is unlikely during colder, wetter months of the year but vigilance around cyanobacteria levels will continue as part of the council’s routine water testing each month and its periodic collection of data from a sensor buoy anchored in the middle of Lake Wairarapa.
Fairbrother said toxic algae risks, and related monitoring and response activities will be subject to review and discussion by GW, the Wairarapa Moana Statutory Board and other stakeholders this winter.
Meanwhile, He Kōtare and its volunteers will be planting karaihe each week at Lake Domain, near Featherston. as the weather permits. People are invited to join the planters by making contact with He Kōtare.
Fairbrother, an ecologist by education, says growth in the sedges will certainly help to combat the lake’s poor water quality over time. “These are plants that trap sediment particles and take up nutrients that have run off into the lake.”
Note: He Kōtare can be contacted at hekotarenursery@gmail.com for plant information and volunteering.
