For more than 20 years NIWA scientists have been nurturing three plants that are the only examples of their kind in existence.
Hamilton-based freshwater ecologists Paul Champion and Mary de Winton retrieved the rare species of the quillwort family – an aquatic submerged plant from Lake Omapere, Northland in the late 1990s and have kept them alive in the hope they may one day be returned.
Quillworts are primitive aquatic relatives of ferns, with this variety first discovered in Lake Omapere in 1972 living in mud between rocks in shallow areas of the lake.
Omapere, 4km north of Kaikohe, is the largest lake in Northland at 1,230 hectares and has had a chequered history environmentally. Treasured by Maori, and once an abundant provider of freshwater mussels, crayfish and eels, it has been prone to toxic algae blooms and submerged vegetation collapse which has badly affected water quality.
In summer it has a maximum depth of just 1.5m leaving it shallow and unstable. Egeria, or oxygen weed invaded the lake in 1984, growing quickly and destroying other animal and plant habitats. The lake then collapsed.
A long period of algal blooms followed but by 1998 it was on the brink of collapse again as the oxygen weed had re-established in the lake.
“We decided we needed to act. If we hadn’t rescued the plants then they would have been lost and it was important to get some material to propagate,” Mr Champion says.
Three plants were removed and taken to a NIWA facility at Ruakura where they were planted in lake sediment covered with sand. Genetic studies showed the plants are distinct from other populations of quillwort and are regarded as extinct in the wild and listed as nationally critically endangered by the Department of Conservation.
The plants were left to reproduce on their own but just grew bigger and bigger without making new plants – until now. They have finally begun to produce new plants. “You can see why they’re rare,” says Champion.
In the intervening years grass carp have been introduced to Lake Omapere to control the invasive oxygen weed and an extensive restoration programme undertaken by the Lake Omapere Trustees. The lake is now doing better but as long as the grass carp are present the quillwort can’t go back. To complicate the issue, egeria has also recently started to regrow in the lake.
Mr Champion says that for the past five to six years NIWA has been working with the Lake Omapere Trustees to find a home for the quillwort in Northland. This week they are meeting again to discuss possible sites for relocation.
“There are a few places which may be suitable, but we need to investigate things like water level fluctuations and the presence of non-native plants. It is also possible we could replant into areas of Omapere but there are many confounding factors. Ultimately it will be up to the trustees to decide but I would really like to see some insurance populations kept elsewhere.”
Mr Champion says he feels a real connection with the quillwort.
“Thinking about the consequences of not collecting the plants when we did is quite satisfying, but also NIWA being the sole guardian is quite a concern”.
“I will be really happy when it finally gets back to its home in Omapere, hopefully sooner rather than later.” Trustees of the Lake Omapere Trust are working together with NIWA in support of its return to Lake Omapere when the conditions are right.
