Rare water plant in dune lake

The native bladderwort, Utricularia australis.

Biodiversity experts are bubbling about the discovery of a rare bladderwort species in a Northland dune lake.

The previously unknown site of the critically endangered native aquatic plant is in pools at the outlet of remote Lake Te Kahika, on privately owned Maori forestry at Great Exhibition Bay, in the Far North.

Lisa Forester, Northland Regional Council environmental assets manager, said the native bladderwort, Utricularia australis, has declined at an alarming rate in the region's dune lakes and wetlands over the past three decades.

The plant's decline is probably due to competition from another non-native bladderwort which seems more able to cope with a reduction in water quality caused by nutrient enrichment in dune lakes and wetlands, Ms Forester said.

Dune lakes are usually formed by sand scouring out hollows which fill with fresh water.

Experts' excitement at the bladderwort find is tempered by the fact that the plant's hold there is probably very tenuous.

"In some ways plants like bladderwort are a keystone species which are an indicator of good ecological health," Ms Forester said.

"If you look after this plant, you're effectively looking after the water quality for a whole system supporting a range of other plants and animals."