ARTICLE : 2007 New discoveries in wetlands

 Monday 16 April 2007 :   New discoveries in wetlands.

In November, I visited three swamps on a property north of Otaki to look at covenanting them with Queen Elizabeth II National Trust.   Two of these swamps were recognised as “eco-sites” on the Kapiti Coast District Plan.   One eco-site swamp was a very degraded Carex virgata swamp with a large area of shallow open water at one end.   This pond contained a thick ‘soup’ of floating and aquatic plants including the free-floating fern Azolla filiculoides, Lemna minor / duckweed, and Myriophyllum propinquum / water milfoil.

Ricciocarpus natans in a recently created QEII Covenant north of Otaki. Photo: Robyn Smith.

Also present in large numbers was another plant which I had never seen before.   I took some photos and looked up my well-worn “Wetland Plants in New Zealand”, by Peter Johnson and Pat Brooke, at home to try identify it – to no avail.   I then e-mailed my photos to Paul Champion at NIWA.   Paul identified the plant as Ricciocarpos natans, a floating liverwort.   According to “The Liverworts of New Zealand”, by KW Allison and John Child (1975), it is found in Europe and has been found several times in Auckland and “should be looked for throughout the North Island”.   Allison and Child also say that it is rarely found with capsules.   The authors presume that reproduction is probably vegetative with the thallus (plant body not differentiated into stems and leaves) splitting into two.   The thallus is shaped like partially opened wings and is green but the most striking feature of the plant is the beautiful dark purple scales attached to its undersurface.

Peter de Lange’s comments on the distribution are as follows “…   I know it from Lake Wairarapa – where it used to be quite common along the Western Lake Reserve shoreline in 1990-1991.   I also saw it in the Te Hapua wetlands, northern end, in 1993.   I also know it from Lake Mangakaware, near Ngahinapouri in the Hamilton Basin… ”

Since the discovery at the Otaki wetlands I have also found it in two other covenants at Te Hapua swamp on the Kapiti Coast but in much smaller numbers than further north.

Paul also identified Wolffia australiana, reputed to be the smallest flowering plant in the world.   Wolffia has a luminous sheen to it in the sun, and according to Peter Johnson’s book, this plant sinks to the bottom over winter.   [There will be more on Wolffia australiana in Bulletin 51.   Ed.]

In another wetland on the property, not listed as an eco-site, the vegetation is a mix of Coprosma propinqua, C. tenuicaulis, Leptospermum scoparium, Carex virgata and C. secta, plus a large area of Baumea teretifolia, which is not common in the lower North Island.   When I moved further into the wetland I came across a large patch of Korthalsella salicornioides / leafless mistletoe, on manuka.

The wetland on the property is a small part of a much larger wetland on the neighbouring property.   The vegetation is very similar to the second wetland, although I haven’t found the mistletoe on it … yet.   Covenants on all three wetlands were approved in March 2007.

Robyn Smith, Wellington Regional Representative, QE II National Trust.