Kelp forests
Map ID Number: Not mapped during the workshop
Location: Location: Different kelp species have specific distributions:
Ecklonia radiata is found around mainland New Zealand and Stewart Island, but not the Chatham Islands. This alga is found elsewhere in the world9, but the New Zealand populations represent the eastern and southern limits of the species.
Macrocystis pyrifera is found around the northern Cook Strait to the subantarctic and on the Chatham Islands.
Lessonia variegata is found around the North, South, and Stewart Islands. L. adamsiae is restricted to the Snares Islands, L. tholiformis is found only on the Chatham Islands, L. brevifolia is found in the New Zealand subantarctic islands – Bounty, Antipodes, Auckland, and Campbell. The Lessonia species found in New Zealand are all endemic to New Zealand, and some species are unique to particular island groups, such as the Snares and the Chathams.10
Durvillaea, known commonly as bull kelp, is an iconic genus with southern hemisphere distribution. New Zealand is the world centre of Durvillaea diversity with four species:
D. antarctica – found around mainland New Zealand to the subantarctic and Chatham Islands;
D. enchathamasis – found only on the Chatham Islands;
D. willana – found on the South Island and Stewart Island; and
D. sp. – found on Antipodes Island.
Approximate area: Approximate area: Not recorded during the workshop.
Description of habitat type:
The presence of a particular kelp species indicates a particular environment type. For example, Macrocystis is found on the open coast where there is current/water exchange, but not in wave-exposed areas. Durvillaea, by contrast, is found in areas with extreme wave exposure.
Biological attributes:
Kelps are major components of coastal systems. They provide three-dimensional structure and shape coastal rocky reef environments. Both invertebrates and fish depend on the kelp canopy and the shade it provides. Macrocystis, commonly known as “giant kelp”, is recognised as a major “forest-forming” taxon globally. Kelps are also major sources of productivity in the coastal environment. Macrocystis has the highest growth rate measured for any seaweed.
Criteria applied:
Species richness; endemism; representation; habitat complexity/diversity
Status and management:
Kelps are vulnerable to human impacts. For example, research conducted at Leigh Marine Lab demonstrates cascades between top predators, herbivores, and forest cover with very significant shifts in vegetation cover within the no-take marine reserve. Commercial exploitation of kelp is developing. It has been proposed that four genera (Ecklonia, Lessonia, Macrocystis, and Durvillaea) be introduced into the Quota Management System. Such commercialisation would have implications for associated species and habitat change. D. antarctica is used to make poha titi (storage bags for mutton birds) and has cultural significance for Mäori, particularly Ngai Tahu.
State of information:
The data that are currently available are very local and restricted. Little is known about Lessonia ecology. Ecklonia data are available for New Zealand’s northeast North Island and Fiordland, but little elsewhere.
References and further reading:
Durvillaea: Hay (1979a, 1979b, 1994), Hay and South (1979), Kelly and Brown (2000), South and Hay (1979). Ecklonia: Andrew and Choat (1985), Andrew and MacDiarmid (1991), Babcock et al. (1999), Choat and Ayling (1987), Choat and Schiel (1982), Cole and Babcock (1996), Jones (1984, 1988), Novaczek (1984a, 1984b), Schiel (1981, 1982, 1988, 1990), Schiel and Hickford (2001), Schiel and Nelson (1990), Shears and Babcock (2002), Trenery (1985).
Lessonia: Choat and Schiel (1982), Hay (1987, 1989), Schiel and Hickford (2001), Schiel et al. (1995).
Macrocystis: Brown et al. (1997), Hay (1990), Kain (1982), McCleneghan and Houk (1985), Moore (1942), Nyman et al. (1990, 1993)
9 Ecklonia radiata is also found in South Africa, Australia, and Oman upwelling zones.