3.3 Marine and Freshwater Plants

Marine Macroalgae

New Zealand has a marine macroalgal flora of approximately 1000 species (classified within the Rhodophyta, Phaeophyta and Chlorophyta). The following list covers genera/species that either are or have been used in New Zealand or have attracted interest because of their potential use.

Seaweeds are used internationally in the following ways:

  • human food - sold either fresh in markets or as a dried or processed product;
  • animal food - in stock feed (e.g. cattle feed, poultry feed); as feed for aquacultured organisms (e.g. paua feed);
  • polysaccharides - alginates (from certain brown seaweeds), agar (certain red algae), carrageenans (certain red algae) - these are complex large molecules, that are unable to be synthesised, and are only found in particular seaweeds. The algal polysaccharides have very specific applications in a wide range of manufacturing processes, food processing;
  • medicinal properties - although there are various "herbal" or traditional medicines based on seaweeds, these are not generally incorporated into western medicines because of their low potency. Recent exploration of algal extracts suggests there is potential for anti-viral, anti-AIDS and anti-cancer drugs to be isolated;
  • biomass - a number of countries have explored the use of rapidly growing algal material as a source of biomass to produce biofuels;
  • fertilisers - seaweed products are used as soil conditioners, and some seaweed based fertilisers have been developed.
Conservation Activities

Location, description and funding of collections

The vast bulk of marine algae are conserved in situ, with very little material held ex situ (e.g. as laboratory cultures) except for the purpose of research on individual species. The locations of the various wild populations are described broadly in Table A.

Documentation and characterisation

Identification and description is mainly done by staff at The Museum of New Zealand, Wellington, and Otago University's Marine Biology Laboratory. The Cawthron Institute has a large collection of algae and undertakes work on introduced species and toxic algae. The National Institute of Water and Atmospheric Research Ltd (NIWA) undertakes marine taxonomy and has a large collection of marine algae. Auckland, Victoria and Canterbury Universities and Landcare Research are also involved in the taxonomy of marine species.

Use, evaluation and improvement

Any evaluation for potential commercial uses is likely to be done by private firms, or by research institutes within New Zealand with funds from private firms. The major commercial operation in New Zealand, which has been involved in considerable evaluation work, is Coast Biologicals Ltd., Opotiki (Bay of Plenty).

Freshwater algae

Freshwater algal research, including identification and documentation takes place at the Universities of Canterbury and Waikato and at NIWA. A number of species are rare or threatened. Although freshwater algae perform an essential role in freshwater systems and provide an indicator of water quality, no individual species has yet been identified as having any other specific economic value.

Table A: Distribution and use of marine algae with existing or identified potential economic uses

Taxon Distribution Uses Threats

Pterocladia lucida, P. capillacea
North Island, Northern South Island.
Source of agar; basis for New Zealand agar industry since 1941, wild harvest has been sustained for more than 40 years.

Porphyra spp. - (Karengo)
6 spp. described in New Zealand, but likely to be 15-20. World-wide genus.
Genus used where ever it occurs world-wide; very high in protein (30% dry weight) and high in vitamins and minerals. Known as nori in Japan. Highly prized by Maori community and harvested throughout the country for local, non-commercial use; some commercial harvest.
Complex life history in which the conspicuous phase alternates with a microscopic phase that lives within shells and/or rock. There is the potential for local over-harvest if harvesters not aware of seasonal/yearly fluctuations in population size/ distribution.

Gracilaria chilensis
New Zealand and Chile.
Contains agar; used as fodder for paua.
Grows in harbours, estuaries, quiet coastal areas - alterations to habitat will influence local abundance (e.g. reclamation of coastal/estuarine land; building of marinas, coastal installations etc.; changes in sedimentation rates, nutrient regimes in estuarine or harbour areas).

Curdiea spp.
4 species endemic to New Zealand each with restricted distributions. Genus distributed in Australasia and Antarctica.
Sources of agar with very distinct properties.
Restricted distributions make these species potentially vulnerable to over-harvest unless managed with full knowledge of growth, reproduction, and recruitment rates.

Gelidium spp.
6 species endemic to New Zealand, some with restricted distribution. World-wide genus.
Contain agar.
Lack of knowledge about resource size and biology of species.

Gigartina spp.
More than 15 species in New Zealand. World-wide genus.
Contains carrageenan. The carrageenan properties are unique to particular species and phases within species.
Require knowledge about biology, growth, reproduction, recruitment before wild harvest or aquaculture can be undertaken.

Durvillaea - (Rimurapa)

(D. antarctica, D.willana, D.chathamensis, undescribed species)


New Zealand and Southern Ocean.
D. antarctica used for poha titi (for storage of mutton birds in fat); contains alginates; harvested in Bass Strait.
Grows only on exposed shores; must be harvested during fertile period otherwise population does not recover from harvesting; considered to provide a buffering role in protecting coastal areas from wave erosion.

Ecklonia radiata
New Zealand, Australia, South Africa, Oman.
Contains alginate; used in production of sheep/animal health products by Coast Biological.
Important Atree@ species in structuring sub-tidal forests therefore harvesting practices need to be careful to minimise habitat changes/impacts on other species.

Macrocystis pyrifera
California, Chile, Australia, New Zealand.
Species harvested extensively for more than 90 years from coast of California; contains alginates, also used for kelp powder/salt.


Other species Within New Zealand we have species that are similar to or related to species used in other parts of the world but have not yet received commercial attention here (e.g. Caulerpa spp. - used extensively as a salad vegetable throughout Pacific and Asia); Asparagopsis spp. (highly prized by Hawaiian community).

3.4 Threats to conservation and sustainable use of indigenous plants

Risks to in situ populations of indigenous plant species include effects of land development on habitats, including:

  • direct modification of habitat, such as through land clearance;
  • indirect effects such as siltation and changing water levels caused by forces acting outside the area concerned;
  • attack by introduced animal and plant pest species.

Other threats include loss of "keystone species" such as kereru (wood pigeon) which disperse seeds of forest plants; effects of climate change, including effects on temperature, water cycle, sea level; and incidence of extreme events.

The threat from introduced pests is of great concern. Many native plants are highly palatable to introduced mammals, having few chemical or morphological defence mechanisms, as they have been subject to relatively mild browsing pressure during their evolutionary history. In addition, many species of introduced plants are strongly competitive with native plants. About 200 species have already been identified as serious weeds.

The harvest of products from indigenous plants is not always compatible with their conservation. Some species are conserved on offshore islands and harvest from wild plants is not permitted in forest parks and reserves, although permits can be obtained to collect small quantities for research purposes.

Most native plants are not legally protected except to the extent that they are located in formal reserves, in which case permission is required from the agency concerned (e.g. DOC or local authority) to remove the plant or parts of it. Although many individual trees and other plants are protected under local town planning regulations, this protection is of little value in terms of genetic protection. If the plant is on private land, the landowner's permission is required. The only native plants which enjoy legal protection in themselves are new varieties which have been developed by breeding and are subject to Plant Variety Rights. A few plants are protected under the Trade in Endangered Species Act 1989. (In contrast, some native animals are protected by the Wildlife Act, including birds, most reptiles and some invertebrates, and fish species and marine mammals are protected by the Fisheries Act 1996 and the Marine Mammals Protection Act 1978 respectively).

New Zealand's indigenous grasses are not systematically conserved at present, although they are valuable for forage and soil conservation on less fertile sites.

Native timber species are difficult to domesticate and hard to store as seed, so living populations need to be maintained.

Few of New Zealand's threatened native plant species are woody plants with timber potential. Nevertheless, within species variation of some woody species might be at risk despite there being considerable numbers of the species as a whole.

Threats to conservation of marine macroalgae include:

  • threats from direct human actions, such as development in the coastal zone, pollution and potentially from overharvesting for some species. In addition to land-sourced pollution, anti-fouling coatings on vessels' hulls and marine structures such as wharf piles have contributed significantly to the destruction of marine organisms. The most toxic coatings based on organotin were banned some years ago. Marine plant species are not well protected by the existing marine reserves system;
  • threats posed by introduction of exotic species, particularly via ballast water. New algae can compete with indigenous species, and pests and diseases can infest indigenous species. However, neither are likely to result in extinction of indigenous species.

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