Look Inside: New Zealand Seaweeds by Wendy Nelson

Contents Introduction 7 Green algae: Chlorophyta

21

Brown algae: Ochrophyta

55

Red algae: Rhodophyta

139

Acknowledgements 327 Glossary 328 Recommended reading 332 Image credits 334 Taxonomic index 339 Index 347

Green algae Chlorophyta PALMOPHYLLOPHYCEAE ULVOPHYCEAE TREBOUXIOPHYCEAE

Although green seaweeds are often conspicuous on the shore

because of their bright colours, in fact there are fewer species than either brown or red seaweeds. Most green algae are found in freshwater or terrestrial habitats. In New Zealand there are approximately 140 species of green seaweeds. This is an estimate because there are still questions about the identity and correct names for many, and also because particular types of green algae – such as small filamentous species, as well as rock- and shell-boring species – have been very infrequently collected or examined in New Zealand.

Green algae are characterised by their pigments, features of their chloroplasts and the presence of starch as a storage material.

In the past they were classified on the basis of their construction – e.g. whether they were branched or unbranched filaments, blades, or were siphonous (multinucleate with few cross-walls).

However, recent research has shown that cell shape, plant form, whether cells are uninucleate or multinucleate, and features of the chloroplasts do not reflect unique relationships or origins – they are evolutionarily convergent.

Of the species treated here, most belong to the class Ulvophyceae, including branched and unbranched filaments, blades (e.g. Cladophora, Ulva) and siphonous species (e.g.

Bryopsis, Caulerpa, Codium). There is a single member of the recently established class Palmophyllophyceae, Palmophyllum umbracola, an intriguing green crust. There are also two genera, Prasiola (small blades) and Rosenvingiella (fine filaments), that are currently placed in the class Trebouxiophyceae.

Some green seaweeds are eaten as fresh sea vegetables – e.g. species of Caulerpa and Ulva – but there are no major commercial industries based on green seaweeds or their extracts.

21

CLASS

ULVOPHYCEAE

Caulerpa J.V.Lamour.

Caulerpa is a large genus with a mainly tropical and subtropical distribution. In New Zealand there are nine species, three of which reach south to Cook Strait and only one of which extends further south to Stewart Island/Rakiura and the Snares Islands/Tini Heke.

Caulerpa thalli are coenocytic. While the species of Caulerpa have very diverse morphologies, all have horizontal stolons bearing erect photosynthetic fronds.

KEY TO SPECIES OF CAULERPA TREATED HERE:

1

2

3

Axes pinnately branched Axes simple or forked Axes densely clothed with short, pointed branchlets Axes with bladder-like branchlets Round to oval bladders surrounding the main axis Cylindrical bladders borne in pairs on beaded axis

C. flexilis 2 C. brownii 3 C. geminata C. articulata

ORDER Bryopsidales FAMILY Caulerpaceae

Caulerpa articulata Harv.

Caulerpa brownii (C.Agardh) Endl.

DESCRIPTION Plants with upright axes; to c. 25 cm in height. Axes bead-like. Branchlets turgid, cylindrical, pinnately arranged.

Attachment by a smooth stolon with pale rhizoids. Colour bright glossy green. Texture crisp when fresh.

HABITAT Subtidal on rock, on open coasts, predominantly a summer species.

DISTRIBUTION Manawatāwhi/ Three Kings Is, North I., northern South I. Western Australia.

TYPE LOCALITY ‘East Coast’ (probably Wairarapa coast), New Zealand.

DESCRIPTION Plants with upright axes; to 30 cm in height. Axes unbranched or forked several times, covered with many branchlets.

Branchlets short, dense, resembling rimu (Dacrydium cupressinum) foliage.

Attachment by shaggy, creeping stolons with rhizoids. Colour dark green. Texture firm.

HABITAT Low intertidal to depths of 15–20 m, on rock on open coasts, deeper populations have been found (to 35 m) in Fiordland.

KEY CHARACTERS:

›› cylindrical branchlets in pairs ›› beaded axes ›› smooth stolons.

26

New Zealand Seaweeds

DISTRIBUTION

Southern North I., South I., Chatham Is, Stewart I./Rakiura, Snares Is/Tini Heke.

Australia.

TYPE LOCALITY Kent Is, Bass Strait, Australia.

KEY CHARACTERS

›› axes covered with short, dense rimu-like branchlets ›› shaggy stolons.

Caulerpa articulata

Caulerpa brownii

Green algae Chlorophyta

27

New Zealand Seaweeds

Brown algae Ochrophyta PHAEOPHYCEAE

The brown algae are the most conspicuous and best understood group of New Zealand seaweeds. They range in size from microscopic filaments through to massive bull kelp plants that are many metres in length. Brown algae can be defined by a cluster of microscopic features and by their pigments (chlorophylls a, c1 and c2, and fucoxanthin). Although there are a few freshwater genera of brown algae found in other parts of the world, all the brown algae in New Zealand are marine.

The brown algae are classified as a class within the phylum Ochrophyta, a very diverse group of organisms that also includes diatoms and silicoflagellates. The brown algae are understood to have evolved much more recently than the other macroalgal groups.

Unravelling the relationships of the brown algae has been challenging. For a long time it was thought that brown algae with a simple shape and lacking complex development were ‘ancestral’, and more complicated brown algae such as the kelps were more highly evolved. These ideas have been overturned by phylogenetic analyses based on molecular sequence data.

Large brown algae, particularly the kelps, are very important along temperate coasts, where they act as ecosystem engineers by providing habitat structure and food. The greatest biomass on temperate coasts comes from the brown seaweeds, and the carbon these algae fix is vitally important to local food chains.

Some brown algae are used commercially as a source of alginates (see box on page 253). Brown algae have also been harvested for fertilisers and animal feed, and as a source of potash.

55

CLASS

PHAEOPHYCEAE

Cystophora J.Agardh Cystophora is a large genus of perennial brown algae found only in New Zealand and Australia. All species grow to a metre or more in length.

Four species are treated here, one of which is found only in New Zealand.

KEY TO SPECIES OF CYSTOPHORA TREATED HERE:

1

2

3

Branching from edge of flattened main axes; receptacles leaf-like C. platylobium Branching from face of axes 2 Receptacles swollen, terete with rounded apex, densely clustered on laterals C. torulosa Receptacles elongate, slightly to strongly flattened 3 Receptacles and ramuli arranged radially, usually narrow C. retroflexa Receptacles and ramuli distichous, lateral branches lying in one plane C. scalaris

ORDER Fucales FAMILY Sargassaceae

Cystophora platylobium (Mert.) J.Agardh

Cystophora retroflexa (Labill.) J.Agardh

DESCRIPTION Plants lying in one plane, large with a flattened main axis; up to 2 m high.

Branches alternate, coming from edge of main axis, each branch divided into alternate broad, flat leaf-like lobes. Vesicles round to slightly oval, without a tip. Attachment by a disc- to cone-shaped holdfast, up to 2 cm wide. Colour dark brown, drying black. Texture leathery and pliable. Reproduction receptacles leaf-like with 2 rows of conceptacles, each opening with an ostiole along margins; bisexual.

HABITAT Subtidal on rock, on open, exposed coasts, typically in deep water.

DISTRIBUTION Southern North I. (Cook Strait), South I., Stewart I./Rakiura. Australia.

TYPE LOCALITY Australia.

DESCRIPTION Plants with compressed and narrow-edged main axes, often twisted between alternate, fairly openly to densely branched side axes; up to 1.5 m or more high.

Side branches arise from flat surface of main axis and are bent back at their point of origin (retroflex), often with broad basal wings (the degree of retroflex branching varies widely between specimens); divisions are irregularly radially branched, round in cross section and elongated, and when mature develop into receptacles. Vesicles ovoid to round on a short axis and without a tip. Attachment by a solid conical disc holdfast, 0.5–1.5 cm across. Colour medium to dark greyish brown. Texture firm to stiff. Reproduction receptacles usually simple, relatively stout, smooth and compressed to slightly pod-like when fresh, with a long, thin, extended tip lacking conceptacles; conceptacles bisexual, with 2 rows of ostioles along the margins.

HABITAT Subtidal to about 10 m, on rock on open coasts.

DISTRIBUTION North I., South I., Chatham Is, Stewart I./Rakiura. Australia.

TYPE LOCALITY Cape van Diemen, Tasmania, Australia.

KEY CHARACTERS

›› ›› ›› ››

branching from edges of flattened axes axes strongly compressed receptacles flat and leaf-like vesicles round to oval without a tip.

KEY CHARACTERS

Cystophora platylobium

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New Zealand Seaweeds

›› receptacles radially to irregularly arranged on the laterals, with a long, thin, extended tip lacking conceptacles ›› primary axes with sharp edges but not otherwise ridged.

Cystophora platylobium

Cystophora retroflexa

Brown algae Ochrophyta

107

Red algae

Rhodophyta BANGIOPHYCEAE COMPSOPOGONOPHYCEAE FLORIDEOPHYCEAE

Red algae vary widely in their size and form – from unicellular species through to branched and bladed species with complex morphology. They are found from the highest levels of the intertidal shore through to great depths, and from harbours and sheltered areas through to very exposed, wave-battered shores.

Although they are called red algae, the colour palette in this group is, in fact, very broad, ranging from pinks through to crimson and burgundy red, and to lilac and purple. It can be difficult to recognise some species by their colour, however, as they may appear brown or khaki green, particularly when growing in bright light, and other species may have a gingery or apricot cast. While green algae all look green, many red algae are not an obvious shade of red!

The life histories of the red algae are more complex than those found in either of the other two main groups. The ‘standard’ red algal life history is triphasic, with two dissimilar sporophyte generations – a carposporophyte attached and partly parasitic on the female gametophyte, and a free-living tetrasporophyte that is either isomorphic or heteromorphic with the male and female gametophytes.

The red algae are understood to have evolved a very long time ago. Red algal male gametes are called spermatia (singular: spermatium) rather than sperm, because they lack flagella and cannot swim. Over the past two decades there have been many discoveries that have changed our understanding of the orders and families of red algae and the relationships between them. It is now thought that there are seven major lineages of red algae; seaweeds are members of five of these classes, although most belong to either the Bangiophyceae or the Florideophyceae. Members of three red algal classes are treated here.

In New Zealand, there are over 600 species of red algae, but there is a critical need for more research. There are many undescribed species that require further study before they can be formally named.

139

CLASS

FLORIDEOPHYCEAE

Synarthrophyton R.A.Towns.

Eleven species of this genus are known worldwide, two of them occurring in New Zealand. Further work is required to understand the relationships and distinguishing features of members of the genera Synarthrophyton and ‘Mesophyllum’ (see page 170). The taxonomy of the species treated below is quite confused – there is more than one species that forms plate-like epiphytic growths (usually identified as S. patena), and more than one species that produces struts on the underside of layered plate-like growths (usually identified as S. schielianum).

ORDER Hapalidiales FAMILY Hapalidiaceae

Synarthrophyton patena

TYPE LOCALITY Flat Point, North I.,

(Hook.f. & Harv.) R.A.Towns.

New Zealand.

DESCRIPTION Plants encrusting to discoid

›› encrusting to discoid to layered coralline alga ›› on rock, sponge and other algae (e.g. Halopteris, Landsburgia, Ballia, Gymnogongrus) ›› flat-topped multiporate conceptacles.

to layered, partially to completely adherent to substrate; to 5.5 cm across. Colour rosy pink to lilac pink. Texture brittle; can be fragile. Reproduction tetrasporangia zonately divided, produced in flat-topped multiporate conceptacles; gametes produced in uniporate conceptacles.

HABITAT Subtidal to at least 10 m, on rocks, sponges and other macroalgae (e.g. Halopteris, page 129; Landsburgia, page 110; Ballia, page 179; Gymnogongrus, page 282).

DISTRIBUTION Southern North I., South I., Chatham Is. Australia, South Africa, subantarctic islands.

KEY CHARACTERS

Synarthrophyton schielianum Woelk. & M.S.Foster

DESCRIPTION Plants encrusting to layered, partially to completely adherent to substrate, with struts on the lower surface between substrate or lower surface of layers; to 5.5 cm across. Colour pink. Texture firm; can be brittle when dry. Reproduction tetrasporangia zonately divided, in multiporate conceptacles with a distinct rim surrounding a sunken pore plate; gametes in uniporate conceptacles.

HABITAT Subtidal to at least 22 m, growing on rocks, sponges and other macroalgae (e.g. holdfasts), on open coasts.

DISTRIBUTION Southern North I., South I., Chatham Is. New Zealand endemic.

TYPE LOCALITY Waihere Bay, Pitt I., Chatham Is, New Zealand.

KEY CHARACTERS

Synarthrophyton patena

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New Zealand Seaweeds

›› encrusting to layered coralline alga with struts on the lower surface ›› on rock, sponges and other algae (e.g. holdfasts) ›› multiporate conceptacles with a rim around a sunken pore plate.

Plate-like epiphytic growth form

Synarthrophyton schielianum

Red algae Rhodophyta

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