identifying red seaweeds of the intertidal rocky shore
By Dr J Floor Anthoni (2007)
Red seaweeds are most suited to grow in dark
places and in the deep. Yet many species survive well near the surface
and in rock pools of the intertidal rocky shore. It is difficult to tell
the various species apart. Many red seaweeds are intrically branched, forming
beautiful patterns when spread out over a white page of paper.
red seaweeds: Red seaweeds are finely structured,
weak and suitable for deeper waters.
red seaweeds Red seaweeds have a red pigment that absorbs blue light,
which penetrates deepest in the sea. As a result, red seaweeds can be found
deeper than brown and green seaweeds. But even in the sunlit shallows of
the rocky shore, one can find a number of species. The red seaweeds comprise
the largest number of seaweeds in New Zealand.
(Porphyra columbina) [karenga] looks like tissue paper.
It flourishes in winter and spring. Small plants fold like a rosette.
Apophlaea sinclaiirii is a dull brown-red rubbery
alga that grows flat over the rock or extends tiny rubbery fingers. It
dries rigid and black like tar but swells when the tide is in.
Apophlaea lyalli grows up to 18cm on high tidal rocks
of the southern South Island. Branches rounded, dark red and bushy with
0703060: blood crust (Ralfsia verrucosa) forms a brown
to deep red wrinkled crust, surviving extreme desiccation. the barnacle
is the sheet barnacle or modest barnacle.
0608219: a crusting red seaweed looking like black goo. Gelidium
pusillum (1-2cm) is a brown to black mat growing in between barnacles.
f032332: rubberweed (Apophlaea lyallii?) feels like
rubber elastic bands.
f051720: (Laurencia elata?)
0703019: moss weeds on a vertical wall in relative shelter.
0703021: the moss weed (Gelidium caulacantheum?)
from the photo on left. It feels like moss, dense and bouncy. compare size
with the modest barnacles on right.
0703032: ?. Also which are the two limpets on left?
Gelidium caulacantheum a turfing small red seaweed
that feels firm and bouncy.
Bryocladia ericoides (2-8cm) has small erect stipes
with short spiny branches (like pine trees or heather), forming dense mats
that are stiff in texture. south from Cook Strait.
Strictosiphonia spp. (up to 5cm) has tufted, rolled
branch tips that are firm and springy. Brown to dark purple, a spongy tufted
plant in the barnacle zone.
Pachimenia himantophora -
Melanthalia abscissa -
Helminthocladia spp. form cushions (15mm high) with
tiny, tightly packed cylindrical stipes. Very firm and erect like tiny
Laurencia thyrsifera has cylindrical stipes branching
in a flat plane. The ends of side branches resemble tiny clusters of grapes.
f051219: ? Champia sp.?
f038114: the iridescent-blue red seaweed (Champia laingii)
has stubby round branches and rounded endings.
f034114: the finely branched Pterocladia lucida branches
in a flat plane. From this seaweed the agar gelatine is made. Agar is used
as a stiffener in foodstuffs, toothpaste, soaps, shampoos etc. It is also
used scientifically to grow bacteria on.
0910044: Pterocladia capillacea is a creeping
alga with thin stems with tufted branches. It prefers to live under water.
This seaweed is also suitable for making agar.
Pterocladia pinnata is a fine, sparsely branching
feather-shaped red seaweed.
Plocamium microcladioides (up to 15cm) has firm cylidrical
stipes that branch in one plane. Terminal hook-like branches in sets of
three on the same side of the blade. Lower intertidal.
Polysiphonia decipiens is the most commonly found
of this genus. It is highly branched with no obvious stipe and covered
with pigmented hairs. It has a soft texture and dark red-brown colour and
sometimes grows on brown seaweeds.
Rhodymenia novazelandica has a fine, open fan shape,
branching dichotomously in one plane. Red.
f051727: a hard red seaweed growing out from a central
clump (Apophlaea sinclairii).
f051729: finely branching (Plocamium costatum)
in the background. In the foreground Melanthalia abscissa?
f051725: (Callophyllis variegata?).
f051211: the fretsaw weed (Vidalia colensoi, Osmundaria
c.) with alternating teeth is found in robust wave action. It does
not feel slimy but rough and can grow to dense patches. North Island.
0703038: a fine, sparsely branching red seaweed found at
spring low tide level.
f051204: a bushy red seaweed (Rhodophyllis membranacea?)
f222613: Pachymenia lusoria has long flat blades that
look green, sprouting from thin stipes clustered from a single holdfast.
Blades have jagged edges. West coast of the North Island and South Island
but rare in central NZ.
f051507: a robust green looking leafy carrageen Gigartina
circumcincta, growing flat in exposed conditions. The name carrageen
comes from an edible Irish seaweed, the Irish moss.
f222610: . West Coast NI.
f222607: parsley weed (Gigartina alveata). West Coast
NI and SI.
f222612: the small-leaved weed is a red seaweed (Gigartina
livida) found on the West coast. The large fronds are ?
0609066: this hairy red seaweed feels like soft-cooked Italian
pasta (Mesogloea intestinalis). It is found in extremely degraded
and sheltered environments, such as inside harbours
Gigartina circumcincta -
Gigartina chapmani (6-7cm) is a gelatinous red turfing
alga with cylindrical to flat fronds that branch irregularly feather-wise.
Gigartina clavifera (15-20cm) has flattened splitting
fronds that are tufted and bushy at their ends, branching in a flat plane.
Gigartina decipiens (20cm) has thick, tough, flattened
fronds branching dichotomously into 'v' type ends. Reproductive plants
have tiny club-shaped structures around the edges, making them look frilly.
Flattened blades ending in a 'v'.
the prickly weeds (Echinothamnion spp.) have
regularly branching, bushy and shaggy branches of unequal length. Reddish
brown, sometimes growing on other seaweeds. Southern half of NI, all of
f048222: a healthy seaweed garden at the Poor Knights islands
shows a high variety of seaweeds against a backdrop of an Ecklonia
kelp forest. From left to right: stalked kelp (Ecklonia radiata),
hugged by strap kelp (Lessonia variegata) and beneath it pink paint.
The red seaweeds are (Rhodophyllis membranacea?) and the broader
leafed (?). The tall bladderweed looks like the featherweed (Carpophyllum
plumosum) but is in fact (Cystophora platylobium). Such seaweed
gardens can be found inside large rock pools.
f210512: an exposed South Island rock pool shows the dominant
species. From left to right: the sheltered form of bullkelp (Durvillea
antarctica), the long strings of giant kelp (Macrocystis pyrifera),
the hardy cartilage weed (Xiphophora gladiata) and in the middle
of the water the spiky-leafed (Echinothamnion sp.?).
f027103: a fine example of a semi-sheltered shore near Dunedin:
From left to right: the giant kelp (Macrocystis pyrifera)
with its thin leaves, the branching bullkelp (Durvillea willana),
the hardy cartilage weed (Xiphophora gladiata) and the featherweed