Phylum Rhodophyta: Rocky Shore Red Seaweeds

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Red algae are the most diverse group of seaweeds on temperate shores.  Colors can range from rose red or maroon to dark red, brown, or even green depending on relative concentrations of photosynthetic pigments (chlorophyll, phycoerythrin, phycocyanin, allophycocyanin).  Pink coralline red algae grow as hard flat crusts or jointed erect forms; as their name implies they deposit calcium carbonate in their cell walls, presumably as a defense against grazers.  
     Red algal life histories are complex and typically comprise three stages: a diploid tetrasporophyte that undergoes meiosis to produce haploid tetraspores, which are released and settle to grow into haploid male or female gametophytes.  Gametophytes may look identical or very different (heteromorphic) from the tetrasporophyte phase from which they arose.  Males and females produce gametes via simple mitosis; males release non-motile spermatia which find and fertilize ova that are retained by the female.  The fertilized diploid zygote grows into the third generation, the carposporophyte, firmly attached to the haploid female.  Eventually, the carposporophyte releases diploid carpospores that grow into tetrasporophytes and the cycle begins again.
     Several hundred species of red seaweeds can be found along the shores of Monterey Bay; only a few of the more common or conspicuous ones are shown here.

Endocladia muricata
Endocladia muricata (Endlicher) J.Agardh
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Endocladiaceae

Thallus 4-8 cm tall, short & bushy; branches cylindrical with sub-dichotomous branching; covered with minute conical spines; blackish-brown to dark red.

Abundant, high to mid-intertidal zones, exposed & protected outer coast; forms top-most conspicuous band of macroalgae in high intertidal zone of central California (see wider view).

Geogr. Range: Alaska to Baja
Synonyms:
Similar species:

Image:
Balanus glandula (right of cntr), Mastocarpus papillatus (top cntr)

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Mastocarpus papillatus Mastocarpus papillatus (C.Agardh) Montagne
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Phyllophoraceae

Morphology highly variable: thallus <15 cm tall,  flattened; varies in width with tips divided ~dichotomously; flattened faces of thalli covered thickly or sparsely with papillae of various sizes; dark brown to reddish black.  Male plants lack papillae & are light rose to yellowish in color (see additional photossee wider view).

Abundant, high to mid-intertidal zones, protected & exposed outer coast; dominant alga of these zones in central Calif., along with Endocladia.

Geogr. Range: Alaska to Baja
Synonyms: Gigartina papillata
Similar species:

Image: Endocladia muricata (top cntr, top rt, bottom rt),

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Petrocelis stage "Petrocelis"
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Phyllophoraceae

Tetrasporophyte life history phase of Mastocarpus papillatus is a crust 2-2.5 mm thick, dark black-red to olive brown. Formerly thought to be a separate species, Petrocelis.  

Abundant; crusts cover large areas of rock surfaces in high and mid-intertidal zones around bases of erect algae; protected & exposed outer coast (see wider view).

Geogr. Range: Alaska to Baja
Synonyms: Petrocelis franciscana
Similar species: other reds (e.g. Mastocarpus jardinii, Pikea) also have crustose phases in their life histories, making field identification to species level difficult.

Image: Corallina (pink erect coralline throughout); blades of Phyllospadix scouleri (surf grass, rt side)

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Masstocarpus jardinii Mastocarpus jardinii (J.Agardh) J.A.West
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Phyllophoraceae

Thallus 10-12 cm tall, narrow with thickened edges making it appear curved in cross section; basal portion more elongate with distal portions more densely branched (dichotomous); reddish brown to blackish.

Common, high to mid-intertidal zones, interspersed with mats of Mastocarpus papillatus and Mazzaella affinis; protected outer coast.  Tetrasporophyte stage is a Petrocelis-like crust, as in M. papillatus

Geogr. Range: British Columbia to San Luis Obispo (central California)
Synonyms: Gigartina agardhii
Similar species:

Image:
fertile Mazzaella flaccida (lower left, middle to lower rt), Endocladia muricata (bottom, left of cntr)

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Mazzaella affinis Mazzaella affinis (Harvey) Fredericq
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Gigartinaceae

Thallus 4-15 cm tall in erect tufts, sometimes covering extensive areas; blades smooth, curved in cross section; dichotomously branched, usually ~2 mm wide (wider in low intertidal); olive-brown to reddish-brown or blackish.

Abundant, often growing in extensive low-lying mats, mixed with Mastocarpus papillatus in mid-intertidal zones; protected outer coast (see wider view).

Geogr. Range: British Columbia to northern Baja
Synonyms: Rhodoglossum affine
Similar species: male Mastocarpus papillatus are similar in color to M. affinis, but are usually taller & grow as more discrete plants rather than  in dense continuous mats.

Image: Mastocarpus papillatus (across bottom)

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Mazzaella flaccida Mazzaella flaccida (Setchell & Gardner) Fredericq
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Gigartinaceae

Blades 20-30 cm long, 8-20 cm wide, elongate to heart-shaped; rubbery & iridescent with short stipe <2 cm long; perennial discoid holdfast. Iridescent yellow-green with purple or brown near base of blade.

Abundant mid- to low intertidal zones; most conspicuous blade-like alga on mid-shore in Monterey; upper limit close to mid-tide level (~+1 m); protected & exposed outer coast (see wider view).

Geogr. Range: Alaska to northern Baja
Synonyms: Iridea flaccida
Similar species: Mazzaella splendens is dark purple with a blue iridescent sheen, a slightly longer stipe, and occurs lower on the shore.

Image:
Endocladia muricata (upper left ), Petrocelis phase of Mastocarpus (dark crust across center)

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Mazzaella splendens Mazzaella splendens (Setchell & Gardner) Fredericq
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Gigartinaceae

Blades 20-40 cm long, heart-shaped; rubbery & iridescent with stipe 3-6 cm long; perennial fleshy holdfast; blade dark purple, violet or blackish with a blue iridescent sheen when wet.

Abundant on rocks in low intertidal zone; protected & exposed outer coast.

Geogr. Range: Alaska to northern Baja
Synonyms: Iridea cordata var.cordata, Iridea cordata var. splendens
Similar species: Mazzaella flaccida has a shorter stipe, is iridescent yellowish green with purple or brown only on basal portion of blade, and occurs slightly higher on the shore.

Image:


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Mazzaella leptorhynchos
Mazzaella leptorhynchos (J.Agardh) Leister
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Gigartinaceae

Thallus 10-15 cm tall, 5-10 mm wide; elongate to bushy, irregularly branched, flattened (more cylindrical in S. Calif.); appears woolly with many elongate papillae on margins & faces of branches; dark brown to blackish. 

Common, but patchy & not as dominant as Mastocarpus & Mazzaella affinis; lower mid-intertidal zone, at or below lower margin of Mastocarpus; protected outer coast (see wider view).

Geogr. Range: Northern California to northern Baja
Synonyms: Gigartina leptorhynchos
Similar species:

Image: surf grass Phyllospadix scouleri (upper left & rt corners); Gastroclonium subarticulatum (across bottom)

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Chondracanthus canaliculatus Chondracanthus canaliculatus (Harvey) Guiry
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Gigartinaceae

Thallus cylindrical to slightly flattened, 2-3 mm wide; branches arise alternately on opposite sides of main axis (distichous); grows in extensive mat-like clumps of entangled branches; greenish-olive to red-brown.

Abundant, mid- to low intertidal zones; protected to exposed outer coast (see wider view).

Geogr. Range: southern Oregon to central Baja
Synonyms: Gigartina canaliculata
Similar species: small brown Analipus japonica is superficially similar but its side branches encircle main axes.

Im
age: Gastroclonium subarticulatum (rt top & middle); probably Mastocarpus papillatus (top left)

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Pikea californica Pikea californica Harvey
Phylum Rhodophyta,Class Florideophyceae, Order Gigartinales, Family Dumontiaceae

Thallus 5-10 cm tall, bushy; main branches 1-1.5 mm wide with pointed, pinnate side branches; dark red, blackish when dry. Tetrasporophyte phase of life history is a crust.

Moderately common, low intertidal; protected outer coast.

Geogr. Range: southern British Columbia to Baja
Synonyms:
Similar species: superficially looks like a miniature version of Mazzaella leptorhynchos.

Image: anemone Anthopleura xanthogrammica (top cntr); sea urchins (Strongylocentrotus purpuratus) along left side

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Sarcodiotheca gaudichaudii Sarcodiotheca gaudichaudii (Montagne) P.W.Gabrielson
Phylum Rhodophyta, Class Florideophyceae, Order Gigartinales, Family Solieriaceae

Thallus 10-40 cm tall, pointed side branches arise from cylindrical main axes 1-4 mm in diameter; side branches may arise radially or opposite (distichous); light rose to reddish.

Moderately common, but patchy, low intertidal zone to subtidal.

Geogr. Range: British Columbia to Baja
Synonyms: Neoagardhiella baileyi
Similar species:

Image:
surf grass Phyllospadix around border.

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Gastroclonium subarticulatum Gastroclonium subarticulatum (Turner) Kützing
Phylum Rhodophyta, Class Florideophyceae, Order Rhodymeniales, Family Champiaceae

Thalli 10-26 cm tall, erect, cylindrical in cross section to 2.5 mm diameter; branching irregular to dichotomous; apices of branches hollow with transverse septa; dark red  to greenish-brown depending on location & time of year.

Common, mid- to low intertidal zones & shallow subtidal, protected outer coast; ~seasonal, regrowing from persistent basal portions after winter erosion.

Geogr. Range: British Columbia to Baja
Synonyms: Gastroclonium coulteri
Similar species:

Image:
Mazzaella leptorhynchos (top left & bottom center, mixed w. Rhodymenia pacifica)

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Rhodymenia pacifica Rhodymenia pacifica Kylin
Phylum Rhodophyta, Class Florideophyceae, Order Rhodymeniales, Family Rhodymeniaceae

Thalli flat 3-13 cm long, dichotomously branched; tips usually rounded, 3-10 mm wide & rather thin. Branch tips broader than Rhodymenia californica.

Abundant, on rocks; very low intertidal zone & subtidal. 

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species: Rhodymenia californica is narrower & mostly subtidal.

Image:
coralline red algae (pink crusts & erect forms, several spp.); Aglaophenia (tan hydroid across bottom portion).

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Prionitis lanceolata Prionitis lanceolata (Harvey) Harvey
Phylum Rhodophyta, Class Florideophyceae, Order Halymeniales, Family Halymeniaceae

Thallus bushy, of 1-2 flattened stipes 20-30 cm tall from discoid holdfast; branches dichotomous 2-5 mm wide with flattened lanceolate lateral proliferations. Branch widths remain ~constant throughout length; relatively stiff; dark red with main axes appearing nearly black in low light.

Abundant, mid- to low intertidal zones, protected outer coast; also grows subtidally where plants are less bushy.

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species:

Image: surf grass Phyllospadix (rt side, across bottom)

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Gelidium coulteri Gelidium coulteri Harvey
Phylum Rhodophyta, Class Florideophyceae, Order Gelidiales, Family Gelidiaceae

Narrow, fine thallus in dense mats or clumps to 10 cm tall; thallus a flattened cylinder in cross section above basal area; side branches distichous (planar & opposite) & ~equal in length along distinct main axis (inset) with ultimate branchlets 0.3-1 mm wide; rose to dark red.

Common, mid- to low intertidal zones on rock or mussel shells; protected outer coast.

Geogr. Range: Washington  to Baja
Synonyms:
Similar species: several other species of Gelidium occur in the Monterey region. Gelidium robustum is larger w. thicker broader branches & occurs lower on the shore (& subtidally).

Image: 

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Gelidium robustum Gelidium robustum (Gardner) Hollenberg & Abbott
Phylum Rhodophyta, Class Florideophyceae, Order Gelidiales, Family Gelidiaceae

Thallus to 40 cm tall, flattened cylinder in cross section; side branches arise from distinct main axis with ultimate branchlets usually >1 mm wide; rose to dark red.

Common, low intertidal zone to subtidal; protected outer coast.

Geogr. Range: northern California to northern Baja
Synonyms:
Similar species: Gelidium coulteri occurs higher on the shore & is much more delicate & finely branched.

Image: Rhodymenia pacifica (down rt side), hydroid Aglaophenia (lower rt), Corallina (lower left)

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Corallina sp. Corallina sp.
Phylum Rhodophyta, Class Florideophyceae, Order Corallinales, Family Corallinaceae

Finely branched erect coralline alga to 15 cm tall; featherlike with closely-spaced side branches arising from main axis; segments (intergenicula) of main axis 1-2 mm long & 1.5 mm wide; flattened. Pink, whitish, purplish.

Common, low intertidal zone; protected & exposed outer coast.

Geogr. Range: Alaska to Chile
Synonyms:
Similar species:  other common local erect corallines are more robust & not so finely branched as Corallina and occur lower on the shore.

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Porphyra perforata Porphyra perforata J. Agardh
Phylum Rhodophyta, Class Bangiophyceae, Order Bangiales, Family Bangiaceae

Thin ruffled blades 15-30 cm tall growing in groups from small discoid holdfast; blade composed of a single layer of cells; gray-green to brownish purple. Resembles crumpled cellophane when dry.  Sporophyte stage ("conchocelis")  is a microscopic filament growing into mollusc shells.

Common, high intertidal zone.  No other conspicuous alga occurs higher on the shore; protected & exposed outer coast.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species:

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Page created by J.M. Watanabe
All images copyright James Watanabe unless otherwise indicated
Contact:  watanabe_at_stanford_dot_edu                                                                                                                                      Last  update: 14 June 2014

































Mid-Tide Red Algae, Protected Outer Coast

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"Petrocelis" Mastocarpus
papillatus
Endocladia
muricata
Mazzaella
affinis
Mazzaella
flaccida
Mid-tide Reds
Mazzaella
affinis
Mastocarpus
papillatus
Mazzaella
leptorhynchos
Chondracanthus
canaliculatus


Page created by J.M. Watanabe
All images copyright James Watanabe unless otherwise indicated
Contact:  watanabe_at_stanford_dot_edu                                                                                                                                   Last  update: 3 November 2009