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/A Diversity of Aquatic Life

The Red Algae, Division Rhodophyta, part 1

To: part 2, part 3, part 4

By Bob Fenner

Fauchea sp. 

New Print and eBook on Amazon

Marine Aquarium Algae Control

by Robert (Bob) Fenner

At long last the red algae, particularly the coralline and encrusting calcareous forms, are receiving their due. These small, unassuming forms play a huge role in the real development of coral reefs, natural and aquarium; growing quickly, utilizing nutrients, packaging them into food-useful formats while generating oxygen... all under lower illumination than most co-photosynthetic animals or Caulerpas.

Though we often refer to coral in labeling tropical reefs, it is the algae, in particular the encrusting and branching reds that make up a good deal of the biomass and productivity of these important areas. Some estimates put the calcareous red algae at more than half of both; providing resistance to wave action, providing habitat and food for other living things.

Here we'll discuss what these "simple plants" are, their recruitment, control and culture.

Classification: Taxonomy, Relation With Other Groups

Talk about misidentified life-forms! Rarely are these organisms made out for what they are; algae. The larger red algae are kelp-like, with leaf-like fronds, attaching holdfasts et al.; the encrusting and branched varieties require closer inspection.

The simplest oxygen-producing life on this planet are the algae. They are for the most part autotrophic (self-feeding), have no complex organization (no leaves, roots, xylem/phloem vascular network); but do contain chlorophyll and other photosynthetic pigments.

The various Divisions (equivalent to the zoological taxonomic Phylum) of algae are classes on several criteria; pigments (by which we may generally identify them), storage foods, make-up of their cell walls and flagella where present.

Most aquarists are more interested in avoiding algae than knowing them better. Some algae are noxious, others indeed strange; all are worthwhile at least in terms of identification and control.

A Classification of Algae

Kingdom Monera (No nuclear membrane, "naked" DNA)

Division Cyanophyta- the blue green algae

Kingdom Protista (Beginning of eukaryotes)

Division Euglenophyta- Euglenoids

Division Pyrrophyta- Dinoflagellates

Division Chrysophyta- golden brown algae

Division Bacillariophyta- diatoms

Division Xanthophyta- yellow green algae

Division Phaeophyta- brown algae

Division Rhodophyta- red algae

Division Chlorophyta- green algae

The Blue-Greens (Division Cyanophyta) are closer kin to bacteria than other algal groups; they can make up slimy sheets or threads in nutrient laden conditions. Diatoms (Division Bacillariophyta) may make a brownish scum where silicate and other foods are available. The dinoflagellate (Division Pyrrophyta) Amyloodinium infects marine fishes... The algae are so diverse in their biology and use that we'll restrict our discussion here to the reds.

Red Algae: Rhodophyta on parade!

Genus Actinotrichia:

Actinotrichia fragilis (Forsskal) Borgeson 1932, Spikeweed. Close up and colony images, in the Red Sea. 

Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Genus Amphiroa:

Amphiroa foliacea.

This one in Tobago.

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The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Amphiroa rigida  Thin, branched 2 in. max segments; pink and white in colour. Roatan 2016

Amphiroa tribulus  Small clumps of flattened randomly branched flexible joints. Whitish w/ pink highlights

Here in Key Largo, FLA.


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The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.


Genus Asgaragopsis:

Asparagopsis taxiformis. Creeping stolons w/ upright branches, expanding to fine branchings. To 20 cm. Widely distributed in tropical seas. Here in Kona 2017

Bigger PIX:
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Genus Bossiella:

Bossiella, a common branched calcareous genus; note wing nut shape and reproductive conceptacles (bumps on the faces). This genus and Corallina are notably tolerant of human pollution, often growing luxuriously near outfall "boils".


Genus Ceramium:

Ceramium nitens, Striving Red Algae. To two foot colonies. Hair-like branches in tangles; consistent red-orange in color. Cozumel 2017.

Genus Coelothrix:

Coelothrix irregularis (Harvey) Boergesen. Bright iridescent blue wiry turf, 2-3 cm. tall. Irregularly branched, upright. To 10 m. Turks and Caicos 2007.

Genus Cryptonemia:

Cryptonemia crenulata, Cryptic Blade Algae. To 4 in. max. Long, flat deep red blades that grow in clusters. Edges crenulated. Roatan 2016

Genus Fauchea:

Fauchea sp. 

Aquarium image.

New Print and eBook on Amazon

Marine Aquarium Algae Control

by Robert (Bob) Fenner

To: part 2, part 3, part 4

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