8 Marine Macro- and Microalgae: An Overview
Euglenophyta
The about 900 known Euglenophyta include unicellular flagellates and colonial forms, which are widely
distributed in marine, brackish, and freshwater systems, soils, and mud (Graham et al. 2009). They are
especially abundant in heterotrophic environments and one of the best-known groups of flagellates.
In the flagellate forms, the flagella arise from a cavity called reservoir, located in the anterior end
of the cell. Cells can also move by a series of flowing movements made possible by the presence of the
pellicle, a proteinaceous wall which lies inside the cytoplasm (Lee 2008).
The Euglenophyta possess chlorophyll a, and b, β and γ carotenes, and various xanthophylls,
although plastids can be colorless or absent in some species, mainly in the ones that use phagocytosis as
the mode of nutrition. The reserve polysaccharide is paramylon, β-1,3-glucan stored in granules scattered
inside the cytoplasm and not in the chloroplasts. Only asexual reproduction has been reported (Bold and
Wynne 1985).
Glaucophyta
The Glaucophytes are simple unicellular flagellates with a dorsiventral construction and bearing two
unequal flagella inserted in a depression just below the apex of the cell. The 13 known species are strictly
form freshwater habitats and characterized by containing chlorophyll a, β carotenes, zeaxanthin, and
phycocyanin, allophycocyanin, and phycoerythrocyanin. The food reserve is a starch (Graham et al.
2009).
Rhodophyta
Red algae, together with many representatives of the Phyla Ochrophyta (Phaeophyceae, brown algae)
and Chlorophyta (green algae), are mostly considered seaweeds and, very frequently, referred to as
macroalgae. Although morphologically closely related, these three phyla have fundamental differences
that are evident when comparing their photosynthetic pigments, reserve foods, cell wall, mitosis, flagellar
construction, morphology, and life history cycles.
The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, the number
of species ranging from 5,000 to as many as 20,000 (Norton et al. 1996; Guiry and Guiry 2017).
The Rhodophyta are predominantly marine and predominantly found in warm temperate to tropical
latitudes. These organisms occur both intertidally and subtidally and some species have adapted to grow
at depths of 200 m and more. They encompass both benthic and free living forms and cover almost all
types of growth and sizes. The Bangiophycidae (Bangiales) range from unicells to multicellular filaments
of sheet-like thalli and retain morphological characters that are found in the ancestral pool of red algae.
The Floridophyceae includes the more complex red algae and a higher variety of growth forms (Barsanti
and Gualtieri 2014).
The Rhodophyta contain chlorophyll a, α, and β carotenes, zeaxanthin, and the phycobilins
phycocyanin, phycoerythrin, and allophycocyanin pigments that allow these organisms to grow at depths
where no other photosynthetic organisms can adapt. Their food reserve is floridean starch, a highly
branched amylopectin insoluble in boiling water. The cell wall has an inner layer of randomly arranged
microfibrils and an outer layer that may contain sulfated galactan polymers, some economically important
such as agar, carrageenan, funoran, and furcellarin. The inner microfibrils are composed of cellulose
polymers except in genus as Porphyra and Bangia (Bangiales), the more primitive red algae, where the
polymers are of xylose and mannose. Calcification of cell walls, enriched by the calcite crystalline form
of calcium carbonate, is characteristic in the coralline algae (Corallinales), which play a critical but often
neglected role in coral reef development (Dawes 1998).
Reproduction can be sexual and asexual. In the great majority of red algae, cytokinesis is incomplete
and daughter cells are linked by pit connections. A proteinaceous plug fills the junction between cells and
can appear refractive under the light microscope, being a distinctive feature in alpha taxonomy (Pueschel
1989). The sexual life cycle is generally diplohaplontic, iso-, or heteromorphic (Bold and Wynne 1985).
Euglenophyta
The about 900 known Euglenophyta include unicellular flagellates and colonial forms, which are widely
distributed in marine, brackish, and freshwater systems, soils, and mud (Graham et al. 2009). They are
especially abundant in heterotrophic environments and one of the best-known groups of flagellates.
In the flagellate forms, the flagella arise from a cavity called reservoir, located in the anterior end
of the cell. Cells can also move by a series of flowing movements made possible by the presence of the
pellicle, a proteinaceous wall which lies inside the cytoplasm (Lee 2008).
The Euglenophyta possess chlorophyll a, and b, β and γ carotenes, and various xanthophylls,
although plastids can be colorless or absent in some species, mainly in the ones that use phagocytosis as
the mode of nutrition. The reserve polysaccharide is paramylon, β-1,3-glucan stored in granules scattered
inside the cytoplasm and not in the chloroplasts. Only asexual reproduction has been reported (Bold and
Wynne 1985).
Glaucophyta
The Glaucophytes are simple unicellular flagellates with a dorsiventral construction and bearing two
unequal flagella inserted in a depression just below the apex of the cell. The 13 known species are strictly
form freshwater habitats and characterized by containing chlorophyll a, β carotenes, zeaxanthin, and
phycocyanin, allophycocyanin, and phycoerythrocyanin. The food reserve is a starch (Graham et al.
2009).
Rhodophyta
Red algae, together with many representatives of the Phyla Ochrophyta (Phaeophyceae, brown algae)
and Chlorophyta (green algae), are mostly considered seaweeds and, very frequently, referred to as
macroalgae. Although morphologically closely related, these three phyla have fundamental differences
that are evident when comparing their photosynthetic pigments, reserve foods, cell wall, mitosis, flagellar
construction, morphology, and life history cycles.
The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, the number
of species ranging from 5,000 to as many as 20,000 (Norton et al. 1996; Guiry and Guiry 2017).
The Rhodophyta are predominantly marine and predominantly found in warm temperate to tropical
latitudes. These organisms occur both intertidally and subtidally and some species have adapted to grow
at depths of 200 m and more. They encompass both benthic and free living forms and cover almost all
types of growth and sizes. The Bangiophycidae (Bangiales) range from unicells to multicellular filaments
of sheet-like thalli and retain morphological characters that are found in the ancestral pool of red algae.
The Floridophyceae includes the more complex red algae and a higher variety of growth forms (Barsanti
and Gualtieri 2014).
The Rhodophyta contain chlorophyll a, α, and β carotenes, zeaxanthin, and the phycobilins
phycocyanin, phycoerythrin, and allophycocyanin pigments that allow these organisms to grow at depths
where no other photosynthetic organisms can adapt. Their food reserve is floridean starch, a highly
branched amylopectin insoluble in boiling water. The cell wall has an inner layer of randomly arranged
microfibrils and an outer layer that may contain sulfated galactan polymers, some economically important
such as agar, carrageenan, funoran, and furcellarin. The inner microfibrils are composed of cellulose
polymers except in genus as Porphyra and Bangia (Bangiales), the more primitive red algae, where the
polymers are of xylose and mannose. Calcification of cell walls, enriched by the calcite crystalline form
of calcium carbonate, is characteristic in the coralline algae (Corallinales), which play a critical but often
neglected role in coral reef development (Dawes 1998).
Reproduction can be sexual and asexual. In the great majority of red algae, cytokinesis is incomplete
and daughter cells are linked by pit connections. A proteinaceous plug fills the junction between cells and
can appear refractive under the light microscope, being a distinctive feature in alpha taxonomy (Pueschel
1989). The sexual life cycle is generally diplohaplontic, iso-, or heteromorphic (Bold and Wynne 1985).