Introduction to the Marine Algae: Overview 7
a consensus view that accommodates taxonomic choices and practical compromises among diverse
expert opinions, public usages, and conflicting evidence about the boundaries between taxa and the ranks
of major taxa, including kingdoms. It reflects a hierarchical system on the basis of similarities between
organisms, each group consisting of a set of organisms that are more closely related to each other than
to organisms of a different group. It considers similarities in the organism’s genomes as a result of a
common ancestral.
There is no easily definable classification system acceptable to all algae, since taxonomy is under
constant and rapid revision at all levels following new genetic and ultrastructural evidence. Keeping in
mind that the polyphyletic nature of the algal group is somewhat inconsistent with traditional taxonomic
groupings, and that taxonomic opinion may change as information accumulates, we will use in this
text the classification adopted by Guiry and Guiry (2017) which considers 10 phyla: Cyanobacteria
(=Cyanophyta) in kingdom Eubacteria; Euglenophyta in Protozoa; Glaucophyta, Rhodophyta, and
Chlorophyta in Plantae; and Ochrophyta, Haptophyta, Cryptophyta, Miozoa (Dynophyceae), and
Cercozoa (Chlorarachniophycea) in the Chromista. From these, only Glaucophyta is restricted to
freshwater habitats. Rhodophyta and Haptophyta are predominantly marine, and the remaining phyla can
be found in both marine and freshwater systems (Graham et al. 2009).
Unlike vascular plants, there are few common names for algae. Species are named according to the
binomial system of nomenclature proposed by Linnaeus (1758, 1759) and in accordance to the rules of
the International Code of Botanical Nomenclature (McNeill et al. 2012).
Algae phyla
Cyanobacteria
The Cyanobacteria is the most widely distributed group of algae and the dominant one in the ocean
ecosystems, with about 2,000 known species (Graham et al. 2009). It includes organisms that are
unicellular, colonial, and filamentous branched or unbranched (also known as trichomes). Some
filamentous colonies have the ability to differentiate into several different cell types: vegetative cells;
akinetes (normal, photosynthetic cells formed under favorable growing conditions); climate-resistant
spores that are formed in harsh environmental conditions; and thick-walled heterocysts, which are
responsible for nitrogen fixation.
Cyanobacteria are the most successful group of algae on earth. They are an important component
of the picoplankton in both freshwater and marine systems and they can grow symbiotically in ferns,
lichens, diatoms, sponges, and other algae. Some even live in the fur of sloths, providing a form of
camouflage. They also have benthic representatives that can grow as dense mats on soils, mud flats, on
the seashore, and in hot springs (Barsanti and Gualtieri 2014).
The Cyanobacteria contain chlorophyll a, β carotenes, zeaxanthin, and blue and red phycobilins
(phycoerythrin, phycocyanin, allophycocyanin, and phycoerythrocyanin). Their cell wall is characterized
by a peptoglycan layer and the food reserve is cyanophycean starch (Dawes 1998). Some marine species
also contain gas vesicles used for buoyancy regulation. A few species produce potent hapatotoxins and
neurotoxins. The reproduction is strictly asexual by simple cell division or by fragmentation of colonies
or filaments (Barsanti and Gualtieri 2014).
Cyanobacteria produced the Earth’s first oxygen atmosphere, which fostered the rise of eukaryotes,
and remain important today. They produce organic compounds used by other organisms, fulfill vital
ecological functions in the world’s oceans, being important contributors to global carbon and nitrogen
budgets, contribute significantly to global ecology and the oxygen cycle, stabilize sediments and soils,
increase water fertility and foster the growth of certain plants and fungi in symbiotic associations. Some
have potential biotechnological application. Aquatic Cyanobacteria are probably best known for the
extensive and highly visible blooms they can form. Some of the species involved in this process produce
toxins and cause the occurrence of harmful blooms well known by their negative effects on the aquatic
systems (Graham et al. 2009).
a consensus view that accommodates taxonomic choices and practical compromises among diverse
expert opinions, public usages, and conflicting evidence about the boundaries between taxa and the ranks
of major taxa, including kingdoms. It reflects a hierarchical system on the basis of similarities between
organisms, each group consisting of a set of organisms that are more closely related to each other than
to organisms of a different group. It considers similarities in the organism’s genomes as a result of a
common ancestral.
There is no easily definable classification system acceptable to all algae, since taxonomy is under
constant and rapid revision at all levels following new genetic and ultrastructural evidence. Keeping in
mind that the polyphyletic nature of the algal group is somewhat inconsistent with traditional taxonomic
groupings, and that taxonomic opinion may change as information accumulates, we will use in this
text the classification adopted by Guiry and Guiry (2017) which considers 10 phyla: Cyanobacteria
(=Cyanophyta) in kingdom Eubacteria; Euglenophyta in Protozoa; Glaucophyta, Rhodophyta, and
Chlorophyta in Plantae; and Ochrophyta, Haptophyta, Cryptophyta, Miozoa (Dynophyceae), and
Cercozoa (Chlorarachniophycea) in the Chromista. From these, only Glaucophyta is restricted to
freshwater habitats. Rhodophyta and Haptophyta are predominantly marine, and the remaining phyla can
be found in both marine and freshwater systems (Graham et al. 2009).
Unlike vascular plants, there are few common names for algae. Species are named according to the
binomial system of nomenclature proposed by Linnaeus (1758, 1759) and in accordance to the rules of
the International Code of Botanical Nomenclature (McNeill et al. 2012).
Algae phyla
Cyanobacteria
The Cyanobacteria is the most widely distributed group of algae and the dominant one in the ocean
ecosystems, with about 2,000 known species (Graham et al. 2009). It includes organisms that are
unicellular, colonial, and filamentous branched or unbranched (also known as trichomes). Some
filamentous colonies have the ability to differentiate into several different cell types: vegetative cells;
akinetes (normal, photosynthetic cells formed under favorable growing conditions); climate-resistant
spores that are formed in harsh environmental conditions; and thick-walled heterocysts, which are
responsible for nitrogen fixation.
Cyanobacteria are the most successful group of algae on earth. They are an important component
of the picoplankton in both freshwater and marine systems and they can grow symbiotically in ferns,
lichens, diatoms, sponges, and other algae. Some even live in the fur of sloths, providing a form of
camouflage. They also have benthic representatives that can grow as dense mats on soils, mud flats, on
the seashore, and in hot springs (Barsanti and Gualtieri 2014).
The Cyanobacteria contain chlorophyll a, β carotenes, zeaxanthin, and blue and red phycobilins
(phycoerythrin, phycocyanin, allophycocyanin, and phycoerythrocyanin). Their cell wall is characterized
by a peptoglycan layer and the food reserve is cyanophycean starch (Dawes 1998). Some marine species
also contain gas vesicles used for buoyancy regulation. A few species produce potent hapatotoxins and
neurotoxins. The reproduction is strictly asexual by simple cell division or by fragmentation of colonies
or filaments (Barsanti and Gualtieri 2014).
Cyanobacteria produced the Earth’s first oxygen atmosphere, which fostered the rise of eukaryotes,
and remain important today. They produce organic compounds used by other organisms, fulfill vital
ecological functions in the world’s oceans, being important contributors to global carbon and nitrogen
budgets, contribute significantly to global ecology and the oxygen cycle, stabilize sediments and soils,
increase water fertility and foster the growth of certain plants and fungi in symbiotic associations. Some
have potential biotechnological application. Aquatic Cyanobacteria are probably best known for the
extensive and highly visible blooms they can form. Some of the species involved in this process produce
toxins and cause the occurrence of harmful blooms well known by their negative effects on the aquatic
systems (Graham et al. 2009).