1
Introduction to the Marine Algae
Overview
Ana Isabel Neto
1,2,
* and Isabel Sousa Pinto
3,4
Definition
The term algae has no formal taxonomic standing but it is routinely used to indicate a large, polyphyletic,
artificial, and diverse assemblage of mostly photosynthetic nonvascular organisms that contain chlorophyll
a and have simple reproductive structures (Barsanti and Gualtieri 2014). As opposed to higher plants,
algae do not have true roots, stems, leafy shoots, and transporting tissues; like mosses and ferns, algae
do not form flowers and seeds, but reproduce and complete their life cycle by releasing gametes or
spores into the environment. The algae concept encompasses a number of life forms that are not closely
related; they are included in four kingdoms: Plantae, Chromista, Protozoa, and Bacteria (Ruggiero et al.
2015) including both prokaryotic and eukaryotic organisms (Lee 2008). The former, often classified as
Cyanobacteria, are in fact photosynthetic bacteria, lacking the membrane-bounded organelles (plastids,
mitochondria, nuclei, Golgi bodies, and flagella) that are present in the latter group.
The profound morphological diversity of forms and sizes, and the cytology, ecology, and reproductive
biology of algae make it difficult to clearly define them (Bold and Wynne 1985). In a simplistic approach,
the term algae refer to both macroalgae and a highly diversified group of microorganisms known as
microalgae.
Species and environments
A conservative approach estimates the number of algal species in 72,500, most of them being microalgae
(Guiry 2012).
1
cE3c - Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group, 9501-801 Ponta Delgada,
Açores, Portugal.
2
Department of Biology, Faculty of Sciences and Technology, University of Azores, Rua da Mãe de Deus, 9500-321 Ponta
Delgada, Açores, Portugal.
3
Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Terminal de Cruzeiros do
Porto de Leixões, Avenida General Norton de Matos, S/N, P-4450-208 Matosinhos, Portugal.
4
Department of Biology, Faculty of Sciences, University of Porto (FCUP), Rua do Campo Alegre, s/n, 4050 Porto, Portugal.
* Corresponding author
Introduction to the Marine Algae
Overview
Ana Isabel Neto
1,2,
* and Isabel Sousa Pinto
3,4
Definition
The term algae has no formal taxonomic standing but it is routinely used to indicate a large, polyphyletic,
artificial, and diverse assemblage of mostly photosynthetic nonvascular organisms that contain chlorophyll
a and have simple reproductive structures (Barsanti and Gualtieri 2014). As opposed to higher plants,
algae do not have true roots, stems, leafy shoots, and transporting tissues; like mosses and ferns, algae
do not form flowers and seeds, but reproduce and complete their life cycle by releasing gametes or
spores into the environment. The algae concept encompasses a number of life forms that are not closely
related; they are included in four kingdoms: Plantae, Chromista, Protozoa, and Bacteria (Ruggiero et al.
2015) including both prokaryotic and eukaryotic organisms (Lee 2008). The former, often classified as
Cyanobacteria, are in fact photosynthetic bacteria, lacking the membrane-bounded organelles (plastids,
mitochondria, nuclei, Golgi bodies, and flagella) that are present in the latter group.
The profound morphological diversity of forms and sizes, and the cytology, ecology, and reproductive
biology of algae make it difficult to clearly define them (Bold and Wynne 1985). In a simplistic approach,
the term algae refer to both macroalgae and a highly diversified group of microorganisms known as
microalgae.
Species and environments
A conservative approach estimates the number of algal species in 72,500, most of them being microalgae
(Guiry 2012).
1
cE3c - Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group, 9501-801 Ponta Delgada,
Açores, Portugal.
2
Department of Biology, Faculty of Sciences and Technology, University of Azores, Rua da Mãe de Deus, 9500-321 Ponta
Delgada, Açores, Portugal.
3
Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Terminal de Cruzeiros do
Porto de Leixões, Avenida General Norton de Matos, S/N, P-4450-208 Matosinhos, Portugal.
4
Department of Biology, Faculty of Sciences, University of Porto (FCUP), Rua do Campo Alegre, s/n, 4050 Porto, Portugal.
* Corresponding author