Phycology is the study of algae. However, just what algae are is difficult to define, because they belong to many different and diverse taxonomic groups and include both prokaryotic and eukaryotic representatives. Broadly speaking, the algae comprise all, mainly aquatic, plants and plant‐like chlorophyll a‐containing organisms that can use light energy to fix carbon from atmospheric carbon dioxide (CO2) and evolve oxygen, but which are not specialised land plants like mosses, ferns, coniferous trees and flowering plants. This is a negative definition, but it serves its purpose. Besides being a principal source of oxygen, algae are important primary producers in many, mainly aquatic, habitats. The prokaryotic Cyanobacteria are important as nitrogen fixers, converting N2 to organic nitrogen. The algae are the source of a number of important commercial products and molecules and are also used in wastewater treatment, as animal feed and as fertilisers.

Key Concepts

  • Phycology is the study of algae.
  • The algae are a very diverse group of plants and plant‐like organisms, but which are not specialised land plants like mosses, ferns, coniferous trees and flowering plants.
  • The algae include both prokaryotic and eukaryotic organisms.
  • Algae are key providers of oxygen on earth and are the basis of aquatic food webs.
  • Algae have a wide range of commercial applications.
  • Endosymbiosis has played an important part in the evolution of the algae.

Keywords: algae; seaweeds; phytoplankton; prokaryotes; eukaryotes; symbiosis; taxonomy

Figure 1. A red cell of Dunaliella salina containing a large amount of carotenoid.
Figure 10. The green alga Caulera racemosa. Source: Reproduced with permission from John Huisman.
Figure 2. The Dunaliella salina production plant at Hutt Lagoon, Western Australia showing the red coloured ponds. The plant is over 700 ha in area.
Figure 3. The filamenous cyanobacterium Phormidium from a soil sample. The small brownish algae are diatoms.
Figure 4. The coccolithophorid alga Discophaera tubifera with its unusually trumpet‐shaped coccoliths. The cell can be seen at the base of the coccoliths (scale = 5 μm).
Figure 5. A mixed population of dinoflagellates in a plankton sample from the river Derwent, Tasmania, Australia. Source: Micrograph, Courtesy of Dr G. Hallegraeff.
Figure 6. Scanning electron micrograph of two cells of the centric diatom Thalassiosira allenii, one in valve view and one in girdle view. Note the various processes on the valves and the wide girdle band which can be seen in girdle view connecting the two valves. Cell diameter = 15 μm. Source: Micrograph, Courtesy of Dr G. Hallegraeff.
Figure 7. Dictyota ciliolata, a brown algae with a flattened thallus. Source: Reproduced with permission from John Huisman.
Figure 8. The red alga Martensia, which has a very complex thallus morphology. Source: Reproduced with permission from John Huisman.
Figure 9. Amphiroa anceps, a calcareous red alga. Source: Reproduced with permission from John Huisman.


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Further Reading

Andersen RA (ed.) (2005) Algal Culturing Techniques. Elsevier: Amsterdam.

Borowitzka MA and Moheimani NR (eds) (2013) Algae for Biofuels and Energy. Springer: Dordrecht.

Borowitzka MA, Beardall J and Raven JA (eds) (2016) The Physiology of Microalgae. Springer: Dordrecht.

Borowitzka MA (2018) Biology of microalgae. In: Levine IA and Fleurence J (eds) Microalgae in Health and Disease Prevention, pp 23–72. Academic Press: London.

Chan CX and Bhattacharya D (2010) The origin of plastids. Nature Education 3 (9): 84‐origin‐of‐plastids‐14125758.

Huisman JM and Saunders GW (2007) Phylogeny and classification of the algae. In: PM MC and Orchard AE (eds) Algae of Australia. Introduction, pp 66–103. ABRS: Canberra.

Lee RE (2008) Phycology, 4th edn. Cambridge University Press: Cambridge.

Richmond A and Hu Q (eds) (2013) Handbook of Microalgal Culture. John Wiley & Sons: Ltd.

Sondak CFA, Ang PO, Beardall J, et al. (2017) Carbon dioxide mitigation potential of seaweed aquaculture beds (SABs). Journal of Applied Phycology 29 (5): 2363–2373.

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Borowitzka, Michael A(Sep 2020) Phycology. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0029195]