Wednesday, July 11, 2018

12/07/2018: Micro-algae, macro-algae, seaweeds, kelps … what are these little-known organisms?

by Thierry Chopin, Professor of Marine Biology, University of New Brunswick, Saint John, Canada

Algae periodically make the news, however, not always for positive reasons: harmful micro-algal blooms toxic to marine life and sometimes to humans; Olympic swimming pools turning completely green in Rio de Janeiro in 2016; large recurrent green macro-algal tides in China; brown macro-algal tides unpleasant to tourists in the Caribbean islands; etc.

It is time to demystify this ‘obscure’, albeit photosynthetic, group of organisms, as they render key ecosystem services to nature and to humans, who eat them almost everyday, in one form or another, without always knowing it.

In fact, the term ‘algae’ does not mean much!
Giving a simple definition of what algae are is not that simple. Since the time of the Greeks and the Romans, algae have been a misunderstood, unappreciated and underused group of organisms, lumped together in a very artificial manner. When they did not know in which group of organisms to classify a new species, they described them as ‘incertae sedis’ (of uncertain placement).

Over time, a lot of algae/seaweeds became ‘incertae sedis’ … The end result of several centuries of neglect is that, systematically, algae do not have much in common and are an unnatural grouping (what is called a polyphyletic group, i.e. with different ancestors and different evolutionary histories).

Algae share only a few characteristics: they are photosynthesising (sequestering carbon dioxide and producing oxygen); they strive on absorbing dissolved inorganic nutrients, such as nitrogen and phosphorus (hence the interest in using them for bioremediation); they do not make flowers and their anatomy is relatively simple (no roots, stems, leaves or vascular tissues, and simple reproductive structures).

We now realise, especially with the progress in molecular techniques, that this mixed bag is completely unnatural, with no real cohesion and with species spread over most kingdoms of organisms, encompassing microscopic microalgae (like the unicellular phytoplanktonic forms) and macroscopic macroalgae (like the giant kelps that grow taller than trees) that colonise the oceans, freshwater streams, trees (associated with fungi in lichens), stones, high altitude snow in glaciers, geothermal sources and even deserts.

Read the full article, HERE.

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