Mixotrophs?!

  • Image: Maira Maselli

All organisms feed; -trophy in biology refers to food or nutrition. Plants are phototrophic, using light to support photosynthesis to make sugars from which they make all else they need. Most other organisms are heterotrophic, using sources of organic matter (such as sugars, proteins, fats), often obtained by feeding on other organisms. However, some organisms combine, or mix, nutritional routes; these are mixotrophs.

In a crude way one could consider a mixotroph as an organism that photosynthesises like a plant and eats like an animal. A well-known example is the Venus flytrap plant.

Far more important, however, are the mixotrophic planktonic (drifting) single-celled organisms that dominate life in the sea.

For the last century, science has described planktonic organism as either plant-like phytoplankton, or animal-like microzooplankton, and has studied their ecology and physiology accordingly.

It transpires now that our understanding of marine ecology, of fisheries, of harmful algal blooms, is based upon a grossly incomplete description of these planktonic organisms. And to put this into a broader context, a large proportion of the oxygen you are breathing in right now was produced by these organisms.

So, why the concern? Well, most organisms labelled as “phytoplankton” and about 50% of the “microzooplankton” are actually mixotrophic plankton. Science has been studying the wrong things, in the wrong organisms.

Confronting this paradigm shift in understanding, developing new tools & protocols and training the next generation of marine scientists is what the project MixITiN is all about. For more information, check out our newsletters!