Why plankton?

To understand why plankton is so important, it is useful to define what plankton is, and for that we turn to one of the pioneers of modern marine biology, Sir Alister Hardy who said:

“Taken directly from the Greek πλαγκτός [translates into planktos] it should not be translated as just meaning wandering or drifting (as so often in the textbooks), for it has a much more passive sense, meaning those which are made to wander; it is applied to all those organisms which are powerless to prevent themselves being carried at the mercy of the moving waters.”

As such, plankton, are those organisms which live in both freshwater and marine environments which are unable to swim against the water currents and so their movement is governed by these physical processes. Although most people think of plankton as microscopic organisms, plankton can range in size from femtoplankton, such as marine viruses, which are less than 200 nanometers in size, up to megaplankton such as jellyfish, some of which can reach up to 2 meters in diameter (e.g. Nomurai’s jellyfish Nepolimea nomurai). Plankton can also be separated into two broad groups based on how they acquire their energy: phytoplankton (the plant component of plankton that photosynthesise e.g. algae) and zooplankton (the animal component of plankton that acquire their energy by consuming other plankton). Both phytoplankton and zooplankton are essential components of marine foodwebs and thus to the overall health of the ocean’s ecosystem. Animals big and small rely on plankton for food– anything from small crustaceans to larval fish to some sharks and even whales feed on plankton. The marine ecosystem would collapse if plankton were removed from it, and not just the marine ecosystem. It is estimated that roughly 50% of the oxygen we breathe is produced by photosynthetic phytoplankton.

The image was taken looking down the microscope. The image is crowded with the dinoflagellate Noctiluca scintillans, with a few copepods and one Muggiaea atlantica visible in the centre of the image. Image taken by Hanna Brownlow.
Image of the dinoflagellate Noctiluca scintillans (phytoplankton) under the stereoscope.

As our oceans are changing due to stressors such as climate change and pollution, it is essential that we monitor zooplankton as they are valuable indicators of change within our oceans. For example, the abundance of the dominant zooplankton species can be a good indicator of the food quality for commercial fish species or the appearance of a new species might indicate a distributional shift due to warming seas. By closely monitoring zooplankton on a monthly basis the Plankton Club hopes to track the seasonal and annual changes in our coastal marine zooplankton community.

John Vaughan Thompson and Cork

Image shows a portrait of John Vaughan Thompson. He is depicted wearing a red Navy Uniform and grey hair.
Portrait of John Vaughan Thompson

There is also a historical connection between Cork and plankton research.  John Vaughan Thompson (pictured above) was a British military surgeon and naturalist who is credited as the first person to use a plankton net. While based in Cobh, Co. Cork, he published an account in “Zoological researches” which fully described the life cycle of a common shore crab for the first time. Indeed, John Vaughan Thompson was the first person to demonstrate that ‘zoea’, were the larval form of crabs, and not a separate animal as previously thought. While this view was received with scepticism at the time, he is now considered a “pioneer planktonologist”.

Zoea – a larval form of crabs and other decapoda