What’s the definition of phytoplankton?

Foundational elements of the aquatic foodchain, phytoplankton are a category of plankton, microscopic organisms which are unable to swim against the current and float around in the upper region of water bodies. Inhabiting either salt or freshwater, plankton are  and are defined more by their ecological niche rather than any shared characteristics. Plankton might include bacteria, archae, algae, protozoa and even drifting creatures like jellyfish. Some creatures (known as meroplankton) are categorised as plankton for the early part of their lifeycle (larval forms of sea urchins, sea stars etc) but then, as adults, take up residence on the seafloor.

What’s the difference between phytoplankton and zooplankton?

Phtyplankton might be classed as the plants of the sea, while zooplankton the animals. While phytoplankton has the capacity to manufacture it’s own food from sunlight and carbon dioxide through photsynthesis, zooplankton are tiny animals which must feed to survive, usually on phytoplankton. Both are key members of the marine ecosystem, and provide primary food sources for larger species like whales. The crucial thing from our perspective is that phytoplankton:

  • Are single celled
  • Can photosynthesize
  • Are entirely vegan/vegetarian

What are the main forms of phytoplankton?

Diatoms, golden brown algae, green algae, blue green algae, and dinoflagellates

Phytoplankton and the Carbon Cycle

Although scientists are still learning about marine carbon cycling, it is clear that phytoplankton play an integral role in the sequestering of carbon from our atmosphere, likely significantly higher than that of terrestrial forests. In a process called ‘the biological pump’, phytoplankton are responsible for approximately half of the carbon fixation on earth. From an ecological perspective, however, we can note than over 99.0% of all the carbon dioxide incorporated into living things over geologic time is buried in marine sediments, suggesting that the role of phytoplankton is absolutely primary to all of life on this planet.

Climate Change

Many scientists now question whether phtyoplankton offers our planet its biggest opportunity for reducing carbon in the atmosphere and combatting climate change. As weather patterns change, scientists are also becoming aware that changes in light, and nutrients in the pelagic region of the oceans could have a major impact on plankton. The biggest threat would be that oxygen levels fall below the level required for phytoplankton to live which would rapidly kill of all oceanic life as we know it.

What is it eaten by?

The most common predators of phytoplankton would be things like krill, and larger plankton like jellyfish. Big mammals like whales are massive plankton eaters. Blue whales can eat  2,000-9,000 pounds (900-4100 kg) per day during the summer feeding season.

Phtyoplankton for human consumption

In terms of it’s consumption as a superfood, phytoplankton is relatively new to the human food chain. The last twenty years have been shift a huge amount of research focussed on it, however, firstly because of it’s extraordinary nutrient profile which attracted it to the cosmetic industry, and secondly it’s ability as a vegetarian oil source which has piqued the interest of biofuel pioneers. As our oceans become more and more polluted, the power of this humble organism to sustain the human species may prove to be most suitable, however, as the whales have always used it: simple nutrition.