Plankton Trivia
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50 free Plankton trivia questions with answers — nature quiz, new questions added Aug 2026.
Plankton make half the oxygen you breathe and most of the biomass in the sea, and this quiz takes them seriously. It starts with the word itself (Greek for drifter, coined in 1887), the difference between plankton, nekton, benthos and neuston, and the four trophic groups from phytoplankton to the newly recognised mixoplankton. Then it works through the cast: diatoms in their glass houses, whip-spinning dinoflagellates and their red tides, chalk-plated coccolithophores blooming visibly from space, one-eyed copepods, Antarctic krill by the half-billion tonnes, the smallest photosynthesiser on Earth and the commonest bacterium in the sea. There are questions on what plankton do for the planet (the biological pump, marine snow, iron and blooms, the viral shunt, the largest migration on Earth every night) and on the people and tools that study them, from Victor Hensen to the silk ribbon of the Continuous Plankton Recorder. And because search engines are honest about what people mean, there are a few questions on Sheldon J. Plankton, Karen and the Chum Bucket. Easy questions suit anyone who has heard of krill; the expert tier asks about the mycoloop and Langmuir circulation. Every answer was checked against Wikipedia's articles on plankton and its many groups, and the supporting sentence is attached to each question.
30 of 50 questions with answers and explanations. Play the quiz
Q 01The word 'plankton' comes from a Greek word meaning what?
Drifter or wanderer
Drifter or wanderer, from the Greek planktos. The name describes a way of life, not a size: anything that cannot swim against the current counts, from single cells to jellyfish.
Q 02What is the scientific term for a single organism of the plankton?
A plankter
A plankter. You need a microscope to see most of them, yet a bloom can cover hundreds of square kilometres and show up in satellite images.
Q 03Which whale feeds almost exclusively on krill, the shrimp-like animals of the plankton?
Blue whale
Blue whale. The largest animal known to have lived survives on prey a few centimetres long, sieving several tonnes of krill a day through the baleen plates in its mouth.
Q 04Organisms such as fish and squid that can swim against currents, unlike plankton, are called what?
Nekton
Nekton, from the Greek for 'swimming'. Membership can change with age: most fish and squid hatch as plankton and join the nekton only once they are strong enough to swim against the current.
Q 05Phytoplankton release about as much oxygen each year as all the world's what?
Land plants
Land plants. They manage it by living fast: a single phytoplankton cell rarely lasts more than a few days, while a tree can stand for decades.
Q 06Which group of plankton grazes on phytoplankton and is in turn eaten by fish and whales?
Zooplankton
Zooplankton. Not all of them are tiny or permanent: the group takes in jellyfish, and the newly hatched young of crabs, snails and fish that later leave the plankton behind.
Q 07What name is given to animals, such as oysters and starfish, that belong to the plankton only as larvae?
Meroplankton
Meroplankton, from mero-, 'part'. Riding the currents is how slow seabed animals travel: an oyster or starfish that barely moves as an adult sends its larvae off to settle somewhere new.
Q 08What name is given to the tiny organisms, spores and pollen carried through the atmosphere by the wind?
Aeroplankton
Aeroplankton. Dust storms and sea spray lift spores, pollen and countless living cells high into the air, where winds can carry them across oceans before they settle back to earth.
Q 09What is the shower of organic detritus that sinks from the sunlit ocean to feed deep-sea life called?
Marine snow
Marine snow. The flakes are scraps of dead plankton, droppings and dust that clump together as they fall, growing to several centimetres across and sinking for weeks before they reach the seabed.
Q 10What kills an estimated fifth of the ocean's single-celled life every single day?
Viruses
Viruses. They are the most abundant biological entities in the sea, and each cell they burst spills its contents back into the water as food for other plankton.
Q 11Some nutrient-rich stretches of ocean stay almost bare of phytoplankton because the water lacks which trace element?
Iron
Iron. Oceanographer John Martin quipped in 1988, 'Give me a half tanker of iron, and I will give you an ice age', and a trial soon after his death showed that a sprinkling of iron really does make such waters bloom.
Q 12Diatoms are encased in a cell wall made of what?
Silica
Silica. The glassy shell cannot stretch, and at each division a daughter cell builds its new half inside the old one, so a diatom population shrinks generation by generation until sex resets the size.
Q 13Diatomaceous earth, a powder of fossil diatom shells, kills bed bugs and fleas mainly by doing what to them?
Drying them out
Q 21During which recurring climate event does plankton growth in the equatorial Pacific slump as the trade winds weaken?
El Niño
El Niño. The trade winds normally drag cold, nutrient-rich water up to the sunlit surface; when they slacken the supply stops and the phytoplankton go hungry.
Q 22The word 'krill' comes from which language, where it means 'small fry of fish'?
Norwegian
Norwegian. The animals are anything but small fry in importance: most of the larger creatures of the Antarctic, from seals to seabirds, depend on krill directly or indirectly.
Q 23The combined weight of all Antarctic krill is thought to be about the same as that of which species?
Humans
Drying them out. The powder is not a poison: it soaks up the oily, waxy coating on an insect's shell, and without that waterproofing the insect loses its water and dies.
Q 14Fossilised diatom shells form a soft rock used in toothpaste, filters and, famously, to stabilise which explosive?
Dynamite
Dynamite. Alfred Nobel found that soaking liquid nitroglycerine into the powdery rock turned a dangerously unstable explosive into a paste that could be shaped into rods and handled far more safely.
Q 15Dinoflagellates take their name from Greek and Latin words meaning what?
Whirling whip
Whirling whip. Each cell carries two whip-like flagella, and their beating sends it spinning through the water, the motion the first observers named it for.
Q 16A 'red tide' is usually a harmful bloom of which kind of plankton?
Dinoflagellate
Dinoflagellate. Clams, mussels and oysters that feed on the bloom store its nerve toxin in their flesh, so the danger reaches people through a plate of seafood.
Q 17The glowing plankton Noctiluca flashes blue at night when the water around it is what?
Disturbed
Disturbed. Each cell flashes when something jolts it, which is why breaking waves and the wakes of boats can glow after dark.
Q 18Coccolithophores cover themselves in plates made of what?
Calcium carbonate
Calcium carbonate. The plates rain down to the seabed when the cells die, and over millions of years thick layers of them hardened into chalk and limestone.
Q 19Blooms of the coccolithophore Emiliania huxleyi turn the sea which colour, in swirls visible from space?
Pale turquoise
Pale turquoise. The colour is not the cells themselves but sunlight scattering off clouds of the tiny plates they shed into the water.
Q 20Cyclops, named after myth's one-eyed giant, is a common genus of which tiny crustaceans?
Copepods
Copepods. Like the giant, a Cyclops has a single eye, and copepods like it carry the larvae of the guinea worm, which is why straining drinking water through cloth keeps that disease at bay.
Humans. Each krill weighs only a gram or two, yet together they come to hundreds of millions of tonnes, in swarms that can pack tens of thousands of animals into a cubic metre of sea.
Q 24When a huge plankton bloom dies and rots, the decay uses up what in the water, leaving a 'dead zone'?
Oxygen
Oxygen. Fertiliser washed off farmland is the usual trigger, which is why a dead zone forms each summer off the mouth of the Mississippi, where fish must flee or suffocate.
Q 25Prochlorococcus, the smallest photosynthetic organism known, went unnoticed in the sea until the 1980s; what is it?
Bacterium
Bacterium, and probably the most abundant photosynthetic organism on Earth: tiny as each cell is, there are so many of them that together they do a large share of all the photosynthesis in the sea.
Q 26Which bacterium of the open sea, with its close relatives, is thought to be the most abundant on Earth?
Pelagibacter ubique
Pelagibacter ubique. It runs on one of the smallest genomes of any free-living cell, yet it and its relatives account for about a quarter of all the living cells in the ocean.
Q 27The largest animal migration on Earth, by weight, happens every night in the ocean, heading in which direction?
Up toward the surface
Up toward the surface. Countless small animals spend the day in the dark depths, hidden from predators, then rise after dusk to feed: a commute called diel vertical migration.
Q 28What is the plankton-driven ocean process that carries carbon from the atmosphere to the deep sea called?
The biological pump
The biological pump. Plankton take up carbon dioxide at the surface, and when they die or are eaten some of that carbon sinks, shifting roughly ten billion tonnes of it a year into the deep.
Q 29The remains of ancient plankton are the main raw material of which natural resource?
Crude oil
Crude oil. Dead plankton sank to ancient seabeds, were buried under sand and silt, and were slowly cooked by heat and pressure; coal, by contrast, began as the plants of swampy forests.
Q 30Foraminifera, or 'forams', are single-celled sea creatures with shells, whose Latin name means what?
Hole bearers
Hole bearers. The shells have openings, between their chambers and often through their walls, and the cell casts out a net of fine threads to catch its food.