Plankton are incredibly diverse and important beings even though they are some of the smallest ones on earth. They are found in our water and air, and they greatly contribute to the food chain. However, there is a fair amount of confusion about what are plankton and the individual creatures that fall under that umbrella term. That’s why we’re going to spend some time looking at plankton vs. krill.
We’ll show you where krill fits into the discussion about plankton, including how they are alike and what makes them different. By the time we have finished, you’ll know how to tell these two beings apart.
Comparing Plankton vs. Krill
|Size||Weight: Less than an ounce|
Length: Most often less than 1 inch, but they can grow several feet
|Weight: Less than an ounce|
Length: Most measure between 0.4 and 0.8 inches, but some measure up to 2.4 inches
|Phylogenetic Family||– Include 20,000 species in 8 taxonomic groups||– Families Euphausiidae and Bentheuphausiidae |
– 11 different genera and dozens of species
– Considered a type of zooplankton, especially in their larval form
|Diet||– Phytoplankton rely on photosynthesis and also absorb valuable nutrients from their environment |
– Zooplankton consume phytoplankton, bacteria, and algae
|– Eat algae, phytoplankton, zooplankton, copepods, and fish larvae|
|Locomotion||– None |
– Float with the current
|– Propel themselves with a swimming motion|
|Predators||– Whales, zooplankton, salmon, crustaceans, coral, sharks, and many other creatures in the oceans||– Whales, various seabirds, seals, and squid |
– Considered one of the most significant creatures in the ocean food chain
The 5 Key Differences Between Plankton and Krill
The most significant differences between plankton and krill can be found in their size and phylogenetic families. All krill are plankton, but not all plankton are considered krill. Krill are small, shrimp-like creatures that come from two phylogenetic families, Euphausiidae and Bentheuphausiidae. Meanwhile, over 20,000 species from eight taxonomic groups exist in the world, representing far more families and genera than krill.
However, krill are larger than many types of plankton. The average krill measures between 0.4 and 0.8 inches, but some of the largest measure 2.4 inches long or more. Many types of plankton weigh less than an ounce and grow less than an inch in length.
Jellyfish are gelatinous zooplankton that drift in the ocean with limited locomotion and can reach several feet long. Thus, while some sorts of plankton are larger than krill, a vast number of them are smaller.
Plankton vs. Krill: Phylogenetic Family
Generally speaking, plankton comprises small organisms that cannot propel themselves against a current. That can apply to creatures at a short period of time in their lifecycle, like fish eggs or krill larvae, or it can apply to creatures throughout the course of their lifecycle.
In fact, over 20,000 species across eight taxonomic groups can be considered plankton. Plankton are incredibly diverse. Krill are less diverse. Only two families and 11 different genera of creatures are considered krill. Specifically, krill come from the Euphausiidae and Bentheuphausiidae families, but they are considered plankton in their larval forms.
Plankton vs. Krill: Size
Several types of plankton are larger than krill, but most of them are smaller. The average krill measures between 0.4 and 0.8 inches in length. Although some of them can grow over two inches long, it’s not their average size. For the most part, they weigh less than an ounce.
Most types of plankton weigh less than an ounce. Some of them can weigh far more than that, like jellyfish. Also, while many sorts of plankton measure less than one inch long, some of them can grow several feet long! So, it’s fair to say that you can find plankton longer than krill, but most krill are still larger than the average plankter.
Plankton vs. Krill: Diet
Juvenile krill are a form of zooplankton, and they feed on algae, phytoplankton, other zooplankton, fish larvae, and other foods. Meanwhile, plankton has a more diverse diet. Phytoplankton, small plants, use photosynthesis to produce energy. They can also absorb some nutrients from their environment.
Some zooplankton have similar diets to krill, and they also consume bacteria, algae, and more. All in all, krill have a similar diet to other zooplankton since they are very similar creatures.
Plankton vs. Krill: Locomotion
One of the defining features of plankton is that it cannot propel itself against a current. However, that is not the case with adult krill, and that is why they’re sometimes considered micro-nektonic creatures rather than plankton.
Adult krill can use their swimmerets to propel themselves to a degree. Still, they are only capable of propelling themselves against a weak current. However, even when massive groups of them form, they are still subject to powerful ocean currents.
Plankton vs. Krill: Predators
Plankton and krill are both important members of the food chain. Phytoplankton are eaten by zooplankton, like krill, and those zooplankton grow to become a major source of food for larger creatures, like fish.
Also, some filter-feeding animals, like baleen whales, consume vast amounts of zooplankton, especially krill, to sustain themselves. Krill are considered some of the most significant creatures in the oceanic food chain, sustaining small and large creatures alike.
All told, plankton and krill have similar features. That’s mostly because krill have many plankton-like qualities. Although krill have some similarities to plankton, they also consume plankton. Major differences are found in their size, locomotion, and phylogenetic families, and those are the simplest ways to tell one from another.
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- Nature, Available here: https://www.nature.com/articles/s41467-019-12668-7
- NOAA Fisheries, Available here: https://oceanservice.noaa.gov/facts/plankton.html#:~:text=Plankton%20are%20usually%20microscopic%2C%20often,like%20some%20crustaceans%20and%20jellyfish.
- Commission for the Conservation of Antarctic Marine Living Resources, Available here: https://www.ccamlr.org/en/fisheries/krill-%E2%80%93-biology-ecology-and-fishing#:~:text=Why%20are%20krill%20so%20important,primary%20production%20within%20their%20range.
- Harvard, Available here: https://ui.adsabs.harvard.edu/abs/2019APS..DFDC27003C/abstract