To survive asteroid impact, algae learned to hunt

Night of the living algae




Tiny, seemingly harmless ocean plants survived the darkness of the asteroid strike that killed the dinosaurs by learning a ghoulish behavior — eating other living creatures.

Vast amounts of debris, soot, and aerosols shot into the atmosphere when an asteroid slammed into Earth 66 million years ago, plunging the planet into darkness, cooling the climate, and acidifying the oceans. Along with the dinosaurs on the land and giant reptiles in the ocean, the dominant species of marine algae were instantly wiped out — except for one rare type.

A team of scientists, including researchers at UC Riverside, wanted to understand how these algae managed to thrive while the mass extinction rippled throughout the rest of the global food chain.

“This event came closest to wiping out all multicellular life on this planet, at least in the ocean,” said UCR geologist and study co-author Andrew Ridgwell. “If you remove algae, which form the base of the food chain, everything else should die. We wanted to know how Earth’s oceans avoided that fate, and how our modern marine ecosystem re-evolved after such a catastrophe.”

To answer their questions, the team examined well-preserved fossils of the surviving algae and created detailed computer models to simulate the likely evolution of the algae’s feeding habits over time. Their findings are now published in the journal Science Advances.

According to Ridgwell, scientists were a bit lucky to find the nano-sized fossils in the first place. They were located in fast accumulating and high-clay-content sediments, which helped preserved them in the same way the La Brea tar pits provide a special environment to help preserve mammoths.

Most of the fossils had shields made of calcium carbonate, as well as holes in their shields. The holes indicate the presence of flagella — thin, tail-like structures that allow tiny organisms to swim.

“The only reason you need to move is to get your prey,” Ridgwell explained.

Modern relatives of the ancient algae also have chloroplasts, which enable them to use sunlight to make food from carbon dioxide and water. This ability to survive both by feeding on other organisms and through photosynthesis is called mixotrophy. Examples of the few land plants with this ability include Venus flytraps and sundews.

Researchers found that once the post-asteroid darkness cleared, these mixotrophic algae expanded from coastal shelf areas into the open ocean where they became a dominant life form for the next million years, helping to quickly rebuild the food chain. It also helped that larger creatures who would normally feed on these algae were initially absent in the post-extinction oceans.

“The results illustrate both the extreme adaptability of ocean plankton and their capacity to rapidly evolve, yet also, for plants with a generation time of just a single day, that you are always only a year of darkness away from extinction,” Ridgwell said.

Only much later did the algae evolve, losing the ability to eat other creatures and re-establishing themselves to become one of the dominant species of algae in today’s ocean.

“Mixotrophy was both the means of initial survival and then an advantage after the post-asteroid darkness lifted because of the abundant small pretty cells, likely survivor cyanobacteria,” Ridgwell said. “It is the ultimate Halloween story — when the lights go out, everyone starts eating each other.”


From EurekAlert!

57 thoughts on “To survive asteroid impact, algae learned to hunt

  1. A coastal algal lineage had already evolved heterotrophy. The catastrophe enabled their spread into the open ocean.

    So the Eureka Alert! headline, “learned to hunt” misrepresents the Science Advances paper.

  2. I are confoosed again. This piece seems to say that the algae were one of the few ocean based life forms remaining, but they also hunted other living creatures. What were the other living creatures? How did they survive the asteroid hit? What did those consumable life forms eat? Were they plants that did not require sunlight? Was there instead abundant sunlight in some parts of the oceans? Were the other living creatures consumed by the algae therefore go extinct?
    Too many unanswered questions remain.

    • Exactly! Did every single living thing is all the oceans of the Earth die from the asteroid impact? Surely this was not the case. Some land creatures must have survived as well. Also, ocean acidification caused by the impact? Local to the impact site off the Yucatan or world wide? So many questions!

    • You and I be very confoosed because this is a fiction story written by a compiuter maudel and the maudel runner did not dress it to see all other living criters that did survive. You see, he says, and I quaote the quote: “This event came closest to wiping out all multicellular life on this planet, at least in the ocean” which is a paleontologic absolute nonsense.

    • The paper says that the mixotrophic algae ate such other surviving unicells as cyanobacteria, thus forming a planktonic base for recovering food chains.

      The EurekAlert! article, as is so often the case, could be a lot more clear.

  3. … the asteroid strike that killed the dinosaurs …

    The dominant class of animals at the time and they ALL died but the arthropods, molluscs, fish, amphibians, reptiles, birds*, monotremes, marsupials and mammals all survived. That’s a very selective asteroid that did that. Disease could do that. I’ve posted this before here with some comments that the birds are dinosaurs and they’re still here. Birds aren’t dinosaurs just like we aren’t monkeys, but they descended from them and the earliest fossil is 130 million years old predating the 66 million year old asteroid hit.

    * A Deep Dive Into the Skeleton of the Oldest-Known Modern Bird

    • 90% of all life forms died, both on land and in the sea. No disease could do that.
      In any catastrophe, certain ecological niches survive better than others. When 90% die, the number of niches where survival was possible are few and far between. It’s not surprising that small omnivores had a better chance of survival than did other life forms.
      Beyond that, the evidence of an asteroid strike is irrefutable, as is the damage that such a strike would cause.

      • MarkW October 31, 2020 at 8:52 am
        90% of all life forms died,

        100% of dinosaurs died. That was one very selective asteroid.

        • Not 100% of dinosaurs, but close. Birds are dinosaurs. Most birds died out too, but a few ancestors of modern birds survived, such as waterfowl far from the impact point and small, seed-eating birds.

          • Birds evolved from dinosaurs 130 million years ago see the link in my post above. The asteroid was 66 million years ago. That’s a lot of time to become distinctly different.

          • All dinosaurs were evolving from the Late Jurassic to end of the Cretaceous, but they never stopped being dinosaurs. Most birds went extinct at the same time as their non-avian dino kin.

            Mammals also evovled a lot from the Jurassic to end Cretaceous, and many were also wiped out, but we’re all still mammals.

            Birds are, among many other clades, vertebrates, tetrapods, amniotes, reptiles (sauropsids), diapsids, archosaurs, avemetatarsalians, dinosaurs, saurischians, theropods, coelurosaurs and maniraptorans. Mammals are vertebrates, tetrapods, amniotes, synapsids and much else.

            Archaeopteryx not only sported teeth, a long bony tail, claws on all three, unfused fingers (still retained by a few birds today) and belly ribs, but the hyperextensible sickle claw on its second toe, characteristic of cinematic “raptors”. So, was it a dinosaur or a bird? Bear in mind that countless other dinosaurs also bore feathers and half-moon wrists. At what point did birds stop being dinosaurs?

            You can’t change your phylogeny.

          • Please permit me to be more specific as to avian traits.

            At what point, in your opinion, did birds stop being dinosaurs?

            When they lost their second toe sickle claws?

            When they evolved keeled sterna?

            When they evolved pygostyles, ie “parson’s noses”, short tails with fused vertebrae?

            When most of them fused their second and third fingers?

            When they lost their teeth?

            When they lost their ventral ribs?

            When they evolved the modern shoulder joint, opposite to the dominant Mesozoic “opposite birds”?

            Or at some other point in their evolution?


    • Yes, birds are dinosaurs, in technical cladistic phylogeny and objective reality.

      The English word “monkey” is not a valid taxon, since paraphyletic. “Ape” is however, since it refers to the monophyletic taxon including lesser and greater apes, and all their ancestors closer to them than to Old World Monkeys.. The Spanish word “mono” is valid, too, as is German “Affe”. “Mono” refers to New and Old World “monkeys” and apes. So does “Affe”, with apes distinguished as “Menschenaffe”. English blows it by having different words for “monkeys” and apes.

      Thus, in scientific nomenclature, apes, OWMs and NWMs are members of Infraorder Simiformes, sister clade to tarsiers, who like us suffer a broken vitamin C gene and are thus subject to scurvy. So humans aren’t “monkeys”, but we are apes and Catarrhini, ie Old World simians (or anthropoid primates). NWMs belong to Parvorder parvorder Platyrrhini.

        • But we are. Biology just uses scientific names in Greek and Latin, but the effect is the same.

          We aren’t fish in common parlance, but we are lobe-finned fish phylogenetically, ie sarcopterygians or crossopterygians. Our closest kin among “fish” are lungfish, which are practically amphibians. Lungfish and coelacanths are the only survivors, besides tetrapods, among all the many lobe-finned fish of yore.

          And again, the English word “fish” isn’t a valid taxon, since it applies both to shellfish and finny fish (vertebrates, or at least chordates, in the case of hagfish and lampreys).

          In cladistic phylogeny based on natural groups, you’re always a member of the higher taxon from which your ancestors emerged. So yes, all we tetrapods are still bony “fish” (Osteichthyes) of the lobe-finned school (so to speak) (Sarcopterygii).

    • Few bird species survived. The ratites split before 66M years ago and the two lines survived. Not tree dwellers would have helped. A diet of ground seeds might have helped. Anything that couldn’t eat hard shelled seeds died out?

  4. Back to Cuvier again? Last time that God as The Great Geological Catastrophist and God as The Great Creator worked was ca. 66 million years ago? Thus, never mind the “climate emergency”: when God The great Catastrophist will wake up again from His million years sleep, every form of life will be destroyed, climate change or no climate change…

    • Discovery of the dino-dooming impact had nothing to do with Cuvier and everything to do with the evidence.

      • My comment des not apply to dino-doom, it regards the paper in discussion. When (at least) one of the authors thinks that “This event came closest to wiping out all multicellular life on this planet, at least in the ocean”, what differentiates him from Cuvier, catastrphism and re-creationism? And (following your note), this assertion from (at least) one of the authors, what has it do do with palentological evidence?

        • The evidence to which I refer is for the fact of K/Pg extinction caused by ET impact.

          The authors are indeed wrong to argue that this MEE came closest to wiping out multicellular life, althoug it did a pretty good job.

          Cuvier did discover the fact of extinction, contrary to the Great Chain of Being, in which none of God’s perfect creations could ever go extinct. He also did propose catastrophes to explain the periodic loss of groups of living things in the geologic record, and in that general regard he wasn’t wrong.

          However ET impacts wasn’t one of the catastrophes which he imagined. He was uniformitarian in that he looked to the kinds of entirely terrestrial catastrophes observed in his time, such as floods and volcanic eruptions. He never referenced the Bible, but concluded that such catastrophes occurred at intervals of up to millions of years. He was on the right track, but of course Earth is not millions but billions of years old.

          Darwim got closer, with his estimate that Earth had to be at least hundreds of millions of years old, based upon his own region, the Weald, alone. In this biologists and geologists were right, and 19th century physicists (including Charles Darwin’s son) wrong.

    • Many vertebrates did survive, not just croc relatives and ancestors, snakes, lizards, turtles, even tuataras, but mammals as well. Being aquatic, burrowing or small increased survival rates, as did being far from the impact site, as was an Antarctic ancestor of waterfowl.

      In the oceans, ammonites were wiped out, but their nautiloid kin made it through the catastrophe.

  5. Hm diatoms move by adjusting their bouyancy to get back into the light when they get sucks too deeply due to ocean currents. Any chance algae might be moving to accomplish the same result?

  6. The mass extinction that ended the Cretaceous period was not the first or worst mass extinction in the Earth’s history. How did algae survive the earlier ones? Why was it only the Cretaceous extinction that taught algae to eat living creatures?

    In reality, algae, like fungus and mold, do not care if their nutrition source is alive or dead. Never did, methinks.

    • The other die offs may have had the same results on algae, we just don’t have the fossils to prove it. The further back you go, the harder it is to find fossils.
      Secondly, if you read the article you will see that the impact didn’t “teach” the algae anything, there was a certain type of algae, already existing, that was better adapted to a low sunlight world, and this form of algae became dominant for a period. After the sunlight returned, that type of algae went back to being a niche player.

    • Fungi aren’t autotrophic. They’re heterotrophs, like us animals, indeed much more closely related to us than to plants. Like us, they need the O2 released by photosynthetic organisms.

      Each mass extinction event was different. The Permian was the worst of the Phanerozoic Eon, but algae survived all five generally recognized MEEs of our present eon.

    • Since yet again my reply is lost in cyberspace, I’ll try once more with the short version.

      Fungi (including molds), unlike autotrophic algae, are, like animals, heterotrophs. With few exceptions, we can’t make our own food, and need the oxygen provided by photosynthesizing cyanobacteria, algae and plants.

  7. “The only reason you need to move is to get your prey,” Ridgwell explained. Have to look it up but I thought swimming stages might be interested in light. This is in their Implications section. “Although high extinction rates across the calcifying plankton could implicate acidification (7), all three major groups survived (nannoplankton, calcareous dinoflagellates, and planktonic foraminifera)…..Together, the selective loss of key open ocean photoautotrophs and prevalence of phagotophy in the surviving algal groups suggests that primary production was drastically disrupted by the K/Pg bolide impact, pointing to a complete cessation of all marine photosynthesis during peak impact darkness.” Heterotrophy could mean using organic compounds, phagotrophy suggests gobble, gobble. It is Halloweeen.

    • That “only reason to move is to get to your prey” statement is so nonsensical that I have to doubt this idiot is any kind of scientist.

  8. “K/PG or Cretacious Paleogence extinction event, refers to the aftermath of the asteroid hitting the Earth 66 million years ago.”

    It used to be the KT extinction event. Now it is the K/PG extinction event.

    Why do they keep changing the names? Inquiring minds want to know.

    Just when you finally memorize some meaningless combination of sounds they up and change it on you. Is it like some secret membership password in an exclusive club of experts where you reveal that you aren’t a member because you have the wrong password? Like Brontosaurus, which was once the proper name of a really big dinosaur, then was no longer the proper name of that really big dinosaur , and I understand is once again the proper name of that really big dinosaur. Gotcha! Ya gotta have the current password. Why not just call it “DAMNIT That’s one really big Dinosaur” and leave it at that for all time. Or the virus that is now causing so much trouble. First it was the Wahun virus, then the Corona virus, then the Covid virus and now it is the Covid 19 virus. (What happened to Covid 1 through 18?) Geeze, find a name already. Or the local high school football team. Since the beginning of time they were the “Niles West Indians.” Now they are called the Niles West Wolves. Is the word “Indian” suddenly a swear word? Meanwhile the competing “Niles North Vikings” are still the “Niles North Vikings.” Go figure.

      • Facts don’t change. Our understanding of facts may change. Our knowledge about what the facts are may change. Facts don’t change.

          • The bones are the facts. When one decides to change the species a bone belongs to because of new found bones, it is the understanding of the facts which is changing.
            But that bone keeps being the same bone with its same characteristics.

          • Disagree Mark: North America existed before Columbus “discovered” it. Just because Columbus didn’t know doesn’t mean it wasn’t there as a matter of fact.

            Just because someone discovers a dinosaur bone that no-one had seen before doesn’t mean that it never existed. Its existence is not a new fact. It was a recently discovered fact.

            If you are assembling a 1000 piece jigsaw puzzle and accidentally knock a piece to the floor does not change what the assembled picture should look like.

            Facts do not change. Our knowledge about facts changes.

    • As geology learned more about our present Cenozoic Era, the 18th century concept of the Tertiary needed to be amended. Tertiary and Quaternary are still used, the latter officially, while Primitive and Secondary aren’t.

    • COVID-19 is the name of the disease caused by a novel coronavirus first IDed in Wuhan, if not in fact evolved in the BSL-4 lab there from a SARS-related coronavirus found in an approximately 1000 mile-distant bat cave in Yunnan Province, whence came SARS-1.

  9. Crockett, A Narrative of the Life of David Crockett, p. 117-118: “We know’d that nothing more could happen to us if we went than if we staid, for it looked like it was to be starvation any way; we therefore determined to go on the old saying, root hog or die.”

  10. The University of California at Riverside “researchers” write, according to the above article:
    “Tiny, seemingly harmless ocean plants survived the darkness of the asteroid strike that killed the dinosaurs by learning a ghoulish behavior — eating other living creatures.”

    Just amazing! . . . I wonder where those ocean plants went to school back then and in what brain cells they stored their “learned” behavior.

    I was taught—many years ago when “institutes of higher learning” actually meant something—that there is a distinct difference between LEARNED behavior and behavior arising from evolutionary ADAPTATION.

    I guess all Earth’s slime algae will now be uprising against humans, having learned in the last 40 or so years that mankind is responsible for climate change™ that threatens their very existence.

    Fair warning . . . it will be worse than The Blob.

    • Even this sloppy writer probably understood such “learning” to result from selection or other evolutionary process, but, as I noted above, the fact is that coastal algae had already acquired heterotrophy via previous evolution, then the calamity allowed them to spread into the open ocean.

      • John
        I think there always were mixitrophic flagellates of many kinds (Chrysomonads, Euglenids, Volvocids, Dinoflagellates etc.) They just came into their own in the meteor aftermath where their lifestyle of photosynthesis and/or heterotrophy – eating bacteria – allowed them to survive the brief darkness then explode in the absence of competition.

        But it wasn’t only mixotrophs that survived. Coccolithophores originated in the early Triassic and reached peak abundance in the Cretaceous. They survived the Chixilub event and are still with us today. The white cliffs of Dover are a slice of coccolithophore cake.

        • Chrysomonads are protozoa. Euglenids are members of Excavata, most of which are heterotrophic, with the exception of euglenids, but in any case aren’t algae.

          Volvocids and dinoflagellates are indeed green algae. Mixotrophic algae are rare, but yes, they had already evolved before and survived the KPg MEE.

        • According to Wetzel 2001 (although he was talking about lakes)

          all the types I listed are both flagellates and mixotrophic. After a mass extinction the main thing was to be able to survive by being mixotropic, taxonomic category less important. They could plug a gap in primary production where needed. But as I mentioned I think Ridgewell and colleagues overstated the plankton extinctions, since many genera of diatoms, coccolithophores and foraminifera and others survived the end Cretaceous event.

          • Your probably right re. Ridgewell, et al.

            In any case, lots of plankton groups survived. Being able eat others surely helped get through any period of lowered sunlight.

    • John
      I think there always were mixitrophic flagellates of many kinds (Chrysomonads, Euglenids, Volvocids, Dinoflagellates etc.) They just came into their own in the meteor aftermath where their lifestyle of photosynthesis and/or heterotrophy – eating bacteria – allowed them to survive the brief darkness then explode in the absence of competition.

      But it wasn’t only mixotrophs that survived. Coccolithophores originated in the early Triassic and reached peak abundance in the Cretaceous. They survived the Chixilub event and are still with us today. The white cliffs of Dover are a slice of coccolithophore cake.

  11. “It is the ultimate Halloween story — when the lights go out, everyone starts eating each other.”

    That’ll be the democrats after Trump wins on Tuesday

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