Listening for Echoes of Krill

Today we went out to search for krill with Dr. Kim Bernard of Oregon State University and Shenandoah Raycroft, her assistant. Krill are an important stepping stone in Antarctic food chains because they eat tiny phytoplankton and then become food for almost all the large Antarctic animals including penguins, seals, and whales. Dr. Bernard and Raycroft use a machine called an echosounder to detect krill in the waters around Palmer Station.

Dr. Bernard set out to sample two areas based on tips she’d received from the radar team and the penguin team. The penguin team had noticed Adelie penguins were staying close to their colony on Torgersen Island, possibly meaning there were krill in those waters. The radar team had noticed an area of light currents near Cormorant Island that might also hold krill. This ability to quickly see data in the field and respond to what it’s telling them is called adaptive sampling, and it’s a major strength of the CONVERGE project.

Read through the slideshow to find out more about how Dr. Bernard’s team measures krill, and then check the bottom of the post to see some of their results:

Euphausia superbaHeading Out With Mrs. ChippyKriller in ChiefEchosounder at WorkSix Hours of DrivingDefender of the EchosounderKrill Suspect Number OneHeading Home With a Boat Full of Data

After the team got back to Palmer Station they analyzed the data they had collected. The result was a plot like the one below that shows the readings that the echosounder recorded. The graph shows time on the horizontal axis and depth on the vertical axis.


To read the graph, you just have to imagine yourself in a boat sailing across the top of the image. The echosounder is sensing what’s beneath it—brighter colors mean the echo was louder, which means the object was more dense. That’s why the water appears white (no color) and the rocky seafloor appears red (the brightest color). Those two blue clouds are more dense than water and less dense than rock—they’re groups of krill.

Dr. Bernard analyzed the group on the right and found it contained about 180 pounds of krill stretched over an area 200 feet long and 20 feet high. At less than 0.04 ounces per krill that means, very roughly, there might have been 80,000 krill or more in that one group. Even so, Dr. Bernard said that today was a relatively slow day for a krill survey.

So what does a big krill day look like? When I asked Dr. Bernard this, she pulled up a graph from Dec. 23, 2011. Here it is:


You can read this graph just like the one above—look at the huge swath of greenish-blue covering most of the right half of the image above the seafloor! The greenish color is brighter than the blue, meaning that the krill are even more densely packed in these areas. And what about that circular white patch in the middle of the cloud of krill? Dr. Bernard said whales were swimming around the boat while they did this survey. She thinks that one had come through this spot with its mouth open just before the zodiac got there.

In the end, there weren’t large groups of krill near Torgersen or Cormorant Islands today. Dr. Bernard and Dr. Kohut think this may be because of the tidal currents that are happening during this part of the month. We’ll tell you more about that possibility in a post next week. Tomorrow, we’re going to go explore some penguin colonies.

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  1. Remy Hebert January 9, 2015 at 10:16 am #

    I think the pictures are super interesting. Thank you for letting me be a part of this experience!

  2. Trevor Kosa January 9, 2015 at 10:20 am #

    I like this website a lot.

  3. Charles January 9, 2015 at 10:35 am #

    This is cool, thank you for letting us be a part of this

  4. Gabe Lebeau January 9, 2015 at 12:14 pm #

    The pictures are amazing!!

  5. Ms. McBride January 9, 2015 at 1:09 pm #

    Thank you for all the information and pictures about your research. We are enjoying learning about this exciting project, and we appreciate the opportunity to take part in this research.

  6. Angela Rose Quinn January 9, 2015 at 1:31 pm #

    How do you know the difference between a female krill and a male krill?

    • Hugh Powell January 15, 2015 at 2:36 pm #

      Hi Angela, Great question—krill are so unusual looking by human standards that it’s hard to imagine what could be different about males and females. I asked Tracy Shaw, who has been studying krill for more than 20 years—she can tell the difference right away. The one in the picture on this post is a male, and Shaw could tell by looking at the first pair of swimming legs (those are the big legs that start about halfway along the krill’s body). If you look at that first pair of legs, she said, you’ll see a thickened, dark stripe of tissue extending from the last joint of the leg and pointing almost straight down. As the krill gets ready to spawn, that’s going to thicken into something called a petasma, shaped like a paddle or a baseball mitt, that only males have. Normally you’d use a dissecting microscope to be sure, Shaw told me. But after so many years looking at krill, she can pick out the differences with her naked eye. Thanks for asking and I hope you learn to identify krill yourself someday! – Hugh

  7. Gillian Nadler January 9, 2015 at 1:34 pm #

    The pictures were educational and cool to look at.

  8. Samantha Davis January 9, 2015 at 1:35 pm #

    The pictures where very interesting. I liked the point of view some of the pictures where taken at and how the pictures showed how you collected data.

  9. Jakob Green January 9, 2015 at 1:36 pm #


  10. Carson Donnelly-Fine January 9, 2015 at 1:37 pm #

    Krill are very minuscule in size and stature. It makes me wonder about their brain capacity. The fact that something so small is so important in the arctic ecosystem is really amazing.

  11. Yannick Ibrahim January 9, 2015 at 1:37 pm #

    nice pictures

  12. Amir Moon January 9, 2015 at 4:13 pm #

    This seems like a lot of fun!

  13. Pat Hester-Fearon January 9, 2015 at 7:06 pm #

    Dr. Bernard,
    Thank you for sharing your information regarding echosounder recorded readings – my 8th graders were interested in your use false color on the graph, and we spent a lot of time discussing why you gave us information about data you collected in 2011. Lincoln Middle School students in Kearny are truly enjoying this project Converge experience. THANK YOU!!!
    Pat Hester-Fearon

    • Hugh Powell January 10, 2015 at 1:12 am #

      Hi Pat – Thanks for reading our blog and sharing it with your students! The graph from 2011 is just used as an example of a day when there were lots of krill in the water. Sorry if this was confusing—it was just intended as a contrast to the relatively small amount of krill that Dr. Bernard found during the day that we posted. When I asked her about what a “big krill day” looked like, she immediately thought of this huge day in 2011 and gave me the data. Thanks for asking, and I hope this helps – Hugh

  14. not bob the builder January 9, 2015 at 7:07 pm #

    why did u resech on krill. why not adeli penguins or chinstrap

    • Hugh Powell January 10, 2015 at 4:18 pm #

      Hi – The CONVERGE project has teams doing research on several different levels of the Antarctic ecosystem. So while Dr. Bernard studies krill, there’s another team that is studying Adelie and gentoo penguins. See today’s post for more about the penguins And keep following the blog—we’ll feature much more about penguins in the coming days! Thanks – Hugh

  15. Alissa January 11, 2015 at 2:09 pm #

    This is amazing learning about all the new things and finding out about the animals and everything. I really appreciate learning the new things about Antarctica and seeing all these amazing pictures!

  16. Lindsey January 12, 2015 at 10:00 pm #

    I am one of Ms. Hester-Fearon’s eighth grade students and I wanted to know if the Krill population were to decrease, would the whales and other animals that live in Antarctica and rely on Krill for food have a “backup” food source that can still provide them with the necessary nutrients for sustaining life?

    • Hugh Powell January 13, 2015 at 10:46 am #

      Hi Lindsey – In Antarctic waters, krill are a major part of the ecosystem. There are other food sources, including small fish known as silverfish. Penguins eat these fish in some parts of Antarctica, although the penguin team’s studies show that Adelie penguins eat almost no fish around Palmer Station. Right now there’s not really a “backup” food source that could support so many large animals. If krill were to decrease, it would have a major effect on penguins, seals, and whales. It’s possible that another small animal would take krill’s place and become numerous, but this would probably still cause a shift in the balance of large animals that we’d see. This is a great question and one that ecologists think about all the time. Thanks for asking – Hugh

  17. Alissa January 13, 2015 at 6:59 pm #

    Hi I’m one of Mrs.Hester-Fearon’s 8th grade students. I am wondering, how does the krill make the noises they do? Does it attract other animals when they make the noise or is it a call for mating like it is for penguins? Thank you so much for doing the blog for us. This is really amazing and I hope you guys will be safe on this trip.

    • Hugh Powell January 14, 2015 at 6:57 pm #

      Hi Alissa – I asked krill biologist Tracy Shaw, and she said krill don’t really make any noises at all. The title of this post, “Listening for Echoes of Krill” may have made you think that the krill are making noises. But what it’s talking about is the sounds made by the echosounder instrument. This instrument sends out very high-pitched pings through the water. The pings bounce off objects in the water to make an echo. The echosounder listens for these, and that’s how it makes a map of where krill are. So, the echosounder is both listening for the echoes and making the sound to begin with. I hope this answers your question – thanks for asking! – Hugh

  18. GabZ January 14, 2015 at 3:41 pm #

    i would like to know: how do zoo plankan effect penguin foraging. thank you for your time to consider this quetsion

    • Hugh Powell January 17, 2015 at 5:15 pm #

      Hi GabZ – I asked your question to Dr. Kim Bernard, who leads the krill team. She said that the way zooplankton affect penguin foraging is by influencing where they go. “Penguins are going to go foraging where zooplankton are,” she said. “So if we can understand where the krill are and why they’re there then we can get a better idea of where the penguins go to forage and why. if the krill are far away, it’s going to take penguins longer to get there, most of the food will be digested by the time they get back. If the krill are closer to shore, penguins will make faster foraging trips.” Thanks for asking – Hugh

  19. Jennifer January 14, 2015 at 3:59 pm #

    Do the penguins affect the krill population? If so by how much? -Jennifer

    • Hugh Powell January 17, 2015 at 5:12 pm #

      Hi Jennifer – Good question. I asked Dr. Kim Bernard, the leader of the krill team. She said that penguins do eat a lot of krill, but probably not enough to significantly affect the entire krill population. The whales that also feed on krill around Palmer Station have a much larger effect, she said.

  20. Tiago January 16, 2015 at 1:19 pm #

    can krill make any noises in the water? If you can plz comment my question thank you. Mrs Hester-Fearons student.

    • Hugh Powell January 16, 2015 at 7:29 pm #

      Hi Tiago – I asked this question to Tracy Shaw, a krill biologist. She said that krill do not make any noises at all. Thanks for asking – Hugh

  21. AnnaMarie January 16, 2015 at 5:21 pm #

    I am one of Mrs. Hester-Fearon’s 8th grade students. I would like to know: Is measuring krill a simple or tough task for Dr. Bernard’s team to successfully complete? Thank you for reading my comment, it is a pleasure reading your Mission Blogs and learning new things!

    • Hugh Powell January 17, 2015 at 4:58 pm #

      Hi AnnaMarie – I asked your question to Dr. Kim Bernard, who leads the krill sampling team. Here’s what she said: “It depends on the weather. On really calm sunny days it’s easy. It still takes a long time but you don’t get as cold. If it’s windy and wet—snowy or raining—it can be tough. You get really cold. Normally i can’t feel my toes after the first couple of hours and then i still have to be out there for another five hours! In terms of the actual work, it’s simple when it’s calm. It’s a bit more tricky when there’s a lot of sea ice or waves. You have to watch what you’re doing because you don’t want to hit the instruments with the ice.” Thanks for your question – Hugh

  22. Dev M January 16, 2015 at 6:03 pm #

    Hi I’m a student of Mrs HesterFearon. I wanted to know than one krill has been lost and that krill is so far away that krill could not find his route to go to their home?Then how could krill communicate with the krill’s?

    • Hugh Powell January 16, 2015 at 7:08 pm #

      Hi Dev – That’s a fun question. I asked krill biologist Tracy Shaw, and she said that krill don’t really have a home. They move around looking for food (phytoplankton) and/or water of a certain temperature. They tend to gather together into groups when they find these conditions, but they don’t communicate with each other to do it. Thanks for asking – Hugh

  23. Brianne O. January 19, 2015 at 3:02 pm #

    Hi, my name is Brianne. I’m one of Mrs. Hester-Fearon’s 8th grade students. I have a question: I read an article a while ago about iron compounds that are in waters under glaciers in Antarctica. I was wondering, have you found any iron compounds in the waters where you have found krill? And if you have, do you know if the iron compounds affect the krill or the chlorophyll concentration in the water or ice? Also, have you found any interesting bacteria in the ice or waters? Thank you for being out there and answering questions to help us! Stay safe and have an adventure!

    • Hugh Powell January 22, 2015 at 7:20 pm #

      Hi Brianne – those are spectacular questions! You should be an oceanographer. You’re right, scientists do think that iron compounds from dust in icebergs and melting glaciers help to create phytoplankton blooms and fuel ecosystems. There’s probably iron in the waters around here, since we are very close to land and to melting glaciers and icebergs. However, we haven’t measured it as part of this project. It’s very difficult to measure iron because it occurs in very, very small concentrations in seawater. There’s so little of it that you have to take extremely careful precautions when you test for iron to make sure you don’t contaminate the sample with iron from your body, clothes, or equipment. Iron compounds definitely do affect chlorophyll concentrations, because iron is a key ingredient in the chlorophyll molecule. When there’s not enough iron in the water, phytoplankton simply can’t grow because they can’t make chlorophyll. And if phytoplankton can’t grow, then krill don’t have anything to eat. To answer your final question, there probably are bacteria in the water, but we aren’t sampling for those, either. Thanks again for your great questions, and I hope you find these answers helpful. – Hugh

  24. Stacy January 19, 2015 at 7:26 pm #

    I am one of Mrs. Hester Fearons students, I would like to know if its hard to locate krill.

    • Hugh Powell January 22, 2015 at 5:47 pm #

      Hi Stacy – I asked Dr. Kim Bernard this question; she’s the leader of the krill team and she goes out almost every day to find krill. Here’s what she said: “It depends on the weather. On really calm sunny days it’s easy. It still takes a long time but you don’t get as cold. If it’s windy, snowy, or raining it can be tough. You get really cold – normally i can’t feel my toes after the first couple of hours and then i still have to be out there for another five. In terms of the actual work, it’s simple when it’s calm. It’s a bit more tricky when there’s a lot of sea ice or waves, You have to watch what you’re doing because you don’t want to hit the instruments with the ice.” Thanks for asking – Hugh

  25. Helder January 20, 2015 at 1:07 pm #

    Hello I am in Mrs. Hester-Fearon’s eigth grade class. i would like to know if the echosounder can miss an object in the water. Thank you and be safe.

    • Hugh Powell January 22, 2015 at 9:25 am #

      Hi Helder – Yes, it’s possible for the echosounder to miss objects in the water. It works by listening for high-pitched sound bouncing off of hard things like krill or other animals. So the softer an animal is, the harder it is for the echosounder to pick up—it has a hard time with jellyfish, for example. Even when it “hears’ an object, the echosounder can’t tell you exactly what the object is. It takes some skill and experience for a biologist like Dr. Bernard to figure out what’s down there. Thanks for asking – Hugh

  26. Keven January 20, 2015 at 1:26 pm #

    Hi my name is Keven. I am a student of Mrs. Hesterfearon and I want to know if you guys can locate krills far from where you are.

    • Hugh Powell January 22, 2015 at 9:22 am #

      Hi Keven – the echosounder can locate krill as deep as 250 meters (825 feet) below it. That’s pretty far, but only straight down beneath the boat. The echosounder can’t locate krill out in front of or behind the boat—that’s why they have to drive the zodiac in a long winding route around the waters here. Thanks for asking – Hugh

  27. Fatiyah January 26, 2015 at 1:44 pm #

    Hello my name is Fatiyah I am a student at Rivera Middle school in Ternton NJ I am interested in the krill. Is hard to find krill without the Echosounder?

    • Hugh Powell January 26, 2015 at 8:10 pm #

      Hi Fatiyah – It is pretty hard for humans to find krill without an echosounder. For some reason whales and penguins don’t seem to have that problem—but to us, unless the krill are right at the surface, the water looks pretty much the same whether it has krill in it or not. Thanks for asking – Hugh

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