Britta Culbertson: The Beat of the Bongo (Part 2) – Catching Zooplankton, September 12, 2013

NOAA Teacher at Sea
Britta Culbertson
Aboard NOAA Ship Oscar Dyson
September 4-19, 2013

Mission: Juvenile Walley Pollock and Forage Fish Survey
Geographical Area of Cruise: Gulf of Alaska
Date: Wednesday, September 12th, 2013

Weather Data from the Bridge (for Sept 12th, 2013 at 9:57 PM UTC):
Wind Speed: 23.05 kts
Air Temperature: 11.10 degrees C
Relative Humidity: 93%
Barometric Pressure: 1012.30 mb
Latitude: 58.73 N              Longitude: 151.13 W

Science and Technology Log

Humpback Whale
A humpback whale. (Photo credit: NOAA)

We have been seeing a lot of humpback whales lately on the cruise.  Humpback whales can weigh anywhere from 25-40 tons, are up to 60 feet in length, and consume tiny crustaceans, plankton, and small fish.  They can consume up to 3,000 pounds of these tiny creatures per day (Source: NOAA Fisheries).  Humpback whales are filter feeders and they filter these small organisms through baleen.  Baleen is made out of hard, flexible material and is rooted in the whale’s upper jaw.  The baleen is like a comb and allows the whale to filter plankton and small fish out of the water.

This whale baleen is used for filter feeding. It’s like a small comb and helps to filter zooplankton out of the water. (Photo credit: NOAA)

I’ve always wondered how whales can eat that much plankton! Three thousand pounds is a lot of plankton.  I guess I felt that way because I had never seen plankton in real-life and I didn’t have a concept of how abundant plankton is in the ocean. Now that I’m exposed to zooplankton every day, I’m beginning to get a sense of the diversity and abundance of zooplantkon.

In my last blog entry I explained how we use the bongo nets to capture zooplankton.  In this entry, I’ll describe some of the species that we find when clean out the codends of the net.  As you will see, there are a wide variety of zooplankton and though the actual abundance of zooplankton will not be measured until later, it is interesting to see how much we capture with nets that have 20 cm and 60 cm mouths and are towed for only 5-10 minutes at each location.  Whales have much larger mouths and feed for much longer than 10 minutes a day!

Cleaning the codends is fairly simple; we spray them down with a saltwater hose in the wet lab and dump the contents through a sieve with the same mesh size as the bongo net where the codend was attached.  The only time that this proves challenging is if there is a lot of algae, which clogs up the mesh and makes it hard to rinse the sample.  Also, the crab larvae that we find tend to hook their little legs into the sieve and resist being washed out.  Below are two images of 500 micrometer sieves with zooplankton in them.

A mix of zooplankton that we emptied out of the codend from the bongo.
Crab larvae
Crab larvae (megalopae) that we emptied out of the codend.

Some of the species of zooplankton we are finding include different types of:

  • Megalopae (crab larvae)
  • Amphipods
  • Euphausiid (krill)
  • Chaetognaths
  • Pteropods (shelled: Limasina and shell-less: Clione)
  • Copepods (Calanus spp., Neocalanus spp., and Metridea spp.)
  • Larval fish
  • Jellyfish
  • Ctenophores

The other day we had a sieve full of ctenophores, which are sometimes known as comb jellies because they possess rows of cilia down their sides.  The cilia are used to propel the ctenophores through the water.  Some ctenophores are bioluminescent.  Ctenophores are voracious predators, but lack stinging cells like jellyfish and corals. Instead they possess sticky cells that they use to trap predators (Source:  UC Berkeley).  Below is a picture of our 500 micrometer sieve full of ctenophores and below that is a close-up photo of a ctenophore.

A sieve full of ctenophores or comb jellies.
A type of ctenophore found in arctic waters. (Photo credit: Kevin Raskoff, MBARI, NOAA/OER)

It’s fun to compare what we find in the bongo nets to the type of organisms we find in the trawl at the same station.  We were curious about what some of the fish we were eating, so we dissected two of the Silver Salmon that we had found and in one of them, the stomach contents were entirely crab larvae! In another salmon that we dissected from a later haul, the stomach contents included a whole capelin fish.

Juvenile pollock are indiscriminate zooplanktivores.  That means that they will eat anything, but they prefer copepods and euphausiids, which have a high lipid (fat) content. Once the pollock get to be about 100 mm or greater in size, they switch from being zooplanktivores to being piscivorous. Piscivorous means “fish eater.”  I was surprised to hear that pollock sometimes eat each other.  Older pollock still eat zooplankton, but they are cannibalistic as well. Age one pollock will eat age zero pollock (those that haven’t had a first birthday yet), but the bigger threat to age zero pollock is the 2 year old and older cohorts of pollock.  Age zeros will eat small pollock larvae if they can find them.  Age zero pollock are also food for adult Pacific Cod and adult Arrowtooth Flounder.  Older pollock, Pacific Cod, and Arrowtooth Flounder are the most voracious predators of age 0 pollock.  Recently, in the Gulf of Alaska, Arrowtooth Flounder have increased in biomass (amount of biological material) and this has put a lot of pressure on the pollock population. Scientists are not yet sure why the biomass of Arrowtooth Flounder is increasing. (Source: Janet Duffy-Anderson – Chief Scientist aboard the Dyson and Alaska Fisheries Science Center).

The magnified images below, which I found online, are the same or similar to some of the species of zooplankton we have been catching in our bongo nets.  Click on the images for more details.

Personal Log (morning of September 14, 2013)

I’m thankful that last night we had calm seas and I was able to get a full eight hours of sleep without feeling like I was going to be thrown from my bed.  This morning we are headed toward the Kenai Peninsula, so I’m excited that we might get to see some amazing views of the Alaskan landscape.  The weather looks like it will improve and the winds have died down to about 14 knots this morning.  Last night’s shift caught an octopus in their trawl net; so hopefully, we will find something more interesting than just kelp and jellyfish in our trawls today.

Did You Know?

I mentioned that we had found some different types of pteropods in our bongo nets.  Pteropods are a main food source for North Pacific juvenile salmon and are eaten by many marine organisms from krill to whales.  There are two main varieties of pteropods; there are those with shells and those without.  Pteropods are sometimes called sea butterflies.

A close-up of Limacina helicina, a shelled pteropod or sea butterfly. (Photo credit: Russ Hopcroft/University of Alaska, Fairbanks)

Unfortunately, shelled pteropods are very susceptible to ocean acidification.  Scientists conducted an experiment in which they placed shelled pteropods in seawater with pH and carbonate levels that are projected for the year 2100.  In the image below, you can see that the shell dissolved slowly after 45 days.  If pteropods are at the bottom of the food chain, think of the implications of the loss of pteropods for the organisms that eat them!

Shelled pteropods after being exposed to sea water that has the anticipated carbonate and pH levels for the year 2100. Notice the degradation of the shell after 45 days. (Photo credit: David Liittschwager/National Geographic Stock)

Read more about ocean acidification on the NOAA’s Pacific Marine Environmental Laboratory (PMEL) website. Also, check out this press release from November 2012 by the British Antarctic Survey about the first evidence of ocean acidification affecting marine life in the Southern Ocean.

Teacher’s Corner

In my last blog entry on the bongo, I talked about using the “frying pan” or clinometer to measure wire angle.  If you’re interested in other applications of clinometers, there are instructions for making homemade clinometers here and there’s also a lesson plan from National Ocean Services Education about geographic positioning and the use of clinometers this website.

If you are interested in teaching your students about different types of plankton, here is a Plankton Wars lesson plan from NOAA and the Southeast Phytoplankton Monitoring Network, which helps students to understand how plankton stay afloat and how surface area plays a role in plankton survival.

If you would like to show your students time series visualizations of phytoplankton and zooplankton, go to NOAA’s COPEPODite website.

Zooplankton time series
Zooplankton time series visualization from the COPEPODite website.

For more plankton visualizations and data, check out NOAA’s National Marine Fisheries Service website.

If you are interested in having your students learn more about ocean acidification, there is a great ocean acidification module developed for the NOAA Ocean Data Education Project on the Data in the Classroom website.

20 Replies to “Britta Culbertson: The Beat of the Bongo (Part 2) – Catching Zooplankton, September 12, 2013”

  1. Britta,
    I am a student of Sue Cullumber and I was wondering how the ocean seems to be handling the global warming change. I was really curious also about why the sea butterfly is becoming so critical.

    1. Well, global climate change is a big issue and it has different impacts around the world. In some places, like Greenland it is both good and bad. For example, due to the warming climate, people in Greenland are now able to grow vegetables like potatoes (when they never could before). However, the ice sheet on Greenland is also melting, which could cause global sea level rise. So you can see it’s a complex problem. Some places flood and other places experience drought – extremes like this are bad.

      You mentioned the sea butterfly and that’s one example of how things in the ocean are affected by excess carbon in the atmosphere. The ocean is a carbon sink, which means it can take up carbon dioxide. However, when it does, it lowers the pH of the ocean by just a little, but it’s enough to effect shelled organisms like the pteropods and oysters. If pteropods are food for whales and salmon and the pteropods die…what do you think will eventually happen to the whales and salmon? Here’s an article from the Seattle Times that does a great job of explaining ocean acidification:

      Thanks for the question!

  2. Wow, that looks so cool! Thanks for telling us your progress on the Oscar Dyson! I’m very impressed with what you and your fellow fishers caught in those bongo nets! I’m especially impressed with the whales. 🙂

    1. Gabe,

      Thanks for your comments! Stay tuned for my next post, which has a photo of the Dall’s Porpoises that I saw yesterday. If you liked the whales, I think you’ll like these too.

  3. Thank you for the information. The world needs people who benefit the world of science, and somday with your reserch and the reserch of many others we might one day solve the excess of carbon in the ocean. I am a student in Sue Cullumber’s science class.

    1. Ed,
      Thanks for your comment! Our research doesn’t focus specifically on carbon in the ocean, however, if scientists notice a change in the population of fish and other species in the ocean, they can investigate what might be causing it. It is true that ocean acidification (from carbon in the atmosphere) is causing some changes that people can see happening now. However, we are just in the beginning stages of learning how ocean acidification might affect walleye pollock. There’s a neat article in the Seattle Times about ocean acidification if you are interested:

  4. How do you manage to get pictures of microscopic creatures with so much detail? Do you take pictures of the creatures in water or out of water?
    -Drew (From Sue Cullumber’s Class)

    1. Drew,
      I found those pictures on the internet, so I can’t take credit for them. There are scientists that work with NOAA who can take those microscopic images so that people can see the zooplankton in great detail. I’m not sure if they are in or out of water when they take the photos. When you look at the zooplankton with the naked eye, sometimes they are so small you can only see a little spot (like the pteropods) and sometimes they are quite large (like the krill). Russ Hopcroft is the scientist behind most of those photos. If you are interested, you can Google his name and probably find more! Thanks for your question!

  5. That is so interesting i would go crazy with the sea sickness i think what you are doing is awesome. the idea of being on the ocean kills me. good work and have a fun and amazing time 🙂

    matt damon
    sue cullumbers class

    1. Matt,
      The seasickness isn’t constant, which is good. For the past two days I have felt great and we have been cruising down the coast near Seward, Alaska. That close to the coast, the water is calm and nice. It was just at the beginning that was rough because we had so many storms. I guess sometimes a little suffering makes you appreciate the beauty in life. Like yesterday, I got to see the most beautiful glaciers that went almost down to the water. We also saw lots of whales and porpoises today. Pretty cool! Look for my next post, which will have some interesting pictures of fish! Thanks for the comment!

  6. This was all very interesting. In my opinion the coolest part of all of this was seeing the little jellyfish. They look like small transparent cookies. I am a student in Sue Cullumber’s Science class.

    1. Sam, I’m glad you enjoyed the blog! Be sure to check out all of the cool fish in the upcoming entry. I think the jellyfish are pretty cool too. But my favorite fish are probably the spiny lumpsuckers, which you will see in my next post. Thanks for your comment!

    1. I haven’t eaten any of it, but one of the scientists said that when she worked aboard a Japanese boat, they fried the krill and served it in the galley. The krill (euphausiids) look like miniature shrimp to me. I was thinking wasabi and soy sauce instead of cocktail sauce. Thanks Woody!

    1. There was a picture in the blog of what a dungeness crab larvae looks like (megalopae). The parts of the larvae are pretty hard to see with the naked eye, but they do have legs and little pincers. They are kind of clear with a little dark coloration in part. Thanks for your question Woody!

  7. Hello Britta C., I hope your doing well. I sawyour blog after my teacher Ms.Cullumber showed it to me and I had a quick question. What are the various stages of a zooplankton? such as there birth to adult hood. I had this question because I had noticed that some zooplankton start off small but can grow up to very large sizes. Also, I am another student from Sue Cullumbers class.

    1. Miguel,

      Thanks for your question! It is a great question, but it has a very lengthy answer. There are a lot of different kinds of zooplankton. As I pointed out in the blog, some zooplankton are the young stages of things like crabs and shrimp. Other zooplankton stay small forever! I’ll just focus on one type, which is my favorite, it’s the crab. First, the adult female crab lays eggs. Those eggs turn into something called zoea and then megalopae. After that, they become juvenile crabs and then adults. Here is a website that has a picture of this life cycle:

      Here is another website that talks about the wide variety of zooplankton:

      I hope that helps answer your question!


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