Arctic Sea Ice Ecology
The doings of creatures under the Arctic sea ice are many, but they are rarely observed by humans; it’s pretty hard to get under the ice to look. In recent years, marine biologist Andy Juhl and his colleagues have gotten around this problem by driving snowmobiles several miles from Point Barrow, Alaska, out onto the adjoining frozen Chukchi Sea, drilling holes in the four-foot-plus thick ice, and poking in a video camera attached to an small underwater vehicle.
Among the things that they have observed: sizable Chrysaora melanaster jellyfish floating by, trailing their foot-long-plus tentacles along the shallow bottom. Their presence came as a surprise: adult jellyfish, or medusae, are generally thought to live only a few months. Scientists had assumed that the species survived winter only in a life stage called polyps–formless masses that cling to rocks and release little baby medusae in the spring. In a scientific paper out this week, Juhl and colleagues say the videos indicate that the creatures in fact last through winter. They could even be several years old–the Methuselahs of medusae.
“One reason we were interested was, first of all, we saw them, and it was kind of weird,” said Juhl, a researcher at Columbia University’s Lamont-Doherty Earth Observatory. “The whole study is based on videos we made over several years.” Also, he says, the rich pollock fishery in the nearby Bering Sea is the engine for “everything fish”–fish sticks, fish paddies and other mystery-meat-type marine fast foods. But in some years, jellyfish numbers in the Bering Sea swell, and fishing nets can get seriously clogged–a problem that may crescendo over several years before dying back again. The study may reveal something about the jellyfish population dynamics that drive these cycles.
Juhl’s working hypothesis: cold winters, when sea ice is thick and long-lasting, are good for Chrysaora survival. He says the ice probably shields the medusae from turbulent winter storms, and the low water temperatures reduce their metabolism enough for them to subsist on relatively little food. “Life under sea ice is like living in a refrigerator–everything slows down,” he said. He said that jellyfish blooms may follow one or two years of heavy sea-ice cover because lots of adults survive.
Juhl points out that many other Arctic creatures also depend on sea ice. These range from lowly algae and bug-like amphipods that thrive on its underside to giant polar bears who roam around on top, waiting to pick off seals that emerge from breathing holes.
With Arctic climate warming and sea ice declining rapidly, what will happen to Chrysaora? Elsewhere in the world, including in the Mediterranean, other species of jellyfish are swarming and becoming pests, apparently in response to warmer waters, overfishing and coastal pollution. These forces are bad for other flora and fauna, but the resilient jellies often thrive, eventually taking over the ecosystem. In the far north, it could be the opposite; ice-loving jellies could decline if things warm up. So could the other, more iconic, creatures of the north that depend on sea ice. But at least jellyfish might not be clogging fishermen’s nets so much. “For most things, there are positives and negatives to climate change,” said Juhl.
One still unanswered question: Do these jellyfish sting? “I don’t know,” he said. “There aren’t that many people around there swimming to find out.”
Related: The Arctic’s Secret Garden
I returned to New York on Monday, but Lamont-Doherty Earth Observatory scientists Andy Juhl and Craig Aumack remain working in Barrow, Alaska for another week. They’ll continue to collect data and samples in a race against deteriorating Arctic sea ice conditions as the onset of summer causes the ice to thin and break up. Even in the two weeks I stayed in Barrow the ice changed dramatically, shifting from a snow-covered ice pack to a nearly snow-free ice pack, covered in cracks and increasingly large melt ponds. An animation from the May 23 Barrow sea ice radar reveals just how quickly shorefast sea ice can change. Soon the ice will be deemed unsafe for travel by snow machine and spring fieldwork conducted on the ice will end.
Our team’s research in Barrow is just one part in the long process of studying and answering questions about algae growing in and under Arctic sea ice and its role in the marine ecosystem. And, it’s a process that does not necessarily have a defined end — investigating the natural world always leads to more questions. From fieldwork, where observations are made and data gathered, new questions arise, new hypotheses are put forward and new ways of collecting data are developed. This work leads to further experiments where new data and samples are collected, observations are made, analyses performed and results interpreted. Some of the findings will challenge existing hypotheses, leading to their modification, which starts the research process over again.
Fieldwork gives scientists the opportunity to observe systems in a holistic way, leading to new insight and further research questions; each piece of data causes a rethinking of ideas and expectations for future results. “Fieldwork is inspiring and it’s critical to the creative process for environmental science because you often see things that you don’t necessarily see in your data,” said Andy. “There are subtleties and patterns that you can pick on if you pay attention to observe the natural world. You can’t do that in the lab or by looking at numbers.”
Some people may be disappointed to learn that we don’t have many immediate answers about sea ice algae and the Arctic ecosystem based on our month of Barrow fieldwork. But, scientists don’t set out to study things that are already understood or to answer questions that already have answers, and it takes time to unravel Earth’s mysteries. On this trip, project scientists discovered and collected lots of algae, observed novel behavior by marine organisms in the water column and on the seafloor, and gathered lots of data. The next steps in this project are to analyze the samples and data collected in Barrow, interpret these, write up findings and report these in journals and at scientific meetings. And, in 2014, Andy and Craig will return to Barrow to continue their study of sea ice algae, armed with new understanding of the algae, as well as new research questions to explore.
The goal of our project is to understand how ice algae functions and its role in the marine ecosystem, but we’ve received many questions about how ice algae, the residents of Barrow and the rest of life in the Arctic will be affected by a climate that is undoubtedly and irrevocably changing. The answer is that we don’t know, but our research may contribute to future understanding of these issues. Though the Arctic is changing faster than anywhere else on the planet, with temperature increasing and ice volume decreasing, it is still one of the least explored places on Earth. In order to know how climate change will impact this region, the basic oceanographic and ecological processes must first be understood.
As our project progresses, we’ll continue to provide updates and look forward to sharing a video of our time in Barrow that’s being produced by our friends at Climate Science TV. For more information on this research project, visit http://lifeintheice.wordpress.com. Our colleagues at Lamont-Doherty Earth Observatory also travel the world exploring our planet; to keep up with more interesting Earth science research and reports from the field, follow Lamont-Doherty on Twitter and Facebook.
And thanks to everyone who followed our expedition, we enjoyed sharing it with you!
It’s near midnight and Lamont-Doherty Earth Observatory researchers Andy Juhl and Craig Aumack, and Arizona State’s Kyle Kinzler are gathered around a table in their lab at the Barrow Arctic Research Consortium discussing the best way to catch an isopod. When scientists do fieldwork, they enter into it with specific questions and science goals in mind, but one of the joys of exploring the world through scientific research is solving challenges and devising new ways to collect data.
Meet Brinson. He’s a remotely operated vehicle (ROV) along on our Arctic expedition and named in honor of a foundation that provided Andy funding to build him. Brinson, originally designed and built by engineer Bob Martin, and modified by Andy, is the result of an idea that evolved over several years of Arctic fieldwork.
“We were deploying just this ice fishing camera, but were frustrated by the fact that there was always something just beyond our range that we wanted to see,” said Andy. “So we wanted mobility and once we got that we were frustrated by the fact that we didn’t know how big things were, and that’s when we decided we needed the laser pointers to provide scale. So Brinson has been a multi-step evolution into a simple, but well-equipped ROV.”
Brinson now consists of a GoPro camera and a standard ice fishing camera attached to a frame made of PVC pipe that can be lowered into a hole in the ice. On the ice surface, the ice fishing camera’s live video feed shows what Brinson sees as he travels through the water. Brinson is equipped with small bilge pumps that act as motors, which enable him to be maneuvered forward, up, down and side to side via his tethered remote control. When Brinson is below the ice, Craig monitors the video feed and describes to Andy what he sees on the screen. When something of interest appears, Craig tells Andy which way to maneuver Brinson, so they can continue to get footage of the organism.
Brinson recently saw small crustaceans called isopods roaming around the ocean floor. Andy and Craig were excited about this find and very curious to learn more about what isopods might eat and their role may be in Arctic the marine food web. Once Brinson, and Andy and Craig, saw the isopods, it was decided that our team should catch some, but we had no trap or means of doing so.
Scientists need to bring absolutely everything they need, and think they might need, with them on research expeditions, especially those to remote areas like Alaska’s North Slope. So, when, for example, you decide you must build an isopod trap late at night in Barrow, you’re pretty much limited to what you have on hand: a plastic buckets, plastic window screening, electrical tape, rocks, string.
With these materials, a little ingenuity and their limited knowledge of isopod behavior, Craig and Kyle constructed isopod traps. The guys hypothesized that isopods might like chicken, so baited their traps with chicken bones saved from our dinner. The traps were attached to eight meters of string and dropped to the sea floor. Kyle’s trap sat overnight and caught two isopods; Craig’s trap sat on the ocean bottom for several days and contained at least 20 isopods when it was pulled up.
The beauty of the isopod traps is that they worked and project scientists will get valuable data about the Arctic marine food web as a result. “From the underwater videos shot by Brinson, it looks like the activity of the isopods increases after the ice algae exports,” Andy explained. “We think there’s a plausible connection there: the ice algae could be a food source for isopods. We never would have posed that as a hypothesis unless we had the opportunity to observe them and make these connections.”
Fieldwork is, in part, a pattern of observing and questioning, and responding to these with new theories, methods and experiments. It’s also part of a larger creative process that involves improvisation and unconventional thinking. Said Andy, “In the field, we make a lot of stuff out of duct tape and epoxy.”
One of the goals of Andy Juhl’s and Craig Aumack’s Arctic research is to determine the role of ice algae as a source of nutrition for food webs existing in the water column and at the bottom of the Arctic ocean. During their fieldwork these Lamont-Doherty Earth Observatory scientists are deploying a plankton net, a common tool used by ocean scientists to catch tiny marine plants and animals in the water column, to collect live plankton for identification and examination in the lab. They’re hoping to determine the different kinds of organisms active in this part of the Arctic Ocean and their food web feeding connections, or who’s eating whom by testing the organisms to see if they contain algae in their guts and muscle tissues.
This information is important because it will provide a baseline understanding of the connection between the algal community in the sea ice and the underlying ecosystem, and how it functions. Once this is understood, scientists may be able to better understand and predict changes that could occur in the marine food web as Arctic snow and ice cover changes.
A few days ago we caught the comb jellies in this video near shore at a depth of about four meters. Though comb jellies have the same type of gelatinous body as a jellyfish, they belong to a completely different phylum called ctenophores. Known for being vicious carnivorous predators, ctenophores use rows of comb-like cilia to propel themselves through the top of the water column and prey on smaller organisms, such as zooplankton. Ctenophores are found throughout the world’s oceans, including Arctic waters — quite a few of appeared in the holes we’ve bored into the ice this week.
These two comb jellies were filmed under a microscope in our lab. Each one is just a few millimeters long, though they can grow to be about 10 cm, sometimes larger. You can also see small copepods, a type of zooplankton and favorite food of ctenophores, zipping around the screen. Seeing a lot of ctenophores in the upper water column is a good indicator that they are feeding extensively on copepod larvae, who in turn are feeding on ice algae. This is an example of a few of the connections that make up the foundation of the food web in this fragile, yet biologically productive ecosystem.
On Wednesday Andy and Craig answered responded to questions about their research during a Reddit “Ask Me Anything” session. While the event is over, the session remains on Reddit and we encourage you to check it out to learn about our research and life in Barrow, Alaska.
Our team spent most of Friday on the Arctic sea ice, drilling and sampling ice cores at our main field site. For each core collected, Lamont-Doherty Earth Observatory scientists Andy Juhl and Craig Aumack take a number of different physical, chemical and biological measurements that characterize the ice and the organisms living inside it. Some of these measurements are recorded right away in the field, others will be taken later using pieces of the cores that we bring back to the lab.
Two of the physical measurements Andy and Craig record are the temperature and salinity of the ice. “Temperature is a critical parameter that controls the rate of almost all biological processes in the ice — almost everything happens slower when it’s colder, and parts of the ice can be colder than others. And if you know the temperature and the bulk salinity of the ice you can calculate how much brine volume there is within a given layer in the ice,” Andy explained.
Brine volume is an important measurement because algae live in brine channels in the ice. As ice gets colder, there’s less brine volume within it, meaning there’s less room for algae to grow. Andy and Craig also measure the concentrations of plant nutrients in the ice cores, including nitrate, ammonia, phosphate and silicate – some of the same elements that plants growing on land need. And, as with terrestrial plants, nutrient availability in sea ice is a factor that controls the growth of algae inside the ice.
Other measurements, such as particulate organic carbon (POC) and dissolved organic carbon (DOC), Andy and Craig take in the lab will reveal the amount of carbon, or organic material in the ice. In addition to algae, carbon found in the ice comes in the form of non-living materials, such as bits of organic detritus from the tundra that become trapped in the ice. Finally, samples are collected for microscope work so that project scientists can identify the different types of organisms found throughout the ice.
All of this information varies in any single ice core from the top to the bottom, and based on where it is drilled. By taking consistent measurements from each ice core in different locations, project scientists can develop an in-depth understanding of the dynamics of the Arctic algal ice ecosystem – and how it may be changing.
Our group spent Saturday and Sunday in the lab processing samples from last week and preparing equipment, including mounting a camera system on our small remotely operated vehicle (ROV). We’re heading back onto the ice early Monday morning with the ROV and are looking forward to working in temperatures that may reach 35F.
On Thursday we lowered a camera into an ice borehole to get a look at the underside of the ice. In the following video, you can clearly see the algae living in the bottom of the ice due to their pigments, which they use to harvest light.
These organisms are not frozen into the ice; they’re living creatures that grow and thrive in tiny pockets of brine inside the ice. You might notice in the video that the underside of the ice is not flat, this is probably a reflection of variability in physical conditions in and above the ice, such as snow cover thickness.
While watching this video, Andy Juhl and I discussed how cool it is that there are vibrant communities growing in extreme environments. “One of the lessons that research in polar regions has taught us is that we need to broaden our definition of where life exists and thrives. In the Arctic, we have life growing inside ice, at below freezing temperatures. This means that we know to look in more unusual places for science of life and that’s one of the interesting things we learn by doing this kind of work,” Andy said. “Ice is not necessarily an inhospitable habitat, and on other planets where we see ice, that’s a place where we should probably look for signs of life.”
The second film shows a bit of life on the seafloor. This video was shot near shore where the water depth is about 8 meters, so it’s fairly shallow; water temperature here is -2C. The bottom consists of soft mud and it looks like there are deposits of algae that probably came from the ice on the surface of the bottom (those are the darker areas). There’s a variety of bottom dwelling organisms that live in the mud, such as the isopod that wanders across the mud in this clip. We don’t yet know how large the isopods are or what they eat; scientists on our team are trying to figure out a way to measure an isopod in situ or capture one to examine in the lab.
As our work in Barrow progresses, we’ll continue to post more videos so that you can get a sense of the life that makes up this fascinating ecosystem.
Fieldwork is exciting and inspiring, leading scientists to new ideas, places and observations about how the world works. Spring on Alaska’s North Slope provides an especially productive environment for fieldwork. When the sun never sets, it’s easy to linger in the field and the lab long into the well-lit night.
Our team spent about six hours on the Arctic sea ice Thursday, enjoying blue skies and temperatures in the low teens, while making observations, maintaining sampling sites and taking measurements. Most of our time was spent at two different field sites Andy and Craig established near Point Barrow, a narrow spit of land that’s the northernmost point in the United States. Traveling to these sites involves loading up two sleds with all of the sampling equipment, hitching the sleds to snowmobiles and carefully traversing the sea ice on said snowmobiles, which, I discovered today, is extremely fun.
One of the research questions Andy and Craig are exploring in Barrow is how the amount of snow covering sea ice might affect the diverse species of algae living in and just below the ice. A thin snow cover allows more sunlight to reach the algae; a thicker snow cover creates a darker environment. As in any ecosystem, many different species are competing for light and nutrients. For this study, Andy and Craig want to see how changing one factor in the Arctic sea ice ecosystem – the amount of available light – might allow some organisms to grow better and become more prevalent than others.
Last week Andy and Craig set up an artificial snow gradient at our first field site, where different snow depths cover the ice in a small, isolated area. Ice cores were drilled here on their first day and Andy and Craig will repeat this same exercise later in May. Collecting data over these specific time intervals will enable them to see how snow depth and distribution affect the community of organisms living in the ice. This information will provide an idea of what might happen to the entire ecosystem if more light is introduced via less snow cover in the future.
At the second field site, scientists used an auger to drill a hole in the ice, which is currently about four feet thick. Then a camera was lowered into the hole, with a live feed to a computer so we could see what was happening in the sea directly below us. A thick layer of algae covered the underside of the sea ice and once lowered eight meters to the sea floor, the camera revealed isopods (small crustaceans), jellyfish and a few unrecognizable members of the Arctic marine ecosystem.
“We do the camera work because there’s no substitute for seeing the ecosystem intact. We need to get cores in order to collect samples, but you get a really different impression of the ecosystem with the camera,“ Andy explained.
Later in the afternoon we searched the ice for a sampling station Andy and Craig used last year, but were unable to find it. The area had become covered with huge pressure ridges, large fragments of ice that pile up when sheets of ice collide, which are hard to cross on a snowmobile. At one point fresh polar bear tracks meandered among the ridges, but we never caught sight of the bear who made them.
While I arrived in Barrow, Alaska on Tuesday, Lamont-Doherty Earth Observatory scientists Andy Juhl and Craig Aumack, and graduate student Kyle Kinzler from Arizona State University, got here one week ago. They took a few days to unpack and set up their lab (everything they need to work here must be shipped to Barrow in advance), scout locations for sampling on the ice and ensure that their tools and equipment are working properly before they begin their fieldwork.
Our team alternates days in the lab and days on the ice. The lab space we’re using is a bit north of town at the Barrow Arctic Research Center (BARC), a newly constructed facility where the National Science Foundation leases space for its researchers. Scientists wishing to work in and around Barrow can use BARC as their home base. At the moment the building is fairly quiet as the only other occupants are a group of international graduate students being trained on how to conduct sea ice research.
Today was a lab day, where recently collected samples were processed, experiments performed and preliminary data analyzed. Fieldwork is just the beginning of a research process that can take several years. The majority of the samples and data collected here won’t be examined until scientists are back at their respective institutes, where it can take months or longer to analyze all of their samples and data and then write up the results. But, to ensure that their research is on the right track, a few experiments and analyses are done while in Barrow.
This afternoon I spent time in a zero degree walk-in freezer talking with Craig Aumack, who’s conducting experiments to learn more about the organisms living in Arctic sea ice. Each year, as soon as any light is available, algae start growing in the ice and continue to bloom through the onset of spring and the Arctic’s long summer days. Algae prefer to live in the bottom of the ice, because, like all plants, they need light and nutrients, and these are plentiful at the sea-ice interface.
Craig’s experiments are called settling experiments, and these help him learn what happens to the organic materials and organisms living in the sea ice when they’re released into the ocean. Craig wants to determine the rate at which these particles sink down through the water column; this information reveals whether particles are more likely to be consumed while falling through the water column or once they accumulate on the seafloor. Particles that sink slowly are more likely to be eaten by zooplankton, tiny marine animals, while those that fall to the bottom will be consumed by worms, crustaceans and mollusks.
Settling experiments must be done in a freezer because organisms that call ice home would quickly die if exposed to a 70-degree temperature difference. Though extreme temperatures can also cause humans to become a bit uncomfortable, we’re able to don parkas and puffy jackets to protect us; algae don’t have this luxury. So, Craig replicates the conditions in which ice algae thrive, and bundled up, works in a frigid environment.
Andy Juhl was happy to explain this experiment and their research further, fortunately outside of the freezer. “There’s a whole ecosystem living inside the ice. Ultimately, we want to know what the dynamics of this special ecosystem are and how this is connected to the rest of Arctic ecosystem,” he said.
“We know the Arctic is changing very rapidly in terms of ice cover, duration of ice cover and extent of ice cover. One of the things we need to understand if we’re going to try to predict what will happen to the Arctic in the future is the ice ecosystem and its importance to the functioning of the entire Arctic,” Andy said.
Tomorrow, Thursday, we head out onto the ice to sample. This afternoon I received my land use permit from the Ukpeaġvik Iñupiat Corporation, the organization that owns the land we’ll be working on, and successfully completed my snowmobile training, so I’m officially ready for fieldwork.
Andy Juhl and Craig Aumack, microbiologists from Columbia University’s Lamont-Doherty Earth Observatory, are spending a month in Barrow, Alaska studying algae in and below sea ice, and how our warming climate may impact these important organisms. They’re investigating the factors that control the growth of algae inside of sea ice, how these algal communities are connected to other Arctic marine organisms and what happens to the organic matter that builds up inside sea ice. I’ve joined them to document and tell stories about their research, how it’s done, why and what they’re learning.
Barrow is the northernmost point in the United States and is situated where the Chukchi Sea meets the Beaufort Sea. Throughout the long winter, these waters are covered with a thick layer of ice. This ice is home to many different microscopic algae, which form the base of the polar food web.
During late winter and spring, large communities of these algae flourish, or bloom, inside and on the undersurface of the sea ice. As the ice melts, algae are released into the nutrient rich waters, feeding plankton and higher trophic levels, including fish, whales and seals.
The Arctic is warming faster than any other place on the planet, shortening winter and causing pack ice to thin and break up earlier and earlier each year. How will these changes impact the Arctic marine food web? Answering this question and understanding how the ice algae respond to our warming climate will inform resource managers and policymakers, as well as local residents, of how the larger Arctic marine ecosystem may be impacted.
Andy and Craig hope to learn how our fast-warming climate and the resulting dissipation of sea ice affect the entire marine food web. This knowledge is essential to assessing the value of the ice community in the Arctic and is paramount to predicting ecosystem-wide consequences to rapidly changing Arctic environments.
We’re based at the UMIAQ field station in Barrow, which provides logistics support for NSF-funded scientists conducting research in the area. From Barrow, we’ll travel across the sea ice by snowmobile to nearby Point Barrow, where we’ll establish sampling stations and drill and remove cores of ice. Samples will be analyzed back in the lab to investigate the flux of the algal organisms and organic matter from the sea ice to the water column during the spring melt.
Over the next few weeks we’ll share stories from the ice about our research, the role sea ice algae play in Arctic ecosystems and how that’s changing, and what’s it’s like to live at the top of the planet. And, if we’re lucky, a few pictures of whales and polar bears.