[MUSIC] Hi, everybody. My name is Carin Karen Ashjian. I'm a senior scientist at the Woods Hole Oceanographic Institution. I'm in the biology department. I'm a biological oceanographer and I've spent much of my career studying polar regions both the Arctic, and the Antarctic. Since the mid-81990s, I've been working in the Arctic Ocean. I'm going to start by introducing you to Arctic marine life. This schematic is a slice of the Arctic Ocean with the sea ice on the top and the Arctic Ocean, the water below. You'll recognize a couple of very familiar organisms or animals in this picture. The polar bear, the seal and the walrus and then we have a whale underneath the sea ice. But there are other organisms in the picture as well and I'm going to walk you through the Arctic food chain to show you who they are. First, we have the algae. These are the plants, ice algae that live on the underside of the sea ice and the phytoplankton that live in the water column. The algae fix carbon dioxide into organic carbon using photosynthesis and they require light and nutrients to do so. The algae, both ice algae and phytoplankton are in the eaten by the zooplankton. The zooplankton in turn are eaten by larger zooplankton. The zooplankton are also eaten by the bowhead whale, which filters the zooplankton out of the water using baleen which is in their mouth and also by the arctic cod which are very small fish to live underneath the sea ice. The arctic cod is important pray for the seals that ive on the sea ice throughout the Arctic Ocean. The benthos are the animals that live on the sea floor are eaten by the walrus that also live on the sea ice. The walrus don't live in the middle of the Arctic Ocean, because they would have to dive to several thousand meters depth in order to get their benthic food. But they're very common in Arctic shelves, especially in the Western Arctic in the Chukchi sea near Alaska. And the walrus and the seals are both prey items for the very large top predator in the Arctic, the polar bear. This is not a quite complete diagram. I don't have the bacteria or the viruses or the seabirds and probably some other organisms on there as well, but it gives you an idea of what the Arctic ecosystem looks like. Because some of these animals and plants are so small, I thought it would be interesting to show you some pictures of what they look like. On the left, we see phytoplankton. These are single-celled alga plants that live in the water column. They're often found in chains such as seen in the photographs here. These photographs were taken using a microscope. You can't really see them with the naked eye. On the right, you see a number of different microzooplankton. These are very small zooplankton that also that feed on phytoplankton using the appendages that you see sticking out the ciliates and the the flagella and they use those to grab the phytoplankton and stuff the food into their mouth, then we have the zooplankton. This is my favorite part, because I actually studies zooplankton. On the top row, we see copepods which are very common in the world ocean everywhere on the very important in the Arctic Ocean. They're eaten by the arctic cod as I mentioned before. On the right, you see what they look like when you're looking at them in a microscope. You can see how beautiful they are. On the lower panel, we see on the left, we see something that looks like a shrimp. That's a euphausiid, which is a bit larger than a copepod. They're also eaten by bowhead whales, then we have a coldoserin and a couple of pelagic mollusks seen in the bottom row. You can see the shell on one of them. This is an animal that lives in the water column, but has a shell similar to a snail, then let's look at the sea floor. These four photographs show the animals that live on the sea floor. On the top left, we see a picture of what the sea floor looks like. This was taken by a camera dangling from a research vessel in the Bering Sea. You can see there's some crabs and also some funny looking little tubes. Those tubes are the tombs in which these arrow bristle worms, the arrow worms live in there a type of a polychaete worm. And in the next picture, you can see one of those tubes taken with a picture taken from the side and the bristles are the tentacles sticking out of the tube of this worm and it's trying to get particles that are in the water of above and bring it back in and eat them. The bottom left, we see basket stars. These are quite large and this is a huge pile of when that was collected using a benthic dredge from the Coast Guard Cutter Healy. And on the bottom right, we see what a polychaete worm looks like when it's not hiding in the sediment. So that was a brief introduction to some of the animals that live in the Arctic Ocean and the plants. Now, moving on to what determines their distributions. Physical drivers strongly influence the Arctic ecosystem. By physical drivers, I mean, currents which carry heat, nutrients and organisms throughout the Arctic Ocean and also in and out of the Arctic Ocean. Sea ice cover. Sea ice is very, very important including its extent which is how much area it covers, its thickness and how much snow it has on it. Environmental seasonality is also very important. Light is extremely seasonal in the Arctic. During the summer, light is present 24 hours a day. During the winter is not present at all, it's total darkness. Air temperature also varies seasonally in the Arctic, because there's no light to warm the air. And finally, we can look at water temperature. Water temperature is important, because many of these organisms have rate processes, such as growth and reproduction that get faster in warmer temperature. Also, some of them can't tolerate really warm temperatures and would not be able to survive, because they're adaptive to live in the very cold water of the Arctic Ocean. Some of the biological responses that we see as a result of these physical drivers are primary production, which is the rate at which the plants in ice algae photosynthesize and fix organic carbon dioxide into organic carbon. We also see changes and the ranges of the organisms where they're found in the Arctic Ocean. How far to the north are they found? How far to the South can be found? And we also look for changes in the structure of food webs. So thinking back to that schematic at the beginning of my talk, which animals are going to be very important? Which ones are not? Who's going to eat who? And all this will feed into sustaining the upper level predators, such as the seals and the polar bears. So as I said before, sea ice is extremely seasonal. It's also extremely important and this movie is going to demonstrate to you what the sea ice cover does over three years, 2016 to 2019 over each of the months of the year. And you can see that during the winter, sea ice is it quite extensive extends out of the central Arctic all the way down along the coast of Greenland and due to the Bering Sea. But during the summertime, they would reach in which sea ice cover is present constricts to the only the central Arctic. So there are regions that lose the sea ice during the summertime. The ecosystem cycles are time to the seasonality in the sea ice cover and the availability of sunlight. This schematic is showing us a year in the life of a spot in the Arctic Ocean where sea ice disappears during the summer and you can see January's on the left, and December is on the right. During the winter months, January February and November and December, there is no sunlight at all. Sun does not rise. You have very thick sea ice and you have a nice snow cover on top of the ice. Then when the Sun starts to reappear in March and into April, you start seeing some sunlight and you start to see the sea ice become thinner and the snow beginning to melt on top of the ice. In the middle of the summer, sunlight is present 24 hours a day. At this spot in the ocean, the sea ice has melted. And so you have no sea ice. When the Sun starts to come back, you start to see the growth of ice algae on the underside of the ice as the light is able to get through the ice which is gotten thinner and also the snow has melted. Then when you get light actually entering into the top part of the ocean, you start to see the phytoplankton grow and they can grow throughout the summer as long as they have enough nutrients to sustain them. At the end of the summer, the Sun starts to decrease in the number of hours a day that its present and also in its intensity. At this time, the phytoplankton will stop growing. The ice will start to get thicker again. And as you move into the fall, you start to get snow cover building up on top of the ice and then you move back into winter. So that's the seasonal cycle in light and in the availability of plant food for the animals. So many of the animals that live in the water of the Arctic Ocean are very well-evolved to take advantage of the seasonal cycle. Their life cycles correspond very well to this seasonal cycle and light, and sea ice. We see a diagram describing the life cycle of one of my favorite animals, the copepod and euphausiid. Again, across at the top, we see the seasonal cycle in light and in snow cover on the ice and in ice. And blow in the water column, we can see the life cycle of this animal. This animal has 14 life stages. It is hatched as a net from an egg and it molds through the different life stages, sort of like insects won't through different life stages. And in fact, it's related. It's a crustacean, but we're going to start the story of its life cycle in the winter time. At this time of the year, it is basically a teenager. It's in a stage what we call C4 and it spends the winter deeper in the water in a kind of hibernation that we call diapause. When light starts to come back in the spring, the animal swims back up in the water column and develops into adult females and males. And at this time, the females and start to eat the ice algae. And based on this food that they're getting, they lay eggs. The eggs then hatch and developed through a number of life stages, and they are eating the phytoplankton that's grown in the water during the summer months. They need that phytoplankton in order to be able to grow. So it's very important that they're developing through these different life stages when food is available. By the time fall comes around. We hope that the copepod has reached that adolescent stage again of a C4. And at that time, they will go back into their hibernation stage. They go down in the water column and they rest as a C4 and then reduced metabolic rate until next spring comes back around. So looking to the future, how can we protect, conserve and manage Arctic marine ecosystems? First, we need to increase our understanding. We need to understand how these ecosystems work. The ecosystems in the central Arctic Ocean are chronically understudied, particularly with respect to seasonal cycles such as during the winter. Historically, it's been very difficult to do studies in the central Arctic Ocean, because it's so hard to get there in the winter time. It's cold. It's dark. It's dangerous and it's very difficult to get there. We also need to do simultaneous sampling over broad spacious scales. So as far as the seasonal cycles go the, Mosaic project which is ongoing right now is going to give us another window into how things work in the central Arctic Ocean. We also need to be able to detect change. Detecting change is usually done by comparing historic conditions with present day conditions. Unfortunately, this is kind of difficult for us, because we don't have a lot of long-term information from the Arctic. Some regions are particularly poorly studied. So it's very hard to detect change. So we need to improve our ability to be able to do that. We also need to limit the anthropogenic introduction of alien species. Alien, meaning, species that are not native to the Arctic Ocean and an example of how of what I'm talking about would be the introduction of subarctic species in ballast water or even temperate species in ballast water. And an example something like this as it has happened is the invasion in the Great Lakes of the United States by zebra mussels and also the Chinese carp. These came in probably in ballast water and now are extremely numerous, and are outcompeting the native species in those waters. And finally, we need to base the management of our ecosystems or fisheries on ecosystem understanding, including understanding of a harvest of all resources and on protection of critical habitats. Regions where some organisms will not survive, unless that habitat is protected.
