Fat vs. thin copepods: What is happening to the Arctic?
Is ice melting really a threat to the Arctic? This question was addressed by Maria Gavrilo, Ph.D. in biology, deputy director for science at the Russian Arctic National Park and a member of 40 ship-borne, airborne, pedestrian and stationary expeditions to the Arctic undertaken during 30 field seasons from Spitsbergen and the White Sea to the Chukchi Sea and the Arctic basin.
A small Antarctic
Things are not as simple as the layperson is used to thinking. There is the belief that the Arctic has a warm climate now, the ice has melted and the polar bears have died. Not at all! Changes are more unpredictable.
There is less ice in summer: that's a fact. At our request, the Arctic and Antarctic Research Institute is monitoring the situation and provides sea ice statistics for the national park area. The data confirm that the summer ice cover is shrinking; there is less ice than there was 30 or 50 years ago.
Apart from forming an ecosystem of its own and largely influencing the life of the surrounding sea, ice protects the coast. The shores have become exposed to sea storms and are eroded by waves, with garbage drifting towards Franz Josef Land.
I visited the archipelago for the first time in 1992. From 2009 on, I have been working there every year. What I can say is that there was no plastic on the shore before that year. Now the coastline on several islands is thick with fishing nets, plastic bottles and crates. There is not a single island where there is no plastic. Thus, totally unexpected changes are occurring, not simply what may come to mind first.
Franz Josef Land is a microcosm apart. A Soviet geographer, Leonid Govorukha, was the first to call FJL the Small Antarctic. FJL is an archipelago and it has no closed external borders. But when we started analyzing its phytoplankton, zooplankton and fishes, it became clear that despite the openness of the sea, the FJL shelf is a semi-closed system with a complicated and practically unexplored water circulation pattern. The depths between certain islands reach 600 meters. The area is washed by water from the Arctic basin and the cold Kara Sea, as well as by warm water from the Atlantic and the Barents Sea. The deep warm Atlantic water comes from the north rather than from the south. Moreover, FJL water is reference oceanic water, the salt content of which is the same as that of oceanic water unaffected by coastal runoff.
Our hydrobiological research led to the discovery of serious changes compared with the investigations conducted 30 or 40 years ago. Specifically, many soft bottom sediments, as we call them, appeared in the coastal zone; rocky ground is being covered with silt deposits. In all evidence, this is the consequence of sea ice shrinking and more active melting of glaciers. Suspended matter is washed into the sea, where it settles on the bottom and changes the habitats of organisms in this environment.
Will the thin copepod change the world?
Scientists use a system of indicators to monitor change in the natural environment. These consist of animals or plants that are sensitive to change and are convenient to observe. In the Arctic, we have chosen the little auk, a small bird weighing about as much as a stick of butter, which feeds on plankton crustaceans. Above all it prefers copepods (Calanus).
Each year we catch little auks, and the food bolus they are bringing to their young tells us what crustaceans are prevalent in the surrounding sea (this food sampling is harmless for the birds). Its composition helps us to understand what water masses and ice conditions were like that year. Little auks pick up food that is most accessible and abundant. When there is a lot of sea ice, certain species of crustaceans prevail. As soon as ice recedes, the zooplankton community undergoes a change.
Different Calanus species keep to different types of water masses. There is a crustacean that prefers warmer Atlantic water without ice. Another one likes cold Arctic waters with ice. Still another prefers more open Arctic oceanic waters. The first crustacean is smaller, the second is larger and fatter, and the third one is even bigger than the second.
The little auks are a machine of sorts that gathers invertebrates. They prefer what is fatter and more beneficial in terms of energy. In a climatic norm, their main food is the Calanus glacialis, the second crustacean from the list.
The problem outlined by researchers is the warming of the ocean and the northward and eastward migration of the fat Calanus. Simultaneously, the little auks' habitat is receiving water with communities of Calanus finmarchicus, a small and thin crustacean. It was assumed that it would be more difficult for the birds to survive because they would have to expend more energy to catch less calorific crustaceans.
The indicator of a bird's wellbeing in summer is the average number of chicks a bird couple can fly with and the weight of a chick as it leaves the nest. We compared the research from the 1990s with that from 2013, when by the end of the summer, the ice edge had receded 200 kilometers north from FJL. Although the chicks' diet was different, their fatness was the same. True, the parents were somewhat lighter. The ice receded, fatty food was in small supply, but the less calorific crustaceans that arrived as a replacement were easier to catch in ice-free water. Moreover, they could be caught closer to "home" (their nesting ground) and the birds did not have to dive as deeply, which ultimately proved more beneficial in terms of energy.
One more point: the sea ice receded; glaciers started to melt more intensively with fresh-water rivers running from them into the sea. Local fronts spring up in the sea, when lighter and warmer fresh water meets with heavier and colder salty sea water. Vertical mixing takes place in the frontal zone, with biogens rising from the bottom and some nutrients coming from the shore. All of this helps to increase bioproductivity. Moreover, declining water salinity is a salt-bearing shock for sea invertebrates. They lose mobility or perish and thus become easy prey.
A theory-based hypothesis does not always take into account all details. The birds have found a new nutrient niche and managed to grow progeny as effectively.
There are species that pose a real danger. One of these is crabs. In the 1960s, Kamchatka crabs were deliberately resettled from the Far East to the White Sea and the Barents Sea. Today their expansion is immense.
They circumvented the Kola Peninsula, the Scandinavian Peninsula, and reached Norway — almost as far as the Lofoten Islands. In the East, they migrated as far as the Kara Sea. The species is highly aggressive and squeezes out or devours certain local species in the marine ecosystem.
The snow crab was brought to the Barents Sea by chance, but it also began to proliferate and migrate to the north and the east. The warming climate is also a factor in the expansion of these species.
My park's task is to monitor the expansion of these and other resettled species. Their arrival to wildlife sanctuaries may trigger a realignment of the local ecosystem.
How to catch a bird with a geolocator
If something happens to birds in the Arctic, then one fine day people living in Africa, for example, will not see the year's arrival of seagulls or sandpipers to their local lake. Birds link the Arctic with the rest of the world. A classic example is the Arctic tern, which nests on FJL, among other places, and winters in the Antarctic.
Our colleagues from Greenland were the first to attach miniature sensors to Arctic terns and to learn how they flew. The trajectory proved far from direct. During its lifetime — and Arctic sea birds live as long as 30 years — an Arctic tern covers three distances to the Moon and back.
We must know what is happening with the birds in all periods of the annual cycle, particularly when they are in the open sea.
Seatrack is one of the projects we have been implementing since 2013. It covers the northeastern Atlantic: Iceland, Svalbard, Britain, the Faeroes, the Scandinavian Peninsula, the White Sea and Novaya Zemlya. There are over 20 points in all, where the project is being handled by eight countries. Thanks to this project, we will know where and how the birds that proliferate in our specially protected area fly after nesting and what territories are used for feeding, passage and wintering.
For that, we outfit birds with geolocators, a simple sensor that records time and lighting. These data make it possible to calculate a bird's coordinates. The device is fairly cheap — about $200 each. But to obtain the data, you have to catch a bird with the sensor one year later. The risks are high: the bird may never come back, or it may settle in a different place; we might overlook it, or fail to catch it, or the instrument may be out of order.
The choice of birds for the project is not accidental. All of them feed differently: on invertebrates or fish, from the water surface or in the depths, near the shore or on the high seas. On FJL we work with kittiwakes and guillemots, little auks and burgomasters. They are indicators of different parts of the marine ecosystem and the data we collect will help to assess the state of health of the ocean as a whole.
FJL is, on the one hand, little explored, but when you compare the archipelago with Novaya Zemlya, Severnaya Zemlya or the New Siberian Islands, you discover that it has been studied to a greater extent than all others. Nevertheless, we are increasingly certain, as we explore FJL, that new discoveries are possible in the Arctic.
Vera Kostamo, RIA Novosti staff writer