Covered in sea ice, enveloped in darkness, buffeted by howling winds, beset by frigid temperatures. Cold, dark, icy, and stormy…what motivates us to leave our cozy lives at home and embark on a 40 day cruise into this inhospitable place? The Arctic Ocean in winter remains a mystery in many ways. Our goal is to explore the early winter ocean conditions, biological, physical, and chemical, in the Bering, Chukchi, and Beaufort Seas to better understand what happens there during winter.
Our overall objectives are to collect some of the first winter information on the overwintering physical and biological characteristics of three important Arctic Seas: The Bering Sea, the Chukchi Sea, and the Beaufort Sea. The Arctic system is undergoing significant changes related to a warming climate, most notably decreased sea ice cover, which may have significant impacts on Arctic ecosystems. Our understanding of seasonality, and of winter conditions and biological and physical processes during that time, in the Arctic is severely limited because it has been so difficult to access these winter seas. In particular, understanding of the overwintering strategies of one of the dominant copepod genera, Calanus spp., is not well understood but is critical to ecosystem modeling efforts. This lack of knowledge has compromised our ability to model and to predict future states of Arctic ecosystems, efforts that are central to our ability to understand the potential impacts of ongoing climate change.
Copepods are small crustacean plankton (6-10 mm or smaller) and are important components of the oceanic food web. They eat phytoplankton (plant plankton), ice algae (algae growing on or under ice), and microzooplankton (zooplankton smaller than copepods) and in turn are eaten by larger crustaceans, jellyfish, fish, sea birds, and marine mammals such as the bowhead whale. One of the more important copepod types in terms of overall biomass are species of the genus Calanus. Calanus spp. follow a life history, or life cycle, in which they spend the summer, productive months near the surface of the ocean feeding on phytoplankton and microzooplankton and then migrate to deeper water (~100-200 m) to overwinter in a type of hibernation called diapause. We know that Calanus spp. found in other parts of the world ocean, such as the northwest Atlantic, can only diapause in the deep water; they are not found on the shallow continental shelves. But what happens on the vast expanses of the Bering and Chukchi Seas? These shelves are too shallow for Calanus spp. to diapause, according to what we believe about their life history. We are also interested in understanding how euphausiids, or krill, overwinter. Krill are larger than copepods and resemble shrimp. They also are important links in the Arctic food web and provide food for upper trophic levels.
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| Four species of Arctic copepods. The first three are obvious; the fourth (Oithona similis) is very small and located just at the end of the antenna of the second copepod in from the left. Large copepods; Metridia longa (left), Calanus glacialis (middle), Calanus hyperboreus (right). C. hyperboreus is about 10 mm long or as long as a grain of long-grained rice. |
We are embarking on a 6-week cruise to the Bering, Chukchi, and Beaufort Seas on USCGC Healy. We leave Seward AK on Nov. 7 and we return to Dutch Harbor AK on Dec. 17, 2011. We have identified a set of key transects in the various cross-shelf-slope regimes along which we will conduct physical (hydrography, circulation), chemical (nutrients, dissolved organic matter), and biological (zooplankton, microzooplankton, chlorophyll, marine bird and mammal) sampling (see map of our proposed station locations). Our objectives include describing the hydrography, circulation and aspects of the planktonic, nutrient, and dissolved organic matter environments environments, describe the transformation of water types during formation of sea ice, identifying the overwintering habitat of Calanus spp. and overwintering strategies of phytoplankton, determining the condition and activity (respiration) of Calanus spp., euphausiids, bacteria, and phytoplankton, describing the interconnectedness between species/populations of Calanus and euphausiids in these regions and quantifying the course- and fine-scale vertical distributions of plankton and particles in relation to the vertical structure of the water column.
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| Locations where we plan to sample during the cruise (red dots). We might not be able to get to all of these spots. |
