UNDERSTANDING ECOSYSTEM PROCESSES IN THE BERING SEA 2007–2013

Bering Sea Ice LIFE IN THE FREEZER While life in association with sea concentrations of algae within helped support the food webs in the ice has been studied for hundreds of these layers that exceeded water water column and at the seafloor. years in many Arctic and Antarctic column phytoplankton concentra- regions, very little information had tions by a factor of 100 to more How We Did It been gathered from the Bering Sea. than 1,000 from mid-March to the During expeditions in spring 2008, This is surprising, as the Bering end of June. The total amount of 2009, and 2010 we sampled dozens Sea has the largest seasonal sea ice plant biomass within the bottom of different ice floes (Figure 2), at extent of any Arctic region. Our 10 cm of the ice is about the same various locations, for the sea ice group focused on the biological as for the phytoplankton integrated algal abundance and growth rates. activity within the sea ice, trying to over the upper 20 m of the water Sea ice samples were taken with understand the amount and fate of column. During the ice covered a specialized ice corer (Figure 3). primary production contributed by period, pelagic crustaceans, mainly Back on the ship, ice cores were tiny algae living within the sea ice. the euphausiid Thysanoessa raschii melted and the melted samples were We discovered that each spring (sometimes known as Arctic krill) is analyzed for concentration of algal vast amounts of sea ice algae accu- likely ingesting sea ice algal mate- pigments, mainly chlorophyll a. mulate in highly concentrated rial. With the onset of ice melt, We compared these data to the algal thin bottom layers of the sea ice the ice algal biomass was rapidly development below the sea ice by floes (Figure 1), and we observed released into the water column and continued on page 2

Fig. 1 The Big Picture The Bering Sea supports an incredibly rich marine ecosystem with a wealth of marine resources exploited by commer- cial and subsistence harvests. Change in ocean conditions, including sea ice characteristics, impact the functioning of marine systems. To enable predictions on future scenarios, we need to understand the interplay between the current system components like fish, birds, plankton, sea floor, and sea ice plant and animal life. Our project provides one of the building blocks to understand how the Bering Sea Vertical distribution of ice algal pigments in an ice floe collected in the Bering Sea. The ice was 50 cm thick, ecosystem functions and how it might and the highest algal pigment concentrations occurred in the bottom 2 cm of the ice floe. Water column change in the future. phytoplankton concentrations at the same locations were two orders of magnitude lower.

SEA ICE ALGAE, A MAJOR FOOD SOURCE FOR HERBIVOROUS PLANKTON AND BENTHOS IN THE EASTERN BERING SEA A component of the BEST-BSIERP Bering Sea Project, funded by the National Science Foundation and the North Pacific Research Board with in-kind support from participants. Fig. 2 R. Gradinger Sea ice covering the Bering Sea as seen from an icebreaker in March 2009 .

Fig. 3 collecting water from below the big questions were (1) how impor- sea ice, using a small water sampler tant are these sea ice related ecosys- deployed through holes in the ice. tems for the Bering Sea food web, We also measured when and how (2) how much ice algal biomass is those algae melted out of the ice formed during spring prior to the by collecting sinking material with ice melt, and (3) how is the produc- sediment traps under the ice. We tion linked to the water column and used chemical markers to follow the seafloor communities. fate of the ice-derived matter in the Rolf Gradinger, University of Alaska Fairbanks (UAF) food web. Bodil Bluhm, UAF Katrin Iken, UAF Why We Did It Sea ice is an integral part of Arctic marine ecosystems, serving as The Bering Sea Project is a partnership between the North Pacific Research Board’s Bering Sea breeding and migration ground for Integrated Ecosystem Research Program and the marine mammals, resting area for National Science Foundation’s Bering Ecosystem birds and seals, and as a realm for Study. www.nprb.org/beringseaproject hundreds of different species, from microscopic, unicellular plants to larger animals. Given all the recent

C. Morel changes in temperature and ice Taking ice samples with an ice corer . conditions in the Bering Sea, the

SEA ICE ALGAE, A MAJOR FOOD SOURCE FOR HERBIVOROUS PLANKTON AND BENTHOS IN THE EASTERN BERING SEA A component of the BEST-BSIERP Bering Sea Project, funded by the National Science Foundation and the North Pacific Research Board with in-kind support from participants.