Melosira arctica under ice and on the ocean floor

Melosira arctica under ice and on the ocean floor

LifeLinkedtoIce Melosira arctica under ice and on the ocean floor

Box 3. Ice algae and deep-sea benthic ecosystems: findings from 2012

In the record low-ice summer of 2012, a scientific expedition to the eastern-central Arctic Ocean basins found widespread deposition of ice algae on the ocean floor at depths of about 4 km [94]. The main species was the diatom Melosira arctica, which grows in long filaments anchored to the underside of ice floes (left photo, Figure 13).

 

The piles of algae strands that settled on the ocean bottom were being eaten by a few larger, mobile invertebrate species, including sea cucumbers (right photo) and sea anemones, but were mainly being broken down by bacteria. The biomass of sea cucumbers was substantially higher in areas with many piles of algae and there were few signs of the small invertebrates such as marine worms that are normally found within the sediment in this type of habitat.

 

Oxygen penetrated only a few millimeters down into sediments beneath piles of algae, due to the bacterial activity. By contrast, oxygen penetrated over 50 centimeters in surrounding sediments. As sediment cores showed no sign that oxygen penetration was reduced in past years, researchers concluded that the widespread deposit of strands of ice algae in the deep central basins is a rare or new phenomenon. They attributed it to the rapid, early melt of ice causing the algae to fall to the ocean floor. Younger, thinner ice with more melt ponds likely also enhances algal growth as more light penetrates to the bottom of the ice floes. Thick multi-year ice in the study area has been largely lost: first-year ice with an average thickness of less than a meter dominated over 95% of the study area and melt ponds covered on average 30 to 40% of the ice surface.

 

Figure 13. Melosira arctica under ice and on the ocean floor

Photos: M. Fernandez-Mendez (left) and A. Boetius/Alfred Wegener Institute (right); Seija Hällfors/ Finnish Environment Institute SYKE (inset microscopic view of the diatom Melosira arctica)

 

Conservation of Arctic Flora and Fauna (CAFF) 

The data can be downloaded freely. Users are requested to reference the source.

Eamer, J., Donaldson, G.M., Gaston, A.J., Kosobokova, K.N., Lárusson, K.F., Melnikov, I.A., Reist, J.D., Richardson, E., Staples, L., von Quillfeldt, C.H. 2013. Life Linked to Ice: A guide to sea-ice-associated biodiversity in this time of rapid change. CAFF Assessment Series No. 10. Conservation of Arctic Flora and Fauna, Iceland. ISBN: 978-9935-431-25-7.

 

94. Boetius, A., Albrecht, S., Bakker, K., Bienhold, C., Felden, J., Fernandez-Mendez, M., Hendricks, S., Katlein, C., Lalande, C., Krumpen, T., Nicolaus, M., Peeken, I., Rabe, B., Rogacheva, A., Rybakova, E., Somavilla, R., Wenzhofer, F., and Sc, R.V.P.A.-.-S. 2013. Export of algal biomass from the melting Arctic sea ice. Science 339(6126): 1430-1432. doi:10.1126/science.1231346.

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