LOMROG III 7th field report

Sea Ice Algae in the Arctic Ocean – LOMROG III

By Lars Chresten Lund-Hansen & Brian Sorrell, Arctic Center, Bioscience, Aarhus University

Our research team studies sea ice algae, microscopic algae invisible to the naked eye that live in sea ice. Lars and Brian are participating in LOMROG III as one of the Danish associated projects, investigating the distribution of these algae, which are restricted to the bottom few millimetres of the ice.

Ice algae support a unique, very productive ecosystem in narrow brine channels that comprises not only algae as their sole plant type, but also a wide range of tiny animals and bacteria. Ultimately, this community supports larger animals in the ocean, including large important species such as seals and fish. As the Arctic ice continues to recede, with record lows in ice cover and thickness recorded in 2012, the consequences of losing the sea ice community for the Arctic Ocean are unknown, largely because the factors governing the presence and productivity of sea ice algae are poorly understood.

Our work on LOMROG III focuses on developing a better understanding of how light penetration through snow and ice, the temperature of ice, and nutrient supply from the seawater are related to the amount of ice algae and their condition in the late summer/autumn season of the cruise. There have been very few studies of ice algae at all in the part of the Arctic Ocean that LOMROG III is exploring, and many previous studies have also been hampered by lack of suitable methods for studying algae in intact ice.

Part of our work involves describing the distribution of algal cells in intact ice more accurately than most previous studies, using a method called fluorescence imaging that allows us to visually isolate where algae are found in ice on a microscopic scale, and how this is related to the tiny amounts of light that penetrate to the underside of the ice where they are most plentiful. The sea ice on the LOMROG III track varies from just over a metre to almost three metres’ thickness, so ice thickness is one of the important variables examined in our work.

Ice coresThese photos show how algal development varies in Arctic sea ice and the fluorescence imaging method we use to investigate their distribution and activity. The left-hand photo is the bottom of an ice core collected during LOMROG III, with a large patch of algae visible as the brownish colour on the ice surface where it was in contact with seawater. More commonly, the algae are invisible to the naked eye as in the centre photo. Yet this core surface, when placed under fluorescence imaging (right hand photo), reveals extensive algal development visible as the vivid yellow, green and blue colours visible amongst the ice crystals, which appear red in the photo.

Participation in LOMROG III is giving us an exciting opportunity to study these important organisms in a place few researchers ever have the opportunity to access, and with exciting new methods not previously used in Arctic sea ice.

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