Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Billions of juvenile fish under the Arctic sea ice

12.10.2015

New under-ice net used in large-scale study on the prevalence of polar cod at the ice underside

Using a new net, marine biologists from the Alfred Wegener Institute have, for the first time, been able to catch polar cod directly beneath the Arctic sea ice with a trawl, allowing them to determine their large-scale distribution and origin.


Polar Cord

Photo: H. Flores / Alfred Wegener Institute

This information is of fundamental importance, as polar cod are a major source of food for seals, whales and seabirds in the Arctic. The study, which was recently published in the journal Polar Biology, shows that only juvenile fish are found under the ice, a habitat the researchers fear could disappear as a result of climate change.

Beluga whales, narwhals, ringed seals and numerous Arctic seabirds have one thing in common: their preferred food is polar cod, Boreogadus saida. As such, the fish is one of the Arctic Ocean’s most ecologically important animals. Despite its importance, there are still gaps in our understanding of it. For example, biologists have known for years that juvenile polar cod live under the sea ice.

However, to date it was not known just how many live there. The journal Polar Biology has now published important new findings by researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Universität Hamburg and the Dutch research institute IMARES.

“For the first time, we’ve been able to use a special net directly below the sea ice to catch a large number of polar cod, and therefore to estimate their prevalence over a large area. If you extrapolate these findings, there could be more than nine billion polar cod living under the ice in the Eastern Arctic. What’s more, we have also collected fundamental biological and physical data,” explains Carmen David, an AWI biologist and first author of the article.

The data was gathered in summer 2012, during an Arctic expedition on board the research icebreaker Polarstern. The researchers dragged a specially developed under-ice net next to the ship at 13 stations between Greenland, Svalbard and Russia.

The net, developed by AWI’s Dutch partner IMARES, is about the size of a car and designed so that its large frame quickly sinks beneath the sea ice every time it’s cast. Floats then push it towards the water’s surface so that it is directly under the ice floe. In addition, this trawl net, known as SUIT (Surface and Under Ice Trawl) is equipped with a camera and various other equipment for measuring ice thickness, temperature and salinity beneath the ice.

This allows the researchers to make catches that provide completely new insights into the polar cod’s lifecycle. “Up until our expedition, catches had only been made at specific points and observations made on individual polar cod caught beneath the ice by divers,” says David.

“Now we know: there are mainly one- or two-year-old juvenile fish living directly below the ice, and these feed on, among other things, amphipod crustaceans. Since some of the polar cod live in overhangs and cracks under the ice, it’s likely that we didn’t manage to catch all of them with our net – which means that the polar cod population beneath the ice may be even bigger than our figures suggest.”

To find out where the young polar cod come from, the researchers used satellite data and computer models, which can retrace the slow movement of the drifting sea ice. It has long been surmised that the young fish reach the Central Arctic from their spawning grounds under drifting ice. These spawning grounds are found in the coastal waters of the Laptev and Kara Seas in northern Siberia. In autumn new sea ice forms there, and is gradually pushed northwards into open waters by the wind. The juvenile fish are assumed to travel along under the ice.

“We analysed the satellite data to determine how far the ice in that particular area has travelled,” says AWI biologist and co-author of the study, Hauke Flores. “It took the ice between 240 and 340 days to travel from the coast to our measurement stations in the sea. These figures correspond with the age and size of the juvenile polar cod that we caught.” These results indicate that the fish caught in the west could have come from the Kara Sea, while those caught at the stations in the east are more likely from the Laptev Sea.

To discover how well fed the fish under the ice are, the scientists analysed their tissue in the laboratory. All the fish were in top condition, which suggests that there was enough food under the ice, making the sea ice a true nursery ground for polar cod.

Above all, the new insights into the juvenile fish under the ice are important because it’s still impossible to say how polar cod populations will change in the face of climate change. The largest and most important population lives in the Barents Sea, to the north of Norway. As climate change causes the Barents Sea to grow warmer, for some years now other fish species like capelin and Atlantic cod have moved further northward, creating new competition that could reduce the polar cod population. In fact, Norwegian researchers recently confirmed that, in a regularly monitored fjord on the island Spitsbergen, for the first time ever there were no polar cod found – but plenty of Atlantic cod.

If the polar cod population in the Barents Sea actually does shrink, the juvenile fish under the ice of the Eastern Arctic could become even more important – especially in order to make up for losses elsewhere. “We want to determine whether or not the young fish under the ice serve as a form of ‘polar cod reserve’, increasing the overall chances of survival for the coastal populations through genetic exchanges with populations in Siberia and elsewhere,” explains Flores.

After all, the estimated nine billion juvenile fish under the ice represent a substantial population. By way of comparison: the Barents Sea, the region with one of the world’s largest polar cod populations, is home to only twice as many one- to two-year-old fish of the species. Carmen David and Hauke Flores now hope to learn even more about the fate of the polar cod in the course of further expeditions.

Notes for Editors:
The study mentioned above was published in the journal Polar Biology under the following title:
Carmen David, Benjamin Lange, Thomas Krumpen, Fokje Schaafsma, Jan Andries van Franeker, Hauke Flores, 2015. Under-ice distribution of polar cod Boreogadus saida in the central Arctic Ocean and their association with sea-ice habitat properties. Polar Biology. DOI 10.1007/s00300-015-1774-0

Printable images can be found in the online version of this press release at: http://www.awi.de/en/about-us/service/press.html

Your academic contact partners at the Alfred-Wegener Institute are:
• Carmen David (Tel: +49 471 4831-1085; e-mail: Carmen.David@awi.de)
• Dr Hauke Flores (Tel: +49 471 4831-1444; e-mail: Hauke.Flores@awi.de)

Your contact partner at the Department of Communications and Media Relations is Sina Löschke (Tel: 0471 4831-2008; e-mail: medien@awi.de).

Ralf Röchert | idw - Informationsdienst Wissenschaft

More articles from Life Sciences:

nachricht Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>