Reporting this month in the journal Limnology and Oceanography, an international team of researchers describe how Antarctic krill (Euphausia superba), once thought to live mostly in surface waters, regularly feed on iron-rich fragments of decaying organisms on the sea floor. They swim back to the surface with stomachs full of iron, releasing it into the water.
Antarctic krill is the staple diet for fish, penguins, seals and whales; and is harvested by commercial fisheries for human consumption.
Lead author from British Antarctic Survey, Dr Katrin Schmidt says, "We are really excited to make this discovery because the textbooks state krill live mainly in surface waters. We knew they make occasional visits to the sea floor but these were always thought as exceptional. What surprises us is how common these visits are – up to 20% of the population can be migrating up and down the water column at any one time."
The scientists painstakingly examined the stomach contents of over 1000 krill collected from 10 Antarctic research expeditions. They found that the krill, caught near the surface, had stomachs full of iron-rich material from the seabed. The team also studied photographs of krill on the sea floor, acoustic data and net samples. All these provided strong evidence that these animals frequently feed on the sea floor.
This finding has implications for managing commercial krill fisheries and will lead to a better understanding of the natural carbon cycle in the Southern Ocean.
Schmidt continues, "The next steps are to look at exactly how this iron is released into the water."
The paper, Seabed foraging by Antarctic krill: Implications for stock assessment, bentho-pelagic coupling, and the vertical transfer of iron by Katrin Schmidt, Angus Atkinson, Sebastian Steigenberger, Sophie Fielding, Margaret C.M. Lindsay, David W. Pond, Geraint A. Tarling, Thor A. Klevjer, Claire S. Allen, Stephen Nicol and Eric P. Achterberg is published in Limnology and Oceanography. 56: 1310-1318. http://aslo.org/lo/toc/vol_56/issue_4/index.html
Notes for Editors
Photos of krill and scientists collecting samples from the research ship RRS James Clark Ross are available from the British Antarctic Survey Press Office as above.
Antarctic krill (Euphausia superba) is one of the most important animals in the Southern Ocean. These shrimp like crustaceans grows up to a length of 6cm and can live for 5-6 years. Krill feed on phytoplankton and are in turn eaten by a wide range of animals including fish, penguins, seals and whales. They are also a potentially valuable source of protein for humans and can be fished easily with large nets.
Antarctic krill are a key species in the Southern Ocean food web, channelling energy from phytoplankton (microscopic plants) efficiently to the large populations of penguins, seals and whales that make Antarctica unique. There is an expanding krill fishery in Antarctica, managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR requires research on the role of krill in the wider food web, in order to manage this expanding fishery in a precautionary manner.
There are an estimated 100-500 million tonnes of krill in the Southern Ocean – similar to the weight of the world's human population.
Primary production (pelagic plant growth) is limited by the availability of iron in about 40% of the Worlds' Oceans including the Southern Ocean. Whilst iron is super-abundant on land, is only present in minute concentrations in the upper productive layers of the ocean. In large parts of the Southern Ocean small additions of iron dramatically increase plant growth and the drawdown of atmospheric CO2 into the ocean.
The supply processes of iron into the ocean are therefore important in the Antarctic carbon cycle, where CO2 uptake is stimulated by plant growth, and the carbon is subsequently stored in the ocean interior due to the settling of dead plant cells. The supply of iron is mainly thought to be due to upwelling from deep sediments, run-off from land and glaciers, melting of icebergs and the settling of wind-blown dust. All of these processes are purely physical, so this work suggests a novel route via biological processes: with krill returning significant quantities of iron in their stomachs after visiting the seafloor to feed.
The Cambridge-based British Antarctic Survey (BAS) is a world leader in research into global environmental issues. With an annual budget of around £45 million, five Antarctic Research Stations, two Royal Research Ships and five aircraft, BAS undertakes an interdisciplinary research programme and plays an active and influential role in Antarctic affairs. BAS has joint research projects with over 40 UK universities and has more than 120 national and international collaborations. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found at: www.antarctica.ac.uk
The Australian Antarctic Division leads the Australian Government's Antarctic program and is a division of the Department of Sustainability, Environment, Water, Population and Communities. Australia maintains three stations on the Antarctic continent – Mawson, Davis and Casey, and a sub-Antarctic station on Macquarie Island. Remote field bases also operate during the summer research season, supporting coastal, inland and traverse operations. Australia's icebreaker, RSV Aurora Australis is the platform for a large annual marine research effort focussed on the Southern Ocean and assists in resupplying our research stations. We also operate a jet aircraft link between Hobart and a 3.5 km blue-ice runway near Casey.
Value from wastewater
16.08.2017 | Hochschule Landshut
Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).
The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
16.08.2017 | Physics and Astronomy
16.08.2017 | Materials Sciences
16.08.2017 | Interdisciplinary Research