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.
Dune ecosystem modelling
23.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Understanding animal social networks can aid wildlife conservation
23.06.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology