Southern Ocean sampling reveals travels of marine microbes

Sep 18, 2013
This image shows the Australia icebreaker, RSV Aurora Australis, from which samples of water in the Southern Ocean were taken at depths of up to 6 kilometers to study the marine microbes living there. Credit: UNSW

By collecting water samples up to six kilometres below the surface of the Southern Ocean, UNSW researchers have shown for the first time the impact of ocean currents on the distribution and abundance of marine micro-organisms.

The sampling was the deepest ever undertaken from the Australian icebreaker, RSV Aurora Australis.

Microbes are so tiny they are invisible to the naked eye, but they are vital to sustaining , producing most of the oxygen we breathe, soaking up carbon dioxide from the atmosphere and recycling nutrients.

"Microbes form the bulk of the biomass in oceans. All the fish, dolphins, whales, sponges and other creatures account for less than 5 per cent of the biomass," says Professor Rick Cavicchioli, of the UNSW School of Biotechnology and Biomolecular Sciences, and leader of the team.

"Microbes perform roles that nothing else can carry out. And if one critical group of was destroyed, life on the planet would cease to exist."

The influence of environmental conditions on the make-up of in different regions of the ocean has been studied, as has the role of physical barriers in preventing their dispersal.

"Collecting samples in the Southern Ocean was an enormous challenge. But it has meant we were able to carry out the first study showing how physical transport in the ocean on currents can also shape microbial communities," says Professor Cavicchioli.

The results are published in the journal Nature Communications.

Twenty five samples were collected across a 3000 kilometre stretch of ocean between Antarctica and the southern tip of Western Australia. Sampling depths were determined by temperature, salinity and dissolved oxygen measurements, to ensure microbes were collected from all the distinct of the Southern Ocean.

These water masses include the circumpolar deep water, which flows toward the from the Indian, Pacific Ocean and Atlantic oceans; the surface water near the Antarctic coastline; and the cold, dense Antarctic bottom water, which flows north, away from the pole, at more than 4 kilometres depth.

Genetic sequencing of the microbial DNA in each sample was carried out to characterise the microbial communities in different water-masses. The research shows that communities that are connected by are more similar to each other.

"So a microbial community could be very different to one only a few hundred metres away, but closely related to one that is thousands of kilometres away because they are connected by a current," says Professor Cavicchioli.

"Researchers need to take this into account when they are studying these important micro-organisms."

The results were tested by Dr Erik Van Sebille, of the UNSW Climate Change Research Centre, who used a computer model of the Southern Ocean to carry out a 100-year long simulation of how particles would move as a result of ocean circulation.

Dr David Wilkins, who carried out the research for his PhD under Professor Cavicchioli's supervision, is first author on the paper. The team also included UNSW's Dr Federico Lauro and Dr Stephen Rintoul, of CSIRO.

Explore further: Science and adventure on first leg of ocean expedition

Related Stories

Science and adventure on first leg of ocean expedition

Jul 04, 2013

Scientists undertaking a UNSW-led expedition to study microbes in the Indian Ocean have weathered huge seas and had a close encounter with giant whales during the first leg of their voyage from South Africa ...

Massive Southern Ocean current discovered

Apr 26, 2010

(PhysOrg.com) -- A deep ocean current with a volume equivalent to 40 Amazon Rivers has been discovered by Japanese and Australian scientists near the Kerguelen plateau, in the Indian Ocean sector of the Southern ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Finnish inventor rethinks design of the axe

(Phys.org) —Finnish inventor Heikki Kärnä is the man behind the Vipukirves Leveraxe, which is a precision tool for splitting firewood. He designed the tool to make the job easier and more efficient, with ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.