The AUSCAN Voyage
Today’s major news comes from the team working on the core collected yesterday, with an exciting find that Patrick De Deckker suspects is extremely significant for two reasons. Initial spectrophotometry (a technique which measures colour changes in sediments) has revealed remarkable similarities to results from the famous Vostok ice cores retrieved in the Antarctic.
“This is hugely significant and exiting,” said Patrick. “What we have here is a “proxy” for a sea level curve that also matches the Antarctic curve to a remarkable degree. This is linked to sea level changes over the past 150,000 years. To have these results correlate so closely with those of the Antarctic cores is very exciting. The similarity has quite frankly astounded us. We couldn’t have hoped for a better result,” he said.
The information gained from the sea level curve gives scientists information about changes to climate, oceanography and the geology of the area from the past. Depending on the age of the core samples, information can be gathered from as far back as the last million years. Our core sample provides information for the past 250,000 years of an exceedingly high quality.
This second exciting find is that early indications show that the core is at a very high resolution, and shows the highest rate of deposition of any core sample ever collected in Australian waters. What this means is that there is a large amount of sediment for every thousand years, enabling researchers to piece together a great deal of information. Patrick’s analysis shows that the core collected provides an archive for the past 250,000 years.
“This again is a phenomenal result,” said Patrick. “We will be dividing the core into 1cm slices, which will represent 100 years of ocean history. We now have the potential to chart the history of the oceans and climate of this region every 100 years for the past 250,000 years.”
Meanwhile, the swath mapping team from GA reports that we have finished the mapping work on the edge of the Lacepede Shelf and are now on a transect south and then south east to just west of King Island where we will be collecting another core sample. This is of particular interest to the German team who are interested in the palaeooceanography and palaeoclimatology of the region.
At about 7pm last night a multicorer was deployed to collect sediment just under the seafloor, and the water immediately above the collection site, south of Kangaroo Island. The Calypso corer used earlier in the day is more suited to collecting long core samples beneath these surface sediments. By using both sampling methods, scientists are able to create a more complete picture.
While the coring was going on, Lachie McCleay, from SARDI, was conducting a plankton tow. The equipment he uses consists of two long, very fine nets similar in shape to wind socks which are immersed in the sea and used to collect plankton from the water column to a depth of 150 metres.
The samples collected included jelly-like organisms known as salps, copepods, fish eggs and larvae. Samples were transferred from the nets to preservation containers, which will be taken back to the SARDI labs in Adelaide for closer analysis. Lachie is expecting to find blue mackerel eggs and larvae, as it is one species currently spawning in this area and it is thought that this area is of significance them.
“No-one really knows much about what goes on in this area,” Lachie said. “The information we are gathering will further our understanding of blue mackerel life-history characteristics and aid in future fisheries management of the south-east region.”
Lachie is also hoping to find new species that may exist in the area. The Murray Canyons region is an area of spectacular topography. Nutrients are carried up from the bottom of the sea and feed phytoplankton which are a food source for zooplankton. Creatures such as fish and whales are attracted to this upwelling area because of the potential food sources.
Little biological sampling has been conducted in this region. No-one really knows what lives here, and in order to fully understand the marine environment in this area, we need to gather all types of biological and oceanographic information.
Meanwhile, Patrick De Deckker from ANU was not so fortunate with his smaller plankton tow, which came back to the surface in tatters, prey to something hungry lurking beneath the surface. Lachie will be conducting further tows throughout the voyage.
A voyage highlight for the passengers came with an invitation by the Madagascan crew members who hosted a party in their quarters. This was a great opportunity for us to enjoy their music, singing, dancing and hospitality. We had heard before we embarked that if we had the opportunity to join the Madagascans, that we shouldn’t miss it. The music and dancing were energetic, and kept on until the wee small hours of this morning.
We have all been looking forward to today, as word has it that it will involve croissants and gateau. The turnout for breakfast this morning is larger than usual, and we are not disappointed, as we are treated to delicious pain au chocolat, or chocolate croissants.
The food on board the ship has been magnificent, with four courses for lunch and dinner, and often providing the Australians with their first taste of French cuisine, including, of course, escargots. Not everyone among the uninitiated can bring themselves to taste the delicacies, especially those whose area of research is gastropods.
With the abundance of fine food, most of us are keen to increase our exercise, although it can be difficult to find ways on board the ship. Deck tennis, badminton, table tennis and darts are the most popular forms of exercise. As the days pass, games are becoming more competitive, and last night the ‘Commonwealth’ team defeated the ‘Europeans’ 2-0 in darts.
The captain’s favourite exercise is deck tennis, which is played on the helipad with a plastic ring. He is never short of volunteer opponents. The helipad is also used for badminton.
Work on board the ship takes place around the clock, with science teams allocated to three shifts: the 0-4, 4-8 and 8-12 shifts. Tonight the midnight to 4am shift is preparing for a calypso core exercise around midnight. The core is of particular interest to the German team, although it’s all hands to the deck when it comes to retrieving and processing the core, with cooperation across nationality and academic discipline.
In preparation for tonight’s coring, at 3pm today everyone available will form part of a human chain to transfer our first core into storage to make room for the new core. A team meeting this afternoon will provide a briefing on what’s involved. Overnight, the Germans have consulted closely with James and Peter from Geoscience Australia , the swath mappers, to determine the best site for deploying the corer.
Dr Dirk Nuernberg from GEOMAR Research Centre for Marine Geosciences in Kiel , Germany , heads up the German team and he explains what the Germans are looking for.
“We will be collecting a core sample west of King Island some time around midnight” he said.
“We are particularly interested in paleoceanography and paleoclimate, and specifically in how current systems have changed through time.”
The German team is part of the IMAGES program, a European multinational project studying paleoclimate and paleoceanography. Dirk is interested in what the core reveals about how things have changed through time on glacial and interglacial timescales.
“The region we will be sampling is an area where there is interplay between warm and cool waters,” Dirk said.
“We hope that through studying the core, we can reconstruct past events by looking at productivity, temperature of the surface of the ocean and looking at the material eroded from the continent.”
Once the core sample is retrieved, it will be processed for shipment back to the GEOMAR laboratories where further testing will be undertaken.
Meanwhile, Lachie McLeay from SARDI has conducted some initial observations on a small part of the plankton tow sample retrieved last night.
“We’ll be conducting more thorough research of the entire sample back at the SARDI labs,” he explained.
“However this small sample reveals mostly salps (planktonic jellyfish) and copepods (planktonic crustaceans).
“This particular sample most likely comes from the top seventy metres of the sea, and we can also see chaetognaths and polychaetes, both types of small, planktonic marine worm.
“There is also evidence of planktic foraminifera - a single celled organism with a calcium carbonate shell. They are important for tracing changes in sea-surface temperature and chemistry.”
In the early hours of this morning, the German team hit a snag. During their first attempt at retrieving a core from west of King Island last night , the equipment hit hard sediment, bending the corer. This meant another attempt had to be made to retrieve a complete core. After further study of the sub-bottom profiler data, a second site was selected, and this time the team was rewarded with a 24.18m core.
The new core was cleaned, marked and segmented by the day-time shift, and put into cold storage for transport and further study at GEOMAR Research Centre for Marine Geosciences in Kiel, Germany.
After the initial attempt, the German team was very pleased to have retrieved the core. Dr Dirk Nuernberg explained: “We have a lot of work ahead of us. Once we have a core, we don’t know where we are in time, and one of the first things we have to do is establish what timescale we are in. There are all kinds of different approaches to determining the age.”
“After this is done, then we can start sampling. We sample the core every 2 or 5 cm in order to get good temporal resolution. With a core of this length, you can imagine we will get hundreds of measurements. You can see that processing sediments can therefore take a long time, sometimes years.”
Two plankton tows were completed at the same time as the second coring exercise – a vertical plankton tow which gathered samples from 30 metres and a horizontal tow which gathered samples at a depth of 150 metres below sea-level.
Initial observations under a microscope of the horizontal tow showed an abundance of copepods (planktonic crustaceans), which are a major part of the food chain. We could also detect a number of acantharians, which are interesting unicellular organisms that share a symbiotic relationship with dinoflagellates (a type of algae) that live inside them.
Patrick De Deckker explains that little research has been conducted into these fascinating creatures since early last century. They were first described in the Southern Ocean one hundred years ago, and are a major part of the food web in the ocean.
“Acantharians are more abundant in Australian waters than many people realize,” Patrick said. “In my research, I have found them everywhere I have tested around Australia.”
After acantharians die, their skeletons dissolve, so there is no evidence of there existence in the sediments or the “marine snow” that geologists study to understand the ecology of the ocean.
The skeletons of acantharians are made of strontium sulfate, a compound which is in short supply in the ocean.
“When these creatures die, their skeletons dissolve, leaving no trace of their existence in the ocean ," Patrick said.
" In fact, if samples are left in seawater or formalin (a common preserving solution), in two or three days there is no trace of there ever having been acantharians in your sample. It is best in this case to store samples in alcohol, as this preserves the creatures intact.”
This afternoon team leaders from each of the groups met to plan the next few days of the AUSCAN program, as we are about to enter our most exciting stage of the voyage.
Over the next few days, we will be exploring the Murray Canyons region, conducting more thorough biological sampling, mapping the spectacular underwater topography of the canyons system, and attempting to learn more about this little understood area.
Today we start an intensive sampling program in the Murray Canyons. The group leaders have met to discuss the strategy, and a roster has been drawn up for the various teams to make the most of the three and a half days we will be exploring here.
During the course of the voyage we have been using a number of sampling methods that provide us with a range of information. While in the Murray Canyons region we will be coring for sediments, using the plankton tows, the benthic sled and getting some CTD (conductivity, temperature and depth) measurements.
The big news of the day is the arrival of a helicopter which brings Heather Deese from the National Oceans Office science team, and ABC journalists Richard Smith (Catalyst) and Nance Haxton (South Australian correspondent for national radio current affairs).
We live in a very separate world on board the ship, and life back on land can seem very far away. The arrival of the helicopter comes at about the half-way mark in the voyage, and we’re all looking forward to hearing news from home.
Today I though I'd include a run-down of some of the scientific methods that are being used on the voyage, as lots of people have been asking about it.
Selection of the most suitable sites is done in consultation with the swath mappers , who look at the topography of the sea-floor and compare this with the sub-bottom profiling data to determine the level of sedimentology. Sites are selected on the basis of thick accumulations of sediment so that we can get long cores.
We use two types of corers . TheCalypso corer, developed by Yvon Balut of the French Polar Institute , weighs about 6 tonnes and can collect long cores up to 60m in length . The second type is the multicorer, which gathers undisturbed sediment from the surface of the seafloor (up to 25cm), and collects the water immediately above the collection site. The CALYPSO core sampler’s immense weight means it penetrates well below the surface of the seafloor, and often disturbs seafloor surface sediments collected. The multicore sample provides this additional surface data. Once we have the cores, they are measured, marked, sectioned and capped. Individual sections are cut lengthways, for initial processing , which includes:
- Samples are digitally photographed.
- Then the samples are logged, which means a description is made of the sediments, structure and colour by a sedimentologist.
- Then a spectrophotometer is used to detect the graduation of colour changes within the core sample.
- A multi-sensor logger is also used to track the magnetic susceptibility, density and porosity of the sediment
The Marion Dufresne uses the latest sonar technology, known as “swath mapping”, to get detailed information about the topography of the sea floor. The ship is also equipped with a sub-bottom profiler which gives an indication of the thickness of the sediment.
During the next three days, the ship will be moving from site to site, and will remain on station for several hours at a time. The Geoscience Team have swathed part of this area, and will take the opportunity to fill in any gaps.
A piece of equipment used to collect benthic (bottom dwelling) micro and macro fauna (small and large organisms) from the substrate sea-floor (the top of the sediment).
No-one has ever tried to find out what lives in this area, and Lachie McLeay from SARDI says there are possibly undescribed animals in the region.
Initial research will be conducted aboard the ship, but further study will be done back at the SARDI labs in Adelaide.
We will be using two sleds - a larger one for deeper waters (Big Bertha) and a smaller one for the shallower depths.
Two large wind-sock shaped nets are deployed vertically down to 200m (roughly the limit of plankton distribution). Samples get transferred to a sieve and then to sample jars where they are preserved in formalin for analysis back at the lab.
CTD (Conductivity, Temperature, Density)
This is an Australian invention which is used to measure conductivity (via measuring salinity), temperature, density and chlorophyll at various depths. It consists of array of sensors on stands plus twenty-four twelve litre bottles which are triggered at various depths during ascent to collect water samples. The CTD is routinely used by oceanographers all over the world to record these kinds of measurements.
“We don’t know the water chemistry in this region,” Patrick De Deckker explained. “Chemistry will measure the oxygen and carbon isotopes in the water at various levels.”
“Isotope measurements have never before been measured in this region. This data is important because foraminifera take oxygen and carbon from the water to make their shells and in doing that they incorporate the isotopic signature of the water. This is important when using foraminifera to study past climates in ocean sediments.”
First day results
During our first day in the Canyons we have conducted two plankton tows, two benthic sleds and two CTD’s. The two sites sampled were at 3800m and 160m depth.
The deepwater CTD measurements showed a sharp drop in ocean temperature below the top water level of 200m. The top 50m showed abundant phytoplankton growth and an increase in oxygen levels.
The sleds brought back some nudibranchs, which are a type of sea slug; many different species of small crab and other crustaceans; bivalves; corals and bryozoans.
There is a great deal of action during the day with the increase of sampling for this region. As biological sampling has never occurred in this area, there is a good chance that we will be discovering previously undescribed species.