Last night as dusk fell we were underway to another station for deep sampling. After a few hours of steaming we arrived and deployed a CTD in about 1000 m of water. Just before midnight we sent down the benthic sled, and then in the small hours of the morning the multicorer brought back delicate samples of the surface sediments for the first time.
As the sun rose we were arriving at the fifth location for sampling, and the CTD was deployed just as the early-risers were waking up and those who had been up all night were headed to sleep. Just before breakfast the multi-corer was deployed again. Mid-morning we attempted another of the long piston cores. Just like the first deep coring site west of Tasmania, we hit very hard clay this time and the core tube bent at a serious angle.
The crew was able to recover about 7.5 meters of sediment, in a tricky operation involving maneuvering a 40 meter long steel pipe with a major banana shape onto a narrow section of deck. Once on deck, crew members set at the pipe with welding equipment, sending sparks flying as they tried to extract as much good material as possible.
Later in the afternoon we had our deepest biological samples yet, in about 1600m of water. The collection included beautiful pink and purple sea stars and brittle stars, hermit crabs and coral. In a finer mesh net, we found lots of fish scales and otoliths - the inner ear bones of fish, which can be used to tell how old fish are. We also continued towing the nets for plankton throughout the day. Comparisons with the net samples from last night showed that more larvae are in the surface waters in the dark, probably following their food.
The sampling program wil continue on a 24 hour schedule for the next two days, to use this valuable time in the canyons as efficiently as possible.
National Oceans Office scientist, Heather Deese, who joined the voyage via helicopter yesterday, said she was thrilled to be involved in the Murray Canyons research.
“I love the experience of exploring the oceans,” she said.
“It is surprisingly beautiful out here: the ocean has many moods. It can be like a millpond in the middle of the ocean, or beautiful white caps, gentle swells or huge waves.
“The sea colour can be slate grey under heavy clouds, or deep, clear translucent blue with sunlight penetrating in shimmery patterns. And yet below the surface there can be a rugged and spectacular terrain like we're seeing here in the Canyons. The dimensions are truly staggering.
“And of course the exciting thing for all of us is that this is all new: none of this exploration has ever been done before. Even more importantly, this kind of information makes such a tremendous difference in our ability to plan for sustainable use of Australia's oceans.”
The expedition remains on schedule and the CTD, sleds and plankton tows continue throughout the night in depths ranging from 3,000 to over 4,500 metres.
Shortly after dusk, one of the deep sea sleds brought back a curious type of rat-tail fish from almost 3,000 metres depth. It was a long, eel-shaped fish with sharp teeth and a lure several centimetres long attached to its head. Other fish are fooled into thinking the lure is a smaller fish, bringing them within striking range of this ferocious looking creature which bears more than a passing resemblance to the monster from the film Alien.
Just before midnight, we were treated to a luminescent display by scores of a type of deepwater jelly which, perhaps attracted by the lights from the ship, came and swarmed around the side of the vessel as the CTD was being lowered over the side. The jellyfish ranged from about 15-30cm in length and glowed a bright blue colour. We also spotted a colonial salp- a long, clear, tubular, gelatinous colony of tiny zooplankton, almost 3 meters long and 30cm in diameter - floating through the water and changing shape along the way. It first appeared in a horseshoe shape, than morphed into a ‘z’ and finally floated away out of view.
A CTD was to be deployed to 4.5km depth, so we decided to add on a mini experiment of our own. In water this deep, the pressure is incredibly high, about 450 times the atmospheric pressure we live in at sea level. In order to get a tangible illustration of these pressures, we all decorated Styrofoam cups with black markers, put them in an old onion bag and tied the bag to the CTD instrument cage. As the cage was lowered into deeper and deeper waters, and the pressure got higher and higher, the air was forced out from the Styrofoam and the cups shrank in size. At the bottom of the sea, where the temperature dropped to 1 degree Celsius, the cups were down to 4 cm. We now all have beautiful, tiny souvenirs, our decorations in miniature - trophies of the deep.
The benthic sled collects some of the mud from the sea-floor, full of shells and organic material. When we look through the microscope we can see forams (some of which look like miniature pink coffee rolls), fish otoliths (ear bones), gastropods (marine snails), crustaceans (amphipods, copepods) and tiny worms and clams.
“We found a predatory crustacean that would put horror movie creatures to shame. It has large claws, and many barbed legs and it must be the stuff of nightmares for the creatures living on the seafloor.
“Of course this creature is only a few millimetres long and fortunately doesn’t get much bigger,” geobiologist and micropaleaontologist Tony Rathburn of Indiana State University said.
Alix King from Geoscience Australia said that few people were aware of the importance of these tiny creatures that are the key to climate history.
“The distribution of species and their shell chemistry can tell us a lot about the past temperature of the sea surface and the productivity of the oceans,” she said.
It is important to understand these past changes in climate so that we have a better idea about how the earth responds to different conditions and how the oceans affect climate change. Forams are very abundant in the cores which we have been collecting and will help us to determine the changes which have occurred in Southern Australia. We will also be able to determine the age of the sediments by measuring their isotopic composition and carbon-14 content.
This afternoon the crew deployed a 16 metre gravity core, a shorter corer which penetrates the sediment using its own weight, rather than the longer Calypso corer which is triggered by a piston to go deeper into the sediment. The gravity corer is useful for areas where we suspect the sediment coverage is thinner. We gathered a 12 metre core that teams will process throughout the night. The crew will then send down the multicorer to collect the surface sediments.
Today we finish exploring the Murray Canyons region and from now we will be mapping the seafloor from here until our arrival in Fremantle on 5 March.
We were expecting to rendezvous with the helicopter early this morning for the departure of National Oceans officer scientist Heather Deese and ABC journalists Nance Haxton and Richard Smith.
Conditions were fine, but we remain in a large swell, and there was uncertainty about whether the helicopter would be able to land aboard the swaying helipad. The chopper flew in around 8.30am, and the pilot safely landed after his third attempt. The departing passengers were quickly bundled in and they were away back to Kangaroo Island where the helicopter needed to stop to refuel before reaching its final destination at Adelaide.
The Geoscience Australia swath mappers took advantage of our rendezvous location high up on the Canyons and collected some sea-floor data to add to the existing maps.
Coring operations continued throughout the night, with a 40 metre piston core being deployed before midnight last night.
Dr Joachim Schoenfield from GEOMAR in Germany said everyone was very pleased with the result.
“We collected a 35.2 metre core, which is a very good level of recovery,” he said.
“Fortunately the sediment was soft right through to the bottom, indicating it is very young mud, possibly only a few hundred thousand years old.”
The core was divided and processed throughout the night, with enough work to keep the teams busy until later today.
As new cores are retrieved, we have to move previous cores down to the giant refrigerators below decks. This can be very dangerous work, as the core sections are 1.5 metres long and can be very heavy, depending on the density and content of the sediment. Everyone pitches in to form a human chain to pass the cores down to the cooler. As exercise is so difficult to get aboard the ship, we are never short of volunteers when it’s shifting time.
This core provided a good lesson for the students on the importance of recording and logging details as soon as the core is retrieved. Once the core was described and logged, the crew took a short break and upon their return noted a distinct change in colour. Parts of the core had oxidized upon exposure to the air, suggesting the possibility of organics in the sediment.
Every country has its superstitions when it comes to things you should never say or do on board a ship. According to French maritime tradition, you should never name the highly prolific little furry hopping creature with big ears, teeth and fluffy bob-tails as it is very bad luck. On American ships it's bad form to whistle on the bridge for fear of whistling up the wind. Across many cultures a widely-held belief is that you should never put your hat on the table, and if you throw your shoes overboard, you are likely to follow. And of course, never kill an albatross.
Currently we are in the eastern part of the Great Australian Bight about 500km south of Adelaide. The water is an unsettled grey with many waves and white horses. Behind us we can see albatross wheeling just above the waves.
Last night we were tossed around on heavy seas, causing the swath mapping team some consternation. The multi-beam sonar equipment which provides the team with most of its data is fitted to the bottom of the ship. The quality of the data can be affected by the thumping of the ship into big swells. Fortunately the morning saw the arrival of slightly calmer conditions.
James Daniell works the midnight-to-midday shift on the swath mapping team. He is a marine geophysicist in the Petroleum & Marine Division of Geoscience Australia in Canberra.
Before the start of the voyage, team leader Peter Hill, of Geoscience Australia, made a survey plan for the expedition. The plan is modified as conditions change. The team closely monitors the position of the ship in relation to the survey lines, as the data they are collecting must slightly overlap previous swath data to fill in the gaps.
“It's really important that we keep a close eye on the data that's being generated by the sonar equipment,” Peter said.
“On board this vessel, we're able to quickly process and see the data so that we can interpret it and adjust our course and maybe change our acquisition parameters if we need to.”
James explained that on some surveys, the data isn't processed until the completion of the voyage. The set-up on board the Marion Dufresne means that the team is able to produce high quality and immediate results.
“I enjoy my work,” James said.
“Basically, we get to revise the course of the ship while we're surveying, to make sure we're getting the best possible results. It's a big responsibility, and a lot rides on our decisions. It's great.”
Dr Thomas Jellinek, from the Forschungsinstitut und Naturmuseum in Germany, has been examining different samples collected from varying water depths during the voyage.
“Depending on depth, you can find different species of ostracods, which are crabs of microscopic size that live in their own shells,” he said.
“Those shells are built up by the animal by extracting carbonate from the water, and therefore their shells get preserved even though the animal may be dead.
“When we retrieve core samples, we pick the shells from the sediment and usually photograph them with a stereo-electron microscope.
“With the pictures available, we are trying to set up a reliable taxonomy (naming an animal scientifically), which is necessary for isotopic analysis that will be carried out back in Germany.
“The isotopic analysis can tell us a lot about the environment the animal is living in.
“Once we have reached the point of understanding the actual cornerstones of a certain environment, we can then make conclusions about what has happened in the past.
“This type of information can also be used to understand the past climate and make predictions about the future climate. The fact that this important information can be gathered from an animal whose size is about one millimetre is fascinating.
“Besides the ostracods, the samples contain a lot of other tiny creatures, each one bearing its own beauty. There are many other kinds of crustaceans as well as the remains of much larger organisms like otoliths (fish ear bones), spicules of sponges (sponge skeletal elements), spines of sea-urchins, gastropods and mollusks.
“Even though this sounds like a pretty long list, the majority of organisms of the deep sea are represented by many different kinds of foraminifera - single celled organisms that secrete shell-like skeletal material.”
Thomas had devoted a lifetime of study to these tiny microscopic creatures.
“From the first moment I started working on ostracods, already 25 years ago, I always was and I still am extremely impressed about the variability of forms Mother Nature can express on probably half a square millimetre,” he said.
“This is what has always fascinated me the most - the intricacy, and the whole array of forms that are found in such tiny creatures - spines, nodes, wings, pointy spines, spines with cauliflower tips, protrusions - the list is endless. And you must keep in mind that there is a living animal within it that builds up these tiny features.”
The Marion Dufresne
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