A day in the life of a sedimentologist

By Jin-Sol Lee, University of Melbourne

Although it would be hard to imagine, you couldn’t have seen a more excited group of adults than when a three-metre rectangular block of muddy sediment was pulled onto the ship. This surreal moment is when you realise you’ve fallen into the rabbit hole and entered a whole new world; the world of a sedimentologist.

This image of the stern (back) deck of RV Investigator shows the A-frame almost at its uppermost position as the 4 members of the crew and support staff work to deploy the kasten core off its track from the back of RV Investigator in a submarine canyon off Portland Victoria as part of hands-on marine science training for students on CAPSTAN's 2019 voyage.
Kasten core being pulled up from the depths of the Southern Ocean

This block of muddy sediment is a sediment core taken from the bottom of the ocean and reveals a whole plethora of wonderful and strange stories from Earth’s history. These stories relate to how our planet’s environment, climate, and ocean currents have changed over time. What is truly amazing is that we know so much about the long and dramatic history of our planet despite the fact that we have not been part of that history for very long. This amazement is humbling and is a reminder of the capabilities of the human race, and the responsibilities we have as stewards of the planet.

Once the core is brought into the lab there is a flurry of activity to open the metal casing, which holds the sediment core, and to see what strange and mysterious tales from the ocean depths have been brought to the surface. With the casing removed heads are bent over to observe the colour, structure and composition of the sediments. Quick, sharp remarks are exchanged between the various parties involved before the processing of the core is started without delay. First, the core is logged which involves documenting the major characteristics of the core. This is important because these observations will underpin the majority of the interpretations which brings the whole story together. From here smear slides and small sediment samples are taken along the core to examine the changes which occur from top to bottom.

The sediment lab is full of students and trainers as the kasten core (3 m long steel pipe) is opened on one side and imaged using a DSLR camera.  Students and trainers described the sediments, sampled plankton, and measured seawater properties as part of hands-on marine science training during CAPSTAN's 2019 voyage on RV Investigator.
The big reveal! A hub of activity as the core is brought into the lab and the task of processing and sampling the sediments begins!

Hours will be spent analysing these slides and samples, with more sampling done along areas of interest until the sediment core looks less than pristine. Not to worry however since before the sediment core was scooped, poked and prodded an archive core was taken and stored in the fridge. This archive core is kept with all its structures and features intact as an original record for safekeeping.

Two students and a trainer stand around the lab bench in the sediment lab working to describe the sediments using a Munsell color chart and several microscopes securely fastened to the counter as part of hands-on marine science training during the 2019 CAPSTAN voyage.
Hard at work! Sediment core being logged to describe the major characteristics and sediments being analysed under the microscope.

There is a certain amount of chaos and untidiness in the lab which may be disconcerting to the casual viewer, but there is a method to the madness with great care being taken to systematically record and sample the sediment core. Furthermore, there are efforts to limit contamination across the core (i.e. avoid mixing sediment from one area of the core to another). In fact, it is quite liberating to be able to conduct science in a lab where things are more practical, and improvisation is encouraged. A day in a life of a sedimentologist will surely shake up the perception of the typical scientist in a lab coat conducting experiments in a clean and well organised laboratory.

Advertisements

It’s definitely better out where it’s wetter

By Sian Liddy, University of Sydney

It was somewhere between popping my first sea-sickness tablet and putting on the hi-vis vest to step on to RV Investigator that it finally sunk in – I was about to spend two weeks sailing across the Southern Ocean on a world-class research vessel. It was simultaneously daunting and indescribably exciting to be spending time on a ship managed by the CSIRO and Marine National Facility, sailing with leading experts from different fields of environmental science.

A double rainbow off the bow

One of the main reasons I applied to CAPSTAN was to get a better understanding of how research vessels function at sea, and to help short circuit the “need job to get experience, need experience to get job” cycle. This experience was jump-started as soon as we switched to ship’s power and began steaming out of the harbour. We dived head-first into preparations for when we arrived on site, labelling sample bags for the sediment cores, prepping petri dishes for the plankton counts, and familiarising ourselves with the OPS room. This period was made that bit more challenging by the waves of tiredness brought on by the sea sickness tablets we were all taking, and the harsh discovery that my coffee addiction was making me seasick! But these little hurdles were promptly forgotten as we arrived on site at the canyons – where it was all systems go. Observing how the infinitely capable chief scientist Leah Moore made the big calls that shaped the rest of the fieldwork (and ultimately the data that we’d get from the trip) as new information came to light that affected our field plans, has given me more confidence to back my own opinions when making informed decisions in my PhD fieldwork.

A picture looking back up at the bridge from the bow to see the orange and blacks of sunset reflected in the window.  Taken on board RV Investigator during the 2019 CAPSTAN hands-on marine science training voyage.
Sunset reflecting in the windows of the bridge

The following two days operating around the clock sending CTDs (Conductivity, Temperature, and Depth water sampling device), Kasten Corers, and Bongo-net plankton tows down into the ocean’s depths was a stand-out period of the trip for me. The mentors’ passion for their chosen subject area was infectious and made learning new advanced techniques from foreign fields a breeze. Coming from a marine ecology background and seeing the excitement on everyone’s faces (…and hearing them spontaneously break into Christmas Carols) as they unpacked the second core taken from 2200 m that contained turbidites was fantastic – it was impossible not to get caught up in the flurry of excitement as well. Equally, it was awesome to share the trip’s cool biological discoveries with the geologists, and build the interdisciplinary understanding of the system we were working on as a collective.

Fine grained calcareous sediment is overlain by coarse broken calcareous shell and bryazoan fragments in a cool-water carbonate turbidite cored as part of hands on marine science training during CAPSTAN's 2019 voyage on RV Investigator
Mud, glorious mud! Cool water carbonate turbidite collected in the kasten core.

Aside from the (literally) ground-breaking science we were conducting, I really couldn’t have asked for a better team of students and trainers to sail with.  From the first night playing Rummy-O in Hobart, to venturing out at sunset to wave hello to our friends and family back home on the live feed camera, to high-intensity games of around-the-world-ping-pong, these guys have kept me smiling from ear to ear for the past 12 days!

CAPSTAN students take a fun group photo overlooking the bow at sunset during the 2019 voyage on RV Investigator.
Fun on deck at sunset

The number of accomplished female scientists on board the ship has also been very inspiring.  Chief Scientist Leah, quantitative ecologist Alice, microbiologist Lisa, oceanographer Veronica, and geochemist April, have all been great role models and mentors to me whilst at sea.  Their amazing knowledge and skillsets, resilience, strength, senses of humour, unwavering positive attitudes and willingness to help at all hours of the day and night are just some of the attributes I hope to learn from them, and encompass in my future career too.

A tiny buddha painted on the ship
You never know what you’ll find around the ship.

After the two-day whirlwind of being on station passed, we got stuck into analysis and writing as we steamed towards Fremantle and returned to a more regular schedule (I’ve never been happier to wake up at 5:30am!). Seminars and skill development workshops have continued, as well as the odd tour or two. However, even after a number of tours of the restricted zones of the ship, it maintains a feeling of discovery in the air. Whether that might be for finding another hidden gem like this little buddha painted somewhere secret on the ship, mapping an unnamed seamount, or identifying an unknown hotspot of biological activity, only time will tell.

Now onto planning my next seafaring research voyage!

Back on Land!

By Annabel Payne, Macquarie University

We’re back! Well, we’re in Fremantle, Western Australia. The past two weeks have flown by, and it feels strange that now it’s all over and we’ll be heading home to our respective cities. Meeting new friends and learning new skills, I think I can safely say we all had an amazing experience.

CAPSTAN students Kaycee, Bella, and Luke join trainers Lisa, James, and CAPSTAN director April for a photo outside at sunset on the last night on RV Investigator for this year's hands-on marine science training voyage
CAPSTAN students and trainers enjoying a little outside time on our last night at sea (photo credit: April Abbott).

I’ve been to sea before, but this was my first time learning about plankton collection, identifying different climate events from microfossils, counting different birds and mammals, understanding CTD measurements… the list goes on! CAPSTAN has been a brilliant learning experience and if you’re thinking about applying for next year, definitely do!

Monkey Island is the upper most deck on RV Investigator and is dedicated to marine mammal and sea bird observations.  From here, trainers and students can keep an eye out from sunrise to sunset.
Ben and April watch for sea birds and marine mammals from Monkey Island (photo credit: Leah Moore)

I decided to work in the wet/dirty sediment lab because I felt like it might complement the work I’ve been doing at university. I’ve been looking at how changes in sediment provenance influence Neodymium, an isotope usually used to track changes in past ocean circulation. A lot of the age models used are derived from oxygen isotopes in foraminifera. Since we had Stephen onboard, our foram expert from Melbourne, it seemed like the perfect opportunity to learn as much as I could. I now know the importance of a certain species for identifying the last glacial maximum in sediment cores from the Southern Ocean, how changes in size and species distribution are influenced by temperature and light!

The Smith-Mac grab, a box-like tool deployed for sampling the seafloor, is deployed over the starboard side of RV Investigator at sunset during CAPSTAN's 2019 hands-on marine science training voyage.  RV Investigator operates around the clock, meaning deployments can happen day or night.
Smith-mac grab sampler is deployed at sunset

My particular mini project while at sea involved sieving samples from the top and bottom of the cores, separating the different fractions out to see how grain size distribution varied down the canyon we were targeting. In these samples we found a huge variety of forams – some look like popcorn, others look like christmas baubles, and others were perfect spheres. The variety of forms within such a small sample gave me a huge appreciation for just how diverse life is at a microscopic scale.

CAPSTAN student uses a metal spatula to scrap off a thin layer of core along the edge to expose a 'clean' surface.
Prepping the kasten core for sampling by cleaning off the smeared edge

The same could be said for in the plankton lab. The tiny jellyfish, starfish, copepods and various other little critters were fascinating, it was certainly a novel experience being able to see what I’m studying for a change!

A tiny amphipod with a huge black eye floats in the view of the microscope.  This amphipod, along with many other microscopic critters, were caught in plankton nets as part of the 2019 CAPSTAN marine science training voyage.
An amphipod we caught in a net tow as viewed down the microscope (Photo Credit: plankton lab)

From the science to dressing up as sea creatures and trivia, we had a great time. Maddie kept us all singing with showtunes, Sian’s whale calls (which may have something to do with the lack of cetaceans – sorry Sian!), movie nights, through to the excellent food and expert crew. A trip on the RV Investigator is one to remember.

End of voyage group photo with CAPSTAN trainers, students, support team, and some of our crew (Photo Credit: Ben Arthur).

An unprecedented life experience in the middle of the ocean

By Umair Mumtaz, University of Western Australia

Today is the last day of the CAPSTAN research voyage IN2019_T01. My excitement is palpable as CAPSTAN has surpassed my expectations. The training provided in multidisciplines ranging from geology, geophysics, oceanography and microbiology will definitely act as a milestone for stepping into a future marine scientist. Time passes so quickly, I spent almost 12 days in the ocean and during these days I observed nature very closely, clear water, blue sky, sea birds and micro organisms with in the ocean.

CAPSTAN students Angela (left) and Umair (right) work together to take discrete sediment samples from the kasten core and place them in a small plastic sample bag as part of the hands on marine science training on RV Investigator during the 2019 voyage
Here, we take discrete samples from the kasten core in the sediment lab (Photo Credit: April Abbott)

This year’s training cruise was targeted on the canyon system on the eastern edge of the Bight Basin, near the outer continental shelf just southeast of Portland, Victoria. This region is unique due to the presence of cool water carbonate turbidite deposits. Such carbonate systems can only be formed with minimal terrestrial input. I was enthusiastic to see these carbonate systems as my masters research project is also related to the carbonates but they are formed in warm and temperate environment.

A bathymetric map of the canyon off Portland Victoria studied as part of hands-on marine science training on RV Investigator during CAPSTAN 2019.  Overlaid on the bathymetric map is color depicting the steepness of the slope with warm colors showing the steepest regions and cool colors showing the less steep regions.
Map of the canyon near Portland showing slope steepness (red is steepest)

Carbonate involves limestone and dolomite (rocks) that consists of mineral calcium carbonate (CaCo3) and dolomite CaMg(Co3)2 respectively. The organisms that live with in the water are zooplanktons (animals) and phytoplanktons (plants). They are made up of calcium carbonate and after their death they accumulated with in the water and after cementation and compaction, limestone is formed. It is important to understand carbonates because they can tell us about sea level changes, paleoceanography, paleoclimates, and marine ecosystems. They also holds around 50% of the oil and gas reserves.

View down the microscope of foraminifera, a sponge spicule, and other coarse grain material from a sieved sediment sample students collected from a kasten core as part of hands-on marine science training on RV Investigator during CAPSTAN 2019
A close up of some of the carbonate sediments we collected. In this view down the microscope, several foraminifera (phytoplankton) are visible. (Photo Credit: April Abbott)

A submarine canyon is a steep sided valley that extends from continental shelf to the sea bed. The turbidity currents carry material from the continental shelf passes through the canyon with an immense speed and may deposited with in the canyon and deep ocean floor. There can be many driving forces behind these turbidity deposits. These can be triggered by earthquake, gravity flows and tectonic forces. Due to density contrast between the sediments, the coarser ones will deposit first and finer will remain in suspension and deposited at the end.  

CAPSTAN 2019 Chief Scientist Leah Moore motions with her hands to illustrate how a rock dredge collects samples during a gear tour on board RV Investigator for students participating in the at-sea hands on marine science training program
Chief Scientist Leah Moore explains the rock dredge during a gear tour (Photo Credit April Abbott)

Our chief scientist, Dr. Leah Moore selected specific depths for coring after looking at the bathymetry (geophysical) data. The bathymetry data uses acoustic (sound) waves to determine the geomorphological features of the ocean floor. The RV Investigator is equipped with the Kongsberg EM122 multibeam echosounders to retrieve high quality bathymetry maps. The cores were retrieved at 1700m, 2200m, 3700m and 4700m depths. I was working in the sedimentology lab to find out the variations in percentage of the fossils present in the top and bottom of each core. I was exposed to using the microscope to identify different foraminifera.

CAPSTAN students collect water from the niskin bottles surrounding the CTD rosette as part of hands-on marine science training on board RV Investigator.
Taking water samples from the niskin bottles attached to the CTD rosette (Photo Credit: April Abbott)

Another exciting thing was CTD as it was new for me. CTD stands for conductivity, temperature and depth. It consists of a carousel that has 36 niskin bottles with sensors at the bottom. In the operations room, a fluorescence curve that shows the chlorophyll activity with in the ocean and helps to decide the locations for samples. These bottles were closed at designated depths while coming back to surface. The polystyrene cups that were decorated by the students were sent down with the CTD to demonstrate the pressure affect. These polystyrene cups became very small in size after coming back from the ocean. Due to this small experiment, it is very easy to understand that pressure increases with depth.

Styrafoam cups shrunken to about the size of a shot glass can be seen in a pile in an onion bag.  These cups were sent kilometers below ocean and the pressure shrunk them from their original size.
Polystyrene cups after being sent down with the CTD are seen here in an onion bag (Photo Credit April Abbott)

On the very last day, we had a lot of fun. Our CAPSTAN director, Dr. April Abbott arranged a quiz to entertain all the participants and crew members. Everyone was in a different costume except me to relish those last moments. Our trainer, Stephen is a great geologist but his sense of humour was also amazing. I am obliged to be a part of this exciting opportunity as it not only increased my knowledge related to marine science but also helped me to thick critically, improved my confidence and science communication skills.

CAPSTAN trainers sit in the RV Investigator's mess looking at a laptop while discussing data students collected as part of the hands on marine science training voyage.
CAPSTAN co-chief scientist Matt (left) and trainer Stephen (right) discuss the results from the sedimentology lab in the mess

The best laid plans

By Suzanne Egan, University of Tasmania

Due to the nature of the support offered by the CSIRO Marine National Facility to the CAPSTAN Program, our story takes place on a transit leg of the RV Investigator.  This means that it was already sailing from Hobart to Fremantle for its next major voyage. For this reason, our Chief Scientist, Dr Leah Moore, had to design a 48-hour sampling program that lay along the route through that part of the Southern Ocean.

Google map of the eastern edge of the Great Australian Bight showing the bathymetry of the region.  9 yellow stars indicate the study sites in 3 canyons next to each other along the slope off Portland that were proposed for the 2019 CAPSTAN voyage.
1) The original plan with three transects along canyons off the Portland Coast

Fortunately, the southern Australian coast offers many unique and varied locations for such an investigation, so Dr. Moore chose to look a little more closely at an area off the south-western coast of Victoria, near Portland. This region is unique due to the low terrestrial sediment input that occurs, so material moving in the submarine canyons that cut across the continental slope is dominated by pelagic sediment (of oceanic origin), some in the form of fluidised flow deposits (cold water carbonate turbidites). The planktonic fossils in these sediments can also be used to help recreate past climatic conditions.

The other interesting phenomenon that occurs in this region from a biological point of view is the Bonney Upwelling, which is the largest and most predictable along the Great Australian Bight. The upwelling of cold nutrient-rich deep ocean water is episodically active along the coast from Portland, Victoria through to Robe, South Australia. The continental shelf narrows to approximately 20 km here and the upwelling water is funnelled up the underwater canyons onto the shelf, where it fuels phytoplankton (microscopic plants) and plankton (microscopic animals) blooms, which in turn feed whales, seals and birdlife.

Map of the great Australian Bight showing the sea surface temperature between 20 degrees C in the northern most part of the Bight (yellow) and 12 degrees C (purple) to the south.  The area focused on during the 2019 CAPSTAN marine science training voyage is outlined by a red box near Portland.
2) Sea surface temperature map for the Great Australian Bight on 26th April 2019 shows warm water adjacent to the coast in the study area (red box), meaning cold bottom water is not present. Satellite data was obtained from Copernicus Marine Environment Monitoring Service and provided by V. Tamsitt.

The plan going into the voyage was to map two canyons (maybe three if there was enough time), collect sediment cores, bathymetry, oceanographic and biological data within the Bonney Upwelling area (Figure 1).

And, of course, the best laid plans… so once on board with access to higher resolution geophysics data Dr. Moore decided to modify our station locations. The easternmost canyon was not going to be suitable to place the cores at the depths originally planned as it was much steeper than expected. The adjacent canyon was an interesting Y-shape and much broader enhancing the opportunity to place cores, with an increased chance of finding the turbidites we were looking for. In addition, consultation of satellite, meteorological, and Argo float data indicated that the Bonney Upwelling was not active, so an alternative plan was required and quickly (Figure 2). 

Bathymetric map of the canyons off Portland showing the ship's track (black line), sample stations within the y shaped canyon, and waypoints to guide the ship's track during the 2019 CAPSTAN voyage.
3) Final voyage track showing waypoints (so the ship would follow the canyon) and station locations.

To maximise the time on station and to try to get as many cores collected as possible (its safer to collect them in daylight) the biological and oceanographic data were collected in the early hours before dawn or in the late afternoon to evening. Overnight we mapped the sea floor at high resolution to assist with the AusSeaBed Project (http://marine.ga.gov.au/). The final voyage map reflects the waypoints for ship navigation and station locations along the canyon (Figure 3).

As a teaching voyage it was an amazing opportunity to see how decisions were made and why (this explanation came after we left the stations due to time constraints) and how to adjust on the fly to changing conditions and circumstances while still ensuring project objectives and data quality were not compromised. As a result, all the equipment we deployed on this scientific voyage generated high quality data and a complete suite of samples, which rarely happens at sea. It was also great for our Chief Scientist to then sit down and talk us through all the decisions she had made and why, and convey that to us.  The best laid plans…

RV Investigator… now that’s what you call a tight ship!

By Angela Russell, University of Adelaide

To conduct the science needed to unravel the mysteries of the ocean and its influence on ecology and climate, you need to take operations up a notch. Some may think it’s simply a matter of dangling a few instruments over the side of a boat but let me tell you…RV Investigator is no ordinary boat!

In this photo, RV Investigator steams across the ocean.  RV Investigator is a 93.9m long, 18.8m wide ship, powered by three diesel engines and two electric propulsion motors (Figure 1). Purpose built for CSIRO, the RV Investigator puts Australia at the forefront of ocean research globally, conducting oceanography, geoscience, atmospheric and marine science, from the Antarctic ice edge to the tropics.
Figure 1: RV Investigator at full steam (Photo Credit: C. Minness)

RV Investigator is a 93.9m long, 18.8m wide ship, powered by three diesel engines and two electric propulsion motors (Figure 1). Purpose built for CSIRO, RV Investigator puts Australia at the forefront of ocean research globally, conducting oceanography, geoscience, atmospheric and marine science, from the Antarctic ice edge to the tropics. Along with a phenomenal team of engineers, navigational crew (Figure 2), technical crew and IT professionals, the ship’s impressive technical capabilities allow us to enhance our investigations to an advanced level.

The navigational control deck faces a long panel of windows in the bridge of RV Investigator.  Part of the at-sea training on board RV Investigator for CAPSTAN's 2019 voyage included a bridge tour.
Figure 2: The navigational control deck within the ship’s bridge. (Photo Credit: Angela Russell)

The vessel is like a mesocosm of the world! It accommodates 40 scientists and support staff, and twenty crew. RV Investigator generates around nine megawatts of power, enough electricity to power a small suburb! It even completely biodegrades all sewerage onboard, so as not to contaminate the samples. Obviously, there is no room for error here, so engineers work around the clock to maintain the workings of the ship, keeping replacements for every part of the machinery. Engineers are also equipped with a workshop to repair engine parts or scientific units on the fly.

Colored bathymetric map of the Discovery Bay Canyon off of Portland Victoria with deeper water indicated by purples and blues and shallower waters in reds and yellows. The Discovery Bay Canyon has a Y shape and was the study area for the 2019 CAPSTAN voyage.
Figure 3: Bathymetric map of the Discovery Bay Canyon (Photo Credit: J. Daniell)

A brief overview of RV Investigators ‘kit’ includes advanced sonar technology which emits acoustic signals in a 30 km wide beam in water depths to 11.5 km to reveal, in 3D, seafloor features such as deep-sea canyons and mountains. We used this swath data and ArcMap (GIS) software to create a high-resolution bathymetry map of a previously unmapped, deep sea canyon we traversed (Figure 3). A drop keel underneath the ship (Figure 4) can be raised or lowered into the water column. This allows water samples to be recovered without interference from the ship.

A view down to the top of the drop keel meters below from RV Investigator.  In this photo the drop keel has been lowered to be even with the ship's gondola (not pictured).  A tour of the ship, including normally restricted areas such as that around the drop keel, was part of the student experience during their at sea marine science training on CAPSTAN's 2019 voyage.
Figure 4: The drop keel lowered to the water’s surface (Photo Credit: Angela Russell)

The ship is specifically designed to an international maritime classification called DNVSilent-R. This means RV Investigator is one of the quietest vessels in the world. Radiated ship noise interferes with acoustic signals, so by building a quiet ship, the performance of the equipment used to monitor the marine ecosystem, and map the seafloor is maximised. Roll stabilization also improves our use of scientific instruments, such as microscopes and balances, which can be tricky on a moving ship.

CAPSTAN 2019 Chief Scientist and support staff describe the sediment grab sampler on deck while RV Investigator transits to the first station for sampling. On the work deck, all personnel must wear hard hats and steel capped boots.
Figure 5: Chief Scientist Leah Moore discussing the deployment of the Smith MacIntyre sediment grab sampler with the technical support and science team. Photo Credit: Angela Russell

The logistics behind the location of sample sites and each sample collection is a strategic masterpiece and one aspect of our mission I was particularly in awe of. The Chief Scientist works in close collaboration with the Technical Operations Team, Integrated Ratings Crew and Master of the ship, to design each procedure in a way that ensures the safety of the crew and their scientific instruments, to meet the research objectives and to optimise sample quality. It really is a symbiotic relationship, in that each is part of the team that is integral to the other (Figures 5,6,8).

RV Investigator crew and support team deploy the CTD (conductivity, temperature, depth) rosette surrounded by niskin bottles over the starboard side of the ship.  Students were involved in monitoring the live readouts of the data to give depths to the winch operators and to fire the bottles as part of their at sea marine science training on board the 2019 CAPSTAN voyage.
Figure 6: Deployment of the CTD (conductivity, temperature, depth) rosette. Photo Credit: Angela Russell

One of my highlights of the voyage was in the operational room on the internal communication system during deployment of the CTD unit (Figure 7). It was my job to request the CTD stops required to collect water samples remotely at different depths, up to the Integrated Ratings crew (IR crew) located in the ‘Cat House’. This area is where the winch and boom are managed, and where all the ships cameras are simultaneously viewed. This gives IR crew the ability to visualise the CTD going over the side, while viewing the winches below deck as it descends. Once the unit was in position at its lowest depth (it went down to 4500m), I fired the closing of each of the 24 sample bottles on the return journey with a single mouse click.

CAPSTAN student Angela oversees a CTD deployment from the operations room on board RV Investigator as part of the hands on marine science training.  She monitors live readings transmitted from the rosette and plotted on the computer screen to determine depths for discrete sampling with the niskin bottles and communicates the next depth to winch operators.  Once the rosette reaches a desired depth, she can fire each bottle with the click of a button.
Figure 7: Firing 4500 m deep niskin bottles on the CTD rosette from the operations room (Photo Credit: April Abbott)

As students of the CAPSTAN voyage, we are spoilt with the level of expertise and state-of-the-art technology provided to us. It’s been a once in a lifetime experience that I will be forever grateful for.

RV Investigator crew and technical support staff secure the kasten core to the stern deck following a successful deployment.  4 kasten cores were collected as part of the hands on marine science training on the 2019 CAPSTAN voyage.
Figure 8: Crew and support staff secure the Kasten sediment corer after recovery using the hydraulic A-frame rig (Photo Credit: Angela Russell)

The hunt for cool-water carbonate turbidites

By Mardi McNeil, Queensland University of Technology

Every marine science voyage has a research plan and specific aims and objectives that the science party wants to achieve. Months, or sometimes (usually) years, goes into planning the voyage and targeted survey site selection in order to achieve aims, test a hypothesis, or answer questions which will fill a knowledge gap in our understanding of the marine system we are studying. This is how science works!

Map of the ship track for CAPSTAN's 2019 voyage.  The map shows the eastern part of the Great Australian Bight showing the ship track from Hobart to the canyons off of Portland and then the planned track as the ship begins its transit from the study site to Fremantle.
The CAPSTAN voyage survey area of the Portland Canyons and Otway basin off southern Australia (green and red dots). RV Investigator will then transit across the Great Australian Bight to Fremantle.

The science objectives for our CAPSTAN voyage have been planned out by our Chief Scientist Dr Leah Moore, and the educational objectives by our CAPSTAN Director Dr April Abbott. On this research cruise we are targeting a submarine canyon system which connects the continental shelf margin off Portland Victoria, to the Otway Basin at 5,500 m water depth in the Southern Ocean. We are literally sailing across the abyss!

Our primary geological objective is the search for a cool-water carbonate turbidites, resulting from the funnelling of sediment down the submarine canyon until it is deposited in a submarine fan at the base of the canyon. Cool-water carbonate systems are not as well studied as their sub-tropical and tropical counterparts as there are fewer places in the world where they occur, and they’re typically in deeper water.

Photos of the sediment collected in the third kasten core with a full core image on the left and a inset with a zoomed in photo of the biological hash visible between 165 cm and 182 cm in the core. The core was collected as part of the hands-on marine science training on CAPSTAN's 2019 voyage.
Photomosaic of Core #3 (left) and inset of the 165 to 182 cm section. This close up shows coarse carbonate bioclasts (grains) of bryozoans and forams, referred to as a bryomol/foramol assemblage and considered typical of the cool-water carbonate factory. The coarser grains are embedded in a muddy matrix comprised almost entirely of planktonic forams (visible only under the microscope). Photo Credit: Matt Jeromson and Mardi McNeil.

The term “Carbonates” refers to sediment grains which are comprised of calcium carbonate minerals, commonly calcite and aragonite. Over geological time these sediments lithify to form limestone rock. Most carbonate sediments are biogenic in origin, which means they are produced by biological organisms. The classic example is a coral reef, where the soft coral polyps precipitate their hard skeletons, and coralline algae produces the calcite cement which glues it all together, resulting in hard limestone.

In a cool-water carbonate system there are definitely no reef building corals. In southern Australia, the main carbonate producers are bryozoans and foraminifera. Bryozoans are colonial, meaning hundreds to thousands of tiny animals called zooids, live together in a colony and collectively produce a hard carbonate skeleton. This skeleton can take many forms, like delicate fan-like nets, or robust upright branching sticks.

Microscope images showing species of calcareous plankton that are being used in the description of the cores collected on the 2019 CAPSTAN marine science training voyage and an image of a smear slide with these species present from one of the cores collected from RV Investigator.
Examples of the micro and nanno fossils we have been using as stratigraphic markers in our sediment cores: A) Scanning Electron Microscope image of planktonic foraminifera Neogloboquadrina pachyderma typical of polar or glacial assemblages (Almond et al., 1993), B) Scanning Electron Microscope image of the coccolithophore Emiliani huxleyi indicating sediments are younger than 80,000 years (www.mikrotax.org), and C) transmitted light microscope image of a sediment smear slide from the current voyage that shows abundant E. huxleyi (photo: Annabel Payne). A and B are not to scale.

Foraminifera (or just “forams”) are single celled organisms similar to an amoeba, but they secrete a calcite “test”, or shell. Foram tests come in an almost endless variety of shapes and sizes, and can be benthic (bottom dwelling) or planktic, meaning they live freely in the water column. Forams have evolved rapidly throughout geological time (hundreds of millions of years), so geologists and micropalaeontologists use foram test shapes to determine the age of the sediments we are looking at. This helps us to quickly “date” our cores in the field, where we don’t have the capacity to use isotope mass-spectroscopy analysis to determine an absolute age. One reason we want to know the age of our cores is to determine whether the sediments we’re looking at were produced during a glacial cold period, or an inter-glacial warm period like today.

Schematic from Passlow 1997 showing a classic turbidite sequence with the coarser grains settling out first (lower in the sediment column) and fining upwards.
A ‘classic’ turbidite sequence showing how sediments are deposited out of suspension after gravitational and hydrodynamical flows (Credit: Passlow, 1997)

On this CAPSTAN voyage we have collected three cores from different water depths within the Portland Canyon, and one from the bottom of the canyon in the fan. We hope to capture evidence of glacial-interglacial cycles, and a cool-water carbonate turbidite system.

In geological speak, a turbidite is a characteristic sedimentary deposit which forms when sediment is transported down-slope in a fluidised (watery) plume under the influence of gravity. Because different sediment grains have different densities and shapes, they settle out of suspension in a characteristic way. The most dense sediments settle first, and the lighter less dense sediments are the last to fall out of suspension. This cycle repeats over and over every time there is a gravity driven turbid flow, resulting in a characteristic cyclical pattern of deposition which we call a turbidite.

Four of the sedimentology team sit around the laboratory bench excited about the preliminary results from the sediment cores and grabs taken as part on marine science training on CAPSTAN's 2019 voyage.
The other heroes of the Sedimentology Lab feeling triumphantly satisfied at the results coming out of the canyon cores. From left to right: Kaycee, Stephen, Jin Sol, and Matthew (missing: Bella and Mikala)

Onboard RV Investigator we have now finished our coring and are working through sampling the cores at 10 cm intervals, looking at the sediments under the microscope to see what carbonate grains we have. Our preliminary results are in, and there is some excitement coming from the Sedimentology lab! We have picked up a glacial – interglacial cycle, and managed to estimate an oldest date based on a nanno-fossil called a coccolith, which we know from the geological record was abundant from about 80,000 years ago, so we now know that our cores cannot be older than 80,000 years.

So the big heroes of the Sedimentology Lab are the tiniest carbonate grains which allow us to read our cores like a history book, and interpret biological and physical processes through geological time. And it turns out that we have indeed, found our cool-water carbonate turbidites, and glacial-interglacial cycles. Science mission accomplished!