Phytoplankton and Pigments – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We have had another great day and have almost completed Station 2 on the 110 East line.

It has been a little cloudy and a little breezier today but the flesh-footed shearwaters are happily gliding just above the waves. Everyone is getting into the swing of having their nets deployed and retrieved and the sample jars are being dutifully labelled and nicely filled!

 

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 19, 2019 Time:  1200 AWST
Latitude: 36.5°S Longitude: 110°E
Wind direction: NNW Wind speed: 27 knots
Swell direction: SW Depth: 5365 m
Air temperature: 16°C Sea temperature: 15.3°C
Notes: It’s a bit rainy and soggy today but this is not dampening the spirits of the scientists aboard RV Investigator! This morning we completed our deepest CTD to date, at over 5 km depth.

 

Phytoplankton & Pigments

By David Antoine and Martina Doblin

Phytoplankton–the microscopic plants inhabiting the surface lit layers of the ocean are among the most diverse group of micro-organisms inhabiting the planet. They comprise eight main groups, have individual cell sizes from less than a micron to about one millimeter (see Figure below) and play various roles in the ecosystem. As they photosynthesize, they collectively represent the first link of the marine food web. All phytoplankton contain the pigment chlorophyll-a, which is measured to ascertain phytoplankton biomass. As well as chlorophyll-a, each phytoplankton group has other accessory pigments, which can be used to determine phytoplankton groups or size classes. Phytoplankton are also responsible for the transfer of carbon dioxide from the atmosphere to the deep layers of the ocean and ultimately the sediments of the sea floor.

Fig 1. An indication of the scale of phytoplankton size in microns relative to larger biota and recognisable land features in metres. Source : Finkel et al. 2010. J. Plank. Res. 32(1), 119-137.

 

Peta Vine (University of Technology Sydney) using the large filtration rack to separate phytoplankton and their associated pigments from water samples collected at different depths with the CTD Niskin bottles. Photo: Micheline Jenner.

 

After the water has been filtered the pigments remain on the small filter papers and here, Peta Vine (University of Technology Sydney) points to a filter with pigments, in comparison to the adjacent clean filter. Photo: Micheline Jenner.

 

Examples of phytoplankton from the south-east Indian Ocean. Top: A diatom chain clearly showing green chlorophyll and a stunning Chaetoceros sp. photographed under a microscope from water samples collected from the RV Investigator on the 110°East line. Photo: Dr Peter Thompson.

 

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

Tiny Microbes, Big Impact – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We have had another fantastic day in the Indian Ocean aboard RV Investigator. The CTD was deployed early in the morning and with a calm sea and light wind, the first station on the 110 East line was successfully completed. Micro and macro zooplankton have been collected with various nets, the CTD rosette was lowered twice and from those water samples, nutrients and microbes have been sampled for analysis.

We even had a minke whale sighted not too far from the ship and then two fin whales passed the starboard side and then across the bow! We have plankton and whales, life is good!

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

 

Date: May 18, 2019

Time:  1200 AWST

Latitude: 38°S

Longitude: 110°E

Wind direction: N    

Wind speed:  15 knots

Swell direction: SW

Depth:  4266 m

Air temperature: 13.7°C

Sea temperature: 13.8°C

Notes: Station 1 is done and dusted. It was a very busy day with lots of samples and data collected by many satisfied scientists.

 

Tiny Microbes, Big Impact

By Dr Martin Ostrowski

Microbes are everywhere, they’re in the soil, on our skin, in our guts and they live in the ocean in incredible numbers. In a similar role to our gut microbes, which are keeping us healthy, research has revealed that ocean microbes play important roles sustaining our planet. What are these microbes and what are they doing? Onboard RV Investigator a team of microbiologists is addressing these questions using modern molecular methods. They aim to identify which microbes are present and determine how they thrive and interact with other species. This work will help us understand how these tiny organisms support the production of food in the ocean, which feeds over 1 billion people, and ultimately plays a fundamental role keeping our planet healthy. 

Most marine microbes are planktonic, but surprisingly, they fundamentally shape their surroundings by transforming over 90% of all organic matter, driving major elemental and geochemical cycles, and making and breaking chemical compounds that have a direct effect on climate. What they lack in size, they make up for in sheer numbers.

The activity of microbes impacts on all levels of the marine systems, from water chemistry and primary production, which ultimately supports all marine life, through to regulating climate and playing a role in the health of the largest mammals on the planet. Over geological time, free-living marine microbes have been the main source of power for the planet. By modern estimates, approximately half of all primary production occurs in the oceans. In very general terms, this means that marine microbes are like the lungs of the planet, but in reverse, drawing in carbon dioxide and releasing oxygen for us to breathe.

 

In the CTD room, several scientists retrieve water samples from the Niskin bottles for microbial analyses. In the foreground from left, Amaranta Focardi (Macquarie University) documenting the details and James O’Brien (University of Technology Sydney) and Dr Peter Thompson (CSIRO) taking water from the rosette. Photo: Micheline Jenner.

 

Microbes are invisible to the naked eye, especially the single-celled species, which make up the bulk of ‘biomass’ in the oceans. Much of the work done in the microbiology lab involves flow cytometry and high-throughput genome sequencing of water samples collected from different depths using the CTD rosette of Niskin bottles. We use the cytometer to count different types of bacteria, cyanobacteria, micro algae and virus particles. There are more than one million microbial cells in each millilitre of seawater, and 10 times more viruses! Sequencing of microbial marker genes provides estimates of total diversity in the Australian marine microbiome.

 

 

Pramita Ranjit (Macquarie University) filters water in one of the laboratories on the RV Investigator to determine the microbiome of the south-east Indian Ocean at the first station on the 110° East line. Photo: Micheline Jenner.

 

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

 

Indian Ocean Nutrients – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

The wind and swell was up a little yesterday. This seemed to keep a few participants in their bunks a bit longer in the morning but by evening, most were feeling fine again. Fortunately, this was a transit day and the weather has improved as we have begun the first station on 110 East meridian. 

The yellow-nosed and black-browed Albatross were soaring beautifully in the fresh 20-30 kts and all is well on the fine RV Investigator.

 

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

 

Date:  May 17, 2019

Time:  1200 AWST

Latitude: 39.5°S

Longitude: 110°E

Wind direction: NNW 

Wind speed: 10 knots

Swell direction: SSW

Depth: 4600 m

Air temperature: 9.6°C

Sea temperature: 12.6°C

Notes: Five species of albatrosses, cape petrels and a minke whale sighted today. The galley is providing wonderful food for a hungry and appreciative crew!

Indian Ocean Nutrients

By Dr Peter Thompson

The CSIRO scientists involved in the original International Indian Ocean Expedition during the 1960s described it as a desert. Huge regions of the Indian Ocean had almost no plant life. The thousands of species and billions of microscopic plants found in most oceans were largely absent. These plants, just like the ones in your garden or paddock, require nutrients to grow. In the garden, we add fertiliser with these nutrients, particularly nitrogen and phosphorus, to ensure a successful crop. These nutrients are in very short supply in the surface waters of the Indian Ocean.

To find out how much nutrient is present it is necessary to get samples of water from deep in the ocean. Special tubular containers, called Niskin bottles, located on the CTD are sent down with the ends open (can you guess why?) on a wire to depths of 5000 m where they are electronically triggered to close and collect the samples. Several hours later when the bottles are winched back to the surface the chemists can start the process of measuring the nutrients. To do this we use sophisticated on board instruments and internationally agreed high precision methods. It is a bit like a blood test to check the health of the ocean.

Dr Peter Thompson (CSIRO) and Dr Karlie McDonald (CSIRO) take water from two of the 36 Niskin bottles in the CTD rosette, to analyse nutrient levels of the south-east Indian Ocean. Photo: Micheline Jenner.

 

In the nearly 60 years since the first International Indian Ocean Expedition we have learned much about the cycling of nutrients in the ocean. A thousand meters below the surface where the water is only 5°C, nitrate is plentiful (Figure 1). However, enough light for plants to grow only penetrates to about 100 m where nitrate is particularly scarce. Processes that we did not understand in the 1960s, we now know are changing the supply of nutrients to the surface and some parts of the Indian Ocean are becoming more productive (more nutrients = more plants = more fish) while others are less productive. On this second voyage (IIOE-2) we are exploring how nutrient supply has changed over the last six decades in the Indian Ocean offshore of Western Australia.

Figure 1. Plots of temperature, light and nitrate in the upper water column. Temperature declines slowly with depth but light disappears dramatically at about 100 m depth in the open Indian Ocean. The amounts of nutrients, such as nitrate, are very low until around 200 m depth. Data courtesy of CSIRO.

 

In particular, we are looking for evidence of changes in nutrients within the deep ocean as a result of changing global ocean circulation patterns. This mix of deep and shallow circulation brings deep nutrients from the North Atlantic and some nutrients from the Pacific into the Indian Ocean (Figure 2).

 

Figure 2. The global ocean and its thermo-haline circulation bring nutrients from deep regions in the North Atlantic and the surface of the Pacific into the Indian Ocean. Image courtesy of NASA/JPL.

These processes are changing faster than ever due to global warming. In addition, we will investigate nutrient recycling near the surface of the ocean. There, an expanding area of low oxygen is impacting on the microbial processes that recycle organic matter. Understanding the impacts of these changes on the ecology of the Indian Ocean is one of the key goals of the 110° East voyage.

Dr Peter Hughes (CSIRO) in the hydro-chemistry lab aboard RV Investigator uses sophisticated and precise equipment to measure chemical composition of the water sampled by the CTD. Photo: Micheline Jenner.

 

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au .

 

 

Micro- and Mesozooplankton – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We had a couple of fronts blow through today, but the 27-30 knots of wind and blustery rain did not hinder the wonderful work of the deck crew. All the nets were deployed and retrieved carefully and efficiently. 

There is blue sky ahead but even in the slightly blustery conditions, the company of Wandering and Black-browed Albatross at Station 3 was appreciated.

 

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 20, 2019 Time:  1200 AWST
Latitude: 35°S Longitude: 110°E
Wind direction: WSW Wind speed: 23 knots
Swell direction: W Depth: 4911 m
Air temperature: 14.8°C Sea temperature: 18.3°C

Notes: The rain has cleared and there are patches of blue sky all around! Rock lobster larvae (phyllosoma) were caught in the surface nets last night and pygmy blue whales were heard calling in the east.

Micro- and Mesozooplankton

By Michael Landry

Planktonic consumers can be divided into two major size classes, the micro- and mesozooplankton, depending on whether they pass through or are retained on 200-µm mesh sieve. The mesozooplankton consists mainly of true multicellular animals, like copepods, euphausiids (krill) and chaetognaths (arrow worms), that are concentrated and collected by towing a plankton net with 200-µm mesh through the water. In contrast, the microzooplankton (<200 µm) category contains mainly protozoans (single-cell flagellates and ciliates) with some very small animals and is best collected by preserving water samples without prior net concentration.

Both micro- and mesozooplankton are diverse assemblages of organisms with varying life strategies and feeding preferences, but they are associated with different functions in ocean food webs. Microzooplankton are typically the main consumers of phytoplankton and bacteria, especially in regions where the dominant phytoplankton Mesozooplankton, on the other hand, are the main food web link to higher level animals (fishes), and they are associated with mechanisms (daily migrations, rapidly sinking fecal pellets) that move organically fixed carbon and nutrients out of the euphotic zone and into deeper layers of the ocean. Studying how ocean systems differ in terms of how productivity moves through micro- versus mesozooplankton is therefore a basic approach to characterizing their different relative functions in nutrient recycling, trophic transfers and carbon export.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

Phytoplankton and Pigments – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We have had another great day and have almost completed Station 2 on the 110 East line.

It has been a little cloudy and a little breezier today but the flesh-footed shearwaters are happily gliding just above the waves. Everyone is getting into the swing of having their nets deployed and retrieved and the sample jars are being dutifully labelled and nicely filled!

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 19, 2019 Time:  1200 AWST
Latitude: 36.5°S Longitude: 110°E
Wind direction: NNW Wind speed: 27 knots
Swell direction: SW Depth: 5365 m
Air temperature: 16°C Sea temperature: 15.3°C

Notes: It’s a bit rainy and soggy today but this is not dampening the spirits of the scientists aboard RV Investigator! This morning we completed our deepest CTD to date, at over 5 km dept

Phytoplankton & Pigments

By David Antoine and Martina Doblin

Phytoplankton–the microscopic plants inhabiting the surface lit layers of the ocean are among the most diverse group of micro-organisms inhabiting the planet. They comprise eight main groups, have individual cell sizes from less than a micron to about one millimeter (see Figure below) and play various roles in the ecosystem. As they photosynthesize, they collectively represent the first link of the marine food web. All phytoplankton contain the pigment chlorophyll-a, which is measured to ascertain phytoplankton biomass. As well as chlorophyll-a, each phytoplankton group has other accessory pigments, which can be used to determine phytoplankton groups or size classes. Phytoplankton are also responsible for the transfer of carbon dioxide from the atmosphere to the deep layers of the ocean and ultimately the sediments of the sea floor.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

Tiny Microbes, Big Impact – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We have had another fantastic day in the Indian Ocean aboard RV Investigator. The CTD was deployed early in the morning and with a calm sea and light wind, the first station on the 110 East line was successfully completed. Micro and macro zooplankton have been collected with various nets, the CTD rosette was lowered twice and from those water samples, nutrients and microbes have been sampled for analysis.

We even had a minke whale sighted not too far from the ship and then two fin whales passed the starboard side and then across the bow! We have plankton and whales, life is good!

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 18, 2019 Time:  1200 AWST
Latitude: 38°S Longitude: 110°E
Wind direction: N Wind speed:  15 knots
Swell direction: SW Depth:  4266 m
Air temperature: 13.7°C Sea temperature: 13.8°C

Notes: Station 1 is done and dusted. It was a very busy day with lots of samples and data collected by many satisfied scientists.

Tiny Microbes, Big Impact

By Dr Martin Ostrowski

Microbes are everywhere, they’re in the soil, on our skin, in our guts and they live in the ocean in incredible numbers. In a similar role to our gut microbes, which are keeping us healthy, research has revealed that ocean microbes play important roles sustaining our planet. What are these microbes and what are they doing? Onboard RV Investigator a team of microbiologists is addressing these questions using modern molecular methods. They aim to identify which microbes are present and determine how they thrive and interact with other species. This work will help us understand how these tiny organisms support the production of food in the ocean, which feeds over 1 billion people, and ultimately plays a fundamental role keeping our planet healthy.

Most marine microbes are planktonic, but surprisingly, they fundamentally shape their surroundings by transforming over 90% of all organic matter, driving major elemental and geochemical cycles, and making and breaking chemical compounds that have a direct effect on climate. What they lack in size, they make up for in sheer numbers.

The activity of microbes impacts on all levels of the marine systems, from water chemistry and primary production, which ultimately supports all marine life, through to regulating climate and playing a role in the health of the largest mammals on the planet. Over geological time, free-living marine microbes have been the main source of power for the planet. By modern estimates, approximately half of all primary production occurs in the oceans. In very general terms, this means that marine microbes are like the lungs of the planet, but in reverse, drawing in carbon dioxide and releasing oxygen for us to breathe.

Microbes are invisible to the naked eye, especially the single-celled species, which make up the bulk of ‘biomass’ in the oceans. Much of the work done in the microbiology lab involves flow cytometry and high-throughput genome sequencing of water samples collected from different depths using the CTD rosette of Niskin bottles. We use the cytometer to count different types of bacteria, cyanobacteria, micro algae and virus particles. There are more than one million microbial cells in each millilitre of seawater, and 10 times more viruses! Sequencing of microbial marker genes provides estimates of total diversity in the Australian marine microbiome.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

Indian Ocean Nutrients – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

The wind and swell was up a little yesterday. This seemed to keep a few participants in their bunks a bit longer in the morning but by evening, most were feeling fine again. Fortunately, this was a transit day and the weather has improved as we have begun the first station on 110 East meridian. 

The yellow-nosed and black-browed Albatross were soaring beautifully in the fresh 20-30 kts and all is well on the fine RV Investigator.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date:  May 17, 2019 Time:  1200 AWST
Latitude: 39.5°S Longitude: 110°E
Wind direction: NNW Wind speed: 10 knots
Swell direction: SSW Depth: 4600 m
Air temperature: 9.6°C Sea temperature: 12.6°C

Notes: Five species of albatrosses, cape petrels and a minke whale sighted today. The galley is providing wonderful food for a hungry and appreciative crew!

Indian Ocean Nutrients

By Dr Peter Thompson

The CSIRO scientists involved in the original International Indian Ocean Expedition during the 1960s described it as a desert. Huge regions of the Indian Ocean had almost no plant life. The thousands of species and billions of microscopic plants found in most oceans were largely absent. These plants, just like the ones in your garden or paddock, require nutrients to grow. In the garden, we add fertiliser with these nutrients, particularly nitrogen and phosphorus, to ensure a successful crop. These nutrients are in very short supply in the surface waters of the Indian Ocean.

To find out how much nutrient is present it is necessary to get samples of water from deep in the ocean. Special tubular containers, called Niskin bottles, located on the CTD are sent down with the ends open (can you guess why?) on a wire to depths of 5000 m where they are electronically triggered to close and collect the samples. Several hours later when the bottles are winched back to the surface the chemists can start the process of measuring the nutrients. To do this we use sophisticated on board instruments and internationally agreed high precision methods. It is a bit like a blood test to check the health of the ocean.

In the nearly 60 years since the first International Indian Ocean Expedition we have learned much about the cycling of nutrients in the ocean. A thousand meters below the surface where the water is only 5°C, nitrate is plentiful (Figure 1). However, enough light for plants to grow only penetrates to about 100 m where nitrate is particularly scarce. Processes that we did not understand in the 1960s, we now know are changing the supply of nutrients to the surface and some parts of the Indian Ocean are becoming more productive (more nutrients = more plants = more fish) while others are less productive. On this second voyage (IIOE-2) we are exploring how nutrient supply has changed over the last six decades in the Indian Ocean offshore of Western Australia.

In particular, we are looking for evidence of changes in nutrients within the deep ocean as a result of changing global ocean circulation patterns. This mix of deep and shallow circulation brings deep nutrients from the North Atlantic and some nutrients from the Pacific into the Indian Ocean (Figure 2).

These processes are changing faster than ever due to global warming. In addition, we will investigate nutrient recycling near the surface of the ocean. There, an expanding area of low oxygen is impacting on the microbial processes that recycle organic matter. Understanding the impacts of these changes on the ecology of the Indian Ocean is one of the key goals of the 110° East voyage.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

Taking the Pulse of the Ocean with the CTD – One Ten East log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

 

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

 

Date: May 16, 2019

Time: 1200 AWST

Latitude: 37.143° S

Longitude: 111.712° E

Wind direction: 182° (S)         

Wind speed: 22 knots

Swell direction: SE, S

Depth: 5,176 m

Air temperature: 11.5°C

Sea temperature: 16.0°C

Notes: Ship steaming to the first station of the 110°East line, albatrosses soaring and Antarctic and pygmy blue whales calling.

 

 

By Helen Phillips

The most reliable way we have to track global warming is by measuring the change in temperature in the ocean. This is because the ocean is absorbing more than 90% of the extra heat. Most of the global warming heat is in the upper 1000 m of the ocean. However, around Antarctica, the surface waters become saltier and heavier as sea ice forms in winter, and they sink all the way to the bottom of the ocean. These Antarctic Bottom Waters spread northward filling the deepest parts of the ocean, including the Indian Ocean, contributing to sea level rise as they warm.

The best way to measure the deep ocean below 2000 m is using a CTD–a Conductivity, Temperature and Depth profiler, lowered from a research vessel. The electronic sensors of the CTD are positioned within a large frame (the rosette) around which are 36 12-litre bottles that are used to capture water at different depths. This water is extremely valuable to the scientists on board as direct chemical analysis in our laboratory is the primary way to measure some water properties and also provides a critical check on the accuracy of the electronic measurements. Biological studies also need actual samples of water to identify tiny microbes in the water. This labour-intensive, costly work means that measurements in the deep ocean are infrequent and sparsely distributed.

The CTD rosette contains 36 Niskin bottles, which are sent down into the water column open at both ends and are remotely closed at specific depths, allowing for sampling of various levels in the ocean. Photo: Micheline Jenner.

 

On the first International Indian Ocean Expedition in the 1960s, the CTD was not yet invented, but bottles could be lowered to collect water samples at specific depths, and a reversing thermometer was used to record the temperature at depth. So there are measurements of the properties of the bottom waters from the 1960s. Sixty years later, our new measurements will reveal how rapidly the changes already detected around Antarctica have progressed into the Indian Ocean, and will help to guide our predictions of future warming and sea level rise. In addition to bottom water changes, we will be able to measure changes at all levels, not only in temperature but in the chemical composition and biological diversity, as well.

Dr Helen Phillips from IMAS, University of Tasmania is processing data collected from the CTD. Photo: Micheline Jenner.

 

Be sure to follow the daily posts of the Log from One Ten East on the IIOE-2 voyage at https://iioe-2.incois.gov.in and www.wamsi.org.au

 

 

Taking the Pulse of the Ocean with the CTD – One Ten East log 16 May 2019

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 16, 2019 Time: 1200 AWST
Latitude: 37.143° S Longitude: 111.712° E
Wind direction: 182° (S) Wind speed: 22 knots
Swell direction: SE, S Depth: 5,176 m
Air temperature: 11.5°C Sea temperature: 16.0°C

Notes: Ship steaming to the first station of the 110°East line, albatrosses soaring and Antarctic and pygmy blue whales calling.

By Helen Phillips

The most reliable way we have to track global warming is by measuring the change in temperature in the ocean. This is because the ocean is absorbing more than 90% of the extra heat. Most of the global warming heat is in the upper 1000 m of the ocean. However, around Antarctica, the surface waters become saltier and heavier as sea ice forms in winter, and they sink all the way to the bottom of the ocean. These Antarctic Bottom Waters spread northward filling the deepest parts of the ocean, including the Indian Ocean, contributing to sea level rise as they warm.

The best way to measure the deep ocean below 2000 m is using a CTD–a Conductivity, Temperature and Depth profiler, lowered from a research vessel. The electronic sensors of the CTD are positioned within a large frame (the rosette) around which are 36 12-litre bottles that are used to capture water at different depths. This water is extremely valuable to the scientists on board as direct chemical analysis in our laboratory is the primary way to measure some water properties and also provides a critical check on the accuracy of the electronic measurements. Biological studies also need actual samples of water to identify tiny microbes in the water. This labour-intensive, costly work means that measurements in the deep ocean are infrequent and sparsely distributed.

On the first International Indian Ocean Expedition in the 1960s, the CTD was not yet invented, but bottles could be lowered to collect water samples at specific depths, and a reversing thermometer was used to record the temperature at depth. So there are measurements of the properties of the bottom waters from the 1960s. Sixty years later, our new measurements will reveal how rapidly the changes already detected around Antarctica have progressed into the Indian Ocean, and will help to guide our predictions of future warming and sea level rise. In addition to bottom water changes, we will be able to measure changes at all levels, not only in temperature but in the chemical composition and biological diversity, as well.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

WAMSI Bulletin May 2019