Yo-yo-ing with an oceanographic instrument

Today, we are back on our cruise track. We arrived in the vicinity of 'Middle of What' seamount this morning and started with a bit of physical oceanography!

You can divide oceanography - ocean sciences - into three parts: the biological oceanography (the part that studies life in the oceans, the patterns of distribution and abundance of species such as the variability of algae bloom, etc.), the chemical oceanography (that surveys how much CO2 is dissolved in the oceans, iron, traces, etc.) and the physical oceanography (the part that explores currents, the formation of water masses and their characteristics, warming of the global ocean, etc.).

The ocean is a 3D fluid environment where movement can be sidewards AND up & down. This is not straightforward for us human beings who live most of our day-to-day life (with the exception of scuba diving and flying in an aeroplane) across a 2D static surface.

Our first activity at 'Middle of What' is a CTD yo-yo deployment. The CTD is the instrument that measures conductivity (salinity), temperature and depth (pressure). And ‘yo-yo deployment’ means that we are going to put it deep down, close to the seabed, and back near the surface and deep down again and so on … for 13 hours! Another instrument (called an ADCP) which is able to measure the speed of the currents is tied to the CTD frame.

Thanks to these accurate instruments we will collect a large amount of data. Jane, the physical oceanographer on board, will then be able to differentiate the water masses (layers of water with their own characteristics), assess the variability of the water column (structure of the layers), she will be able to compile the whole water column current velocities and see what tidal effects there are around the seamount, such as internal waves. Tides can have a strong impact on the small biota (fauna and flora) both at the sea surface and at the seabed.

The men (and woman) in charge

There are 22 crew members on board the RRS James Cook on this cruise. The most important thing you have to know is that THEY are running the ship. We are their guests.

The crew includes the four people working in the galley - Chris, Wally, Graham and Roger - who prepare excellent food for us 3 times a day. Then we have Anthony who is responsible for everything related to administration on board, ordering stores and interactions with local authorities in every port. He is the shopkeeper as well (the shop is a cluttered room where everyone on board can buy T-Shirts, chocolate, toothpaste, and sweets, and did I mention chocolate, three times a week).

At the bridge we have the Chief Officer (Richard), the Second Officer (Michael) and the 3rd Officer (Amy – only female crew member and on her first cruise on board the RRS James Cook!) who are sailing the ship.

Everything that functions 24/7 on board such as the engines, air conditioning, water, electricity, is provided thanks to a very dedicated engineer team – Bob, Chris, Ian, Innes, James and David.

Mick and Andy are responsible for loading of the equipment and everything that has to be moved from one part of the ship to another, for example.

Then we have Dave, Ian, Kenneth, Peter and Will who are providing support regarding the deployment and recovery of every scientific instrument.

And last but not least, we have Bill, the captain of the RRS James Cook, in charge of everyone and everything happening on board this vessel.

The crew usually spend a total of 6 months a year at sea generally for periods of 2 months maximum but it can go up to 10-12 weeks.

They have had a diverse range of experience before joining this research vessel … and their image of scientists is kind of clichéd like "they all look like Jesus Christ and wear sandals with socks" (which is not always wrong) but on the other hand they like the scientists' enthusiasm and love to learn new things every time new experiments are conducted on board. It is nice for them to have a different group of people of various ages on each cruise (PhD students to senior scientists).

And it makes it interesting for them when we make new discoveries on board their ship!

Bill adds that "It is even nicer if they laugh at my jokes." And, he admits that the crew are always amused when the scientists get seasick.

Quote of the day

"Man cannot discover new oceans unless he has the courage to lose sight of the shore." 

André Gide

[1869-1951]

Have you heard about hydrothermal vents?

Research on seamounts will pause as another science project will divert our expedition cruise for the next 3 days. It will focus on hydrothermal vents.

Hydrothermal vents are another special feature of the deep-ocean. They mostly occur on mid-ocean ridges (long, narrow, natural elevations on the floor of the ocean where oceanic crust is formed). The one Leigh and Jon are going to explore - and sample for the very first time - is located on the Southwest Indian Ocean Ridge at 2800m depth.

Chimneys, formed on hydrothermal vent fields, release hot fluid filled with chemicals from the inside of the Earth. Hydrothermal vents support very specific fauna. Communities that developed in these very deep sea habitats use the chemical energy of the vent fluid to live and thrive.

The hydrothermal vent area will be investigated through several ROV dives in order to take HD images of the whole structure and characterize the composition of the vent fauna.

An additional blog is in place for this other research project for the next few days; you will find more info about what is going on on board the RRS James Cook regarding hydrothermal vents here:
http://www.thesearethevoyages.net/jc67/index.html

ROV screens during the first dive on the vent field

Hydrothermal vent; ROV images

Far reaching human impact

Today is our last day at Melville bank. So what have we discovered?

Melville bank painted a very different picture to that of Coral seamount. We found that incredibly this area, despite being thousands of miles out into the ocean, has been heavily exploited by the fishing industry. Unlike Coral seamount, a large area of Melville bank has clearly been fished. We found most places covered only by dead coral rubble. We could see what damage deep-sea trawling can do to the seabed. It literally destroys everything. However, even on such a heavily exploited seamount there were areas that were rich with life. This was because the terrain was so rugged that mobile fishing gear could not be used.

Throughout our exploration of Melville bank we have come across evidence of human impact. We saw many lost lobster pots, drifting pieces of fishing long lines, broken trawl wires and even rubbish (mainly bottles). All these pieces of equipment were floating around on the seabed as ghosts.
It was always impressive and frightening to see this gear appearing on the ROV screens in the devastated landscape of the seamount and caused us a great deal of difficulty in completing our research dives.

Sky at sunrise 5:15 am (ship time)

Digging in the seabed for very very small animals

We have 6 people on board whose main scientific interest lies in sediments, or more exactly, in what animals you can find in the sediments.
Sediment is matter that has been deposited by some natural process on the seafloor. It can consist of mud, sand, gravels and pebbles and it may harbour high biodiversity. Its inhabitants range in size from a few millimetres to 45 micrometres (=0.045 millimetres) and are mainly tiny worms, crustaceans (like shrimps) and molluscs (like mussels).

There are different ways to collect sediments. Usually you core sample with a transparent plastic tube that you drive into the seabed which allows you to see the different layers.
In the vicinity of seamounts, the seabed is either too hard or sediments are too coarse to stay in the coring tube and we have had some unfortunate attempts.

We are now using the robot HYBIS and its big jaw to grab a pile of sediments which makes our 6 people – Natalia, Adam, Tim, Peter, Margaret and Lucy - very happy!

In these areas sediments contain organic debris such as dead corals, shell fragments and plankton remains. Sediments on the seabed might not look as attractive as other marine habitats but if you look closer …. closer …. closer …… you can see amazing forms of life!

Polychaete (0.5 mm wide) © P. Lamont

Crustacean (2 mm) © P. Lamont

Surprisingly colourful

Brisingid (sea star)

Before the cruise and my first look at ROV images, I thought that the deep-sea world would range from light grey to dark grey.

I was wrong! From the bright red urchins to pale green, yellow, orange, red and purple corals, this place is full of different colours!
We saw small bright pink crabs, pink lobsters, snow-white and orange sea stars and … fish in disguise!

Centriscops humerosus

We met this funny looking fish during our ROV dives at Melville. It is a banded yellowfish ... real name Centriscops humerosus.
It is from the same group of fish as sea horses. Any resemblance?

Centriscops humerosus

We can find it at this range of latitude all around the southern hemisphere (Southeast Atlantic: South Africa; Southwest Atlantic: Argentina. Southwest pacific: Australia and New Zealand). Its depth range is usually 450 – 700m.

Octocorals

Unknown octocoral with brittlestar

Anthomastus sp. (coral)

Lepidion sp.

The escape of the lobster or how it is not always possible to steal the secrets from the deep

During our first ROV dive at Melville bank this morning, there was a suspenseful moment or two when the robot tried to capture a very cunning 20cm-long lobster.
After some unsuccessful trials, we managed to get it into the collecting net but as we were trying to put the net into the bio box, it jumped out of the net and landed on the ROV.
Then we tried our best to have it fall into the box by creating some currents with the thrusters in its direction.
And … it worked. It was in the box!
All we had to do was to put the net with the sediments on the lobster and close the box.
But things are not so straightforward at 900m depth. And our very brave lobster, gathering its strength, jumped and swam out of the 30cm deep box!
We will never know what species it was! For now it will remain a mystery of the deep ...

Coral and critters

By Michelle Taylor, Post-doctoral Researcher, University of Oxford

The words ‘coral reef’ conjure up mental images of tropical sandy beaches, cocktails and colourful fish. For me however they conjure up images of long oceanic voyages (sea sickness tablets), large pieces of deep-sea sampling equipment and all manner of colourful animals (Nemo doesn’t have a patch on these guys…). You see, corals are not confined to the shallow warm sections of this planet; they in fact occur in every Ocean, even the very coldest, and have been found thousands of metres down where the water is anything but tropical. Deep-sea corals exist by filter feeding from the water around them. As such, they need to be in areas of strong currents. They also need a solid base to grow on making seamounts ideal locations.

There are just a handful of hard skeleton deep-sea coral species that grow into large reef frameworks. When this does happen these reefs are a sight to behold; even the small areas seen so far on this expedition have been home to a bewildering array of animals. We have seen baby-pink lobsters (whose abodes are immediately filled by another once one is sampled), the tiniest yellow sea spiders, intense-red anemones, flame orange fish and electric purple octocorals (who are unusually always home to the same big snake-armed brittlestar species).

In general, the deep sea of the Indian Ocean is very understudied, certainly one of the least studied regions for deep-sea corals globally, making discoveries to be made on this expedition very important and very interesting indeed.

ROV images; Coral seamount;
Isididae sp. - unknown, next to some bottlebrush octocoral

ROV images; Coral seamount;
Isididae sp. - unknown bamboo coral with Galatheid crab
and brittlestars

Steaming for Melville

We left Coral seamount yesterday evening after the mooring recovery and we have just arrived at the second site: Melville bank.



We are going to stay a few days in this area to explore the site, mainly conducting the same surveys as on Coral seamount (CTD transect, ROV and other robot dives, coring, bathymetric survey, etc.). We'll do our best to collect as much information as possible about this site. It will be very interesting to compare our results knowing that this seamount is in warmer waters than Coral seamount. Seawater temperature at the surface is now around 17°C (that’s a 7 degree rise overnight)!

Hunting for a package of whale bones

Two years ago during the previous cruise, two moorings, each carrying a package of whale bones and a package of mango wood logs, were placed on the seabed at Coral seamount and Atlantis bank. They are attached to a vertical line with floats at one end and 150kg of ballast at the other end.

 

The idea is to study the life that will settle on these new substrates and identify what organisms (worms) will grow while the bacteria that colonize the bones and wood during their decomposition recreate a similar chemical environment to those found at hydrothermal vents and cold seeps (both special deep-sea habitats).
We will hopefully be able to analyse the variety and distribution of the worms associated with these environmental conditions.

Slow growing and slow recovery are typical features of the deep-sea communities. If we learn more about this process through experiments like this, it will help us to understand how marine ecosystems are connected and determine the best strategies for protecting these deep-sea habitats.

We spotted the first mooring four days ago during one of the ROV dives at Coral seamount and today we dived again at the same location to try and recover them at 743m depth.

And we were successful!

James Cook vs mysteries of the deep (1-0)

We have been around Coral seamount for a week now. It’s time to have a look at what's been done already. We have had an impressive number of events: 1 wire test, 1 test of acoustic interferences between instruments, 4 ROV Kiel6000 dives (see Remotely Operated Vehicle blog post), 3 SHRIMP dives, 2 HYBIS dives, 8 CTD (see CTD and Anni’s microbes), 1 ring net deployment (see Clare and the Jellyfish), 1 microprofiler (mixing; see Overnight work), 6 boxcorer deployments and 7 megacorer deployments to collect sediments (see upcoming blog posts...), 1 multibeam survey (see How to map the seafloor), a lot of seawater collected and filtered, a lot of organisms and samples labelled and preserved. We have still not unlocked all the mysteries of Coral seamount though. Over the last few days the weather has frustrated our progress and we are yet to see what lives on the top of the seamount. So tonight and tomorrow we will attempt to tow SHRIMP, our towed camera system, up the upper slopes and onto the summit where we have seen a strange hole in the top of the seamount with the echosounders..........

We've been happy to see many fur seals, 2 Sperm whales, hundreds of albatrosses, white-chinned petrels, cape petrels, terns, prions and other seabirds.

Air temperature (daytime) range: 7 and 13°C.
Seawater temperature: around 10°C at the surface, 4°C at the seafloor
Area covered (latitude, longitude): [41°20’:41°28’] South, [42°50’:42°57’] East

© L. Rolley

© L. Rolley

© L. Rolley

Anni's microbes

The weather calmed down during the night and work could resume. We did a CTD transect above the Coral seamounts area. CTD stands for Conductivity Temperature Depth. It goes along with a Rosette of 24 Niskin bottles, each one of those can be closed at a chosen depth.

It allows you to bring back on board bottles of seawater collected all the way from the bottom to the surface at any depths you choose.
The instrument itself gives you the salinity (conductivity) and the temperature at each depth. Nowadays other parameters have been added as, for example, oxygen.
With all this information you can distinguish different layers (water masses) and get a pretty good idea of the origin of the seawater at this depth.

Anni, a student from Oxford University, is very interested in microbes. Seawater is full of microbes quite different than the ones we have on land. Anni filtered the seawater from the Niskin bottles to see what species of microbes she will find after a DNA analysis. Did you know that we can find up to 1 million bacteria per millilitre in seawater?!

FORCE 8 up to force 9 today!

Today we are encountering a rather rough sea. Work had to stop. It is impossible to put any measuring instruments in the water ... the winch cable would have to bear too much pressure and the instrument might bang on the hull.
The Beaufort scale of wind force is an empirical measure that relates wind speed to observed conditions at sea or land.
This scale was devised by Sir Francis Beaufort in the year 1806 for use in vessels of the Royal Navy. It was adapted in 1874 and in 1939 the International Meteorological Organisation (now WMO) agreed to the use of a sea criterion by which the wind force was judged from the appearance of the sea surface.

Force 8 on the Beaufort scale corresponds to a gale, winds of 34-40 knots (62-74 km/h) and moderately high waves with breaking crests forming spindrift, well-marked steaks of foam blown along in the wind direction and considerable airborne spray.

Seasickness pills are quite fashionable today!

How to map the seafloor?

As you can imagine, bathymetry (the topography of the bottom of the sea) is not an easy thing to measure.
Satellites get a pretty good image of the surface of the ocean - they produce amazingly accurate images of the surface of the planet - but they cannot see through water, below the waves.

Lily, a student from Oxford University, is using the data of the Multibeam Swath (an instrument attached to the keel of the ship which sends many beams of sound in the water column and gets back the echoes after they bounce off the seafloor) to compile a map of the seafloor in the seamount’s area.

In the old times, measurements of water depth were made with a sounding machine. It consisted of piano wires with a plumb bomb at the end deployed until the weight touched the seabed and then the length of the wire was measured. It was a very long process; the ship had to stop!

Around World War II, the echosounder was invented and it enabled us to measure the depth of the seabed while the ship was moving. These echosounders had a single sound beam only, and would measure the depth along the ship’s track. Multibeam echosounders are essentially doing the same thing but with a fan of sound beams that survey a whole swathe of seabed, sometimes kilometres to the left and right of the ship’s track.

Once this data has been collected, it has to be processed to get rid of errors, otherwise you may end up with 100m tall spires which are impressive but not actually there! The bathymetry from this trip will be compared with previous maps to determine whether there may have been submarine landslides or underwater eruptions in the past two years.

Coral seamount; 2009 data collected aboard the R/V Fridtjof Nansen, hopefully we will fill some of the holes!

Overnight work!

A lot of work was carried out last night. The samples and biological specimens brought back on board the ship by the ROV had to be identified, measured, labeled, recorded and put in formalin or ethanol to be preserved. Pictures of each of them were taken. Some samples were saved for DNA analysis. It’s a huge amount of work!

In the meantime, Jane put an instrument in the water that measures turbulence, temperature, salinity and pressure (depth). It started at 10:30 pm and went on until midday today measuring these parameters between the surface and 250m in repeated vertical profiles. We can learn a lot about mixing and physical processes in the water column above the seamount this way.

Clare and the jellyfish

Today, let's talk with Clare.

Clare is a PhD student from St. Andrew's University in Scotland. This expedition is her first research cruise.
She is interested in jellyfish and more generally in pelagic ecology.
Jellyfish are members of the gelatinous zooplankton (animals that live in the open water and are at the mercy of the currents).

So why do we care about jellyfish? They have important impacts on human activities: negatively affecting important tourist beaches (with their sometimes painful and even deadly stings!), clogging fishermens' nets, and competing with commercially-important fishes for food. But they also have often overlooked positive impacts – providing shelter for young fish in the open ocean and apparently make a tasty satay in Asian cookery!

Clare is hoping to use acoustics echoes to detect them and other zooplankton in the water column, which means we send a sound through the water and measure the echo we get back at the ship after its reflection on the animal. Also we will be putting out nets in the ocean to collect organisms that she will identify and analyse later. Who knows what we will find!