Sunday 27th June 2010

Snow in June?

I know we have reported that adverse weather condition out here occasionally interrupt our sampling programme but I don’t think anyone has mentioned that it has been snowing every day we have been out here.  Well, not so you would have noticed if you looked outside – the view from my cabin at present is of grey, turbulent seas with a sky to match – but no snow!  That’s because we need to look below the surface.

Whenever we deploy our ROV, the cameras reveal a constant fall of snow – white particles drift past constantly, occasionally reaching blizzard intensity.  This ‘marine snow’, unlike its atmospheric namesake, is not made up of crystalline snowflakes but of amorphous (shapeless), often slimy aggregates. Not quite as glamorous as snow then!  However, as unattractive as it may sound, ‘marine snow’ has a vital role to play, both during its journey to the deep-sea floor and upon arrival.

A Chimera circles Grant’s amphipod trap

Tube sponges stand tall (wearing ophiuroid scarves?) while ‘snow’ falls all around them

Animals that live in the ocean depths do so without the benefit of sunlight. With the exception of fauna associated with hydrothermal vents, the majority of animals on the ocean floor rely directly, or indirectly, upon nutrients produced in the surface waters arriving as ‘marine snow’.  This is not exactly what you might call a ‘fast food’ service and dinner is often served much later on the sea floor than it is prepared in ‘kitchens’ at the surface.  Imagine being at the end of a long queue, down which a food trolley is travelling, hoping that there will be some left when your turn comes! As the ‘marine snow’ descends it is fed upon by animals along the way, animals such as salps and appendicularians, which drift around in the water column filtering water – quite literally for a living.  The ‘snow’ is also added to along the way – imagine the food trolley is also collecting leftovers as it moves down the line – so that when it finally reaches the sea bed, it is a mixed assemblage of ‘goodies’ that appears on the menu for the benthos (bottom dwellers).

As you might imagine, the food arriving on the deep-ocean floor is not particularly nutritious and you have to eat a lot of sediment to stay alive.  If you eat a lot, then you ‘poo’ a lot. The holothurian (sea cucumber) responsible for this little lot has clearly been feasting!

Holothurian poo

The coiled deposit in the photograph is the same size, approximately 12 cm, as the animal that produced it and the sea bed is littered with the aftermath of what is termed ‘deposit feeding’ activity; piles of poo, tracks, scrapes and mounds, evidence of animal activities that we refer to as ‘lebensspurren’ (‘life traces’).

Filtering the water is another option, allowing you to intercept your food before it arrives on the bottom.  To do this well it is useful to be raised off the sea floor on hard surfaces, as shown by these sponges.  The stalked crinoid, or ‘sea lily’, raises itself high above the surface to intercept food as it falls giving it a palm tree appearance (it looks like it might be growing out of the sediment but is actually standing on a small rock rather like the sponge you can see in the background).

Sponges on a basalt cliff

A stalked crinoid rises above the sea floor

In order to understand this supply chain and how it might influence the pattern of life on the deep-sea floor, we deploy sediment traps to intercept the falling ‘snow’ so that we can determine such important parameters as the timing, quantity and quality of the material heading down to the ocean depths.

At each of our four sites, either side of the Charlie-Gibbs Fracture Zone, we have recovered a ‘mooring’ that had been deployed on a previous cruise, in 2009. These moorings comprise a number of current meters, which log the speed and direction of water movements, and two sediment traps, one set at 100m and the other at 1000m above the sea bed (approximately 1500m below the surface).  The line to which these are attached is anchored to the sea-bed by ballast weights; recovery entails triggering a sonar activated release mechanism, causing the weights to be jettisoned and allowing the mooring to float slowly to the surface.

One of the current meters is brought on board

A sediment trap is recovered, its yellow and orange flotation buoys lie behind it on the deck.

Each sediment trap comprises a carousel of tubes into which falling sediments, and occasionally misguided shrimps, are directed by a large funnel.  The tubes contain preservative so that the contents do not decompose before we have the chance to examine them.  The carousel rotates to take sequential samples at monthly intervals allowing us to look for seasonal influences on the quantity and quality of our ‘marine snow’ supply chain. Comparison of the two traps provides information relating to changes in the nature of the ‘snow’ as it falls to the sea floor.  Studies of this nature have shown that the supply of food to the animals of the deep-sea floor is indeed seasonal, reflecting the seasonal productivity of sun-lit surface waters and imparting a rhythm to the growth and reproduction of many of the species that we are finding here.

Well, if all this talk of snow makes you feel cold, just remember that, while it’s not real snow that falls on the animals below us on the mid-Atlantic Ridge, they really are cold.  The temperature down there, according to our CTD readings, is 3.60C and they have no warm summer in the offing!

Geoff Wigham

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Saturday 26th June 2010

Midsummers Day back home in Sweden. Here onboard the James Cook it is Curry Day (we get curry for dinner on Saturdays), and one week to go before we land in Vigo and have to go home and cook meals for ourselves once again.

Saturday's menu = curry night

After almost two days of no work due to the bad weather, everybody was eager to collect more samples and data. Luckily, the Atlantic Ocean calmed down sooner than expected, and we could retrieve the PAL lander and the Amphipod trap before lunch. Despite the sun shining outside, most people were working in the main lab until the next Isis dive began.

Debbie, Grant, Thom and Ben

After lunch the ROV was deployed for a 30 hour dive with eight benthic survey transects and one bioluminiscence transect on the schedule. Our photographer David Shale climbed up to a higher vantage point to film the launch of Isis on a sunny day.

David Shale with a birds eye view of the Isis launch

David Shale with a birds eye view of the Isis launch

During the benthic video transects we observe the larger animals living on the sea floor, for example sea stars, sea cucumbers, corals, anemones, and fish. However, on flat areas of  sea floor these animals can often be found living far apart from each other and it could lead you to believe that there is only very few inhabitants. What we cannot see on the video transect is all the smaller animals that live on the seafloor or in the soft mud. To study those we need different sampling equipment, and on this trip we use a megacorer. With a megacorer it is possible to do quantitative studies of the fauna. A core has a diameter of 10 cm so the volume of sediment can be measured, and the animals in there are identified and counted. Many of the smaller animals living on and in the sediment are worms, and I work on polychaetes, also called bristle worms. I examined a sediment sample from the upper 5 cm of a core and found, some small crustaceans, nematodes and 14 bristle worms belonging to 13 different species. Unfortunately these beautiful animals are very delicate and do not at all like the sampling-and-sieving procedure, so it’s rare to find a complete specimen.

Polychaete

Helena Wiklund

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Friday 25th June 2010

The weather has continued to dominate our programme.  Again we find ourselves at the mercy of wind and waves.  Too much of both, has meant us heading into the sea and unable to work.  This does not mean of course that we are idle.  There is plenty to do and from my point of view as the photographer I have many images I have to edit.  The advantage of being on board with specialists is that I am able to come away with pictures that have all the necessary identifications.  This saves me a lot of time.  It is not always a guarantee as even specialists change their mind, but we work together on this.  An area lacking in my knowledge has been the holothurians (sea cucumbers) but having Andrey Gebruk on board has made my life much easier.  I have also developed a new interest in that group too!   Previously they were one of my most difficult subjects in the benthic trawls as they always come up covered in sediment which is impossible to remove.  With the ROV we can selectively collect specimens in perfect condition.  Delivered to the 4.5 degrees of the cold room never out of water they become excellent subjects for my tanks where I can do them justice.

I have added a few examples of deep-sea holothurians (plus a specimen from last year as comparison) and maybe you can change your mind about what is beautiful from the deep sea!

Holothurian recovered from a trawl

Holothurian - Amperima

Holothurian - Deima validum, Polychaetes - Polynoids

Holothurian - Amperima sp

Holothurian - Peniagone

David Shale

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Thursday 24 June 2010

Well only 5 days to go before we have to end science on this ECOMAR cruise and head for Vigo. However, just as we were getting into these last few days of work the weather once again reminded us who was in charge. So our plans to complete a 30 hour ISIS ROV dive to survey the seabead slopes and terraces of this South East mid Atlantic ridge site were put on hold. Although the weather was freshening it was still Ok to use the Megacorer. The Megacorer is deployed on a wire from the ship and takes a number of sediment corers from the sea floor. Once on deck these cores are sectioned and sieved to look for animals living in the sediment. The Megacorer is a robust piece of gear and is always the sampling instrument we turn too if the weather gets a bit marginal for other work. So with nothing else to do and the need for 3 Megacorers at this final site we set off to do three in a row.

Now that sounds easy but in reality it is  very difficult for the guys involved in processing the sediment. They have to go out on the aft deck and spend 2 to 3 hours in increasing winds and ship role to sieve and process the sediment.  Brrrr! So after the second Megagcorer in trepidation I headed out to the aft to see how the troops were doing. I needn’t have worried all the guys we working hard and still cheerful … amazing dedication, well done guys!

Grant, Debbie, Mark and Helena still smiling after processing two Megacorer drops

In the end the weather kept getting worse and we could not do the third Megacorer, a relief for the processing team, but a worry as this storm was predicted to carry on for 36 hours and we have only limited time left.

Phil Bagley

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Wednesday 23rd June 2010

Earlier today Isis provided us with a glimpse of what lives on a seamount located just a few miles from the SE Station. Estimates inferred through remotely-sensed altimetry data suggest that about 100,000 seamounts with an elevation higher than 1000m are spread throughout the world’s oceans. Because they are topographically isolated features, and are often associated with particular hydrographic processes that promote larval retention, it is believed that seamounts play a pivotal role in evolutionary divergence and speciation of deep-sea benthic fauna, contradicting the early view that they could increase connectivity by acting as stepping-stones for dispersal. Evidence, however, is not consistent across regions and taxa, which calls for further surveys to obtain a clearer picture of biogeographical patterns.

The seamount we visited rises from the abyssal plain at 4000m and has its summit around 700m below the surface. Due to time restrictions, the plan was to perform one video transect up a slope between 1050m and 850m depth, obtain high-definition video footage of benthic fauna and collect voucher specimens of the most representative species. The later part of the dive was to be devoted to finding and, if possible, retrieving an accoustic lander that had been lost during a previous cruise.

The diversity and abundance of benthic fauna were staggering. The more gentle slopes were mostly covered with gorgonian and sponge gardens with a diverse associated fauna including brittle-stars, crinoids and squat lobsters. Another significant feature of these areas was the presence of extensive layers of coral rubble (fragments of dead scleractinian corals which accumulate over hundreds of years or more).

Brisingid and coral rubble

Anemone and Acanthogorgia

Steeper slopes and vertical walls were densely inhabited by sponges, Gorgonocephalus sea stars, anemones, gorgonians, sea-pens and a few black corals. There were also numerous small colonies of reef-building scleractinian corals, probably Lophelia pertusa or Solenosmilia variabilis (not easy to distinguish through video). A closer look at the rock walls revealed a myriad of solitary scleractinian corals, as well as countless small sea stars and brittle stars.

Gorgoncephalus

Lophelia and Acanthogorgia

Gorgonocephalus and Acanthogorgia

So much to explore and so little time available. After a brief, yet fruitful, period spent at collecting specimens, we headed for the waypoint where the accoustic lander (hopefully) was. It showed up on screen, not far from its suspected location, turned upside down with a few floats missing, presumably because they have imploded. Unfortunately it was too risky to retrieve it during the night, and dawn was still a few hours away. Because the cruise runs on a tight schedule we could not afford waiting for suitable conditions so it was decided to leave the lander for now and come back for it later.

The last week of science has just begun. There’s still a lot to explore at the southeast station, so stay tuned for more news!

Pedro Ribeiro

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Tuesday 22nd June 2010

The main focus of today was the transit to the South Eastern station and the opportunity that it presented. During our transit we would pass over a seamount. These undersea mountains create boundaries, forcing currents to shift and different water depths to mix. These currents, and the hard substrate provided by the mount itself, support large populations of filter feeding invertebrates. These in turn support many other animals creating isolated hotspots of life. Usually the complex terrain makes only limited sampling possible but with the ROV we were able to closely explore these complex structures.

Life was abundant and diverse. Wolf fish, False Borfish, Codling, Orange Roughy and Chimera were just a few of the most striking fish species seen. Many were attracted to the lights of the ROV and would come to investigate us before we could move towards them.

Orange Roughy: This slow growing fish doesn’t even reach maturity until about 30yrs old and can live well into its hundreds. When relaxed they are a cream colour but flush this salmon pink when they feel threatened.

The rocks were coated with a variety of colourful invertebrates, the majority facing into the current with a variety of filtering appendages. The same biological problem had been solved in the development of many different forms.

Diverse filter feeding communities.

We were seeing some beautiful things and this moment served to take us out of ourselves. Most of us have ended up here through fascination with exactly this sort of thing. It’s easy to get too narrow sighted: will the new program work properly, will the housing fail and your equipment flood, is the data you have good enough, is there enough for statistical analysis?

For me and a few others in that room watching these images widened our view again. Suddenly we regressed to kids looking in rock pools and we realised how lucky we were to live this life and to witness these things first hand.

This has been a long and intense cruise but I know those few hours will hold significant for me, a little reminder of why I do it.

A full house in the ROV control room.

Thom Linley

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Monday 21st June 2010

What is Isis?

Today we had another successful ROV day. We got a good collection of specimens up in the morning, after a very successful 12 hour collection dive during the night.

I am going to take the opportunity to talk a little about the ROV. ROV stands for Remotely Operated Vehicle and is, according to a member of the ROV team (who wishes to stay anonymous), ‘the best thing since sliced bread’. The ROV is basically a big robot designed to go into the deep sea to explore and to collect samples. Our ROV lives in the National Oceanography Centre, Southampton, and spends about half the year sailing the Atlantic from pole to pole. Isis is being looked after and cared for by a crack team of 8 technicians. Using a 12 hour shift system, she gets 24h care from a team of 3 at a time.

Isis being prepared for a dive

Isis is connected to the ship via a 10km umbilical cable which allows her to dive down to depths of 6000m.  She has her own 128multibeam and 200kHz sonar, which gives a 120° swath angle for producing very detailed swath images of the seabed. Flying Isis at about 30m from the seafloor gives a swath width of about 70m. The sonar is not only used for swath but also for obstacle avoidance and target detection, it has been particularly helpful when looking for lost landers (DOBO, amphitrap etc).

Isis being depoloyed for the test dive

Onboard the ship we have the ROV control centre, from here Isis is sent commands from the ship. The core team for every dive consists of 3 members of the ROV team sitting in the front operating Isis and communicating with the ship’s bridge, 2 scientists who sit in the back logging and recording, and finally a mission scientist who is responsible for whatever mission we have during that dive… may that be collection, observation or something else.  Everyone gets rotated in order to maximise the work output.

A logger's view inside the ROV control room

In order to see the deep sea, we rely on 10 cameras, 2 of which shoot in high definition. The feed from these cameras is sent to the ship via the umbilical cable and displayed on nice big flat screens in the ROV van. All footage is also recorded for later reference and analysis. Lasers affixed to the ROV provide a reference point for judging distance when looking at footage; it would be very difficult to judge the sizes of specimens without these.

In terms of sampling and storage devices, Isis has a biobox and push cores, a slurp gun, and most importantly two functional manipulators, also known as arms, which have being used for sample collection and lander rescue operations. She has her own hydraulic power unit that operates the swing arms, forward drawer manipulators, the slurp pump and the carousel rotation (one of the storage options). As well as the carousel it also has bio-boxes on either side, so we have plenty of space to store samples. The configuration of tools and storage can be altered depending on requirements.

Back at the surface after a night dive

Potentially, Isis could stay in the water indefinitely, provided all systems remain functional. Normally the time she stays down is limited by either storage capacity or leakage of hydraulic fluid. It takes quite some time to get her down to the seafloor, in our case it takes about 2 hours to reach a target depth of about 2500m.

Oh and on a completely different matter we made the astounding discovery today that Grant’s legs have gotten shorter, the good news is that they are still expandable when pulled hard enough.

Claudia Alt and Dave Edge

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