Deep-sea Sampling

We are now south of the South Orkney Islands in the marine protected area (MPA), where we are investigating the deep-sea habitats and animals that are found there. The MPA covers an important foraging area for penguins and whales.The notch out of the top is an area of a proposed fishery.

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Above: Location of the MPA (box) and the South Orkney  Islands relative to South Georgoa and the Falkland Islands (top left).

We have been lucky enough to have whales all around the ship for the last couple of days, sometimes as many as 50 at a time. They are mostly humpbacks but we have also seen fin whales. Whale watching provides an interesting interlude while we are waiting for our samples to come back to the surface, which can take over two hours when we deploy the equipment to 2000m.

Images: Left courtesy of Al Howard. Right: Angelika Brandt

We are also encountering small areas of sea ice blown up here from the Weddell Sea. Quite often there are seals and penguins hauled out on it.

Once we reach our site we have various tasks we must complete. The first thing we do is to run the CTD. This is a frame housing a collection of tubes which open and collect water samples. The equipment also records the conductivity (effectively the salinity) and temperature along the depth profile, hence the acronym CTD (Conductivity, Temperature and Depth).

ctd deploy

At the shallower sites (up to 1000m!) we send down a camera system (the shallow water underwater camera system or SUCS for short). This is linked to the surface by a fibre-optic cable, which means we get real time images of the seafloor and any animals that happen to be in the area. This is useful as we can check whether there are any large rocks or other dangers, which may pose a risk to our more delicate equipment. The camera takes images of 50cm x 50cm of the seabed. It also has a GoPro attached so once it is back on the surface we have a video recording of the general area.

Images above-  Left: The SUCS ready to be deployed Right: three images of the seafloor at 750m. In the top image you can see a small octopus, middle image has  anemones on a rock  and bottom image shows the mystery “shells” and purple octocoral

As you can see from the three images of the seabed is mostly mud, but we did find an interesting area that was covered in some unidentified debris. There was much debate as to what it might be as we waited for our trawl to come back to the surface. When we retrieved it we found it was full of giant barnacle plates (the dead shell of the animal). These plates were all sub-fossil, meaning they have been there for a VERY long time, possibly tens of thousands of years (see marinescience.ie for Louise Alcock’s excellent blog about this. We have an expert (Laura Richardson) on the cruise who will try to age the plates once we get back to the UK.

After completing the camera survey we deploy the Agassiz trawl (AGT). This is a large metal frame with an outer and inner netstowed behind it. It catches the animals living on the bottom (and in the sediment). It is quite robust so can usually be used without too much risk of loosing it (although it does happen sometimes!). We have caught quite a few large rocks covered in bryozoans, which is good for me as I work on this group of animals, but not great for the rest of the samples in the net as most of it is delicate animals such as urchins, brittlestars and sponges that don’t survive being pounded with rocks on the way up very well. Despite this we have collected lots of beautiful and interesting animals and even found new species.

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Images above: Deploying the Agassiz trawl. We work 24 hours so the trawl is used day and night. Below: Samples ready for sorting.

It reminds me of Christmas as we wait for the trawl to come back to the surface. Once on deck we all gather round to see what has been collected. We carefully remove the animals from the net and take them into the wet lab for sorting into taxonomic groups. As we work two 12 hour shifts and the experts aren’t always present when we find their beasties, we use the protocols posted on thelab wall to record and preserve the animals in the way that they  have asked for.  It is interesting to see the differnce between the boys and girls protocols (see image below).Once we have identified (where possible) counted, weighed and recorded the specimens, we pack them away carefully and store them in the walk in -80oC freezer.

Above – Left:the wall of protocols. Middle : Example-boys protocol. Right:Example -girls protocol

Finally we send down an epibenthic sledge (EBS), which is a lightweight trawl that uses two nets one above the other to catch smaller animals living on or just above the seafloor. These samples often contain sediment and very small and delicate animals. We try to sort through them and then preserve them in ethanol and store  in the -80oC freezer.

ebsAbove: EBS ready for deployment.

We deploy the equipment at 500m, 750m, 1000m, 1500m and 2000m at each site. We do three AGTs at all but the deepest depth at each site, one EBS, one CTD and three 100m camera transects (at the shallow stations).

As it is International Women’s Day I will finish with pics of some of the team. We have twelve female and seven male scientists on this cruise so it really is a case of girl power.

Some of the Women in Polar Science SOAntEco Team. Left image L- R:  Mel Mackenzie, Helena Wiklund, Cath Waller, Suzie Grant and Laura Robinson. Right Image L-R Rachael Donwey, Michelle Taylor and Maddie Brasier.

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Swathing and Signy

We have spent the last day or so swathing. This involves bouncing an acoustic signal off the seafloor, which will give a 3d image of the topography. We are sailing in a zigzag pattern at right angles to the part of the seafloor we want to survey. We have to overlap each band of swath and make sure we don’t leave any gaps. This may sound simple but when there are sizeable icebergs directly in the path it can be difficult for the bridge officers to steer a straight course. You can see how it works from the picture below.

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Image: British Antarctic Survey.

We dropped the three scientists who are working on Signy Island and spent the morning ashore. Some of the team walked over a promontory to Cemetery flats where there are a number of whalers’ graves and lots of elephant seals. Elephant seals are noisy and smelly but generally don’t move too quickly. Unlike fure seals which are noisy, smelly and can waddle surprisingly fast!

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Young male Elephant seals: Image – Angelika Brand.

A few volunteers and myself went on a seaweed hunt to add to the samples collected by Caroline Pindar (https://seaweeddownsouth.wordpress.com/) earlier in the season. We dodged fur seals and chinstrap penguins and managed to find enough algae to fill seven bags, which are now frozen ready for their return to the UK in June.

 

We have also been testing the winches and running a test trawl at around 100m depth to iron out any problems with the equipment and to familiarize ourselves with the routines of sieving, sorting and cataloguing the animals we catch.

AS you can see from the picture below, there was plenty of mud! Once we washed and sieved it we found a wide  variety of species but not many individual animals of any. The highlight for me was finding the only  known species of pelagic bryozoan (Alcyonidium fabelliforme) which might look like a blob of jelly but is a colony of tiny animals closely related to “Dead Mens Fingers” that are found around the coasts of the UK.

Left- the trawl straight from the net Right – Pelagic bryozoan

We will start to survey and sample the designated sites tomorrow, weather permitting.

kelp Watch

We have been steaming towards the South Orkneys for a couple of days now and taking turns to do half hour “kelp watch” slots on the bridge, which isn’t as easy as it sounds. The Southern Ocean is huge and the kelp rafts quite small and widely spread, so spotting them is a challenge even in the relatively calm waters we have been experiencing.We have seen fin whales, fur seals and penguins, which breaks the monotony of scanning the waves as there hasn’t been much kelp.

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The one that didn’t get away. Floating kelp raft in Southern Ocean. Image courtesy of Hilary Blagborough

So far we have spotted 4 kelp rafts but only managed to collect one. Luckily it still had the holdfast attached. The holdfast is the “root” that attaches the kelp to the seabed and is the part that houses the most animals. It was quite a small raft. Even so it weighed around 18kg! We then had the job of sorting through it looking for animals. We found a small fish, which must have been using it for shelter.

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Sorting through the kelp. Image courtesy of Mel Mackenzie.

Some of the finds. Images courtesy of Vassily Spiridonov and Helena Wiklund.

There were also thousands of juvenile goose barnacles covering the holdfast and some of the blades. These are pelagic hitchhikers and are not what we are looking for, but they are amazing animals. They can grow up to 50 mm with a stalk length of 40 – 900 mm and are an expensive delicacy in Spain and Portugal.

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Juvenile goose barnacles: Image courtesy of  Claudio Ghiglione.