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.

mpa -s_orkneys copy

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.

trawl fro web

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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Author: cathwaller

I'm an Antarctic ecologist working mainly on intertidal and nearshore ecosystems. I have worked at various locations around the Scotia Arc and Antarctic Peninsula. I am interested in what can survive in these environments, how things get there and how they might survive in a rapidly changing world.

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