Land ahoy!

After spending two successful weeks surveying the Pobie Bank Reef, we finished the planned acoustic work in block four on Wednesday evening, before starting our journey back to Aberdeen.  We’ve really enjoyed finding out more about the seabed within the survey area, but are now looking forward to the prospect of getting back to dry land!

The day shift

The night shift

We were welcomed back into Aberdeen harbour by a friendly seal and a lovely sunny evening. We’d like to thank the scientists from Marine Scotland Science and the great crew on board the Scotia for all of their help over the last few weeks!

Entering Aberdeen harbour

Rock around the clock

The last few days have been busily spent ground-truthing at stations across section 3 of the site. The seabed within box 3 has been particularly interesting, with complex sections of bedrock and boulders, providing homes for a range of wildlife. The underwater video has identified some especially vibrant scenes, such as the wall of brittlestars, orange dead men’s fingers (Alcyonium digitatum) and as yet unidentified purple encrusting species shown here.

We’ve also seen several sunstars, different types of crab and anemones. We had another ling follow the camera plum line and a large cod came into the view of the video for a while – our camera seems to be getting lots of attention from the locals! We’ve seen lots of sponges, ranging in colour from white to bright yellow and orange.

The slight time delay on the digital camera and the motion of the camera in the water means that taking the perfect picture requires a mixture of skill and luck. It's important that the pictures are of good quality, to ensure that the animals and habitats can be successfully identified. This has led to a bit of friendly rivalry between the JNCC staff on board as to who can capture the best image. Watch this space - the winning image will be shown on the next blog entry!

In addition to using the underwater camera, we’ve also been taking grabs of sediment where possible. Once samples of sediment have been taken, the sample is then washed in a washing machine like sieve to washing away the finer sediment. The water pressure in the sieve seems to have a mind of its own, frequently splashing both the user and unsuspecting passers by!

The dayshift were surprised to find a “mermaid’s purse” in one of their grabs, which is the egg case of a shark or ray. The night shift found two small cup corals (Caryophyllia smithii) on a stone in one of their grabs. This species of stony coral is similar to anemones but produces hard chalky skeletons to support and protect their bodies.

Now that the ground-truthing has been completed, we’re back to collecting acoustic data for an additional section of the bank. We’ll continue with this until around 8pm this evening, when we will say goodbye to Pobie Bank Reef and begin our steam back to Aberdeen.

Whale song!

Conditions have certainly livened up over the last 48 hours! The wind has been gusting up to 45 knots and lots of small birds have landed on the boat to shelter from the weather. Luckily the Scotia (and its crew!) are taking it well and we’ve been able to continue collecting data without problems so far.

It’s been over a week now since we left Aberdeen, and we’re starting to get a good picture of our survey site. The main section of Pobie Bank Reef is located at depths of 70 – 100m, and is made up of bedrock and large boulders, surrounded by a mixture of sediments. We’re currently collecting acoustic data in the third survey block, where we’ve detected some large, dramatic rocky outcrops. Previous studies of the site have mentioned these topographically complex areas, and we’re looking forward to putting the camera down to find out more.

The rocky reef provides a hard surface for a range of sea life to establish on, including communities of encrusting sponges and bryozoans. The cup-shaped Axinellid sponge (Axinella infundibuliformis), has been seen regularly during the camera tows. Other species commonly spotted include cup corals (Caryophyllia smithii) and the brittlestar Ophiura albida. We’ve also seen hermit crabs in abundance, several squat lobsters, and even had a ling (Molva molva) following the camera plum line on one of the tows. We’re not sure if he was curious or hungry!

As certain people onboard are very enthusiastic about Cetaceans (whales and dolphins), the bridge kindly called down to the office on Friday morning to let us know when four killer whales joined us right next to the ship! Unfortunately, the whales did not take into account that the day shift had just started a camera tow and were busy following a transect. Stuck in front of the computer in a windowless lab, the scientists desperately hoped that the whales would stick around long enough for them to finish the line. Having just finished work, the night shift were obliviously eating their dinner upstairs, until they spotted the others on the look-out. We were all too late, of course, and so none of us got to see the “pandas of the sea” this time. But we are, somewhat optimistically, hoping they might come back soon. Anything can happen at sea!

Sea Sea TV?!

Our progress has gone well over the last few days which has been helped by the good weather! The sea has been kind to us, which has made our job much easier. Whilst processing grab samples on Tuesday night, the day shift was treated to a beautiful sunset over Shetland in the far distance, and the night shift got to see the sun rise the following morning.

Finally, the acoustic work for box 1 has been completed!! The data has been used to identify 18 ground-truthing stations distributed throughout the box. Ground-truthing usually involves towing a camera just above the seafloor, which transmits a live video feed back to the ship showing us the different species and habitats that are down there. We’re also able to see how the seabed changes within and between stations, from sandy sediment to boulders and bedrock; it keeps the camera operator on their toes as big rocks often loom out of the darkness with no warning!

As well as collecting video, we also take regular photographs to help with identifying the animals we find. So far, we’ve seen several species of fish, including a well camouflaged monk fish, as along with an assortment of sponges, sea urchins, anemones and plenty of impressive starfish. This has started a competition between the scientists on board as to who can take the best photo!

If we find areas of sediment on the seabed, we may also collect samples from it using a grab. The stuff we scoop up can be analysed to determine exactly what type of sediment is present and also to identify any animals that like to burrow into it. But more about this in a future entry!

Now that the 18 stations have been completed, we have moved on to section 2 and have started to collect more acoustic data. The weather charts are showing lots of bright colours over the weekend, which generally means that stormy conditions are around the corner. We are trying to get as much data collected beforehand as possible, whilst also hoping that the forecast turns out to be wrong!

Sounds of the seabed

Since reaching Pobie Bank Reef cSAC on Saturday lunchtime, we have been focusing on collecting acoustic data using sidescan sonar and a multibeam echosounder. These data provide information about the seabed; sidescan uses diagonal sound waves to identify features on the seabed, whereas multibeam measures the depth of the seabed and collects 'backscatter' data which give an indication of the hardness and roughness of the seafloor.

Multibeam data

The data are collected in ‘swathes’ using sensors that are fixed to the ship's hull or pulled behind it on a torpedo-like 'towfish'. The sidescan has been collecting some interesting data so far, the detail in the images has allowed us to make out rock formations, different sediment types and even underwater pipelines!

The towfish out of the water

The towfish being deployed

We’re currently in the first of three survey sections, which is a 50km long rectangle where a single tow can take up to five hours! We hope to complete the acoustic work for this section later today. After the data have been processed by our colleague from the British Geological Survey, we can use some of the outputs to help inform where to focus the groundtruthing work.

Today the clouds have lifted slightly, but it's still very grey! This afternoon we’re due to collect another of our Marine Scotland Science colleagues from Shetland so we may even get a rare glimpse of land...

Fog on the brine

On Thursday afternoon, JNCC staff from Peterborough and Aberdeen boarded the MRV Scotia, which will be our home for the next two weeks. The original plan was to set off from Aberdeen harbour at 05:30 on Friday morning, but due to heavy fog (causing poor visibility) and the tides our departure was delayed until midday. The captain told us that we’d been lucky to get out of the harbour when we did because the fog was rolling back leaving a narrow window in which we could make our departure. We are all keen to start the survey of the Pobie Bank Reef cSAC!

We steamed up the east coast of Scotland past Fraserburgh and Peterhead to an area known as the Southern Trench, where we started the calibration of the survey equipment, including testing the cameras and acoustic equipment. We had heard that killer whales had been spotted outside of Peterhead a few days previously, so we were keeping our eyes peeled for cetaceans. From the bow, we spotted a blow in the distance. Very excited, we scanned the horizon and saw the dorsal fin of a minke whale. It was moving fast in differing directions, and once even surfaced within a stone’s throw of the ship!

During the steam we also spotted puffins, gannets, razorbills, kittiwakes, fulmars and guillemots. We also had an unusual visit from a kestrel. We think it got lost in the fog, and it is now resting in a sheltered area of the ship.

 

Puffin in the fog

Gannet



Kestrel

Kestrel on the ship

Overnight we continued the journey towards the Pobe Bank Reef cSAC, and we should arrive at the first survey area by lunchtime. The plan is to start by collecting multibeam and sidescan data, which will help us understand the composition of the seabed and help inform our groundtruthing strategy.

Offshore survey of Pobie Bank Reef cSAC due to commence

On the 23rd August another two week JNCC commissioned survey will commence, this time to Pobie Bank Reef candidate SAC (cSAC) aboard the MRV Scotia with Marine Scotland Science. Pobie Bank Reef is located in the North Sea, approximately 20km east of Unst, Fetlar and Whalsey in Shetland and is separated from Shetland by the Unst Basin (see map below). The cSAC is approximately 70km long and up to 21km wide. The reef is composed of a combination of stony and bedrock reef which meet the definition of the Annex I habitat reef, under the EU Habitats Directive. The reef is located on a bank of metamorphic and sedimentary rocks covered by a patchy veneer of sediment, ranging from sandy gravels to slightly gravelly sands and the bank overlays a flat plain of sedimentary rock, known as the East of Shetland Platform. 

The aim of the survey is to gather additional evidence to help improve our understanding of the seabed character and distribution of benthic communities within the site boundary. This information will then be used to facilitate discussions in relation to possible management measures at the site.