Thursday 29 November 2012

Nearly finished surveying Turbot Bank…

Over the last two days we’ve focused on finishing the grab samples and drop camera transects.  On Wednesday, faced with winds from the north and a northerly swell, we were limited to running multibeam lines across the Turbot Bank area for the first part of the day. Due to the size of the site and the fact that we could only run lines in one direction, it took the first seven hours of the day to complete just three! The screengrab below shows some of the raw multibeam bathymetry data. The data show a depth range across the survey area of 80 metres (in the north) to roughly 60 metres (in the central area).

Screen grab of multibeam data. Note: To increase data coverage, further survey lines will be completed in due course.

Throughout the rest of Wednesday and some of Thursday, the day and night shifts shared the effort of grab sampling and sieving.  There was a collective sigh of relief when the final grabs were processed. We were able to use the remaining contingency time to complete some extra drop video tows. In order to facilitate the interpretation of the multibeam backscatter data, the video tow stations were positioned to intersect with the multibeam survey lines. The backscatter data show the sound energy reflected back from the seabed and this can be linked to the physical properties that make up the sediment (see image below; energy values are shown using a grey scale). On the screen grab below, the darker areas indicate higher reflectance.  The video tows confirmed our predictions that the darker regions were indicative of gravel dominated substrates while the lighter areas were indicative of sandier substrates. 

Screen grab of multibeam backscatter data. The darker areas indicate relatively high sound energy reflectance.

With our survey time at Turbot Bank coming to an end, we’re getting ready for our final transit home in the early hours of tomorrow morning.

A shot of the day shift team in the plot lab…

Wednesday 28 November 2012

The boat that rocked

Today has involved a mixture of survey methods, with the early hours involving finishing the remainder of the priority grab sites. The next task of the day was to focus on getting video footage from a subset of those areas from which we had already taken grab samples. The visibility at this survey location is really good and we could get a clear picture of the seabed. The sediment here ranges from coarse sand with the odd pebble or cobble to much coarser gravelly sediment with boulders. There is a lot of Hornwrack (the bryozoan Flustra foliacea)  growing on cobbles and pebbles in the sediment as well as cushion stars (abundant Porania pulvillus but also Hippasteria phrygiana which apparently is rather rare in British waters) urchins, anemones and plenty of squat lobsters and crabs. The squat lobsters and crabs were especially prevalent in the areas containing cobbles and boulders.
 Dahlia anemone Urticina felina 

 Edible crab Cancer pagurus and Flustra spp.

Plumose Anemone Metridium senile

 Red Gurnard Aspitrigla cuculus

Seven armed starfish Luidia spp.

Starfish Henricia spp.

Starfish Hippasteria phrygiana

Sunstar Crossaster papposus

The day shift continued with the camera tows. We also planned some supplementary multibeam lines, in case we got some rougher weather which was forecast to arrive towards the end of the day. The four ‘corridors’ of additional survey lines ran in a north-south direction and supplemented the east to west survey lines, providing a grid of acoustic data. The new lines were placed across many of the planned drop-down camera tows and Hamon grab stations within the area. Due to the sheer size of the site, it won’t be possible to get full acoustic coverage….that would take many days of intensive multibeam survey. The intersecting lines that we have planned should nevertheless provide a set of acoustic data which are representative of the area. Towards the latter part of the day, the wind picked up and the sea became a little too rough to use the Hamon grab, so we switched to the planned multibeam lines to finish off the day. 

Tuesday 27 November 2012

Sieved to see another day…

When the night shift took over at midnight, the weather was still a little too rough for anything other than multibeam and so we continued to run some acoustic lines from East to West. The Turbot Bank survey site is large in comparison to the cSAC sites (nearly 30 times bigger than the Braemar and Scanner cSAC sites combined). Good quality data could only be gathered when the vessel travelled in one direction, with each line taking nearly two  hours. Just before sunrise we deployed the drop camera and found a number of interesting species. Some of the highlights have included squat lobsters, sandeels, sea urchins, occasionally some scallops and plenty of brittlestars and starfish.  It was evident when watching the footage of the seabed that this was a high energy site, with significant currents sweeping across the seafloor.

Squat lobster

Porania pulvillus

Echinus esculentus

A key sampling method at the Turbot Bank site will be using the Hamon grab to take samples of the seabed. We plan to deploy the grab at over 70 stations spaced evenly across the survey site. Particle Size Analysis (PSA) and macrofauna analysis will be undertaken on these samples in order to better characterise the substrate and the organisms that it supports. Sampling the sands and gravels at Turbot Bank presents some challenges compared with the soft muds at the Braemar and Scanner Pockmark sites. Occasionally grab samples have to be discarded if insufficient volume of sample material is collected and this is most likely to occur if the grab strikes cobbles or boulders. It will take some time to complete the sampling and so it’ll be important to prioritise the good weather windows for using the Hamon grab.

The first few grabs of the day brought up coarse sandy sediment, with some cobbles. This sediment had fewer worms than seemed to be present in the mud that we sieved at the cSAC survey sites, instead containing sand eels, burrowing urchins and brittlestars that live in the sediment. As the sediment was coarse it collected more readily in the 1mm sieves, extending the sieving time per sample. By lunch time a number of grabs had been taken but there was plenty left to go!

Some images of the species we found in the grab samples. Top left: spider crab, disguised with marine life growing on its shell. Top right: Purple heart urchin (Spatangus purpureus). Bottom: Sandeel, a key food source for seabirds in the North Sea.

Monday 26 November 2012

Going cyclonic on the transit to Turbot Bank

The day commenced with continuation of video tows, a mixture of lines crossing those already carried out within the four main pockmarks and some additional video tows over some smaller pockmarks within the south of the Scanner Pockmark cSAC.  The multibeam bathymetry/ backscatter showed that these smaller pockmarks had some interesting ‘scour pit’ features trailing off their south end. After the last tow was completed we changed gear type to the Day grab to take some final sediment samples from within the four main pockmark features in the site. By the end of the third grab station the swell and wind had really picked up and it was no longer safe to deploy the Day grab from the ship.

A glimpse of the gale force weather

Soon after this, having collected sufficient acoustic and groundtruthing data for the Scanner pockmark cSAC, we began to transit to our third and final site Turbot Bank. As explained in yesterday's post, the decision was made to survey the site of a potential Nature Conservation MPA called Turbot Bank instead of one further north in the Fladen Grounds. This journey was especially eventful, with by far the largest swell we have experienced and with the weather on the beam, the ship was lurching all over the place with people and belongings sliding everywhere. At one point whilst sat in the lounge, people were sliding across the room whilst sat in their chairs!

At 2pm the ships general alarm sounded for our weekly emergency muster drill. We all donned our PPE (Personal Protective Equipment) - steel toe-capped boots, wet weather gear and hard hats, to brave the inclement weather to muster up on deck for a safety briefing.

Can you spot the stowaway?

We arrived at Turbot Bank just after dinner, and started running multibeam lines across the bank.  There is existing MCA Civil Hydrography Programme data for the western part of survey area, so we were careful to avoid duplication.  The weather was still too rough to deploy the Hamon grab or camera gear.  The forecast is looking slightly better over the next few days gale warnings at least.

A grabbing and video marathon

A week into our survey and despite the ‘weather gods’ doing their best to hinder us, we’re still not far off schedule. We had a spell of calm weather at the start of the weekend and we made good progress with the Scanner cSAC survey. The first eleven hours of the day were spent using the day grab to get samples of the mud sediment for particle size analysis (PSA) and sieving for macrofauna  A subset of meiofauna and ‘organics’ were also taken.  In today’s samples we found the burrowing urchins, brittlestars, the sea pen Pennatula phosphorea and many different types of worms! A warm cuppa offered occasional respite from the cold work out on deck. 

Some of the creatures brought up in the grab samples

As the swell calmed down, the next task was to deploy the camera and take video and still images within the cSAC boundary. The first video tow showed a slightly different picture to that at Braemar with mud sediment rather than sandy mud and consequently many more Nephrops (scampi) and Nephrops burrows. We also saw lots of seapens and burrowing anemones. We planned single drop down camera tows across some of the smaller pockmarks and more intensive camera transects (four tow lines) intersecting with the Scanner pockmark.

Nephrops norvegicus
Burrowing cerianthid anemones
The sea pen Virgularia mirabilis and prawn

There has been a change of plan for the rest of the survey and assuming we complete the work on schedule, we’ll be leaving Scanner for Turbot Bank ( rather than the Fladen Grounds) tomorrow morning.   Similar to the Fladen Grounds, Turbot Bank is also a proposed area for a national Nature Conservation MPA but is located further south and closer inshore, 25 miles due east off Peterhead.

Sunday 25 November 2012

The Scanner squall

The day commenced much the same as the last, with strong winds and large swell inhibiting us from carrying out any further work on our new study site. This weather was worse than we had suffered earlier in the week and the ship was pitching high over the large rolling waves. Even though there was still significant swell, at around breakfast time we made the decision to recommence with multibeam tows across the site to see what the quality of data would look like. It turned out that lines could only be run in one direction with the weather, to get acoustic data of an acceptable quality. This meant that gathering this data would take double the time and we were aiming to get 100% coverage of the site by the afternoon. By late morning we had some blue sky and even some sunshine breaking through the grey cloud which did well to lift the spirits!

Reviewing the survey plan

Unfortunately, this lift in the gloomy weather didn’t last long and the swell increased just enough to prohibit the use the mulitbeam. The weather was still too rough to use to Hamon grab or camera equipment and so we planned a series of Day grabs. The Day grab is smaller and lighter than the Hamon grab and is therefore safer to deploy over the side of the vessel, in poor weather. We designed a sampling grid which provided good coverage across the Scanner Pockmark cSAC and extended into the area outside (an area which is part of a proposed area for a national Nature Conservation MPA (under the Scottish MPA project). We made good progress over the remainder of the day. Samples taken were composed primarily of mud and one sample contained the seapen Virgularia mirabilis.

We’ve adopted a large amount of seabirds that spend the day circling around the ship and sitting on the water beside us, most likely hoping we are a fishing boat with some sort of food!

Friday 23 November 2012

One site down, two to go!

The night shift took over from the day shift to continue grabbing the remaining stations at the Braemar Pockmarks cSAC site. The completion of the grab sampling signified the end of our work at the Braemar Pockmarks site. Content with the data we had collected despite the weather being thrown at us, we were looking forward to moving down to our next study site Scanner Pockmark cSAC located in an area known as the Witch Ground Basin.

Unfortunately we were due another blast of bad weather which we heard was affecting mainland UK over the last 24 hours. With this in mind, once we arrived we set to with gathering acoustic data for the site to see how far we could get! Our first tow line picked up the two pockmarks in the north of the site known as the Scotia pockmarks complex, followed by another tow which picked up the larger pockmarks within the site. The multibeam data extract below shows the depth profile of the largest of the pockmarks within the Scanner Pockmark cSAC boundary, which previous surveys had identified as containing submarine structures made by leaking gas.

Multibeam depth profile and 3D view of Scanner Pockmark.

Working away in the plot room, processing side-scan sonar and miltibeam data.

The wind picked up mid-afternoon creating white peaks and spray; an extremely large swell developed, sometimes reaching 8-10m.  A grim prospect for the plot room as sunset approached. After a further two multibeam and side-scan sonar lines, a halt was called as data quality deteriorated.  This weather was worse than before, with chairs sliding across the room as you sat on them and the ever-changing feeling of weightlessness and then being pinned to the floor.  Walking around the vessel was tricky, and resembled Monty Pythons Ministry of Silly Walks.  Most of us hunkered down and waited for it to pass.

Shell hash and submarine structures...

The day started with the night shift taking over the seabed imagery work, continuing to carry out camera transects of the seafloor over features spotted on the acoustic data. We saw a range of wildlife typical of sandy mud habitats, including seapens, numerous flatfish and plenty of burrows, some of which were created by the prawn Nephrops (also known as Dublin Bay Prawn or Scampi).  We also saw what looked like carbonate structures and shell hash within some of the pockmarks. 

The pockmarks are crater like depressions on the seabed which are thought to have been produced by either gas or fluid seeping up through the seabed. The shell hash is often found associated with the carbonate structures within the pockmarks.

This work took us up until breakfast, after which we carried out some final bits of multibeam and sidescan sonar to make sure we filled all the remaining gaps in the acoustic data.

Hag fish and starfish on sandy mud sediment
Anemone on shell hash

Shell hash within a pockmark

The remainder of the day was consumed with carrying out grab samples at planned stations. This work comprised of using two different types of grab; the hamon grab which is used to take samples from coarser sediments (such as the shell hash in the bottom of the pockmarks) and the day grab which is used for softer sediments. Once a grab has been deployed from the ship it is winched down to the seabed where the mechanism is activated to scoop up some of the seabed. The hamon grab has a nifty device called a HamCamTM which is a camera attached to the grab allowing you to see what you are about to sample.  The grab is then winched back onboard where it is then processed. This is done through a number of stages using a sieving system. The hamon grab samples were photographed and a sediment sample taken for particle size analysis (PSA) and finally the remaining sediment is then processed ready for macrofaunal analysis using a sieve with mesh size 1mm. Subsamples of the sediment collected in the day grab were taken for PSA, and meiofauna (very small animals), before it was processed for macrofaunal analysis using a sieve with mesh size of 1mm. This work is done out on deck and involves getting quite wet and muddy!

Collecting macrofauna off a sediment sieve

Deploying the hamon grab

As the day drew to a close, we were greeted by an amazing sunset.

Wednesday 21 November 2012

Further exploration of the pockmarks begins

Day four of the survey begun with little change in the weather, the wind still howling outside and the swell huge, and so we continued to wait for it to ease up. Eventually at 7:30am it appeared to have settled enough to get going again with the acoustic work. We completed the final two mutibeam lines which had been planned, followed by two additional multibeam and sidescan sonar lines which crossed the other multibeam and sidescan lines at 90 degrees. This is good practice in terms of quality control for the acoustic data.  Whilst using the sidescan sonar, gas bubbles (likely to be methane) could be seen escaping from the seafloor at some of the pockmarks.

Using the initial outputs from the acoustic data, we planned a suite of video tows and grab stations. We prioritised these video tows just in case the inclement weather returned, so that these could be carried out at the locations of the pockmarks and more importantly where there have been previous data gathered for the submarine structures made by leaking gases.

In the afternoon we started off with camera work, consisting of a series of video camera tows with still images being taken at regular intervals. The images below show a snapshot of the wildlife that we saw at these survey locations.  We found evidence of carbonate structures on the seabed in some of the pockmarks, as well as a range of animals living on the seabed, including seapens, hermit crabs, angler fish and wolf fish.  On one of the tows, a large shoal of saithe appeared, making seeing the seabed quite challenging.

Muddy sediment with the Phosphorescent seapen (Pennatula phosphorea) and starfish

Angler fish (Lophius piscatorius)

Saithe (Pollachius virens)

Spot the Wolf fish (Anarhichas lupus)

Carbonate structures on the seabed

Tuesday 20 November 2012

Batten down the hatches!

After the night shift took over we completed the last priority line of multibeam and sidescan sonar, followed by another six lines of multibeam to fill the remaining gaps in the data we had collected so far within the Braemar Pockmarks cSAC. After warnings of gale force winds we attempted to get as much completed as possible before the weather deteriorated.   Unfortunately by around 9am, the weather had really taken a turn for the worse, and data quality was suffering, so we had to call it a day.

As predicted the weather stayed poor for the rest of the day with wind speeds averaging 42 knots and gusts above 50 knots.  The swell was in excess of 5 metres! Needless to say the waves in the images below were a common sight for those on the day shift and no further progress was made in terms of data gathering.

Swell off the aft deck

Wind speed indicator on the bridge showing averegae wind speed and maximum (gust) speed

After reviewing the options, we decided to stay on site and wait for the storm to blow through. This was decided on rather than do a 30 hour round trip to take the ship into sheltered inshore waters to carry out work on some of our contingency survey sites, which could potentially result in us missing a good weather window back at Braemar Pockmarks.  We’re keeping our fingers crossed that the conditions will calm down and we’ll be able to start work again soon.

Monday 19 November 2012

Here comes the swell

It took until 11:00 on our second day at sea to reach our first study site, Braemar Pockmarks cSAC. The weather had gradually worsened since leaving Hartlepool and although there was only a little rain, both the wind and swell (approximately 2.5 meters) had picked up considerably, resulting in an uncomfortable roll on the boat. In the morning light the horizon was dotted with gas and oil rigs as we passed through towards our study site. In spite of the weather, the preparation for the acoustic work commenced and the side scan sonar equipment was made ready. We started off on our first survey line using both multibeam and sidescan sonar after using the CTD (Conductivity Temperature Depth) to calculate sound velocity throughout the water column  (~120m depth), so that appropriate corrections could be applied to the acoustic data.

The quality of the data was suffering due to the rough weather, so the orientation of the survey lines was changed; data quality was best when travelling in a north-easterly direction and we restricted the survey lines to this direction only in order to keep the weather behind us. To further improve the quality of the data, we narrowed the footprint of the multibeam and reduced the vessel speed.

Despite the weather, we got some good data and throughout the rest of the day managed to carry out multiple survey lines. Braemar Pockmarks is a relatively small site (5.18km2), and we’re aiming to get 100% acoustic coverage of the seafloor within the cSAC and some of the surrounding area. This will allow us to better understand the bathymetry and seabed texture, and identify areas to target with both video camera and sediment grab sampling. Our main interest at this site is the condition of the Annex I feature ‘submarine structures made by leaking gases’ which the site is designated for. In addition to undertaking planned sampling stations we will also target key areas which have been indicated by the acoustic work as potential further examples of this feature.

The day passed with intermittent squalls of hail which turned the sea and sky white and some sunny spells. By the end of the second day of the survey, we had completed most of the priority multibeam and sidescan sonar survey lines with some infill of multibeam lines still left to do, before starting on the camera work. The day shift finished just as the shipping forecast reported ‘gale force winds’ with wind speeds approaching severe gale nine....

Sunday 18 November 2012

Full steam ahead

We arrived at Hartlepool docks at lunch time on Friday 16th November to join our home for the next two weeks, the RV Cefas Endeavour. After going through both a safety briefing for the dock yard and the ships safety induction we had a bit of time on our hands to familiarise ourselves with the ship and settle into our cabins.

RV Cefas Endeavour at Irvines Quay, Hartlepool

After dinner we sat down to review existing data for the areas we plan to survey over the next two weeks and further refine the survey plans. We also went over possible contingency plans if the weather offshore gets too rough for data collection. Those of us who have landed the night shift 00:00 – 12:00 tried to have a late night in an attempt to start to become accustomed to the unusual working hours.

The next day commenced with an early start casting off from the docks at 07:00 in hope of reaching our first destination, Swallow Hole (a geological feature), by the afternoon, where we planned to calibrate the multibeam equipment. The weather was good with a calm sea, light winds and a slight swell. En route we received a talk by the ships Master, followed by a drill in which the ships general alarm was sounded (seven short blasts followed by one long blast on the ships whistle) and we all had to muster as if it was an emergency. We were then taken though the steps to be followed in an emergency and how to launch the life rafts.

We finally arrived at Swallow Hole at 14:00 where Cefas staff proceeded to carry out the calibration. Carrying out these checks on the equipment will reduce any error when using this acoustic technique within the study sites. After the calibration checks were completed, we recommenced the journey to our first survey site, Braemar Pockmarks cSAC.  This was going to take until midday on Sunday and so the ship’s crew continued to take the boat full steam ahead.

Friday 16 November 2012

Offshore survey due to commence in the northern North Sea

On Saturday 17th November another two week survey will commence of three areas within the Scottish offshore area. Three members of JNCC staff have joined the Cefas Endeavour research vessel, and over the next two weeks, will undertake a detailed survey of both Braemar Pockmarks and Scanner Pockmark candidate Special Areas of Conservation (cSAC), as well as a proposed area for a national Nature Conservation MPA in the Fladen Grounds.

Braemar Pockmarks and Scanner Pockmark were both submitted to the European Commission as examples of submarine structures made by leaking gases and have both since been approved as Sites of Community Importance (SCI). These sites are both located in the northern North Sea regional sea, with Braemar Pockmarks located about 240km east of the Orkney Islands and Scanner Pockmark approximately185km off the north east coast of Scotland.

Map showing Braemar Pockmarks cSAC and Scanner Pockmark cSAC

The Braemar pockmarks are a series of crater-like depressions, two of which contain submarine structures made by leaking gases. Also within the site boundary, and to the south-west of these pockmarks, there is an additional submarine structure that is not associated with a pockmark. These large carbonate blocks and pavement slabs are formed during the oxidation of methane gas. The habitat created supports chemosynthetic organisms that feed off the bubbling methane and provides shelter for fish species such as wolf fish and cod. Scanner Pockmark is a seafloor depression containing submarine structures made by leaking gases. The large carbonate blocks lie in the base of the pockmark, supporting chemosynthetic organisms and animals usually associated with rocky reef, such as squat lobsters and anemones and providing shelter for fish such as haddock and hagfish.

The main aim of this survey is to gather additional information to aid the development of management measures for these sites as well as assisting in the development of a baseline for future site monitoring.  After surveying the cSACs, the vessel will transit to an area within the Fladen Grounds to gather additional evidence to support and refine a number of Nature Conservation MPA proposals for the Scottish Marine Protected Area Project.

Thursday 15 November 2012

Wyville Thomson Ridge survey summary

Now we have returned from the stormy seas of northern Scotland and got our land-legs back, we have been able to look back over the work we achieved. During our 15 day survey of the Wyville Thomson Ridge and Faroe-Shetland channel we were able to employ a wide variety of data collection techniques and cover a large area within the two survey areas.

Some summary statistics of what was accomplished during our time is shown below:

  • Sidescan: ~307 km of Sidescan Sonar on the slopes of Wyville Thompson Ridge and in south-west of the Faroe-Shetland Channel.
  • Mulitbeam: In excess of 170 km of multibeam on Wyville Thompson Ridge and Noss Head.
  • Video tows: 61 completed – 29 on Wyville Thompson Ridge and 32 in Faroe Shetland Channel
  • Grab samples: 5 successfully completed in Faroe-Sheltand Channel and Noss Head
  • Rock dredge: 1 sample taken in the north of Faroe-Shetland Channel

Wyville Thomson Ridge survey map

We would like to thank the captain and crew of the MRV Scotia, our partners from Marine Scotland Science, Rebecca and Gillian for their help and assistance during this survey.

As this cruise has come to an end another is just about to begin with colleagues from JNCC due to depart onboard CEFAS Endeavour on 17th November heading to the Braemar Pockmarks and Scanner Pockmark SCIs, which contain the Annex I feature ‘Submarine structures made by leaking gas’ as well as the Scottish offshore Nature Conservation MPA proposals within the Fladen Grounds.

Friday 9 November 2012

High tailing it back

After yesterday’s weather and equipment setbacks, lunchtime comes around and we’re able to hit the ground running once again. With a further eight video tows planned in our mission to map deep sea sponge aggregations and to hopefully collect some samples for analysis later, we certainly had an ambitious work plan laid on the table. Luckily we weren’t disappointed, with sponge grounds out in force. Particular highlights include massive sponges such as the cathedral sponge (pictured below with pencil urchins either side) and the general high diversity of different sponge species observed.

Cathedral sponge with pencil urchins

Sponge grounds of the Faroe-Shetland Channel

Sponges, red banded fish and sea cucumber on boulder

Once we’d completed our camera work in the Faroe-Shetland Channel the weather finally started to creep in and it was time to high tail it back to port. With time on our hands we used an opportunity en route back home to conduct some further survey work in an area of interest for a Marine Protected Area in Scotland known as Noss Head. Here the feature of interest is beds of the horse mussel (Modiolus modiolus).

We conducted multibeam sounding over the area of interest to try and get a feel for the extent of horse mussels in the area, followed by some grab sampling work so we could assess the biodiversity associated with the beds. Unfortunately, our grab samples were a bit hit and miss but we still got some interesting stuff such as many different types of worms and clams.

Suited and booted ready for grab work

Hamon grab sampling at Noss Head

Grab sampling

After a brief period of calibrating our multibeaming equipment in the Moray Firth on the way back home we finally arrived back into Aberdeen at 19:30 hours on 8th November 2012, weary but satisfied with the achievements we’ve made on the cruise.