Cashel

Mission 2

Images | Videos

Location: Cashel, Northeast Atlantic, Republic of Ireland
Position: 54° 42’ 23.58” N 10° 26’ 20.37” W
Depth: 174 m
Water Temperature: 10ºC
Dates: 13 – 18 June 2008
Industry Partners  
Gas & Oil Company Statoil
ROV Operator: Oceaneering
Rig operator: Diamond Offshore
SERPENT Representative: Dr. Andrew Gates
   

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Mission Plan

Following the successful first mission to StatoilHydro’s Cashel well off the west coast of Ireland, Dr. Andrew Gates returned to the Diamond Offshore operated Ocean Vanguard armed with a good knowledge of the ecology of the area, gained from analysis of the video data collected during the first visit, and a plan to carry out experimental work on the seabed.

Biological experiments are notoriously difficult in the deep sea and although the 174 metres of water underneath the Ocean Vanguard is by no means deep by ocean standards, it is still inaccessible to biologists meaning that this kind of work is reliant on technology available through this collaboration and the expert manipulation skills of the Oceaneering ROV team. This work represents a good step forward for SERPENT building on the successes achieved last year in partnership with StatoilHydro.

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Experiments

The experiments were designed to investigate the impacts of drill cuttings on the animals on the seabed around the well. Analysis of video surveys taken on the first visit in May showed that the starfish Porania pulvillus was one of the most common animals at the site and probably the easiest to collect so an experiment was planned to translocate specimens of this species to different areas around the well. The images below show an example specimen of the starfish (left) and adding a starfish to experimental chambers on the sea bed using a core tube held in the seven-function manipulator arm on the ROV.

Cashel experiments

After exposure to the different amounts of drill spoil around the well, tissue samples were taken which have been returned to the labs at the National Oceanography Centre, Southampton for analysis. We will be looking to see if the energy reserves (sugars and lipids) of the starfish were negatively impacted by exposure to the drill cuttings. This would give an indication of the general health of the animals because if stress was caused by the drill cuttings it is expected that energy reserves will have been used up to maintain the animal’s normal metabolic functions.

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Eco Highlights

In addition to the organisms seen during the first visit there were some interesting observations made on this visit:

Squat Lobster

This squat lobster (Munida sarsi) was not intimidated by the attentions of the ROV; in fact it was positively aggressive towards the submersible.

Monkfish

Another animal unconcerned by the close proximity of the vehicle was this monkfish (Lophius piscatorius) seen here lying on the seabed awaiting a prey organism to venture too close.

Hake

This Hake, (Merluccius merluccius) was observed and filmed during the course of the experimental work.

Brittle star

This ophiuroid (brittle star) moved surprisingly rapidly across the seabed to find a temporary shelter under the ROV’s tether – the yellow cable seen in the bottom right corner of the image.

Images of all the species observed during the SERPENT work at Cashel alongside taxonomic information can be viewed in the SERPENT image database under the Cashel section http://archive.serpentproject.com/view/sites/cashel.html

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Cashel location map Dr Andrew Gates

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T: +44 (0)2380 596363
E: arg3@noc.soton.ac.uk