Friday, 6 July 2012

Day 1 - Setting out

After a busy few days getting the ship packed up and everyone on board, it is finally time to leave Southampton and set sail for the abyss! On this cruise, we’re hoping to answer some fascinating questions about how variable the deep-sea environment really is, and what this means for the animals that live there.

Discovery at NOC
Deep-sea environments have traditionally been considered to be highly stable and relatively unchanging over long periods of time and over large spatial scales. However, there is increasing evidence that deep-sea systems may be far more heterogeneous and dynamic than was previously thought, and so one of the major aims of this cruise is to assess how the abundance and diversity of deep-sea organisms varies over a range of spatial scales (from metres to 10 kilometres).

Mobilising
In order to do this, we intend to travel to the Porcupine Abyssal Plain (PAP; approximately 350 miles from Southampton) to conduct highly detailed surveys of the seabed using an Autonomous Underwater Vehicle (AUV) called Autosub6000 which will hopefully allow us to understand how abyssal animals utilise fine-scale variations in habitat and how they are distributed over the seafloor. For this expedition, Autosub has been fitted out with two time-lapse camera systems; the first is a colour camera which points vertically downwards and will be used to create a photographic mosaic of the seabed and to analyse the distributions of invertebrate megafauna, while the second is a black and white camera which has been set up to capture images of fish and other mobile fauna occurring in front of the AUV (hopefully before they are startled by it!). In addition, Autosub6000 is fitted with multibeam sonar and a sub-bottom profiler which will allow us to create an extremely detailed map of the sediments on the seabed and will help us understand how the seabed is changing over a range of spatial scales. By tying together the acoustic (physical) and photographic (biological) data, we hope to be able to determine the amount of spatial heterogeneity present at the PAP.

Of course, there is also a need to collect samples from the seabed so we can ground-truth the image data we are collecting and make sure that what we think we are seeing is accurate. So while the Autosub is underwater on one of its 20 plus-hour missions, we will use the time to deploy the megacorer and boxcorer which will hopefully provide plenty of samples for us to assess sediment grain size, the abundance and diversity of the infauna (animals that live in the sediment), bacterial counts and much more.

En route to the PAP site we will make a stop in shallower water at a site called the Goban Spur so Charlie Main (NOC PhD student) can collect sediment and water samples to start her experiments to study the effects of crude oil on infaunal seabed community ecosystem functionality, which we will hopefully hear more about from her once everything is set up and running! After that, we head onwards to the PAP site and aim to start working there first thing on Sunday morning (weather permitting!).

Leaving NOC
In the meantime, we’ve got plenty to do to make sure that all our equipment, computers and laboratories are set up correctly and safely for three weeks at sea and that all our systems are ready to go as soon as we arrive on site. For now though, it’s time for the ship’s safety briefing and muster drills so I will sign off now and make sure I can find my lifejacket!

Images and text by Rosanna Milligan