Science

Introduction

The deep-sea environment, into which BP operations are gradually extending, is generally poorly understood. Surveys regularly discover new habitats and communities of animals previously unknown to science. Inevitably, there is a lack of historical data which can be used for baseline knowledge and prediction. It is, however, apparent that all deep-sea environments support a wide range of animals that contribute significantly to global biodiversity.

Rationale

By establishing long-term monitoring of the deep sea physical environment, and biological activity in that environment, it should be possible to compensate to a large degree for previous lack of knowledge. Hitherto only two deep-sea sites in the world's oceans have been the subject of long-term studies exceeding 5 years: Station M in the NE Pacific Ocean (Smith et al. SCRIPPS Institute of Oceanography, University of California) at 4100 m depth, studied since 1989; and the Porcupine Abyssal Plain (Bengal) station at 4800 m in the NE Atlantic Ocean. At both stations, important annual cycles have been observed with considerable variability from year to year as well as changes in dominant fauna over decadal time scales. In an oil production area such natural changes need to be distinguished from any anthropogenic (man-made) influences imposed on the deep-sea environment.

A series of scientific meetings were set up (held at the Scripps Institution of Oceanography) to discuss the feasibility of establishing a long-term monitoring station within BP operating areas. The first meeting (September 2004) concluded the establishment of a long-term monitoring station in the Atlantic Ocean would, after a minimum 3 - 4 year time span, begin to allow discrimination of patterns of local change that could be compared with global changes. An objective should be the achievement of a 20 year time span of operation to allow monitoring for the lifetime of oil production in the area. This would provide long-term environmental assurance but also make a major contribution to science.

At the conclusion of the first meeting, Oceanlab (University of Aberdeen) were tasked with developing a number of design options to satisfy the compromise between scientific requirements and the practicalities of deploying a platform in the vicinity of BP offshore operations. A further meeting of the Steering committee in April 2005 discussed and enhanced both the scientific objectives and the specification for the Oceanlab designs. The DELOS platforms were deployed in February 2009..

Camera Module (Near & Far field platforms)

The camera modules contain two camera systems, a close view and wide view camera system.

Camera module

Close view camera

The close view camera takes time-lapse close up photographs of the sea floor and associated fauna. In a relatively unstudied area, such as the Angolan continental slope, it is vital that we obtain good quality, high-resolution images of the indigenous fauna. The close view stills camera will give us the flexibility required to correctly identify both invertebrates and fishes. These high-quality images also have considerable public outreach potential.

Examples of high quality close view camera photographs

Wide view Camera

The wide view camera takes time-lapse photographs of a large area of the sea floor. These observations enable a visualisation of seasonal sea floor sedimentation processes, passing animals and disturbance events over a large 20 m2 area. This scale of observation is essential to categorise any patterns of long-term change in the benthic environment over the 25 year life span of the project. This imaging set up has been used to excellent effect in the deep Pacific Ocean, by Dr. Ken Smith of Scripps, USA, and is proven technology. The synergy between the close view camera and the wide view camera allows us to assess large scale and long-term patterns of diversity and community change with accurate identification of anticipated new and novel species.

An example of a time lapse wide view camera tracking a deep sea holothurians' movements across the sea floor

Oceanographic module

Oceanographic Module (Near & Far field platforms)

A suite of oceanographic instruments is essential for any long term monitoring station. They provide background measurements to fully characterise the environment for all other observation modules in the docking station.

Each oceanographic module will house

  • 300kHz Acoustic Current Doppler Profiler (current profiles of water column above DELOS)
  • Transmissometer (Wet labs C Star). Measures the total particle load in the water column (this includes organic matter/ sand/ sediment/ etc)
  • Fluorometer (Chlorophyll a). Measures the organic matter content of the particle load identified by the transmissometer ie the "fresh" material or "food" arriving on the sea floor
  • Local seabed current meter (sea currents close to the sea floor)
  • Conductivity, Temperature, and Pressure sensors
  • Oxygen sensor (measure dissolved oxygen levels available to the local sea floor community)
Acoustic module

Acoustic Module (Near & Far field platforms)

Passive and active acoustics. A passive bioacoustic sensor monitors the natural sounds generated by animals within its detection range, as well as the background noise level. This system allows passing vocalising cetaceans to be identified (from characteristic sound spectra) and counted.

High frequency active sonar systems enable fish movements to be observed at a lower resolution but at much greater range than photographic systems. This module contains an active sonar system to record movements of fish with suitable target strength to ranges of up to 150 m from the DELOS platform. In conjunction with the passive acoustic module, that records (amongst other things) background noise level, fish reaction to acoustic disturbance events could be monitored.

An example of an active sonar visualising images on the sea floor

Sediment trap

Sediment trap module (Far field platform only)

Phytodetritus from plankton in the surface layers falls to the sea floor in seasonal pulses. This input of material is the major source of energy for the deep-sea community. A sediment trap collecting and periodically storing this fallout enables the composition and quantity of this energy input to be measured. To represent an unbiased record of phytodetrial fallout the sediment trap must be a minimum of 100m above the sea floor.

These data along with Transmissometer and Flourometer data will build up a comprehensive picture of food input into the deep ocean site.

Example of long term phytodetrital input to the deep sea caught in sediment traps showing a seasonal cycle

Guest Modules (Near & Far field platforms)

There are three guest modules in total: two in the Near field platform, and one in the Far field platform. Guest modules will initially be left empty and will be available for use in the future. Currently we have applications from both the science community and BP to use some of these modules for new research.

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