Our Ocean Planet - Exploring the depths

IMPORTANT LEGAL NOTICE - The information on this site is subject to a disclaimer and a copyright notice.

Exploring the depths

The chasms and trenches of the great oceans are mostly unexplored territory.
Research is only just beginning to uncover some of the secrets that lurk in their mysterious abyssal depths.

Extreme deep-sea hydrothermal environments are caused by underwater vents that open in the Earth's crust. Researchers worldwide have been very surprised to find that these hot and highly toxic waters are teeming with very odd forms of life. Some of the micro-organisms present could be sources of valuable biochemicals.

Hot stuff

Deep-sea hydrothermal (hot water) vents have generated much research interest recently. They were discovered in 1977 and are now known to occur in many places on the ocean floor. A vent opens where the Earth's crust is unstable. As cracks form, seawater seeps down into the hot rock and is then expelled again as the temperature inside the vent causes it to boil. The temperature around such a crack can be as high as 420¡C. Small particles and hot water enriched with minerals from the rock spew out of the vent, making the surrounding water highly toxic.
Researchers worldwide have therefore been very surprised to find that these hot and poisonous environments are teeming with life - very odd life. 300 new species have been found in hydrothermal vents since 1977. The ecosystems are based around bacteria, which use hydrogen sulphide and the heat from the vent to build complex food molecules. These bacteria are the energy source for all other organisms living nearby.

Some vent organisms just eat bacteria to get their energy, but there are also wierd vent worms that have a more unconventional approach. They have no gut or digestive system. Instead they are filled with living bacteria which pack their tissues (every gram of worm contains 10 billion bacteria) and supply them with all the food they need. In return, the worm's blood supplies the huge bacterial colony with all the hydrogen sulphide it needs.

The European project AMORES is being co-ordinated by scientists who are intrigued by this strange environment. Not only are the studies very valuable because they increase our knowledge of the natural world, but there might also be an important practical consideration. The bacteria that can thrive around a hydrothermal vent could be used to solve pollution problems closer to home since the conditions created near to a hydrothermal vent - no oxygen, high levels of hydrogen sulphide and high concentrations of heavy metals - are the very conditions that are often found in the polluted coastal waters of Europe.

AMORES is studying four contrasting hydrothermal fields in the Atlantic Ocean to find out how heat and matter are dispersed into the Atlantic. It is using large surface ships combined with smaller submersibles for deep-sea investigations to collect information about the physical and chemical processes that occur around hydrothermal vents and to identify potentially useful bacterial species.

A sub-ocean pharmacy?

Other European researchers are investigating micro-organisms that live in deep-sea vents and marine hot springs as potential sources of valuable biochemicals. Thermophilic bacteria produce compounds and enzymes with unique properties since they must remain active at the high temperatures at which the organism lives. Screening marine micro-organisms known first for their environmental potential has found some interesting biological molecules including unusual enzymes, antibiotics, anti-algal compounds, anti-cancer substances and secreted sugars.

Cold stuff: underwater avalanches

The physical nature of the seabed is also of great interest, particularly the large-scale sedimentation processes that occur at the margins between coastal areas and the deep sea. One area of study in the ENAM project is the European North Atlantic margin between the Norwegian margin and the Celtic Sea. Scientists from ENAM 2 are studying sedimentation patterns from the shelf edge, down through the continental slope and finally into the deep-sea trench of the North Atlantic.

This area is known to oil companies for its potential as a rich field of oil and natural gas and many intend, in the future, to build rigs here. But there is a problem. In the deepest trenches of the ocean, the water is very cold and gas hydrates (ice-like crystals) form just above the sea floor. Oceanic gas hydrates are now recognised as a major, little understood hazard that can threaten the stability of rigs in deep water oil fields. The stability of gas hydrates depends on the temperature and pressure conditions on the seabed. The recent increase in global temperature has caused changes in sea levels that have increased the instability of gas hydrates, making the whole of the ocean floor much more liable to shifting and sliding. Large underwater 'avalanches' called 'mass wasting events' are increasingly common (see figure). In a single event, an enormous volume of sediment can slide, like an underwater avalanche, from the top of the margin into the deepest part of the trench.

Jürgen Mienert, co-ordinator of ENAM II says, "Our work is providing new insights into the different sedimentary processes that shape the sea bed of the North Atlantic margin. We hope to be able to understand better the variations that occur at the shelf edge and on the continental slope and to develop computer models to help us work out which areas are the most stable. This part of the project is obviously generating a lot of interest in the oil industry."

The depths of the North Atlantic are rich in as yet unexploited oil but the sea floor is prone to instabilities under some physical conditions. In the ENAM2 project, European researchers are studying underwater "avalanches" that cause sediments to slide down the continental shelf and could make oil exploitation unsafe

Deep-sea technology

Exploring the waters of the deep oceans and the features on and below the seabed cannot be done without highly specialised equipment. New technology is needed to enable researchers to study the often dangerous environment of the seabed. Many projects supported by the European Commission MAST programme (Marine Science and Technology) are developing technology in this area, as are a large number of EUREKA projects, co-ordinated under the EUROMAR umbrella. Here are just four examples.

Pictures 1. ALIPOR Project - This automatic lander can sink to the sea floor under its own weight and then conduct experiments, gather data and return to the surface when finished.

2. SIRENE is a remote-controlled-carrier, which can position underwater laboratories with extreme precision at depths of up to 6000 metres using advanced tele-acoustic communication

3. The EUROMAR project ROMAN has developed a heavy duty deep-sea robot that can carry out heavy jobs at great depths, taking over tasks that are too dangerous for human divers.

4. AMADEUS is a research programme to improve the dexterity and sensory ability of remote-controlled underwater manipulation systems. This final prototype should be able to sample organisms, sediment and rocks with extreme accuracy.

The treasure of marine life