Introduction

Deep sea environments for years were thought to be lifeless due to the extreme conditions, until the 1800′s when many scientists including Charles Wyville Thomson started to dredge for species found at high depths. However it is only now with developments in technology that we have discovered the variety of life living at depths in large numbers most of which have never been seen before e.g. Riftia, Calyptogena ponderosa. The vastness of the deep sea environment means most life is spread throughout a large area, making them hard to find, however at certain points organisms congregate due to chemicals issuing from the seabed e.g. at Hydrothermal vents and Cold Seeps. This website concentrates on Cold Seeps; their formation, the associated  fauna and the future of these unique habitats.

A submersible taking a sample of Vestimentiferan tube worms. Photo from NOAA/OER

What are Cold Seeps?

Cold seeps are sites where methane, hydrogen sulphide and hydrocarbons (oil) seep out of the sediment this leads to dense microbial communities consisting of sulphate reducing and methanogenic bacteria which are fueled by organic matter falling from surface waters (Gibson et al. 2005). Only 24 deep cold seeps have been discovered so far and only half of these sites have been well studied biologically (Tunnicliffe et al. 2003)  They are found along geologically active and passive continental margins (Gibson et al. 2005), examples of well studied sites are the Gulf of Mexico and the Eastern Pacific. However they are also geologically diverse as they occur in every ocean apart from polar regions and also in inland lakes and seas (Gibson et al. 2005). They are considered an extreme environment due to the high pressures of up to 750 units of atmospheric pressure, the absence of sunlight and the presence of ‘dangerous’ chemicals in the water. The fauna found at cold seeps therefore show adaptations to living in these conditions with most being dependent on autotrophic and chemotrophic nutrition, this is only possible due to symbiotic bacteria living inside the organisms which use the chemicals issuing from the sediment for energy. Some organisms blood is adapted to adsorb sulphide so it does not suffer from sulphide poisoning, whilst all the organisms are adapted to living at high pressure; if they were to be brought to the surface they would no longer be recognisable as their cell membranes are less viscous due to the modification of lipids found in the membrane, organisms also contain pressure insensitive enzymes so that cell processes can still take place.

Leave a Reply