HADEEP / Life at extreme depth; Fishes and scavenging fauna of the Abyssal to Hadal boundary.

Lead Research Organisation: University of Aberdeen
Department Name: Inst of Biological and Environmental Sci


A team from the University of Aberdeen Oceanlab will join forces with the University of Tokyo, Japan and University of Tuebingen, Germany to undertake the first directed study on the distribution and behaviour of the deepest-living fishes in the world. Two unmanned autonomous lander vehicles will be built in Aberdeen; one equipped with a video camera and a second with a high resolution digital stills camera. They will be launched to depths of 5km to over 10km around the Mariana, Tonga and Kermadec trenches in the North and South Pacific Ocean from Japanese and German ships in 2007 and 2008. At the surface these ocean areas have clear blue water with low productivity and there is likely to be very little natural fall-out of food to the sea floor in the form of detritus and dead carcasses upon which the deep-sea animals living kilometres below are entirely dependent. Baits will be deployed on the sea floor in view of the lander cameras to mimic natural packets of food arriving from the surface and recordings will be made of fish, deep-sea shrimps and any other animals attracted into the observational area. The landers, equipped with depth sensors will provide accurate information on the depth of occurrence of different species, information that was difficult to obtain with equipment used to capture dead specimens that are found in different museums around the world. There is a chance that the team may capture the first living images of the world's deepest fish Abyssobrotula galatheae thought to occur down to 8370m. The deep sea is divided into three main depth zones, Bathyal down to 3000m, Abyssal between 3000 and 6000m and Hadal depths greater than 6000m. On the sea floor sharks are mainly limited to depths less than 3000m around the edges of the oceans, islands, sea mounts and on mid-ocean ridges. The abyssal zone accounts for 75% of ocean area and is populated by a surprising variety of life including active scavenging bony fishes such as grenadiers, cusk-eels, snail fishes and abyssal eels which have been filmed consuming fish and marine mammal carcasses at depths down to 5900m. It is not known what defines the boundary between the relatively rich life of the abyss and evidently sparse life of the hadal zone. The Hadal zone is mainly confined to trenches around the margins of the Pacific Ocean extending down to the deepest point on the planet, the Challenger Deep 10,896m in the Mariana trench. Two main explanations are likely: Firstly with increasing depth, food supply from the surface becomes sparser and a point is reached where there is insufficient energy to support active forms of life. Secondly pressure increases with depth and most animals have a maximum lethal pressure at which nerves, muscles and vital processes cease to function. Deep-sea animals have special adaptations to allow function at high pressures but there may be limits beyond which such adaptations are no longer possible. This project will not answer these questions directly but will make comparisons with information from shallower depths. If fish thrive down to 6000m with a constant cut-off at the start of the hadal region this would suggest a physiological pressure limit. However if the abyssal species peter out at different distances from the hadal boundary in different areas this may suggest limitation by local food availability. The time of arrival of animals at baits, their sizes, speeds, numbers and rate of consumption of bait will be measured. Comparisons will be made between species living at different depths. In particular fishes, which apparently do not penetrate the deepest parts of the trench systems, will be compared with amphipod shrimps that occur down to full ocean depth. Analysis will allow derivation of the first estimates of abundance and biomass of mobile life at these depths. This study will extend the depth range over which proposed fundamental laws of life in the deep sea can be tested.


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Description The aim of this project was to investigate distribution and behaviour of the deepest-living animals in the world. These are found in the specialised environment of the hadal zone which is defined as ocean depths greater than 6000 m mainly in deep trenches around the rim of the Pacific Ocean. The work was done in collaboration with colleagues from the University of Tokyo, Japan and University of Tuebingen, Germany

Two unmanned autonomous lander vehicles were built in Aberdeen capable of diving to maximum ocean depth of over 10,000 m. One was equipped with a video camera and a second with a high resolution digital stills camera. Additionally baited traps were on occasion fitted to the vehicles to capture deep sea animals. The basic concept was that baits (dead mackerel), mimicking natural food falls (dead animals) from the surface were deployed on the sea floor and the cameras recorded images of any deep-sea creatures attracted to the food source. During the first year of the study in 2007 the HADEEP landers undertook eight dives at depths from 5469m to 9729m in the eastern Pacific Ocean. Small crustaceans known as amphipods were the first animals to appear, arriving most rapidly (within 5 minutes) at the deepest location in the Tongan trench indicating the presence of maximum population density at the bottom of the trenches. Population size was estimated as 10 times higher than at the abyssal-trench boundary of 6000m depth. By 4.5h after arrival of the bait on the sea floor 680 amphipods were seen swarming all over the bait at 9729m.

First observations were made of species not previously known to occur at Hadal depths. Decapod crustacea (crabs, lobsters and prawns) had never been recorded deeper than 6000 m but two species of large prawn, Benthesicymus crenatus and Ancanthephyra spp. were seen with as many as 18 individuals of the latter at 6945m in the Japan Trench. Abyssal grenadier fishes Coryphaenoides yaquinae were also spotted at this location.

The first living images of endemic hadal fishes were recorded from 6890 m in the Kermadec trench (SW Pacific Notoliparis kermadecensis) and 6945 m in the Japan trench (NW Pacific Pseudoliparis amblystomopsis). These fish were found to be surprisingly active, swimming with different gaits, hunting down and capturing fast-moving crustacean prey. Analysis of the arrival times of fishes at the baits showed that rate of interception of food falls reaching the hadal sea floor could be predicted from trends observed at depths from 500m - 6000 m in the world's oceans. This fits the concept that fish populations become sparser with greater depth which is contrary to the observation concerning amphipods that populations are greatest at the bottom of the trenches.

In 2008 on board the Japanese vessel Hakuho-Maru two dives were done at 7700 m depth in the Japan trench. Video images were captured of over 20 individuals of the fish Pseudoliparis amblystomopsis attracted to the bait at this depth. This remarkable grouping of individuals of different sizes directly contradicted the view that life in the trenches should become sparser with greater depth and requires further analysis. Traps deployed on the lander also captured 3 juvenile fishes, crustacea, two whelks, a small holothurian and a polychaete. Retrieval of these fresh specimens to the surface in good condition from such great depths will enable further work on hadal animals which have been preserved for biochemical and genetic analysis.

Under the Education and Outreach programme two undergraduate students from Scotland participated in the 2008 Hakuho-Maru expedition producing a blog that appeared on the NERC Planet Earth online. The video of the swarm of hadal fishes reached the top ten in video clips on YouTube and attained world-wide media coverage.
Exploitation Route The involved development of new ultradeep water technology has resulted in new findings about physiology including limits of pressure tolerance by vertebrates
Sectors Aerospace, Defence and Marine,Education,Environment,Pharmaceuticals and Medical Biotechnology

URL https://hadeep.wordpress.com/about/
Description The information from the HADEEP project is being used in development of policy regarding conservation of trench environments, off Japan, New Zealand and US sectors of the Marianas Trench
First Year Of Impact 2010
Sector Aerospace, Defence and Marine,Environment
Impact Types Cultural,Policy & public services