The Hadal Zone Deep sea Trenches Hadal Ocean habitats deeper than 6 000m Deep sea trenches comprise the overwhelming majority of these habitats Deepest Mariana Trench 10 998 m The Hadal Zone Map 6000 m Not only trenches World Hadal Trenches Jamieson et al 2009 37 deep sea trenches Most in the Pacific deepest 9 in the Pacific Trench Environment Temperature 1 0 2 5oC Temperature increases below 4000 m due to adiabatic heating South Pacific trench temperatures increase from 1 16 to 1 91oC between 6000 and 10000 m 40 North Pacific trench temperatures rise from 1 67 to 2 40 oC between 6000 and 10000 m 30 Temperatures in trenches are comparable to 3000 m cont margin Tonga Trench Temperature Jamieson et al 2009 TREE Challenger Deep Cross Section CTD Casts Temperature and Salinity Taira et al 2005 J Of Oceanography Flow regime Deep currents ventilate trenches with values up to 8 1 cm sec in the Challenger Deep Up to 32 cm s in other trenches Currents exhibit lunar and semi lunar tidal cycles Mean oxygen in N Pacific trenches 3 43 ml L 1 Why is the Mariana Trench so deep 1 Plate configuration Pacific plate is old and cold and plunging beneath the Philippine plate The Philippine plate is young and soft and is carried downward with the Pacific plate 2 Remoteness from sediment sources it doesn t fill up over time Trench Biology Historical courtesy of L Blankenship Challenger sounding to 8200 m no fauna Incidental collection of arenaceous foraminiferan at 7228 m Japan Trench Brady 1984 14 spp In 1899 the Albatross trawled the Tonga Trench deeper waters for the first time All that was caught was fragments of a siliceous sponge whose origin could not be determined In 1901 Princess Alice successfully trawled a deep sea basin at a depth of 6 035m Generally regarded as first authentic samples from depths greater than 6 000m 1948 Swedish deep sea expedition on the Albatross II landed 2 Polychaetes 1 Isopod and 1 holothurian from 7 7 km Japan Trench 1949 Soviets on the Vityaz obtain rich collection of benthic invertebrates from Kurile Kamchatka Trench 8100m Identified 20 species in 10 classes Jan 23 1960 Trieste bathyscape dive confirms life at 10 9km in the Marianas Trench Jacques Piccard Donald Walsh 4h 48 min descent 20 min on bottom 3 h 17min ascent red shrimp observed No fish Are hadal depths really a separate zone 1953 Initially named super ocean 1954 Ultra abyss proposed by Russians 1955 Hadal used outside USSR Hadal originates from Haides or kingdom of the dead 1967 Trench floor fauna used but quickly squashed by opponents The case for the Hadal zone as distinct from the abyssal zone Physical Properties Hydrostatic pressure Temperature Sediments Animal samples An analysis in 1964 showed that 2 3 of all hadal animals are endemic to the hadal zone Ecological Isolation from abyssal zone Wolff 1964 Early observations about hadal fauna In 1960 Wolff stated that 58 of species endemic to hadal zone using 6km boundary 6 km If boundary extended to 6 8 7km then 74 of species endemic 7 km Species list at 85 from 8 8 km trenches More than expected Benthic species richness and 9 km biomass directly correlates with 10 km overlying water production species found 11 km Actual Expected Wolff 1971 The hadal fauna relative to the abyssal zone a higher percentage of species of amphipods polychaetes bivalves echiurids and holothurians than in abyss b a lower percentage of species of asteroids echinoids sipunculids and ophiuroids than in abyss c the insignificance of several groups including in addition to the four latter groups coelenterates except actinians and scyphozoans bryozoans cumaceans and fishes d the total lack of decapod crustaceans Barophilic bacteria in the Trench MT 41 from amphipod Hirondellea gigas guts Yayanos et al 1981 Optimal growth at pressure less than site of origin Adaptations to high P low T Use of intracellular protein stabilizing osmolytes TMAO Increases cell volume to counteract the effects of pressure Increased use of unsaturated fatty acids in cell membrane phospholipids to maintain fluidity and cell function Reduced metabolic rate Not directly linked to pressure Note an animal going from 6k to 10K m only experiences a doubling in pressure but animals on abyssal plains may be stenobathic Wax esters for storage in animals between bouts of feeding also act to maintain neutral buoyancy Absence of calcareous siliceous structures Calcium compensation depth of 4000 5000 m opal undersaturation leads to Organic walled soft bodies foraminifera Soft bodied holothurians Challenger Deep Foraminifera Conicotheca nigrans Nodellum aculeata Photos by A Gooday Resigella bilocularis Resigella laevis Agglutinated surfaces on at least parts of Nodellum Gooday et al 2008 Metazoan Meiofauna in Trenches Atacama Trench N Chile Danovaro et al 2002 DSR Trench sediments have TOC chloroplastic equivalents to bathyal depths 50 chlor a High OM quality Meiofauna contribution to total biomass microbial metazoan meiofauna 50 at bathyal depths 70 at 7800 m More food channeled to higher trophic levels Composition Nematodes 80 density 50 biomass at 7800 m Also copepods polychaetes kinorhynchs Meiofaunal dwarfism 30 40 body size reduction NOT OLIGOTROPHY Alternatives More juveniles selective predation on lg animals barophily associated with small size Puerto Rico Trench Meiofauna abundant 91 97 nematodes and harpacticoids 17 000 ind m2 at 8560 8580 m in Brownson Deep George and Higgins 1979 Eutrophic setting Lots of plant debris anthozoans pogonophorans gastropods Isopods amphipods cumaceans at 7600 m RICHARDSON et al 1995 DSR Depauperate meio and macrofauna Refractory OM and turbidite flows Macrofauna in Trenches Macrofauna were studied from the Aleutian Trench by Belyaev 1966 2 cores and Jumars and Hessler 1976 1 core between 6460 m and 7298 m Density high 1272 ind m 2 but less than abyssal samples 2000 3800 ind m 2 in Rathburn et al 2009 One box core at 7460 m in Japan Trench 3 000 ind m2 Shin 1984 d 7298 m Hadal Limpets Cocculinidae and Pseudococculinidae in the Cayman and Puerto Rico Trenches 6740 7247 m on wood and turtle grass Jos H Leal and M G Harasewych 1999 Invert Biol Fedikovella caymanensis caymanensis Caymanabyssia spina Lots of Scavenging Amphipods http planetearth nerc ac uk blogs post aspx id Uristes sp 363 pid 143 Photo by L Blankenship 3D model of Tonga Trench Blankenship papers Amphipod structure and diet Zonation below the Abyss Vertical zone partitioning by amphipods in Tonga Kermadec Trenches