Preface Part I. History, Geology and Technology: Introduction 1. The history of hadal science and exploration 2. Geography and geology 3. Full ocean depth technology Part II. Environmental Conditions and Physiological Adaptations: Introduction 4. The hadal environment 5. Hydrostatic pressure 6. Food supply to the trenches Part III. The Hadal Community: Introduction 7. Microbes, protists and worms 8. Porifera, mollusca and echinodermata 9. Crustacea 10. Cnidaria and fish Part IV. Patterns and Current Perspectives: Introduction 11. Ecology and evolution 12. Current perspectives Appendix References Index.

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The Hadal Zone: Life in the Deepest Oceans

The effects of pressure and temperature on an integral membrane protein, Na+/K+-adenosine triphosphatase (Na+/K+-ATPase), were studied in fish gill membrane preparations from shallow- and deep-living marine teleosts. The inhibition by pressure of maximal velocity of the enzyme is nonlinear, increasing at higher pressures. Na+/K+-ATPases from deep-sea fish were less inhibited by pressure than those of shallow-living species. Habitat temperature also affected the pressure response of the enzyme. As a function of physiological pressure and temperature, the order of increasing pressure-sensitivity was cold, deep-sea less than warm, deep-sea (hydrothermal vents) less than polar = shallow and mid-depth, cold less than shallow, warm. Activation volumes in all species were conserved at 30-60 ml mol-1 at physiological pressures, which may reflect a similar membrane physical state at the actual pressure the animal experiences. Arrhenius plots [In(Na+/K+-ATPase activity) vs 1/T] were steeper for warm-water and shallow-living species than for deep-sea species. The depth at which adaptation was first observed was about 2000 m (approximately equal to 200 atm: 1 atm = 101.3 kPa). The data are consistent with a model of increased membrane fluidity resulting in reduced pressure-sensitivity of Na+/K+-ATPase from deep-sea species.

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Pressure adaptation of Na+/K+-ATPase in gills of marine teleosts.

Bathymetric biodiversity patterns of marine benthic invertebrates and demersal fishes have been identified in the extant fauna of the deep continental margins. Depth zonation is widespread and evident through a transition between shelf and slope fauna from the shelf break to 1000 m, and a transition between slope and abyssal fauna from 2000 to 3000 m; these transitions are characterised by high species turnover. A unimodal pattern of diversity with depth peaks between 1000 and 3000 m, despite the relatively low area represented by these depths. Zonation is thought to result from the colonisation of the deep sea by shallow-water organisms following multiple mass extinction events throughout the Phanerozoic. The effects of low temperature and high pressure act across hierarchical levels of biological organisation and appear sufficient to limit the distributions of such shallow-water species. Hydrostatic pressures of bathyal depths have consistently been identified experimentally as the maximum tolerated by shallow-water and upper bathyal benthic invertebrates at in situ temperatures, and adaptation appears required for passage to deeper water in both benthic invertebrates and demersal fishes. Together, this suggests that a hyperbaric and thermal physiological bottleneck at bathyal depths contributes to bathymetric zonation. The peak of the unimodal diversity–depth pattern typically occurs at these depths even though the area represented by these depths is relatively low. Although it is recognised that, over long evolutionary time scales, shallow-water diversity patterns are driven by speciation, little consideration has been given to the potential implications for species distribution patterns with depth. Molecular and morphological evidence indicates that cool bathyal waters are the primary site of adaptive radiation in the deep sea, and we hypothesise that bathymetric variation in speciation rates could drive the unimodal diversity–depth pattern over time. Thermal effects on metabolic-rate-dependent mutation and on generation times have been proposed to drive differences in speciation rates, which result in modern latitudinal biodiversity patterns over time. Clearly, this thermal mechanism alone cannot explain bathymetric patterns since temperature generally decreases with depth. We hypothesise that demonstrated physiological effects of high hydrostatic pressure and low temperature at bathyal depths, acting on shallow-water taxa invading the deep sea, may invoke a stress–evolution mechanism by increasing mutagenic activity in germ cells, by inactivating canalisation during embryonic or larval development, by releasing hidden variation or mutagenic activity, or by activating or releasing transposable elements in larvae or adults. In this scenario, increased variation at a physiological bottleneck at bathyal depths results in elevated speciation rate. Adaptation that increases tolerance to high hydrostatic pressure and low temperature allows colonisation of abyssal depths and reduces the stress–evolution response, consequently returning speciation of deeper taxa to the background rate. Over time this mechanism could contribute to the unimodal diversity–depth pattern.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/brv.12061

Explaining bathymetric diversity patterns in marine benthic invertebrates and demersal fishes: physiological contributions to adaptation of life at depth

Literature on the biology and ecology of bait-attending, deep-sea lysianassoid amphipods was critically reviewed to assess our current understanding of their foraging Olfaction, possibly combined with a rheotactic swimming behavior, is probably the principal means of detection and localization of bait, but alternative or complementary means have been proposed (territorial collapse, mechanoreception of bait impact on bottom or of sounds of aggregated feeders) Deep-sea, bait-attending lysianassoids seemingly divide into two functional groups Individuals of the first group (Eurythenes, possibly Paralicella and others) have mandibles and guts modified for rapid and gluttonous feeding, process food in discrete batches, and may survive long periods without feeding Individuals of the second group (genera of the Orchomene complex) have mandibles which do not appear to be suited for the rapid ingestion of bait, rather small guts, process food in a more or less continuous manner, and may withstand only short periods of starvation Although lysianassoids in the former group appear to be very well adapted for the detection, localization and consumption of carrion, it seems unlikely that any deep-sea species is an obligate necrophage The extensive vertical range of deep-sea lysianassoids above bottom indeed suggests that species compensate for deficient bottom resources by foraging in the water column Deep-sea lysianassoids may be able to sequester carrion from other scavengers The quantity and quality of carrion or of carrion byproducts (scavenger feces, biomass and offspring) which are passed along to the non-scavenging fauna, as well as the time scale for dispersal of these resources, should largely depend on the kinds of scavengers aggregated to consume bait

Foraging of Scavenging Deep-Sea Lysianassoid Amphipods

Effects of pressure and temperature on the electrocardiogram (EKG) and heart rate of crabs from the Galapagos deep-sea (2500 meters) hydrothermal vents were studied. Vent crabs require high hydrostatic pressure for long term survival. During decompression their EKG is disrupted and their heart rate is reduced. Low tem perature reduces these decompression effects. The crabs have a higher temperature tolerance while at their environmental pressure (238 atm) and can withstand short term exposure to temperatures as high as 37Â°C. Possible mechanisms for the action of pressure on neuromuscular systems are discussed. Habits and physiological ca pabilities of the crabs in the unusual vent environment are suggested on the basis of their physiological tolerances. INTRODUCTION More than 89% of the ocean bottom is at depths greater than 1000 meters. Yet, so little research has been done in the deep-sea that hydrothermal vents with their associated biological communities have only recently been discovered (Corliss et a!., 1979). The vent habitat, at a depth of 2500 meters, is characterized by high pressure, high biomass and variable, high temperatures. This contrasts with the bulk of the deep-sea which is also characterized by high pressue but has low biomass and stable low temperatures. By comparing aspects of the physiology of vent species and species adapted to the â€œ?�typicalâ€ deep-sea it is possible to gain insight into the relative importance of certain environmental factors in selecting for physiological characteristics of deep-sea species. In addition, the influence of physiological char acteristics on the distribution of deep-sea species can be studied. This study investigates the adaptations of the hydrothermal vent crab, Bytho graea thermydron, to the high pressure and fluctuating temperatures (Corliss et a!., 1979; Speiss et a!., 1980) of the vent environment to determine how these adaptations might affect the crabs' distribution in the deep-sea. This species is predominantly found in the mussel and pogonophoran beds in the warm vent water (up to 22Â°C, anoxic, up to 300 1iM H2S/l) but, they are found also at the periphery of vent areas where the water temperature is 2Â°C (110 @zM 02/1, no H2S). Although few data are available on the temperature tolerance of other deep-sea species, the general belief is that they tolerate a range of only a few degrees (George, 1979a; Childress et a!., 1978). Many studies have examined high pressure effects on shallow-living species (Rice, 1961; Bayne, 1963; Knight-Jones and Morgan, 1966; Macdonald, 1972;

Effects of pressure and temperature on the ekg and heart rate of the hydrothermal vent crab bythograea thermydron (brachyura)

A deep-sea benthic trap is described with which amphipods (Tmetonyx cicada) were both collected and observed at their ambient pressure of 134 atm. T. cicada collected with decompression from the same depth and locality were more sensitive to subsequent recompression than those amphipods brought to the surface at their ambient pressure. T. cicada from 2700 m experience irreversible injury during decompression to atmospheric pressure. The pressure tolerance of the deep-sea mysid Gnathophausia zoea was measured and compared with the tolerance of mid-water decapods and the shallow-water Crangon crangon. G. zoea became more sensitive to high pressure with prolonged exposure to atmospheric pressure. Deep sea animals exhibit a tolerance to high pressure related to their normal ambient pressure; sensitivity to decompression is also related to normal ambient pressure.

I. Gilchrist

Papers

Further studies on the pressure tolerance of deep-sea crustacea, with observations using a new high-pressure trap