Chapter 11 The Deep-Sea Floor The deep-sea floor descends sharply down continental slopes to the...
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Chapter 11 The Deep-Sea Floor The deep-sea floor descends sharply down continental slopes to the dark, cold, and featureless abyssal plains, punctuated only by a scattering of tectonically active ridges, rises, and trenches. yright © 2004 Jones and Bartlett Publishers
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Transcript of Chapter 11 The Deep-Sea Floor The deep-sea floor descends sharply down continental slopes to the...
Chapter 11
The Deep-Sea FloorThe Deep-Sea Floor
The deep-sea floor descends sharply down continental slopes to the dark, cold, and featureless abyssal plains, punctuated only by a scattering of tectonically active ridges, rises, and trenches.
Copyright © 2004 Jones and Bartlett Publishers
Living Conditions on the Living Conditions on the Deep-Sea FloorDeep-Sea Floor
Most of the seafloor is covered with Most of the seafloor is covered with thick accumulations of fine sediment thick accumulations of fine sediment particles, mineralized skeletal remains particles, mineralized skeletal remains of planktonic organisms, known as of planktonic organisms, known as oozes, that accumulate very slowly oozes, that accumulate very slowly (about 1 cm/1000 yr).(about 1 cm/1000 yr).
Chapter 11
Living Conditions on the Living Conditions on the Deep-Sea FloorDeep-Sea Floor
Chapter 11
Living Conditions on the Living Conditions on the Deep-Sea FloorDeep-Sea Floor
Fig. 11.1 Fine-grained bottom sediments off the Oregon coast disturbed Fig. 11.1 Fine-grained bottom sediments off the Oregon coast disturbed by the impact of a current-direction indicator by the impact of a current-direction indicator (Courtesy of NOAA)(Courtesy of NOAA)..
Chapter 11
Transfer of Oxygen and Transfer of Oxygen and Energy to the Deep SeaEnergy to the Deep Sea
The diffusion and sinking of cold dense water The diffusion and sinking of cold dense water masses are the chief mechanisms of Omasses are the chief mechanisms of O22 transport transport into the deep sea,into the deep sea,Dissolved ODissolved O22 is slowly diminished by animals is slowly diminished by animals and bacteria, leaving an Oand bacteria, leaving an O22 minimum zone at minimum zone at intermediate depths. intermediate depths. Below this zone, dissolved OBelow this zone, dissolved O22 gradually gradually increases to just above the sea bottom.increases to just above the sea bottom.
Chapter 11
Transfer of Oxygen and Transfer of Oxygen and Energy to the Deep SeaEnergy to the Deep Sea
Food for deep-sea benthic communities sinks Food for deep-sea benthic communities sinks from above at rates that are tightly coupled from above at rates that are tightly coupled with primary productivity at the sunlit surface. with primary productivity at the sunlit surface.
Chapter 11
Transfer of Oxygen and Transfer of Oxygen and Energy to the Deep SeaEnergy to the Deep Sea
Fig .11.6 Seafloor images showing the deposition of phytodetritus before Fig .11.6 Seafloor images showing the deposition of phytodetritus before (a) and 2 months after (b) a phytoplankton bloom in the photic zone above (a) and 2 months after (b) a phytoplankton bloom in the photic zone above (Courtesy of R. Lampitt). (Courtesy of R. Lampitt).
Chapter 11
Life on Abyssal PlainsLife on Abyssal Plains
A shift in dominant taxonomic groups occurs A shift in dominant taxonomic groups occurs in deeper waterin deeper water– echinoderms, polychaete worms, pycnogonids, echinoderms, polychaete worms, pycnogonids,
and isopod and amphipod crustaceans become and isopod and amphipod crustaceans become abundantabundant
– mollusks and sea stars decline in number.mollusks and sea stars decline in number.
Chapter 11
Life on Abyssal PlainsLife on Abyssal Plains
Although both density and biomass of Although both density and biomass of organisms decline markedly at greater depths, organisms decline markedly at greater depths, species diversity on abyssal plains is species diversity on abyssal plains is comparable with or even exceeds that of soft-comparable with or even exceeds that of soft-bottom communities in shallow inshore bottom communities in shallow inshore waters.waters.
Chapter 11
Life on Abyssal PlainsLife on Abyssal Plains
Fig. 11.8 Comparison of deep-sea species diversity (for polychaete Fig. 11.8 Comparison of deep-sea species diversity (for polychaete annelids and bivalve mollusks) with three other marine environments. annelids and bivalve mollusks) with three other marine environments. Adapted from Sanders, 1968Adapted from Sanders, 1968
Chapter 11
Life on Abyssal PlainsLife on Abyssal Plains
Most benthic animals in the deep sea are infaunal Most benthic animals in the deep sea are infaunal deposit feeders, extracting nourishment from the deposit feeders, extracting nourishment from the sediment in much the same manner as earthworms.sediment in much the same manner as earthworms.Croppers have merged the roles of predator and Croppers have merged the roles of predator and deposit feeder by preying heavily on populations of deposit feeder by preying heavily on populations of smaller deposit feeders and bacteria.smaller deposit feeders and bacteria.
Chapter 11
Vent and Seep CommunitiesVent and Seep Communities
Deep-sea hot springs, recently discovered along the Deep-sea hot springs, recently discovered along the axes of ridge and rise systems, support unique axes of ridge and rise systems, support unique communities of deep-sea animals and bacteria. communities of deep-sea animals and bacteria.
Chapter 11
Vent and Seep CommunitiesVent and Seep Communities
Fig. 11.11 Approximate locations of confirmed hydrothermal vent Fig. 11.11 Approximate locations of confirmed hydrothermal vent
communities (red dots) and cold seeps (blue dots).communities (red dots) and cold seeps (blue dots).
Chapter 11
Vent and Seep CommunitiesVent and Seep Communities
Hydrothermal Vent CommunitiesHydrothermal Vent Communities– Dissolved HDissolved H22S emerging from seafloor cracks is S emerging from seafloor cracks is
used as an energy source by chemosynthetic used as an energy source by chemosynthetic bacteriabacteria
– These bacteria become the source of nutrition for These bacteria become the source of nutrition for dense populations of the unique animals dense populations of the unique animals clustered around these springs.clustered around these springs.
Chapter 11
Vent and Seep CommunitiesVent and Seep Communities
Hydrothermal Hydrothermal Vent Vent CommunitiesCommunities
Chapter 11
Fig. 11.16 Comparison of primary production in phothsynthetic and chemosynthetic systems.
Vent and Seep CommunitiesVent and Seep CommunitiesHydrothermal Vent CommunitiesHydrothermal Vent Communities
Chapter 11
Fig. 11.18 External appearance (a) and internal anatomy (b) of the tubeworm, Riftia.
(a) (b)
Vent and Seep CommunitiesVent and Seep Communities
Cold-Seep CommunitiesCold-Seep Communities– Densely populated animal communities Densely populated animal communities
dependent on chemosynthetic bacteria, include dependent on chemosynthetic bacteria, include cold-water brine seepscold-water brine seeps methane seepsmethane seeps earthquake-disturbed sediments of deep-sea fansearthquake-disturbed sediments of deep-sea fans
Chapter 11
