Transcript Deep Sea, lecture 7

LIFE
IN
THE
DEEP:
THE
OCEAN
DEPTHS
(the mesopelagic, bathypelagic and
abyssopelagic zones)
Alvin
© Rod Catanach/MCT/Landov
Living Conditions
on the Deep-Sea Floor
– Most of the seafloor is covered with thick
accumulations of fine sediment particles:
– mineralized skeletal remains of planktonic organisms,
known as oozes, that sink to the deep sea and
accumulate very slowly (about 1 cm every 1000
years).
Living Conditions on the
Deep-Sea Floor
•
Two types of seafloor samplers: (a) bottom dredge, which skims the surface of the sediment, and (b) grab sampler, which removes
a quantitative “bite” of sediment and its inhabitants.
Living Conditions on the
Deep-Sea Floor
•
Fine-grained bottom sediments off the Oregon coast disturbed by the impact of a current-direction indicator.
Living Conditions on the
Deep-Sea Floor
•
Manganese nodules scattered
on the surface of the seafloor
in the Pacific Ocean.
© Woods Hole Oceanographic Institution
•
Part 1 “reminder:”
WHERE ARE WE?
(1)Mesopelagic
(2)Bathypelagic
(3)Abyssopelagic
Marine zones
MESOPELAGIC:
1. Below the epipelagic zone
2. No primary photosynthesis, but there is still
productivity (i.e. still in the photic zone but it is
disphotic)
3. 200-1000 m depth
BATHYPELAGIC, ABYSSOPELAGIC
1. The “deep sea,” aphotic, twilight zone
2. After 1000 m in depth (to ocean floor)
• Part 2 “reminder:”
WHAT IS THE “WATER
CHEMISTRY” IN THIS LAYER?
Living Conditions on the
Deep-Sea Floor
Deep water
originates near
the surface
Deep water oxygen is circulated and replenished w/
open ocean circulation from the surface
Where
does
the
oxygen
come
from?
Transfer of Oxygen and Energy to the Deep Sea
– The diffusion and sinking of cold, dense water masses
are the chief mechanisms of O2 transport into the deep
sea.
– Dissolved O2 is slowly diminished by animals and
bacteria, leaving an O2 minimum zone at intermediate
depths.
– Below this zone, dissolved O2 gradually increases to
just above the sea bottom.
• Part 3 (new)
(a) WHO LIVES THERE?
(b) WHAT SPECIAL ADAPTATIONS
DO THEY HAVE (and why)?
Living Conditions on the
Deep-Sea Floor
Life on Abyssal Plains
•
Adapted from Sanders, H. L., Am Nat. 102 (1968): 243-282.
Comparison of deep-sea
species diversity (for
polychaete annelids and
bivalve mollusks) with
three other marine
environments.
Living Conditions on the
Deep-Sea Floor
•
© WaterFrame/Alamy Images
Gigantism is
surprisingly common
in the deep sea. The
Greenland shark,
Somniosus, a dogfish
that occurs down to
at least 1200 meters,
can exceed 6 meters
in length unlike its
diminutive relatives.
Mesopelagic (lantern vs. dragonfish)
Mesopelagic fish
• Mesopelagic, Bathypelagic and Abyssopelagic zone
species have many unique characteristics to adapt to
their “extreme environment.”
(1) Fish start to show different characteristics…
(a) Based on light availability:
--higher eyes; 2 fields of vision
--photophores; bioluminescence, countershading
(b) “other” adaptations:
-- musculature changes
-- jaw adaptations
Where are we?
Light????
(mesopelagic) Bristlemouth w/ tubular eyes
w/o photophores
w/o photophores
•
•
•
•
…DEEP SEA FISH…
Everything has a BIG MOUTH
Everything is LONG and “SKINNY”
Everything is BIGGER
viperfish
Rattrap fish
Swallower eel
Credit: © HBOI/Visuals Unlimited
Stomias deep-sea bioluminescent fish.
Credit: © HBOI/Visuals Unlimited
Angler Fish (Melanocetus johnsonii) uses lights to attract prey, an example of
bioluminescence.
Credit: © HBOI/Visuals Unlimited
The Fangtooth (Anoplogaster cornuta) is a bioluminescent fish found in the deep sea.
Some still live on the bottom…
A bait can quickly attracts mobile scavenging fishes
© Scripps Institution of Oceanography Archives, UCSD
• Not everything is a “fish,” but adaptations
are still very similar!
Deep Sea Amphipod (1’!)
Mesopelagic shrimp
Mesopelagic squid
Vampyroteuthis
infernalis
BENTHOS TOO: Fine-grained bottom sediments disturbed by a current
direction indicator
Life on Abyssal Plains
• A shift in dominant taxonomic groups occurs in
deeper water
– echinoderms, polychaete worms, pycnogonids, and
isopod and amphipod crustaceans become abundant
– mollusks and sea stars decline in number
Life on Abyssal Plains
– Most benthic animals in the deep sea are infaunal
deposit feeders, extracting nourishment from the
sediment in much the same manner as earthworms.
– Croppers have merged the roles of predator and deposit
feeder by preying heavily on populations of smaller
deposit feeders and bacteria.
Sea-floor images showing the deposition of phytodetritus (marine snow)
Deep-sea cucumber
© David Wrobel/Visuals Unlimited
Slower invertebrates at the bait can
© Scripps Institution of Oceanography Archives, UCSD
• The “Deep” even contains an entirely new (and very
different) Marine Community –
Hydrothermal vents!
An artist's rendition of the research submersible Alvin exploring the deepsea floor
© Phototake, Inc./Alamy Images
Vent and Seep Communities
–Deep-sea hot springs, recently discovered along the axes
of ridge and rise systems, support unique communities of
deep-sea animals and bacteria.
–Seep communities are more dispersed in areas where
hydrocarbons, particularly methane or other natural gases,
are percolating up through deep-sea sediments.
Vent and Seep
Communities
• Hydrothermal Vent Communities
– Dissolved H2S emerging from seafloor cracks is used
as an energy source by chemosynthetic bacteria
– These bacteria become the source of nutrition for
dense populations of the unique animals clustered
around these springs.
Vent Ecosystem
Discovery
1. Life in extreme
environments
2. Life independent of
sun
type of primary
production
Photosynthesis  uses sunlight + carbon dioxide  coverts to food
Chemosynthesis  uses sulfur + carbon dioxide  converts to food
Photosynthesis reaction:
CO2 + H2O + sunlight  CH2O + O2
Chemosynthesis reaction:
O2 + CO2 + H2O + H2S  CH2O + H2SO4
where H2S is hydrogen sulfide,
H2SO4 is sulfuric acid, and
CH2O is “food” or organic material
+
CO2 + H2O
O2 + [CH2O]
PHOTOSYNTHESIS
CHEMOSYNTHESIS
CO2 + H2O + H2S + O2
[CH2O] + H2SO4
Importance of Vent
Bacteria
• Base of vent ecosystem -- chemosynthesis
• Possible origin of life on Earth
• Illustrate link between biology and habitat
Vent and Seep
Communities
• Diversity of Vent Inhabitants
– Just as the geology of hydrothermal vents is dissimilar
in the eastern Pacific versus the North Atlantic, so too
is the assortment of organisms living around the vents
in each ocean
– To date, six major seafloor provinces have been
defined
Approximate locations of confirmed hydrothermal vents and cold seeps
Cross-section of a ridge axis and the plumbing connected to a vent
chimney
Sidescan sonar image overlaid onto multibeam bathymetry
A black smoker on the Galápagos Rift Zone.
Courtesy of UCSB, University S. Carolina, WHOI/NOAA
“Black
Smoker”
Hydrothermal
Vent
(at a
Mid
Ocean
Ridge)
Red-plumed tube worms
Courtesy of Monika Bright, University of Vienna, hydrothermalvent.com
External appearance of Riftia
© Dr. Ken MacDonlad/SPL/Photo Researchers, Inc.
Internal anatomy of Riftia
Aggregations of large vent crabs
Courtesy of Dr. Ana I. Dittel, University of Delaware
Aggregations of large vent clams
Courtesy of Dr. Ana I. Dittel, University of Delaware
Hydrothermal Vent Crab: Galtheid Crab (“Pinchbug”)
Vent and Seep Communities
• Diversity of
Vent
• Inhabitants
Eyeless vent shrimp, Rimicaris,
dominate deep hydrothermal
vents in the North Atlantic
Ocean.
© Tim Shank, Woods Hole Oceanographic Institution
• Final Thought:
??? Connection to our “earliest life forms?”
Paleodictyon
(500 million yr. old fossil)
Paleodictyon, 1976
• For more information on Paleodictyon, hydrothermal vent
communities and deep sea research try the following web page link:
http://www.naturalhistorymag.com/0904/0904_feature.html
Covering: Dr. Peter Rona (Rutgers) and his Alvin research team
Film: “Volcanoes of the Deep” (IMAX)