Download Depths divided: Energy: Oxygen: Thermohaline Circulation

Lecture #16 (part 2)
Week #14
Depths divided:
y Mesopelagic: Immediately below epipelagic
y dim light (1%, no photosynthesis)
y ~ 200‐1000m
No light (0% light)
Oxygen:
y Oxygen exchange occurs @ surface
y Respiration & decomposition in deep
y Why not use up?
y How can oxygen‐rich water move deeper?
A.K. Morris, Ph.D.
y Energy in the deep sea:
y No PP
y Rely on carbon from above
o
(Except hydrothermal vents & cold seeps)
y Low abundance
y 5x fewer organisms at 500m
DEEP SEA
y Bathypelagic
y Abyssopelagic
Energy:
y 10x fewer at 4,000m
Thermohaline Circulation
y Ocean circulation driven by differences in H2O density, due to temp & salinity
y Cold, salty water sinks
y Great ocean conveyor: global circulation replenishes O2 to the deep
Lecture #16 (part 2)
Mesopelagic
Week #14
Shrimp and shrimp-like animals a-plenty
y ‘Midwater’ organisms (no structures, just like epipelagic)
y Diverse organisms
y Most w/ photophores (light organs)
y Squid, vampire squid, shrimp, lanternfish & bristlemouth
Oxygen Minimum Zone
y Despite Thermohaline
Circulation
y Just below photic zone, O2
minimum
y Diversity generally low right
here but increases just below
as O2 returns with depth Feeding (getting energy)
y Midwater depends on surface productivity
y 20% of surface PP sinks to mesopelagic
y Different strategies for saving E & getting E
y Mesopelagic fish are small
y Require less E
y Large mouths & extendible jaws
y Hallmark generalists!
A.K. Morris, Ph.D.
Midwater
Anglerfish
Lecture #16 (part 2)
Mesopelagic feeding strategies:
Vertical migrators
1.
y
2.
Zooplankton and fish
Stay in mesopelagic
Week #14
Hide & seek: Body shape & camouflage
Midwater predators:
y Rely on vision
y Weak muscles, poor swimmers, few defense structures (too heavy)
Midwater camouflage:
y Countershade
y Translucent, red or black y Reduction of silhouette
y Lateral compression
y Counterillumination
Eddie Widder
Abralia sp.
Bioluminescence
y Most midwater critters are bioluminescent
y Photophores (light organs)
y Counterillumination: produce
light that breaks up silhouette
and helps animal blend w/
background light
Firefly squid
Video…
Bathypelagic and Abyssopelagic
y < 5% of food produced in photic zone y No vertical migration, why?
y Too far, too much energy
y Fish are larger than mesopelagic fish
y E to growth & reproduce late
Huge mouths & expandable stomachs
Periphylla periphylla video…
A.K. Morris, Ph.D.
Lecture #16 (part 2)
Week #14
© Eddie Widder
Gulper Eel
Deep Sea Anglerfish
Reproduction
in the deep:
Hard to find a mate
Adaptations:
1. Hermaphroditism
2. Communication
y
3.
Light or pheromones
Male parasitism
male “parasitism”
© Bruce Robison
© Eddie Widder
PRESSURE:
y Need specialized enzymes or chemical stabilizers
y Pressure limits depth range
Benthos (sea bottom)
y Advantage: food accumulates
y Lower in nutrients, but more volume
y Deepest fish @ 27,460’
y Almost impossible to bring things to the surface
Diversity:
Gigantism
y Many spp in deep‐sea are much larger than cousins in shallows
Whale falls:
y Dead whales:
important source of E
y Huge input, but temporary
y bottom scavengers:
y Rattails
y cusk eels
y hagfish
A.K. Morris, Ph.D.
Lecture #16 (part 2)
Week #14
Bacteria
y Are they different?
y Alvin’s lunch:
y 1968 multimillion dollar oops.
y 10 mos. Later
y Bacteria different in deep sea
Hydrothermal vents
Bacteria
y Adapted to pressure
y 1977 geologists observe hydrothermal vents
y Slower y 1000X longer to decompose
y Free‐living, symbiotic, etc.
y Chemosynthetic bacteria in large #s in sediment
www.marum.de
Hydrothermal vents
•
•
•
•
Rich biological community
Most spp. new to science
Similar patterns: West Pacific, Mid-Atlantic
Contrary to William Forbes ‘Azoic Theory’
(deeper than 2000 ft, no life)
A.K. Morris, Ph.D.
Environmental Factors
y Hot, mineral‐rich H2O from cracks in sea floor
y Up to 300°C (Surrounding H2O ~ 2°C)
Lecture #16 (part 2)
Week #14
Fig. 16.28
y H2O heated up & rises w/ dissolved minerals
Hydrothermal vent video…
Chemosynthesis
y HIGH primary productivity
y Mineral rich water Æ H2S for chemosynthetic bacteria
y Produce organic matter using chemical Energy
Using bacteria
y Filter out bacteria
y Symbiosis: maintain bacteria in tissues
y Provide w/ H2S & CO2
Archaea & Bacteria
y Riftia (tubeworms)
• Some Archaea live >110C
(230F)
– Highest temp of living org
Cold Seeps
y Communities relying on chemosynthetic bacteria but NOT @ plate edge
y Worms & mussels dominate
y Cold methane seeps from bottom
y Not hot like vents
y 400‐6000m
Cold seeps video…
A.K. Morris, Ph.D.