Download Life in the Deep Sea

Life in the Deep Sea
The Deep Sea Environment
• 200 - 11000 m depth
• Largest environment on earth
• Angler fish photo
• 80% of ocean floor
• =2X total land area above sea
level
• Extremely poorly known even today
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Environmental Zones Of The Deep Sea
• The Bathyal Zone (200-4000m)
• Continental Slope Benthic Environments
• The Abyssal Zone (4000-6000m)
• Continental Rise, Abyssal Plains,
Abyssal Hills and Mid Ocean Ridge
Benthic Environments
• The Hadal Zone (>6000m) Benthic
• Trenches
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• The Deep Sea Pelagic Zone
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Exploration
Early explorers noted less O2 with depth,
therefore thought deep seas likely to be
anoxic/devoid of life. Turned out to be wrongtrend reverses
below ~1000m
and deepest
waters are
generally
oxygenated
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Sampling and observation with ROVs and
manned submersibles
Difficulty of exploration even today
•Remote sampling using grabs, dredges & nets
•Hard to know how representative your samples
are
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Environmental Limitations On Deep Sea Life
•Oxygen? Generally not limiting
•Kept high by combination. of Antarctic bottom
currents and low oxygen consumption
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Light
•No sunlight below ~250m max
•Bioluminescence (minor)
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Temperature/Salinity
Currents & Pressure
•Very uniform
•~-2 near poles to 7-8 C at 1000 m near equator
• Warmer in Mediterranean (12-13 C)
•Salinity also very uniform
•What about seasonal cycles?
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Currents & Pressure
• Rate of bacterial decay is
reduced under high
hydrostatic pressure.
• Organic material that
settles onto the sea floor
remains for a long time
before it decays.
• It is thus more likely to
be consumed by large
scavengers.
•Currents to 1m/sec
•Filter feeders
orient to currents
•Pressure
•1 atm/10m depth
•1000 atm in deep
trenches!
•High hydrostatic pressure
slows metabolic activity.
•Slow growth & long lives!
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Food In The Deep Sea - major challenge!
What are the sources?
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• from surface (photosynthesis based)
• Rains down as particles
• Transported in laterally in turbidity current
• from chemosynthesis
• Hydrothermal vents
• Cold-seep vents
• Predation
• Sediment/deposit feeders
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Food In The Deep Sea - major challenge!
Food In The Deep Sea
•Coastal productivity
•Transported by turbidity currents
•Decreases away from coasts to very low levels
What are optimal strategies?
• Capture particles effectively
• Take advantage of currents
• Sticky nets, feeding structures
• Keep your mouth wide open and pointing upwards
• Vertical diurnal migration
• Specialized organs for detection or capture of prey,
storage of food
• Dig in the sediment
• Be opportunistic (whalefall)
• Lure prey with light
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• Avoid capture with optical, camouflage, other strategies
• Get energy from chemosynthesis (sulfides, methane)
Pelagic Rain
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Pelagic Rain
•Small particles settle 1-3m/day (i.e. takes 5-10 years to
reach abyssal plain)
•Speed up if in aggregates (“
(“marine snow”
snow”) or fecal pellets
•~90% is consumed in photic zone-little reaches bottom
•Food chain over most of ocean floor is based on deposit
feeding
•Windfalls of whales
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Example: Whale-fall communities
-2891 m deep
-Monterey
Canyon
-Worms and
sea cucumbers
• New species of worm that feeds exclusively
on whale carcasses
• How to get food? Roots that extend into bone
• How to find mates? Female incorporates
dozens of males, larval/microscopic but
making gametes
• Broadcast larvae widely, in hope that a few
will find other whales
Deep-sea coral
communities
• Non-photosynthetic corals
• Incredible biodiversity of reefs
• More species of coral than in shallow
water!
• 1100 invertebrates on one reef in N
Atlantic
• Often species are endemic (especially
on seamounts)
• Important role for fisheries
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http://w w w .mbari.org/new s/new s_releases/2004/w halefall.html
Deep-sea coral communities
• Slow growth, reproduction = very
old systems and individuals
• Challenging to study - early days!
Deep-sea trawling
and deep-sea reefs
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before
• Drag net along bottom
• Incredibly destructive
• Nationally restricted;
UN considering ban
after
Cold water, Widely distributed
200-1500m depth (or more?)
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Chemosynthesis on black smokers & other
hydrothermal vents/seeps
•Normal photosynthesis (by photosynthesizing plants and
bacteria) vs. chemosynthesis by sulphur bacteria, archaea
and other microbes using chemical reducing agents for
energy sources
•Leads to locally exceptionally high biomass and
productivity compared to surrounding deep sea
Types Of Organisms Encountered
•Bony & cartilaginous fish, cephalopods
•Benthic invertebrates mostly deposit or filter
feeders, few predators
•Planktonic invertebrates-tendency towards
large body size
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Adaptations
Giant squid
•Body features which maximize chances of finding
a meal or mate
•Enormous mouths/ extrusible jaws
•Very sharp, grasping teeth in fish & body lures
•Expandable stomachs/body cavities
• Up to 60’
60’ (18m) long
• Eaten by sperm
whales
• Can attack humans,
but not common
• Very hard to track
and study
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Fish adaptations
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More Deep Sea Adaptations
•Ability to find food items at great distances for fish
•Parasitism in dwarfed males (angler fish)
•Body photophores for spacing, lures, camouflage
•Bioluminescence is less common than in photic zone
•Most deep sea animals are blind
• Delicate tissues
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Characteristics of deep ocean life
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•
•
Few in number
Year-round reproduction
Small broods, slow growth, long life
• Consistent with very low temperature
• Surprisingly high diversity
• Relate to consistent physical environment
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• Interesting ecosystems where unusual
species cluster: vents, seeps, deep-sea reefs,
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whalefalls
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