The Deep Sea

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The Deep Sea

• Marine Biology
• April 2007

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Key Questions of this unit

• How are the different vertical zones of the ocean
  connected and how does this impact deep sea
  organisms?
• What are some of the extreme conditions found in
  the deep sea and what are critters adaptations
  to survive and reproduce here?
• What makes the hydrothermal vent ecosystem unique
  and what can it tell us about the evolution of
  life on the planet?

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Deep Sea Habitats

• Largest habitat for life on earth
• Makes up almost 80 of available volume of planet
  earth (land is only0.5)
• Least studied part of our world
• Environmental conditions are extremely harsh and
  make exploration difficult
• Some of the most unique ecosystems and organisms
• tell us about the evolution of life on early
  earth as well as on other planets

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0-200m
PHOTIC
200-1000m
TWILIGHT
DARK
1000-5000m
Abyssal Plain
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Environmental Conditions in Photic Zone

• Warm
• Sunlit
• Phytoplankton are basis of the food web
• Pressure is not that great
• 1 atm pressure each 33ft (10m) 2lbs/in2

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Environmental Conditions in Twilight Zone

• Colder water temperatures
• Tropical waters drop from 68oF to 41oF in first
  hundred meters
• Below 1000m, temperature ranges from 39oF to 30oF
• Less/very little light
• No photosynthesis below 500ft (150m)
• Deepest minute amounts of light can penetrate is
  1000m
• Much greater pressure than surface
• Lack of food is driving evolutionary factor
• Where does the energy come from?

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Life in Twilight Zone

• Only 10 of the diversity of the photic zone
• See but dont be seen/Hunt but dont become
  hunted
• Arms race between predator and prey (constant
  hide and seek game!)
• Common adaptations of prey
• Transparent life forms/counter-shading
• Flattened bodies/ways to break up silhouette
• Bioluminescence
• Common adaptations of predators
• Various adaptations of the eyes
• Ambush predators (stand still to conserve energy)
• Mouth and teeth adaptations
• Vertical migration each night into photic zone
• Go up at night to photic zone return to depths
  by dawn
• Vital for all life in the ocean
• Massive daily injection of new energy carried
  from surface to deep

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Some Critters of the Twilight Zone

• Sperm whale/Giant Squid
• Amphipod Cystisoma (pg. 316-17)
• Crustacean Phronima (a parasite on salps) p.317
• Transparent squid/octopii p. 320
• Jellies comb, jellyfish, siphonphores p.
  320/321
• Hatchetfish p. 325 only a few inches
• Winteria p. 324
• Lantern fish and bristlemouths p. 328

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Lanternfish
SIDE
BELLY
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Giant Squid attacking Whale
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Giant Squid
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Squid
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Siphonophore
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Zooplankton
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Comb Jelly
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Dark Zone (below 1000m)

• Largest single habitat on earth
• High biodiversity but low abundance
• True monsters!
• Extreme environment
• No light whatsoever
• Temperatures are near freezing
• Extreme pressure
• Difficult to find food and mates

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Environmental Conditions in Dark Zone

• Cold water temperatures
• Temperature ranges from 39oF to 30oF
• No light
• Absolutely no light below 1000m
• Black and red are most common colors- why?
• Tremendous pressures
• 1000m deep pressure is 100x surface
• Lack of food and mates are key obstacles
• Only 5 of the energy of the photic zone reaches
  the twilight zone
• Very low abundances of critters make finding a
  mate a real problem

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Life in Dark Zone

• Find food and a mate but dont become food in the
  process
• Common adaptations
• Critters that are red or black
• Sluggish fish with flabby muscles (nearly all
  fish lack swim bladders)
• Small or no eyes (vision is not very helpful)
• Use as little energy as possible while waiting
  for next meal to come along OR lure prey to you
  in various ways
• Catching a meal in the darkness has resulted in
  many interesting adaptations
• Sense vibrations with lateral line system (or
  with sensitive antennae)
• Sense noise/sounds
• Must capture and kill any meal that comes along
• Crazy big jaws/teeth
• Expandable jaws and stomachs
• Lure prey to you by fishing with bioluminescent
  lure
• Some lures even hang from the roofs of the
  mouth!
• Hermaphrodites
• Bioluminescence
• Used for LOTS of different purposes
• Note on the strange sex life of the anglerfish
  (pg. 342)

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Bioluminescence How does it work?

• Two compounds
• Luciferin (substrate)
• Sometimes produced by symbiotic bacteria in
  anglerfish and other species
• Luciferase (enzyme)
• Two compounds mix in light producing cells called
  photophores
• Most produce blue light though yellow, green, and
  red light is also possible
• Why do it?
• Come up with at least FOUR different reasons

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Bioluminescence
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Some critters of the dark zone

• Angler fish of various kinds p. 331-333
• Hairy/whip nosed/many others
• Gulper eels p. 334-335
• Dragonfish p. 337
• Periphylla and Atolla (deep sea jellyfish)
  p.339
• The squid Heteroteuthis p. 338
• Vampire squid p. 340
• Hagfish and rat-tails (decomposers) p. 349 357
• Tripod fish p. 358

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Hydrothermal Vent Communities

• Discovered in 1977
• Shattered some pre-conceived notions of science
• First ecosystem discovered on planet earth to be
  independent of the energy from the sun
• Tremendous diversity and abundance of life in
  deepest oceans
• Represents an extreme environment quite similar
  to the conditions present on early earth
• Occurs along mid-ocean ridge (where new seafloor
  is formed) in all oceans
• Growth lasts only a few decades (until vent no
  longer active)

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Hydrothermal Vent locations
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Abiotic Conditions Are Among the Most Extreme on
Planet Earth

• No light
• Major temperature extremes within inches
• 400oC scalding hot vent water next to freezing
  cold water
• Pompeii worms can be 140oF hotter at one end than
  another
• Extreme pressures
• 200 atm _at_ 2000-3000m deep
• Large quantities of toxic hydrogen sulfide (H2S)
  and other noxious gasses
• Extremely acidic (avg pH2.8)
• Little food reaches here from photic zone

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Amazing Diversity of Life _at_ Vents

• Over 300 species at some vents
• Most are unique to science
• Community rich in thermophilic bacteria
• Use the energy in the bonds of H2S to make
  organic compounds (these guys are the 1o
  producersvia chemosynthesis)
• Live within various worms, crabs, amphipods,
  giant clams, and mussels (among others!)
• nutrients absorbed into tissues of host
• HOW IS THIS FOOD WEB LIKE A CORAL REEF?
• Pacific Vents are dominated by 2m tubeworms
  (Riftia)
• No mouth, anus, gut packed with bacteria (50 of
  weight)
• Reddish gills have a special type of hemoglobin
  that binds to oxygen and H2S simultaneously

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Hydrothermal Vent Formation

• Seawater percolates through cracks in seafloor
• Water meets hot rocks of ocean crust and is
  superheated
• In the process, the water picks up a variety of
  minerals and rises
• The minerals precipitate out of solution when the
  superheated water touches the cold water
• The minerals are deposited as Chimneys called
  black smokers around the vents

Go here for more info
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Some critters of hydrothermal vents

• Riftia (know all of this guys tricks!)
• Clams, mussels, crabs, amphipods
• Pompeii worms
• Atlantic vents vs. Pacific vents
• 2 in shrimp Rimicaris feed off bacteria (no
  tubeworms)
• These shrimp have rudimentary eyes to possible
  find the glow of new vents
• Be able to also contrast H vents to cold seep
  communities