Water, water, everywhere

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Water, water, everywhere

• Which organisms occur at a given place in the
  marine environment is determined by the physical
  and chemical properties of the surrounding water
• Marine organisms depend on water for metabolic
  demands, but also as a medium through which they
  must travel, hunt, reproduce, avoid predation,
  find mates, etc.

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The unique properties of water

• Water is the only substance that occurs naturally
  in all 3 phases solid, liquid and gas
• In liquid water, hydrogen bonds hold most of the
  molecules together

Hydrogen bonds
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• Recall that in a water molecule, two hydrogen
  atoms share electrons with an oxygen atom,
  completing the outer shell of all 3 atoms

H
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• But the electrons do not spend an equal amount of
  time with hydrogen as they do oxygen

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• This is because oxygen has 8 protons in its
  nucleus,
  while hydrogen only has 1
• Remember that opposites attract. The difference
  in positive
  charges pulls the
  shared electrons
  toward oxygen, and
  away from
  the two
  hydrogen atoms

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• The abundance of electrons near oxygen makes the
  oxygen atom in a water molecule slightly negative
• Likewise, the 2
  hydrogen atoms
  become slightly
  positive
  since their
  shared electrons
  spend so little
  time
  near them

(-)










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• A water molecule is said to be polar in that it
  has two ends of opposing charges a slightly
  positive charge near the hydrogen atoms, and a
  slightly negative charge near the oxygen atom

(-)
O
H
H
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Water Heat Capacity
HEAT
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Water Heat Capacity
HEAT
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Water Heat Capacity

• We experience the benefits of waters high heat
  capacity every time we sweat.
• Our body provides the heat to evaporate water
  from a liquid to a gas (water vapor), keeping us
  cool
• This is the same reason why
  dogs pant and pigs
  wallow in
  the mud!

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Waters amazing properties

• Water is unique in that it naturally exists in
  all phases (gas, liquid, solid) on Earth
• Water is also unique in that its solid phase
  (ice) is less dense than its liquid phase (water)

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The unique properties of water

• As water cools, the movement of the molecules
  slows and they pack together more tightly
• Colder liquid water is denser than warmer water
• Water freezes when the molecules
  move so slowly that the
  hydrogen bonds take over,
  locking the molecules into
  a 3-dimensional pattern

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• Because the same mass of water now occupies more
  volume as ice than as liquid water, ice is less
  dense than liquid water and floats
• Extremely unusual and very important for aquatic
  (freshwater and marine) organisms living on, in,
  or beneath the ice!

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Got water?

• In ice, the water molecules are held together by
  the hydrogen bonds in the ice crystal
• When ice melts, energy (in the form of heat) is
  required to break the hydrogen bonds and to
  increase the speed of the molecules
• Because of the hydrogen bonds, more heat is
  required to melt ice or to convert liquid water
  into water vapor gives water a high heat
  capacity how much heat is needed to raise a
  substances temperature by 1 degree

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What does this mean for marine life?

• Because of waters high heat capacity, marine
  organisms do not experience sudden swings in
  temperature that may occur on land (although
  shallow water ecosystems are more vulnerable)
• Because of waters hydrogen bonds, water is also
  an excellent solvent water can dissolve more
  things than any other natural substance

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Ion in solution
Salt crystal
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Seawater

• The oceans contain enough salt to cover the
  entire planet with a layer more than 500 feet
  thick!
• The salts in seawater come from the chemical
  weathering of rocks (via river flow) and the
  out-gassing of hydrothermal vents
• The total amount of solid material dissolved in
  water is a measure of its salinity

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Salinity of seawater

• The salinity of seawater is typically 3.5
• A salinity of 3.5 indicates that seawater
  contains 96.5 pure water and 3.5 solutes
• Only 6 ions compose 99 of the solids dissolved
  in seawater, and of these sodium and chloride
  account for 85
• More commonly, salinity is referred to as parts
  per thousand or (3.5 35)

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Could you please pass the salt

• The salinity of water greatly affects the
  organisms that live in it
• Most marine organisms will die in freshwater, and
  vice versa (well come back to this)
• Salinity also influences the density of seawater
  the saltier the water, the denser it is
• The density of seawater therefore depends on its
  salinity and its temperature

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Dissolved gases in seawater

• Gases in the air easily dissolve in seawater at
  the oceans surface
• Organisms living in the ocean require these
  dissolved gases to survive
• The major gases in seawater are
• Nitrogen (N2)
• Oxygen (O2)
• Carbon dioxide (CO2)

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Dissolved gases in seawater Nitrogen

• Nitrogen constitutes 48 of the dissolved gases
  in seawater
• Nitrogen is essential for organisms and can be a
  limiting factor for phytoplankton
• Most dissolved Nitrogen is unusable since it
  exists as N2 gas, a form that cannot be
  assimilated by most organisms
• Nitrogen can be a pollutant when added to
  seawater in large quantities!

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Dissolved gases in seawater Oxygen

• Oxygen constitutes 36 of the gases dissolved in
  seawater
• Oxygen is essential for all aerobic life forms
• Dissolved oxygen comes from photosynthesis and
  diffusion from the atmosphere
• Gases, such as oxygen, dissolve better in colder
  water than in warm water, and so concentrations
  are highest in polar waters and in colder, deeper
  seawater

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Dissolved gases in seawater Carbon Dioxide

• Carbon dioxide comprises 15 of the dissolved
  gases in seawater and is much more soluble in
  seawater than oxygen
• CO2 is low at the surface and increases with
  depth
• O2 is high at the surface and decreases with
  depth
• Why???

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• CO2 is used near the surface and produced at
  depth
• O2 is produced near the surface and used at depth

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Ocean AcidificationThe other CO2 problem

• The ocean stores 50 times as much CO2 as the
  atmosphere!
• CO2 reacts chemically with water when it
  dissolves forming H2CO3 (carbonic acid),
  therefore seawater can hold a tremendous amount
  of CO2
• The acidity of the oceans has increased by 30
  since the Industrial Revolution!

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Normal Ca CO3- ? CaCO3 ?
Acidic H Ca CO3- ? HCO3- Ca2 ?
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http//www.youtube.com/watch?vkxPwbhFeZSw
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Let there be light!

• One of the most biologically important properties
  of seawater is its transparency, allowing
  sunlight to penetrate into the water
• This is vital because all photosynthetic
  organisms need light to grow and survive
• Sunlight contains all the colors of the rainbow,
  but not all the colors penetrate seawater equally

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Increasing energy
105 nm
103 nm
1 nm
103 nm
106 nm
1 m
103 m
Radio waves
Micro- waves
Gamma rays
Infrared
X-rays
UV
Visible light
380
400
750
500
600
700
Wavelength (nm)
650 nm
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Light waves with shorter wavelengths contain more
energy and penetrate deeper than those with
longer wavelengths. However, by 300 meters, even
blue light has been absorbed and darkness prevails
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You light up my life

• Where light penetrates, photosynthesis proceeds
  very important!
• The thin film of sunlit water at the top of the
  surface zone is the photic zone and is dependent
  on the amount of suspended material in the water
• lt100 meters in open ocean
• lt40 meters in coastal regions
• lt600 meters in clear tropical regions

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Hey, who turned off the lights???

• Ocean below the photic zone lies in blackness
• Except for light generated by living organisms,
  the region is in perpetual darkness
• This dark water beneath the photic zone is known
  as the aphotic zone
• Dark
• Cold
• High pressure

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Deep-sea shrimp Survival adaptation
Eggs are red, too!
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Sea no evil, hear no evil

• Sound travels nearly 5 times faster underwater
  than on land (in the air)
• In water, sound is transmitted by water
  molecules since water molecules are densely
  packed (more so than molecules in air), they
  transmit sound more quickly
• Because sound waves travel more efficiently
  underwater than light waves, marine organisms
  frequently rely on sound (hearing), much more so
  than light
  (vision)

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Talk about singin the blues

• Blue whales produce deep rumbling sounds deep,
  low-pitched sounds that are the loudest noise
  produced by any animal
• You will feel a blue whale vocalization before
  you ever hear it
• Whale vocalizations can travel over entire ocean
  basins!!!

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Under Pressure

• Another factor that changes dramatically with
  depth is pressure
• Organisms on land are exposed to 1 atmosphere of
  pressure at sea level
• Marine organisms, on the other hand, are under
  the weight of the water above them and as well as
  the atmosphere
• Pressure increases dramatically with depth for
  every 10 meters of increased depth, another
  atmosphere of pressure is added

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Under Pressure

• As pressure increases, gases are compressed
• Gas-filled structures inside organisms, such as
  air bladders, floats, and lungs shrink or
  collapse under the pressure
• Limits the depth range of many organisms
• Others have evolved
  physiological adaptations
  to survive in the depths
  (well come back to
  this)

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