The Marine Environment

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Unit 2

• The Marine Environment
• and the chemistry of it all.
• Chapters 6 and 7

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Waters Characteristics

• Polarity and Specific Heat/Heat Capacity make it
  a very stable place.
• Water has its highest density at 40 C, therefore
  ice floats.
• What is the relationship between temperature and
  density of seawater?

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Water molecule
Hydrogen bond
Fig. 6-2, p. 156
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• Note that points C and D both represent 0C
  (32F) but different densities and thus different
  states of water. Ice floats because the density
  of ice is lower than the density of liquid water.

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Ice crystals, fewer H bonds and further apart
Water molecules
Hydrogen bonds
Fig. 6-5, p. 159
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Heat Capacity

• Measured in calories per gram
• Water has among the highest HC of all known
  substances. This means it can absorb large
  amounts of heat and change its temperature very
  little .

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Temperature

• Greatest heat is at the vents _at_ 3500 C/6620 F
• Least is at the poles lt 00 C
• Seawater freezes lower due to salts
• Seawater temperature
• ranges from -20 C 300 C
• 280 F 860 F

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How do organisms cope?

• All life has an ideal/optimal temperature range
• Poikilotherms (Ectotherms) invertebrates, most
  fish
• Sluggish in water colder than optimal
• Need less food/kg of mass
• Homeotherms (Endotherms) cetaceans,
  pinnipeds,polar bear, otter
• Retain muscle/metabolic heat
• Increase/decrease cellular respiration to adjust
• Active regardless of temp (within limits) but use
  energy
• Need more food/kg of mass
• Often insulated (fat and/or hair)
• Warm-bodied (able to be a few degrees warmer than
  environment)
• Loggerhead turtles, tuna and some sharks

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Surface Water Moderates Global Temperature
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Warming Oceans

• Link to MM CD 4

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Ocean-Surface Conditions Depend on Latitude,
Temperature, and Salinity

• Average surface temperature and salinity for the
  world ocean. As you would expect, temperatures
  are lowest in the polar regions and highest near
  the equator. Heavy rainfall in the equatorial
  regions freshens the ocean near the equator,
  whereas hot and dry conditions near the tropic
  lines (Tropic of Capricorn and Tropic of Cancer)
  result in higher surface salinity in those areas.

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• Sea-surface average salinities in parts per
  thousand ().

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Salinity

• A measurement of all the dissolved salts
• Changes with seasons, rainfall and currents
• Based on addition and removal of pure water

• grams of salts
• 1000grams H20
• 35g NaCl
• 1000g H20 35
• Salinity is measured in
• parts per thousand or
• Whats really in seawater?

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Salinity continued

• 99 of salts are Cl, Na, So4, Mg, Ca, K,
• Varies from 32-41
• 41 Red Sea
• 39 Mediterranean
• 35 Equator
• 32 Estuaries

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The Components of Ocean Salinity Came from, and
Have Been Modified by, Earths Crust

• Processes that regulate the major constituents in
  seawater. Ions are added to seawater by rivers
  running off crustal rocks, volcanic activity,
  groundwater, hydrothermal vents and cold springs,
  and the decay of once-living organisms. Ions are
  removed from the ocean by chemical entrapment as
  water percolates through the mid-ocean ridge
  systems and seamounts, sea spray, uptake by
  living organisms, incorporation into sediments,
  and ultimately by subduction.

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Constant Proportions

• The concentration of the salts relative to each
  other remains the same in all samples of water.

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Seawaters Constituents May Be Conservative or
Nonconservative

• Conservative constituents of seawater are those
  constituents that occur in constant proportions.
  Conservative elements have long residence times
  and are the most abundant dissolved material in
  the ocean. Salts.
• Nonconservative constituents have short residence
  times, and are usually associated with seasonal,
  biological or short geological cycles. Gases,
  silica, calcium, nitrates, phosphates.

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Changes in salinity

• Due to addition or removal of fresh water either
  from evaporation or from rain.
• Salts are added from weathering of rocks,
  volcanoes and hydrothermal vents (earths
  interior).
• What is the relationship between salinity and
  density?

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Density

• As salinity increases, density increases.
• Salinity, density and temperature are all
  related.
• Cooler seawater is more dense and sinks.
• Ice floats and insulates the water underneath.

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Note that different samples of water can have the
same density at different combinations of
temperature and salinity.
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Can organisms adapt to changes in
salinity?Osmosis occurs through a selectively
permeable membraneOrganisms must maintain a
water and salt balance

• Euryhaline
• Tolerate a wide range of salinities
• Stenohaline
• Tolerate a narrow range of salinities

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• Osmoconformers dont regulate- stay where
  salinity doesnt change much, let body change
  with salt ex. Seastar
• During heavy local rainfall(el nino) decrease in
  local seastar pop.because of decreased salinity
• Osmoregulators- control internal salt - keep it
  stable.
• ex sharks, salmon

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Example of osmoregulators-cartilagenous fishes
(sharks, skates, rays)

• Still less salty than sea water
• Lose water by osmosis if no regulation
• They retain urea (normally excreted as a waste)
  to increase their solute concentration.
• Urea normally toxic (but they can tolerate)
• Also absorb water through gills excrete salt
  through anal gland.

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Example of osmoregulation- bony fishes

• Bony fish blood is also less salty than sea
  water.
• Lose water through osmosis
• To replace lost water, swallow seawater
• Kidneys capture the extra salt (from drinking)
  and its excreted through chloride cells of the
  gills
• The kidneys also conserve water by producing very
  little but very concentrated urine

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Some Gases are dissolved in seawater as well

• Nitrogen (from atmosphere,bacteria)
• Oxygen (from atmosphere, photosynthesis)
• Carbon Dioxide (from atmosphere, cellular
  respiration)
• Gases dissolve better in colder and less saline
  waters

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Gases continued

• Dissolved Oxygen (DO) increases with turbulance-
  more waves means more O2 from atmosphere
• DO changes with depth
• Oxic and anoxic zones
• 60X more CO2 dissolved in ocean than atmosphere
• 50 of atmospheric oxygen comes from oceanic
  photosynthsis
• Nitrogen (nitrates/nitrites)needed for producers
  proteins

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Gas Concentrations Vary with Depth

• How concentrations of oxygen and carbon dioxide
  vary with depth. Oxygen is abundant near the
  surface because of the photosynthetic activity of
  marine plants.
• Oxygen concentration decreases below the sunlit
  layer because of the respiration of marine
  animals and bacteria, and because of the oxygen
  consumed by the decay (aerobic bacteria) of tiny
  dead organisms slowly sinking through the area.
• In contrast, because plants use carbon dioxide
  during photosynthesis, surface levels of CO2 are
  low.
• Because photosynthesis cannot take place in the
  dark, CO2 given off by animals and bacteria tends
  to build up at depths below the sunlit layer. CO2
  also increases with depth because its solubility
  increases as pressure increases and temperature
  decreases.

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The Oceans Acid-Base Balance Varies with
Dissolved Components and Depth

• What are acids and bases?
• An acid is a substance that releases a hydrogen
  ion H in solution.
• A base is a substance that combines with a
  hydrogen ion or releases a hydroxide OH- in
  solution.
• A solution containing a base is also called an
  alkaline solution.
• Acidity or alkalinity is measured on the pH
  scale.

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The Oceans Acid-Base Balance Varies with
Dissolved Components and Depth

• (right) The pH scale.
• A solution at pH 7 is neutral higher numbers
  represent bases, and lower numbers represent
  acids.

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pH (see pg 196)

• Varies during the day, with CO2 and temperature
• Buffering system
• 1. CO2 H2O H2CO3 carbonic acid,
  weak acid
• 2. H2CO3 HCO3- H bicarbonate, weak
  base
• 3. HCO3- H CO3 2- 2H
  carbonate, stronger base
• When strong acids are added to seawater, reaction
  shifts step 3 towards 1, resulting in an overall
  smaller pH shift .
• When strong bases are added to seawater, reaction
  shifts step 1 towards 3, resulting in a overall
  smaller pH shift. HCO3- is how most of the CO2
  ends up.

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The Oceans Acid-Base Balance Varies with
Dissolved Components and Depth

• Carbon dioxide (CO2) combines readily with
  seawater to form carbonic acid (H2CO3). Carbonic
  acid can then lose a H ion to become a
  bicarbonate ion (HCO3-), or two H ions to become
  a carbonate ion (CO32-). Some bicarbonate ions
  dissociate to form carbonate ions, which combine
  with calcium ions in seawater to form calcium
  carbonate (CaCO3), used by some organisms to form
  hard shells and skeletons. When their builders
  die, these structures may fall to the seabed as
  carbonate sediments, eventually to be
  redissolved. As the double arrows indicate, all
  these reactions may move in either direction.

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Acid Rain

• Sulfur and phosphorus combine with water and form
  sulfuric and phosphoric acids.
• Calcium carbonate sediments and shells dissolve
  in acidic solutions

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Pressure

• Sea Level is 1 atmosphere
• Each 10 meters of water depth (33 ft) adds
  another atm. Gas compresses, water doesnt.
• Gas bladders are absent in deep sea fish
• Deepest fish-8400m (27,000 ft)
• Chambered nautilus- 500 m depth before shell gets
  crushed
• SCUBA (max about 132 m)

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Diving

• Nitrogen gas dissolves better in blood under
  pressure
• Need to decompress on way up- allow nitrogen to
  come out of soltn slowly
• Air embolism- Nitrogen gas bubbles get lodged in
  joints and/or Central Nervous System - Called
  BENDSvery painful can be fatal

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Marine Mammals

• Lungs collapse during dive (pressure) to push air
  to places in trachea that blood doesnt go to
• Some pinnipeds exhale before diving

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Light transmission

• Light gets filtered as depth increases.
• Red light absorbed first, blue goes the deepest.
• When a flash camera is used, the light from the
  flash has all the colors in it and get reflected
  off of fish

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Water Transmits Blue Light More Efficiently Than
Red

• Only a thin film of seawater is illuminated by
  the sun. Except for light generated by living
  organisms, most of the ocean lies in complete
  blackness.
• (a) The table shows the percentage of light
  absorbed in the uppermost meter of the ocean and
  the depths at which only 1 of the light of each
  wavelength remains.
• (b) The bars show the depths of penetration of 1
  of the light of each wavelength (as in the last
  column of the table)

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Under normal oceanic light
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Same fish with light reflection