Introduction to the Marine Environment

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Introduction to the Marine Environment

• Ocean planet
• 72 of surface is water
• 70 seawater
• 2.0 fresh 1.51 ice, 0.49 liquid, .00007
  vapor
• Life present 10x longer than on land
• 3 D habitat
• 98 of biosphere

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Origin of Water

• 4.5 bya during planet formation
• dirty snowball comets

http//www.scienceclarified.com/scitech/images/lsc
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Hydrologic cycle

• Vapor short residence (10 d), rapid travel
  (gt100 km)
• Molecule in cycle 38,000 yrs

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Physical-Chemical Properties of Water

• Polar molecule binds with other charged ions
• Hydrogen bonds gives water cohesion, surface
  tension
• Universal solvent - dissolves more substances
  than any other liquid (gt65)

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• Hydrogen bondig produces
• Surface tension
• Makes water cohesive (tends to bond to itself)
• Adhesive (bonds with other molecules)

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Heat and Water

• High heat of vaporization
• High boiling point
• High latent heat of fusion
• High specific heat (heat capacity)
• High thermal conductivity
• High freezing and melting points
• Decreases density as it changes to solid

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An on-line Periodic Table is available by
clicking here,
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Salinity ppt or PSU

• Amt of dissolved solid per unit water (gm/Kg)
• Little variation in sfc waters worldwide
• Sfc waters vary little in chemical composition
• Constant for long geol periods - evaporites
• Inorganic salts, organics, gases
• Dissolved solids
• Major (99.28)
• Minor ions (0.71)
• Nutrients and trace elements (lt0.01) - critical
  for marine life

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Dissolved solids

• 1000 g of seawater 965 g water
• 35 g dissolved salts
• Avg. salinity 35 (ppt)
• Cl most abundant, constant prop.
• Salinity 1.80655 Cl
• Variations add or remove water
• coastal zone, poles
• Baltic Sea 7 ppt
• Red Sea gt 40 ppt

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Nutrients and trace elements

• Phosphate, nitrate for photosynthesis
• ions not constant proportions bio active,
  limiting
• Si dioxide, Ca carbonate shells
• Fe, Mn, Co, Cu - bioactive
• essential to marine life, may become limiting in
  sfc waters

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Density (g/cm3)

• Affected by
• Temperature (colder denser)
• Salinity (saltier denser)
• Pressure (higher pressure denser)

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• Density Add salts
• gt24 ppt, density cont. to increase to freezing
• At 35 ppt freezing point reduced to -1.9 C, even
  more dense
• Salts excluded on freezing so what happens???
• What happens to ice?
• What happens to surrounding water?

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Salinity (cont.)

• Dissolved gases two metabolically important
  oxygen, carbon dioxide also nitrogen
• Solubility function of temp., pressure,
  salinity
• Decrease temp., pressure, incr. solubility

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Oxygen and Depth

• Not distributed evenly with depth
• Oxygen Minimum Zone
• Max _at_10-20m atmosphere exchange, photosynthesis
• Decline with depth minimum _at_200-1000 m
• Why?
• No photosynth.
• Decomposition
• Deep water influx

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Carbon Dioxide and Solubility

• Differs from oxygen reacts with water
• Abundant
• Capacity to absorb

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Carbon Dioxide
Chemically reactive in water tends to
equilibrium CO2(diss) H2O H2CO3 H
HCO3- H CO3-2 (carbonic
acid) (bicarbonate) (carbonate) Provide
s buffering capacity for oceans -- keeps seawater
at pH 7.8 - 8.4
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pH of sea water

• Produces H ions extra H acidic
• Pure water pH 7 (equal no. H and OH)
• CO2, alkaline ions inc. pH to 7.5-8.4
• Does SW pH change???

CO2(diss) H2O H2CO3 H HCO3-
H CO3-2 (carbonic acid)
(bicarbonate) (carbonate)
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Chemical cycles

• Major cycles carbon, phosphorous, nitrogen,
  sulpher (sulfate)
• Sources and sinks - box model
• Ocean well mixed, steady state (elements added
  and removed equal rate)
• Residence time how long an element can be
  expected to stay in system
• Reactivity