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Introduction to the Marine Environment

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. Origin of Water. 4.5 bya during planet formation

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Introduction to the Marine Environment

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  1. 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

  2. Origin of Water • 4.5 bya during planet formation • “dirty snowball” comets http://www.scienceclarified.com/scitech/images/lsca_0001_0001_0_img0017.jpg

  3. Hydrologic cycle • Vapor – short residence (~10 d), rapid travel (>100 km) • Molecule in cycle ~38,000 yrs

  4. 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 (>65%)

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

  6. 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

  7. An on-line Periodic Table is available by clicking here,

  8. 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 (<0.01%) - critical for marine life

  9. 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 > 40 ppt

  10. 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

  11. Density (g/cm3) • Affected by: • Temperature (colder = denser) • Salinity (saltier = denser) • Pressure (higher pressure = denser)

  12. Density –Add salts: • >24 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?

  13. Salinity (cont.) • Dissolved gases – two metabolically important: oxygen, carbon dioxide; also nitrogen • Solubility – function of temp., pressure, salinity • Decrease temp., pressure, incr. solubility

  14. Oxygen and Depth • Not distributed evenly with depth • Oxygen Minimum Zone • Max @10-20m – atmosphere exchange, photosynthesis • Decline with depth: minimum @200-1000 m • Why? • No photosynth. • Decomposition • Deep water influx

  15. Carbon Dioxide and Solubility • Differs from oxygen; reacts with water • Abundant • Capacity to absorb

  16. Carbon Dioxide Chemically reactive in water – tends to equilibrium CO2(diss) + H2OH2CO3 H+ + HCO3- H+ + CO3-2 (carbonic acid) (bicarbonate) (carbonate) Provides buffering capacity for oceans -- keeps seawater at pH ~ 7.8 - 8.4

  17. 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)

  18. 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

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