Chemical and Physical Features of Seawater and the World Ocean

1. Chemical and Physical Features of Seawater and the World Ocean

2. The Waters of the Ocean • All matter is made of atoms • Elements are made from one kind of atom • A molecule is two or more different atoms combined

4. The Unique Nature of Pure Water

5. Water is a polar molecule • One end is positively charged and the other is negatively charged

6. The attraction between the negative end of a water molecule and the positive end of another water molecule give rise to a “weak” attractive force known as hydrogen bonds.

7. The Three States of Water • Only substance on Earth to naturally exist in three states! • Solid water molecules pack close together & locked in fixed three dimensional pattern • Becomes more dense until about 4°C (get less dense) & expands

9. When water freezes in fresh and marine water the ice forms on top allowing organisms to live underneath the ice • When marine water freezes it acts like an insulator to stop freezing all the water

11. Water as a Solvent • Dissolve more things than any other natural substance(universal solvent) especially salts • In water, strong ion charges attract water molecule, water molecules surround the ions and pull them apart (dissociation)

13. Seawater • Characteristics due to nature of pure water & materials dissolved in it • Dissolved solids due to chemical weathering of rocks on land & hydrothermal vents

14. Wieliczka Salt Mine in southern Poland

16. Salt Composition • Salinity is the total mass, expressed in grams, of all inorganic substances dissolved in one kilogram of sea water (with additional stipulations, we’ll ignore) • Sodium chloride account for 85% of all solids dissolved

17. Salinity Measurement • Often measured in parts per thousand • Abbreviated ppt or o/oo • Average salinity of the ocean is about 35 o/oo.

18. Example: 1000g of sea water is evaporated. 35g of salts remain behind. Salinity of the sample would be said to be 35 parts per thousand Red Sea salinityisabout40 ‰ Baltic Sea salinityisabout6 to 8 ‰

19. Why is Red Sea salinity so high and the Baltic Sea so low?

20. Salinity, Temperature, and Density • Get denser as it gets saltier, colder, or both -2° to 30°C • temps. below zero possible because saltwater freezes a colder temps. • Density controlled more by temperature than salinity • There are exceptions therefore salinity & temp need to be measured to determine density

21. Dissolved Gases • O2, CO2 and N2 in atmosphere & sea surface • 80% of gasses is carbon dioxide • Gas exchange happens between the surface & atmosphere • Dissolved gas concentration higher in cold water, lower in warm water

22. Dissolved Gases • Amount of oxygen in water is affected by photosynthesis & respiration • Most oxygen is released into the atmosphere • More susceptible to oxygen depletion than atmosphere

23. Transparency • Sunlight can penetrate, but it’s affected by the materialsuspended in the water • Important to the photosynthetic organisms • Runoff makes coastal waters less transparent than deep blue waters of open ocean

24. Pressure • On land, organisms are under 1 atm at sea level • Marine organism have the pressure of the atmosphere & water • With every 10m increase depth another atm is added • Submarines & housing must be specially engineered to withstand pressure

26. As atms increase gases are compressed • Organism have air bladders, floats and lungs that shrink and collapse • Limits depth range, some organism are injured when brought to the surface.

27. Barotrauma- physical damage due to significant changes in ambient pressure -Uncontrolled assent from an extended deep dive can cause a condition known as decompression sickness or “the bends”

28. A Yelloweye rockfish having a bad day.

29. PRESSURE DEMO! • What a difference an atmosphere can make!

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