1. Chemical and Physical Features of the World Ocean

2. To understand the biology of marine organisms we must know something about the environment in which they live.

3. The Waters of the Ocean The presence of water makes our planet unique. Most other planets have little to no water and the ones that do, have water in the solid (ice) or gas (water vapor) form The presence of water makes our planet unique. Most other planets have little to no water and the ones that do, have water in the solid (ice) or gas (water vapor) form The oceans play a crucial role in regulating our climate and atmosphere The oceans play a crucial role in regulating our climate and atmosphere

4. Without water LIFE would be IMPOSSIBLE!!! Without water LIFE would be IMPOSSIBLE!!! Oceans make up about 75% of the Earth’s surface Oceans make up about 75% of the Earth’s surface Commonly classified into 4 large basins: Pacific, Atlantic, Indian, and Arctic Commonly classified into 4 large basins: Pacific, Atlantic, Indian, and Arctic

5. Water makes up 80% of most marine organisms. Jellyfish are actually made up of over 95% water! Water makes up 80% of most marine organisms. Jellyfish are actually made up of over 95% water!

6. The States of Water Water is the only substance that naturally occurs as a solid, liquid, and gas on earth. Water is the only substance that naturally occurs as a solid, liquid, and gas on earth.

7. Phase Changes 1. Evaporation – liquid to a gas 2. Melting – solid to a liquid 3. Freezing – liquid to a solid 4. Condensation – gas to a liquid

8. As seawater gets colder it gets more dense and therefore tends to sink in the ocean As seawater gets colder it gets more dense and therefore tends to sink in the ocean D = M/V Density = mass / volume

9. Since water expands as it freezes the water molecules become farther apart making the solid state less dense than the liquid state Since water expands as it freezes the water molecules become farther apart making the solid state less dense than the liquid state (ice floats on liquid water)  This is extremely unusual - for a substance’s solid phase to be less dense than its liquid phase  This unique characteristic is extremely important for aquatic organisms (both marine and fresh water)  b/c ice floats it acts as an insulating blanket that helps keep water below from rapidly cooling off in cold weather  This keeps organisms alive beneath the ice

10. Seawater The solids dissolved in seawater come from 2 main sources: The solids dissolved in seawater come from 2 main sources: 1. Chemical weathering of rocks on land 2. Earth’s interior – ex. Hydrothermal vents or volcanoes

11. Salt Composition 6 main solutes of seawater (98% of solids in the ocean): 6 main solutes of seawater (98% of solids in the ocean): 1. Chloride (Cl) 2. Sodium (Na) 3. Sulfate (SO 4 ) 4. Magnesium (Mg) 5. Calcium (Ca) 6. Potassium (K) 85%

12. Salinity Salinity is the total amount of salt dissolved in seawater Salinity is the total amount of salt dissolved in seawater  Salinity of water strongly affects the organisms that live in it.  Even slight changes in salinity will harm some organisms

13. Rule of Constant Proportions States that the relative amounts of various ions in seawater are always the same States that the relative amounts of various ions in seawater are always the same  Chloride always = 55% of the ions no matter how much salt is present  Marine organisms don’t have to worry about ion ratio changes only total salinity levels

14. Salinity, Temperature, and Density Density of seawater depends on both temperature and salinity  seawater gets more dense as it gets colder and saltier Density of seawater depends on both temperature and salinity  seawater gets more dense as it gets colder and saltier +/OR =  Density

15. Transparency One of the most biologically important properties of seawater is that it is relatively transparent One of the most biologically important properties of seawater is that it is relatively transparent  Sunlight can go fairly deep into the ocean  Vital to plants that need light for photosynthesis

16. Pressure Pressure increases as depth increases Pressure increases as depth increases  This limits depth range of marine organisms (gas- filled body structures could shrink or collapse)