1. Challenges to Life at Sea

2. Light Sunlight: most abundant source of energy
Necessary for photosynthesis
Euphotic Zone: sufficient sunlight for growth and phototsynthetic organisms
Aphotic: no light penetrates
Determined by 1)the angle of the sun, 2)absorption of light by the water, 3)turbidity

5. Photosynthesis 6CO2 + 6 H2O + sunlight  C6H12O6 + 6O2
Phytoplankton are the most abundant photosynthetic organism in the ocean

6. Bioluminescence Light generated by organisms Produced by cells
Used for predator avoidance
Lure food

7. Salinity and Osmosis Different concentrations in the ocean
Organisms must maintain balanced internal salt conditions
Osmosis: type of diffusion in which water moves across a cell membrane from areas of low salinity to areas of high salinity

8. Osmoregulators
Regulate their internal salt concentrations (not the same as the environment)
Saltwater fish: less salt internally than seawater
lose water to their environment
Drink seawater and excrete salt through the gills
Concentrated urine
Freshwater fish: more salt internally than freshwater
Excrete water through urine
Take in salt through gills

9. Osmoregulators
Saltwater Fish
Freshwater Fish

10. Osmoconformers
Internal salt concentration is the same as their environment.
Only marine organisms
Water moves equally in both directions across the cell membrane.
Example: sea cucumbers and sponges

11. Salmon Anadromous Spawn in rivers
At 1 or 2 years the juvenile fish migrate to the ocean
After several years they return to the rivers to spawn

12. Eels Catadromous Spawn in open ocean
Migrate into estuaries and up rivers where they live for up to 10 years before returning to spawn

13. Temperature The average temperature of the ocean is 2°C to 4°C
Hottest is 350°C, Coldest -35°C
Hyperthermophiles: can live at really high temperatures.
Bacteria can survive at 121°C.
Psychrophiles: can live at really low temperature.
Cryoprotectants: lower freezing pts of body fluids

14. Poikilotherms: exotherms
Poikilotherms: exotherms. Possess no means of regulating their body temperature and rely on their surroundings
Ex: Invertebrates and most fish.
Homeotherms: Maintain a constant body temperature well above the temperature of the surrounding environment
Ex: mammals and birds
Endotherms: maintain temperature higher than their surrounding but don’t have as good of control as homeotherms
Ex: great white sharks and tunas

15. Pressure Sea surface = 1 atm (14.7 psi)
Pressure in the ocean increases by one 1 atm every 10 m.
6000 m (3.7 mi)= 600 atm or 4.5 tons per square inch
Most organisms at great depths have no gas-filled cavities

16. Pressure Ways of coping: -mammals (ex:dolphins): flexible ribcage
-fish: swim bladders (air filled sacs) for bouyancy. Deep sea fish will fill bladders with oil.

17. Pressure at the bottom of the mariana trench is 1100 atm
Pressure at the bottom of the mariana trench is atm. (this is like one person trying to support 50 jumbo jets)
Deepest a human can dive is 1089 feet (scuba) at which the pressure is 34 atms

18. Humans and Pressure Barotrauma: any injury associated with pressure
Descent: pressure increases; sinus squeeze and ear squeeze
Ascent: pressure decreases; bends- gases dissolved in body fluids come out of solution and form bubbles in the blood.
Air embolism: gas bubble blocks a blood vessel
Nitrogen narcosis: breath N2 under pressure, cause symptoms like too much alcohol. Replace N with He.