Challenges to Life at Sea

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

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

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

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

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

Osmoregulators Saltwater Fish Freshwater Fish

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

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

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

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

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

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

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.

Pressure at the bottom of the mariana trench is 1100 atm Pressure at the bottom of the mariana trench is 1100 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

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.