Unit 10: Marine Life Physical Factors

Physical Factors Affecting Marine Life Most important factors (physical factors): 1. water transparency 2. salinity 3. dissolved nutrients 4. temperature 5. dissolved gases 6. acid-base balance 7. hydrostatic pressure

1. Transparency Sea water is relatively transparent allowing photosynthesis to take place at good distances from the surface. The depth that light can penetrate is limited by the water molecules and particles suspended in the water. These particles absorb and scatter light (particles absorb blues and reflect greens).

Light will penetrate: A. 1,700 feet (measured by photometers) B. 660 feet – human eye (blue light) C. 130 feet – becomes dark to human perception Photic zone – sunlit area at the oceans surface Euphotic zone – upper ½ of the photic zone; area where organisms trap more energy than they use.

The light spectrum is well known. "ROY G The light spectrum is well known. "ROY G. BIV" is an acronym used to remember the colors from one end to the other. From left to right the letters stand for: Red, Orange, Yellow, Green, Blue, Indigo, and Violet.  A mixture of all the colors makes white light.

Water acts as a selective filter. If one were to suspend a white light above the surface of a tank of water that was 1000' deep, the colors from the white light would be GRADUALLY filtered out selectively one-by-one. At 10’ most of the red is gone At 25' most of the orange is gone. At 35' most of the yellow is gone. continues through the spectrum until all that is left is violet light and that fades out after hundreds of feet. So, at the bottom of this 1000' tank of water there would be little or no light!

2. Dissolved Nutrients Nutrients are all needed substances an organism obtains from its environment except: oxygen, carbon dioxide and water Nutrients contain: nitrogen potassium sodium Calcium silicon manganese phosphorus sulfur zinc copper cobalt iodine

Some necessary nutrients are always present in seawater. Most are not. 2 main nutrients needed in primary productivity are: 1. Nitrogen in the form of nitrates (NO3-) 2. Phosphorus in the form of phosphate (PO4-) These are in very short supply and must be recycled within the living system Primary productivity is high when light is available living mass can not increase until inorganic nutrients become available. accomplished by recycling, upwelling and runoff from the land.

3. Temperature Too much heat agitates and distorts large molecules. Too little slows molecular movement so much that molecules no longer react. optimum temperature and very wide range of “operating” temperature for most organisms. Since agitation brings reactants together – warmer temps increase the rate at which chemical reactions occur.

The majority of marine organisms are: metabolic rate - rate at which energy releasing reactions proceed within an organism. The internal temperature of an organism is directly related to the rate at which it generates ATP, moves, thinks and lives. The majority of marine organisms are: Ectotherms – “cold blooded” – have an internal temperature very close to that of their surroundings.

Few marine animals (mammals and birds) are: Endotherms : “warm blooded” – have a stable high internal temperature The higher the temperature of the environment (within the limits of the ectotherms) the faster the metabolism. Tropical fish will eat more, grow faster and to greater size (the upper limits of temp is often not much more than the optimum).

4. Dissolved gases Atmospheric gases can dissolve in water at the surface. The proportions present in water are much different than their proportion in air. There is 100x as much O2 in the air as in ocean water. N2 & O2 do not easily dissolve. CO2 is much more soluble – 1,000x as much CO2 can dissolve as N2 or O2. (CO2 is critical to primary productivity)

CO2 builds up in deep water because: Because of the ease at with it dissolves and its abundance, marine plants never run out of CO2. CO2 builds up in deep water because: colder water contains more gas at saturation polar waters sink (temp. & density) only heterotrophs live and metabolize in deep water ( no primary producers in deep water) The levels of CO2 decrease and the levels of O2 increase at the surface due to rapid photosynthesis.

5. pH The acidity or alkalinity of a solution a logarithmic measurement of the concentration of hydrogen ions The pH scale runs from 0 – 14 The closer to 0 the more acid something is. The closer to 14 the more alkaline something is. 7 is neutral

pH 2 - Lemon juice and gastric juices pH 4 - Tomato juice pH 6.5 - Saliva pH 5-8 - Urine pH 7 - Distilled water pH 7.4 - Human blood pH 8 - Egg white and seawater pH 10 – Milk of magnesia pH 11 – Ammonia

As primary productivity takes place: CO2 is taken out of the water pH rises slightly As CO2 is released it combines with water to form carbonic acid which will lower the pH. Marine organisms cannot stand a wide variation in pH Natural Buffers

6. Hydrostatic pressure The constant pressure of water around a submerged organism Land animals live in air pressurized by the weight of the atmosphere 14.7 lbs/square inch (at sea level) 14.7 lbs/sq. inch = 1 atmosphere In sea water the pressure increases by 1 atm every 30 feet of water

Sea level = 1 atm. = 14.7 lbs/sq. in. 30 feet = 2 atm. = 29.4 60 feet = 3 atm. = 44.1 90 feet = 4 atm. = 58.8 Pressure inside and outside the organism are the same so marine organisms do not need any shells to keep them from being crushed. With an increase in pressure: 1. gases become more soluble 2. some enzymes are inactivated 3. metabolic rates tend to be higher Unless organisms have gas filled spaces in their body, a moderate change in pressure has little effect.

7. Salinity Total amount of salts dissolved in a volume of water average salinity of sea water is 34.7 ppt (3.4%) The proportions of major salts stays nearly constant due to mixing; overall salinity can vary from place to place due to: rainfall evaporation runoff

Salinity also will affect : Fluctuating salinity can damage cell membranes and alter protein structures. Salinity also will affect : specific gravity density buoyancy Salinity also causes water to enter or leave a cell changing the overall water balance of the cell.

Osmosis and Diffusion Diffusion – random movement of molecules from areas of greater concentration to areas of lesser concentration. The energy comes from heat (vibrations of the molecules) The warmer the molecules the faster the diffusion. Selected substances can diffuse (passively) through a cell membrane (from areas of greater conc. to areas of lesser conc.)

Osmosis – diffusion of water Random movement of water molecules from areas of greater conc. to areas of lesser conc. Through a semipermeable membrane In osmosis and diffusion the net movement of molecules is along the concentration gradient. The movement of water across a membrane is due to differences in the conc. of water. The dissolved salts can not pass through due to the nature of the membrane.

Types of Solutions Determined by the [ ] of solute 1. Isotonic: Equal amount of solute on either side of the membrane, water moves but no net movement Most marine organisms have the same conc. of dissolved materials in their body as seawater has.

Types of Solutions 2. Hypotonic solution Less solute outside of the cell than inside In fresh water, marine organisms would be to their environment Water moves in (to even out the high [ ] inside the cell) When water moves in, the cell is “full” and swells up to look like an “O” (hypOtonic)

Types of Solutions 3. Hypertonic solution More solute outside of the cell than inside Water moves out (to even out the high [ ] of solute outside of the cell) Cell appears “shriveled”