Dissolved Gases in Seawater and Light Energy Wave Lengths

     Gases in the air dissolve easily in seawater at the oceans surface.  Organisms living in the ocean require these dissolved gases to survive.  The major gases in seawater are Nitrogen (N2), Oxygen (O2), and Carbon Dioxide (CO2).  Nitrogen and Oxygen always naturally occur as N2 and O2 because they are 2 out of the 7 DIATOMIC ELEMENTS.  The 7 diatomic elements are Bromine (Br2), Iodine (I2), Nitrogen (N2), Chlorine (Cl2), Hydrogen (H2), Oxygen (O2), and Fluorine (F2). Diatomic elements mean these elements are present in the gaseous state as molecules composed of 2 atoms.  Nitrogen constitutes ~48% of the dissolved gases in seawater.  Nitrogen is essential for organisms and can be a limiting factor for PHYTOPLANKTON.  Phytoplankton are unicellular microscopic plant-like organisms that utilize sunlight to photosynthesize like trees or plants do on land.  Most dissolved Nitrogen is unusable since it exists as N2 gas, a form that cannot be assimilated by most organisms.  Oxygen constitues ~36% of the gases dissolved in seawater.  Oxygen is essential to all AEROBIC life forms.  Life forms that use aerobic respiration (you and i) are generating energy by the full oxidation of nutrients through Krebs cycle where Oxygen is the final electron acceptor.  What this means is English is your body uses nutrients in the air (when you breathe) with Oxygen to react with the nutrients so the electrons get transported to your cells throughout your body for energy to survive.  Dissolved Oxygen comes from photosynthesis and the DIFFUSION from the atmosphere.  Diffusion simply means having a substance naturally move down it's concentration gradient from high to low.  For example, you stand in the front of the line.  You spray perfume on yourself.  You smell it first because it is so highly concentrated.  I'm behind you in line so I smell it second, the person behind me smells it third and so on and so forth until the substance hits it's equilibrium.  Gases such as Oxygen dissolve better in cold water than in warm water, and so concentrats are highest in polar waters and in cold, deep seawater.  Carbon Dioxide (CO2) comprises ~15% of the dissolved gases in seawater and is much more soluble in seawater than Oxygen.  CO2 reacts chemically with water when it dissolves to create Carbonic Acid H2CO3, there fore seawater can hold a tremendous amount of CO2.  (Carbon Dioxide) CO2 + (Water) H2O ---> (Carbonic Acid) H2CO3.  The ocean stores 50 times as much CO2 as the atmosphere. 

CO2 is used near the surface and produced at depths.  O2 is produced near the surface and used at depth.  Notice the difference!

    
     One of the most biologically important properties of seawater is it transparency, allowing sunlight to penetrate into water.  This is vital because all photosynthetic organisms need light to grow and survive.  Sunlight contains all the colors of the rainbow, but not all the colors penetrate seawater equally.  Light waves with shorter wavelengths contain more energy and penetrate deeper than those with longer wavelengths.  However,  by 300 meters, even blue light has been absorbed and darknes prevails.  The thin film of sunlit water at the top of the surface zone is the PHOTIC ZONE and is dependent on the amount of suspended material in the water.
     <100 meters in open ocean
     <40 meters in the coastal
     <600 meters in the clear tropical regions

Aphotice Zone!!!!

Deep sea Shrimp are red.
Blue light reaches the deepest
so Shrimp are red so they
can't be seen!
Their eggs are red too!
(Taken by Professor McNamara
on research trip.)

Ocean below the photic zone lies in blackness.  Except for light generated by living organisms, the region is in pertetual darkness.  This dark water beneath the photic zone is known as the APHOTIC ZONE.  Unlike the photic zone, the aphotic zone is dark, cold, and has high pressure.