Biological Foundations 112, Lecture 36


Aquatic and Marine Habitats

Chapter 46, pages 1081-1092


I.   Introduction to Aquatic and Marine Habitats

     A.   Significant limiting factors

     B.   Osmoregulation is very difficult in freshwater.  Some animals like echinoderms never live  
            there.

     C.   Primary ecological subdivisions of aquatic/marine organisms:

            1.   Plankton

                  a.   Generally microscopic feeble swimmers

                  b.   Carried by waves and currents

                  c.   Many species migrate vertically on a diurnal basis

                  d.   Two categories:

                        (1)  Phytoplankton - plankton of plant origin

                        (2)  Zooplankton - plankton of animal origin

            2.   Nekton

                  a.   Larger more strongly swimming organisms

                  b.   Examples:  fish and whales, etc.

            3.   Benthos

                  a.   Bottom-dwelling organisms

                  b.   Some sessile - barnacles

                  c.   Some burrowing - worms and echinoderms

                  d.   Some walking about on the bottom - lobsters and crabs

            4.   Abyssal

                  a.   Organisms that live in very deep water

                  b.   Generally has no light

                  c.   Creatures that live in the zone may or may not live on the bottom

II.  Aquatic Habitats

      A.   Freshwater habitats

      B.   Location - streams, lakes, and ponds

      C.   Diversity of species

             1.   Protists and algae

             2.   Mosquito larvae, tadpoles, fairy shrimp, water striders

             3.   Depends upon:

                   a.   Strength of current

                   b.   Water temperature

                   c.   Oxygenation

      D.   Aquatic zones

             1.   Littoral Zone

                   a.   Shallow water area around the margin of a freshwater body

                   b.   Contains algae, diatoms, frogs, turtles, annelid worms, crayfish, insect larvae,    
                         and many nongame fish

                   c.   Neuston - surface-film dwellers like water striders

             2.   Limnetic Zone

                   a.   Open water

                   b.   Sparse life

                   c.   Large fish live here

             3.   Profundal Zone

                   a.   Deep regions of lakes

                   b.   Not enough light for photosynthesis

                   c.   Producers cannot live here because it is beyond their compensation                 
                         point
(point where photosynthesis and metabolism are equal)

                   d.   Much food drifts into this zone

                   e.   Tends to be mineral-rich and anaerobic

                   f.    Few forms inhabit this region

             4.   Thermal stratification

                   a.   Cooler temperature layers as one travels toward the bottom

                   b.   Thermoclines - layers of water at progressively colder temperatures as one      
                                                   progresses toward the bottom

                   c.   Fall turnover - water at the bottom of a lake comes to the top in the fall and    
                                                  the water at the top of the lake goes to the bottom as air          
                                                  temperatures decrease and cool the surface water

                   d.   Blooms occur in the spring because of the spring turnover in a lake

III. Marine Habitats

      A.   Saltwater habitats

      B.   Marine Life Zones

            1.   Estuaries and Salt Marshes

                  a.   Coastal river system that is influenced by the tide

                  b.   Salinity fluctuates with the salt and freshwater that moves in and out of the          
                        marshy area

                  c.   Estuaries and Salt Marshes have marked variations in temperature, salinity, and  
                       other physical properties during the the daily tidal cycle and yearly seasonal          
                       cycle

                  d.   One of the most fertile and productive areas of the earth's ecosystem            
                        because:

                        (1)  Action of the tides promotes circulation of nutrients

                        (2)  Importation of nutrients from adjacent lands and rivers draining into the        
                               estuary

                        (3)  Many kinds of plants present that help to trap nutrients in and around plants  
                               and roots

            2.   Intertidal Zone

                  a.   The area between the high and low tides along the coast line

                  b.   High levels of:

                        1.   Nutrients

                        2.   Light

                        3.   Oxygen

                  c.   Very stressful place

                        a.   Sandy beaches are unstable because of shifting sand

                        b.   Rocky shores are good for anchorage of organisms

                        c.   Organisms get exposed to air

                              (1)  They dry out

                              (2)  They freeze or get too hot because of sun or cold air

                              (3)  Get burned by the sun

                              (4)  They get eaten by predators

                        d.   Get beaten about by the waves as they crash ashore

            3.   Subtidal Zone

                  a.   Below the lowest tidal zone

                  b.   Still shallow enough for photosynthesis

                  c.   Largely protected from wave action

                  d.   Tidal currents do exist in this region

            4.   Neritic Zone

                  a.   The intermediate depth waters out to the continental shelf

                  b.   Generally to 200 feet deep

                  c.   Most of the production of the ocean takes place in this zone (commercial  
                        fishing occurs here)

                  d.   Most of the production occurs here because of its size even thought its                
                        production is not as efficient as the estuary

                  e.   Very important zone for determining a nation's territorial waters

            5.   Deep Waters

                  a.   88% of the ocean is more than 1 mile deep

                  b.   Essentially a marine desert at this depth or deeper

                  c.   Thermal vents that exist along the Mid-Atlantic Ridge is an exception

                  d.   Animals at this depth have strange appearances and luminating organs


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