CHAPTER 6 

    ALGAE & EUTROPHICATION

       
      • Algae - Phycology (seaweed). -30,000 kinds
       
        a) Attached - Plant body (Thallus) holds fast
          Food for sea urchins and some fish.
       
        b) Unattached - Plankton - microscopic, free floating
          • Form the base of the aquatic food chain
       
          • Eaten by Zooplankton - Daphnia - Copepods
       
          • And are the principal food for clams, mussels, oysters and scallops (Herbivores);
              • and Fish (Omnivores).
       
      • THE ALGAL COMMUNITY
       
          •  Changes throughout the year depending on temperature and light.
          •  Produces its own food (autotrophic) using sunlight and dissolved nutrients 

            • from the surrounding water during photosynthesis.
             
          • Uses different wavelengths of light.

            • Chlorophyll…….. one species of algae )    Zonation
            Phycobilins…….. another species         )     and
            Carotenes………. another           )             Photic Zone

       
              Longer wavelengths of light filtered the deeper you go.
       
      •  All algae contain the pigment chlorophyll A.
       
      • So how do we measure algae?
       
      •  The depth to which sunlight penetrates such that photosynthesis exceeds respiration is called the photic zone.
       
       
       
            Photic Zone or Epilimnion
            Compensation point  
            Aphotic Zone or Hypolimnion
             
      • How do we measure the Compensation Point?
       
      •  Algae is made up of C106  H263  O110  N16  P1

        • The most important aspects are C N & P (sunlight).
        Given the generic chemical composition of algae protoplasm:

         C106  H263  O110  N16  P1

         C:  106 x 12 = 1272 (35.8%)
         H:  263 x 1  =   263 (7.4%)
         O:  110 x 16 = 1760 (49.6%)
         N:   16 x 14  =    224 (6..3%)

                     P:    1   x 31  =      31 (.9%)
       
          3550 grams of algae require 224 grams of N & 31 grams of P to facilitate proper growth.
       
      • Algae blooms are the rapid and unrestricted reproduction of algae to the point where dense mats or profuse growth occurs.
       
        What happens if only 15.5 grams of phosphorus are available?
        How would this relate to an algal bloom?
        The algae production would be theoretically limited to 1775 grams.

      •  The Brown Tide Phenomena - One of the very small types of algae that can dominate the phytoplankton community during the summer.  Under certain conditions, it can undergo explosive population growth resulting in serious ecological damage.

      • The Red Tide - Several species of "flame-brown" algae can cause a red tide.  Some species can undergo tremendous reproduction causing severe pollution problems, and the red tide has been the cause of death of many aquatic vertebrates and invertebrates, even porpoises and turtles.  The water of the red tide can acquire an oily quality, and in 1972 and 1974, red tides caused the closing of 50% of the fishing industry in New England.  

      •  Eutrophication - The addition of nutrients to an ecosystem, such as a lake, is a natural aging of the lake.  The addition of nutrients is good in the right amounts but detrimental when in excess.  Wastewater discharges from sewage treatment, along with a variety of other sources caused by man add surplus nutrients to a lake.  When the pollution is accelerated by man, the appropriate term is then "cultural eutrophication".   The most effective but probably the least desirable from an ecologic standpoint is the use of chemicals.  Chemicals such as the algicide copper sulfate can be used to control algae, but it also kills fish and has undesirable long-term effects.
 
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