SECTION TWO 



CHAPTER 



6 



PLANTS OF THE SEA 



With the notable exception of eelgrass, 7:ostera, and turtle grass, Thalassia, 

 flowering plants, most of the marine flora is made up of algae. The word "algae" 

 is a catchall for several very distinct groups. Their variation in size is immense, 

 ranging from microscopic to 200 feet in length. The variation in color is no less 

 striking, ranging from blue-greens and greens to reds, violets, and browns. All 

 of them, however, possess the pigment chlorophyll, which is without doubt 

 the single most important plant compound known. Without it, plants would 

 not be able to utilize the sun's light energy to manufacture carbohydrates (and, 

 by addition of minerals, proteins) from carbon dioxide and water. This process 

 is known as "photosynthesis" and is responsible for all life on earth since it is 

 at the very base of the food chain. Chlorophyll absorbs light at the blue and 

 red ends of the spectrum and reflects green, the color it appears to our eyes. 

 The blue and especially the red light that is absorbed provides the energy used 

 in photosynthesis. Since sea water absorbs light difl^erentially, eliminating the 

 reds and then the yellows until, at over 65 feet, very little but green and blue 

 are left, the quality of light available at various depths influences the distribution 

 of the variously colored algae. This subject will be considered as each group is 

 discussed. 



The smallest algae as well as the most important in the sea's economv are 

 the planktonic ones, which are single-celled, usually enclosed in a skeleton, 

 and which float or swim near the ocean's surface in immense numbers. There 

 they form the grass of the sea, a vast and nourishing pastureland. The larger 

 algae are mostly confined to shore, shoal, rocky, and reef waters, where they are 

 anchored to rocks, shells, wharves, or even other algae (in which case they are 

 said to be "epiphytes"— epi, meaning "on," fhyte, meaning "plant." These tvpes 

 are most dense on shores sheltered from beating surf and, for that reason, Long 

 Island Sound and Monterey Bay have particularly dense and varied floras. The 

 large algae are easily separated from all other plants bv their lack of true roots, 

 stems, or leaves, although thev have basal holdfasts which look superficially 

 like roots and an upright, usually branched structure that looks like a stem and 

 bears flat, leaflike extensions. 



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