78 UNDERWATER GUIDE TO MARINE LIFE 



rectangular, round, ovoid, or oddly club-shaped but are almost always marked 

 by regular lines or pores, which may be, in some instances, so fine and regular 

 that they are used to test the resolving power of the finest microscopes. The 

 accumulated shells are deposited as diatomaceous earth, which has a number 

 of extremely important commercial uses, such as insulating furnaces, preventing 

 afterglow in matches, filtering oil and beer, acting as an abrasive in silver and 

 car polishes, purifying water, and clarifying antibiotics. The accessory pigment 

 fucoxanthin is present as in the brown algae, and its role will be discussed 

 under that group. 



BLUE-GREEN ALGAE: Phylum Cyanophyta 



The dark, blue-green color of most of these most primitive algae is a com- 

 bination of the blue of phycocyanin and the green of chlorophyll. Some of them 

 also have a red pigment. Trichodesniiiini is one of these algae and is sometimes 

 present in such quantities that it gives the sea a reddish color. The Red Sea is 

 said to have been named because of the occasional presence of this alga. Blue- 

 green algae are small, inconspicuous, slimy algae found most typically in 

 fresh-water ponds as scum and in the sea adhering to mud, rocks, or wharves. 

 Their small size frequently requires microscopic examination for identification. 

 Mermaid's hair is found adhering to rocks, mud, and wharves of both coasts. 

 Like other blue-green algae, it forms a dark, fuzzy, somewhat slimy mat on the 

 surface to which it is attached. 



The pigment phycocyanin absorbs orange and red very efficiently and passes 

 on the energy so acquired to chlorophyll, which uses it for photosvnthesis. 

 Almost no blue light is absorbed by these algae so they must live in very shallow 

 water, although Marshall (1954) reports the presence of blue-green algae in the 

 deep sea. They must live on decaying organic matter, somewhat like fungi, 

 there. 



GREEN ALGAE: Phylum Ghlorophyta— F/^wr^ 19 



The vivid green color of these plants is due to chlorophyll, which identifies 

 them. They are very numerous and are the most diversified and complex of 

 algal groups, having 5,700 species the world over. They are especially familiar 

 as pond scum, on rocks in streams, or on the bark of trees CProtococciis^ . In 

 the sea, the green algae are mostly small and of temperate to tropical distribu- 

 tion, being more varied to the south. Thev are not as conspicuous as red and 

 brown algae. The marine green algae varv from flagellated, planktonic, micro- 

 scopic, colonial, or single-celled forms, Dunaliella, to the small, branched, 

 filamentous forms found attached to rocks in the intertidal zone, Clado-phora, 

 and the showy, large sea lettuce, Lllva, which is usuallv found attached to rocks, 

 other algae, or wharves just below the low tide mark. Sea lettuce reaches 3 to 4 

 feet in length and has a very wide distribution from the subarctic to the sub- 

 tropics. It is fragile and is frequently broken by wave action and thrown up on 

 beaches. Enteroiuorpha, sometimes called "grass," is a genus of manv species, 

 most of which are very small. Some, however, reach 2 feet or more in length. 

 The plant is either single or branched, and the blades are usuallv round and 

 tubular and are always hollow. Most of the species are of the temperate zone. 

 Sea moss, Bryopsis, is a lovelv, plumose plant which grows to 8 inches high. 



