CHAPTER 5. COMMUNITY COMPONENTS 



PLANTS OTHER THAN MANGROVES 



5.1. ROOT AND MUD ALGAE 



The aerial root systems of mangroves 

 provide a convenient substrate for at- 

 tachment of algae. These root algal com- 

 munities are particularly noticeable on 

 red mangrove prop roots but also occur to 

 a lesser extent on black mangrove 

 pneumatophores located in the intertidal 

 zone. Productivity of prop root algal 

 communities can be appreciable if shading 

 by mangroves is not too severe; as dis- 

 cussed in section 3.6, Lugo et al. (1975) 

 found a prop root community net primary 

 production rate of 1.1 gC/m /day, a level 

 comparable to mangrove leaf fall. Biomass 

 of these algae can be as high as 200 to 

 300 g per prop root (Burkholder and 

 Almodovar 1973). Of course, production of 

 this magnitude only occurs on the edge of 

 the forest and is virtually nil in the 

 center of the swamp. Nevertheless, this 

 algal carbon has considerable potential 

 food value either to direct grazers or 

 detriti vores. 



Vertical distribution of prop root 

 algae has been studied by many researchers 

 (Gerlach 1958; Almodovar and Biebl 1962 

 Biebl 1962; Post 1963; Rutzler 1969 

 Burkholder and Almodovar 1973; Rehm 1974, 

 Yoshioka 1975); only one of these studies 

 (Rehm 1974) was conducted in Florida. 

 There is a tendency for certain genera of 

 algae to form a characteristic association 

 on mangrove roots around the world (Post 

 1963). Four phyla tend to dominate: 

 Chlorophyta, Cyanophyta, Phaeophyta, and 

 Rhodophyta; the last is usually the most 

 important in terms of biomass. Of 74 

 species of marine algae recorded as prop 

 root epiphytes between Tampa and Key 

 Largo, 38 were Rhodophyta, 29 Chlorophyta, 

 4 Phaeophyta and 3 Cyanophyta (Rehm 1974). 



Zonation to be expected on Florida 

 mangroves is shown in Figure 9; this se- 

 quence comes largely from Taylor (1960). 

 Near the high water mark, a green band 

 usually exists which is dominated by spe- 

 cies of Rhi zocl oni urn . Below this is a 

 zone dominated by species of Bostrychia , 

 Catenel 1 a , and Cal ogl ossa . It is this 

 association that most people think of when 

 mangrove prop root algae are mentioned. 



Because much mud is often deposited on the 

 Bostrychia-Catenell a - Cal ogl ossa complex, 

 it often has a dingy, gray appearance. 

 There are many other algae found in this 

 zone, but these three genera usually domi- 

 nate. At brackish or nearly freshwater 

 locations, they are replaced by species of 

 Batophora , Chaetomorpha , CI adophora , and 

 P e n i c i 1 1 u s . The pneumatophores of 

 Avicennia , when colonized, are often 

 covered with species of Rhi zocl oni urn , 

 Bostrychia and Monostroma (Taylor 1960). 

 Hoffman and Dawes (1980) found that the 

 Bostrychia binderi -dominated community on 

 the pneumatophores of black mangroyes had 

 -tanding crop of 22 g dry wt/m and a 

 production of 0.14 gC/m z /day. 



a s 



net 



If there is a permanently submerged 

 portion of the prop root, it may be 

 covered with rich growths of Acanthophora , 

 Spyri da , Hypnea , Laurencia , Wrangel i a , 

 Valonia , and Caulerpa (Almodovar and Biebl 

 1962). Additional genera which may be 

 present below mean high water are: 

 Murrayel 1 a , Polysi phoni a , Centroceras , 

 W urde m annia , D i c tyota , Hal i m ed a , 

 Lau renci a , and Da sya [Taylor 1960; 

 Burkholder and Almodovar 1973; Yoshioka 

 1975). In addition, anywhere on the moist 

 sections of the prop roots there are 

 usually epiphytic diatoms and filamentous 

 green and blue-green algae of many genera. 



Rehm (1974) found a significant dif- 

 ference in the prop root algae between 

 south and central Florida. South of Tampa 

 Bay the standard Bostrychia - Catenel 1 a - 

 Caloglossa dominates. In the Tampa Bay 

 area, species of the orders Ulotrichales 

 and Cladophorales are dominant. 



The mud adjacent to the mangrove root 

 community is often richly populated with a 

 variety of algae. These can include 

 species of CI adophoropsi s , Enteromorpha , 

 Vaucheria , and Boodleopsis (Taylor I960) 

 in addition to a whole host of benthic 

 diatoms and dinofl agel 1 ates (Wood 1965) 

 and other filamentous green and blue-green 

 algae (Marathe 1965). 



Adjacent to mangrove areas, on the 

 bottoms of shoals, shallow bays and 

 creeks, there is often a variety of 



41 



