180 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



dm. of water at low tide, then colonization by 

 marine vascular plants, such as Ruppia maritima 

 L., Halodule wrightii Asch., or perhaps Zanni- 

 cheUia palustris L., may occur, and the flora re- 

 sembles that of the next section. With or without 

 this colonization, the growing conditions are so 

 greatly improved that many larger algae grow in 

 abundance. The Myxophyceae form larger 

 masses of such coarser species as L. majuscula, 

 and on the vascular plants occur epiphytic growths 

 of other species, Myxophycean, diatomaceous, or 

 of larger types, inconspicuous in form and color 

 but very general. 



PROTECTED COVES AND POOLS WITH A 

 MARINE CHANNEL 



The numerous deeper pools near the edges of 

 salt marshes partake of the character of these 

 ponds barricaded from the sea, though they may 

 show a distinctive growth of algae including 

 Bostrychia rivuLaris. Others receive too much 

 fresh water to have a well-developed marine flora, 

 while on the contrary yet others are more like 

 protected coves. 



The floras of these smaller coves vary greatly 

 one from another, but no one in itself shows much 

 range. One will have the bottom studded with 

 Penicillus capitatus (fig. 48-d), another will be 

 dominated by Thalassia festudinum K. & S., or 

 Halodule, bearing epiphytes, another by Amphiroa 

 fragilissima, by Spyridia filamentosa, or by Graci- 

 lariaconfenoides (fig. 50-e) . This last is sometimes 

 exceedingly abundant and is harvested com- 

 mercially for its gel content. It is about the only 

 economically important alga recognized in the 

 area. Others have advantageous features of their 

 own, however, and await the discovery of har- 

 vestable quantities. 



PROTECTED BAYS AND LAGOONS 



The transition from these small coves to large 

 ones, to protected bays and lagoons, is easy and 

 is accompanied by an increase in the variety of 

 the marine flora. In shallow water the same 

 species are found and many others in addition. 

 Characteristic is the excellence of vegetative de- 

 velopment of all the plants whenever there is a 

 good circulation of sea water. On the other hand, 

 even if the lagoon is large, a muddy bottom and 

 a reduced communication with the sea generally 

 will be reflected in a poor flora of Myxophyceae 



and a few Chlorophyceae. Under good condi- 

 tions, Sargassum is tall and freely branched, Ecto- 

 carpus and Padina vickersiae flourish, as do Ace- 

 tahularla crenulata (fig. 48-a), Batophora oerstedi, 

 Cymopolia barbata, Codium decorticatum, Udotea 

 flabellum (fig. 49-e) , and many other Codiaceae and 

 Caulerpas, especially C. racemosa (fig. 49-c) and C. 

 sertularioides, which form magnificent colonies. 

 A great many of the species common on the more 

 open rocky coasts and reefs may appear here, 

 more luxuriant and loosely branched than else- 

 where. The list is too long to give here, but it 

 points sharply to a greater variety in the Florida 

 Keys sector and a poorer one on the northern 

 shores of the Gulf. 



The larger area of these bodies of water in- 

 volves the occurrence of natural or artificial rock 

 or concrete walls, jetties, piers, or other solid 

 structures which afi^ord a new type of habitat, and 

 here an intertidal zoned band will often be recog- 

 nized in which Enter omorpha, Caloglossa, Cate- 

 nella, and especially Bostrychia tenella will gener- 

 ally be conspicuous features. 



MANGROVE THICKETS 



These lagoons, inlets, and coastal islands may, 

 in some localities, especially in southern Florida, 

 be bordered or even nearly filled by mangroves, 

 pi-imarily Rhizophora mangle, with Avicennia 

 nitida higher along the shore. The prop roots of 

 Rhizophora and the pneumatophores of Avicennia 

 offer excellent support for algae, and a strongly 

 developed belt of Bostrychia tenella, or even more 

 conspicuously B. monfagnei (fig. 50-c) may en- 

 circle each root, with Folysiphonia macrocarpa a 

 little lower down, while on emerging ground which 

 receives a little sunlight between the mangroves 

 there may be a green mat of Vaucheria or a mossy 

 growth of brighter Cladophoropsis membranacea. 

 Around the border of such a thicket where light 

 is ample, a few species of other larger algae may 

 grow luxuriantly attached to the submerged parts 

 of the roots, as Padina vickersiae, but the flora of 

 mangi-ove thickets is not marked by great variety. 



TIDAL STREAMS 



Tidal streams commonly discharge through 

 these protected coves and thickets. Their flora 

 is largely determined by the light received and 

 the admixture of fresh water. Near the mouth, 

 marme Myxophyceae, Vaucheria, Enteromorpha, 



