GULF OF MEXICO 



187 



and Dujenia, with genera which, like Hypnea and 

 Gracilaria, are suited to and widespread in warm, 

 quiet water. On a nearby roclvy causeway ap- 

 pear Ectocarpus, Caloylossa, and other Rhodo- 

 phj-ceae and marine Myxophyceac, but apparentlj- 

 Dasychidaceae are ah'eady few and do not go 

 much farther. 



From tliis point the red mangrove ceases to 

 play a significant part in the shore vegetation, 

 and the black or Anicennia mangrove which is 

 present but not exclusive to the South takes over 

 and continues, somewhat reduced m stature, 

 around the coast. The pneumatophores of Avi- 

 cennia, like the prop-roots of RMzophora, can 

 support a Bostrychia-Caloglossa-Catenella algal as- 

 sociation but arise from the tidally immersed mud 

 for only a few inches and do not extend out into 

 water of more than a very slight depth. While 

 the flora here mcludes an abundance of Gracilaria 

 and other mud-favoring, widespread types, there 

 are still manj' characteristicall}' tropical species. 



North and west of Cedar Keys the algal flora 

 changes much for the worse owing to the un- 

 favorable factors suggested earlier. Although 

 Batophora has been reported from Adams Beach 

 and Acetabularia from near Panama Cit^^ the 

 family Dasycladaceae is now unimportant. The 

 last records of Caulerpas and Codiaceae are from 

 about Apalachee Bay. Unfortunately, the data 

 for Phaeophyceae and Rhodophyceae are not so 

 sharp, for the more distinctive, less cosmopolitan 

 types disappear early as we go up the coast. The 

 remaining flora of Gracilaria and Hypnea in pro- 

 tected bays, of Bostrychia and its associates on 

 the mangrove roots, with Ulva (fig. 48-f), Entero- 

 morpha (fig. 48-c), and Myxophyceae, dominates 

 the vegetation throughout the northern arc, so 

 far as it is known. As studies progress with the 

 establishment of marine laboratories, doubtless 

 numerous other species will be recorded, and more 

 exact detaOs will become available, but the gen- 

 eral pattern probably will not change, i. e., no- 

 where will a diversified flora of conspicuous species 

 appear. Near Carrabclle there is some Thalassia, 

 and some associated small forms like Fosliella 

 may be expected. Near and a little west of 

 Pensacola considerable growths of attached Sar- 

 gassum are reported. However, this district repre- 

 sents the outpost of numerous things, for on cause- 

 way rocks east of here Bryothamnion, Laurencia, 

 and other tropical Rhodophyceae appear. This is 



our last reported outpost of Cafenella of the man- 

 grove association. Still, the most characteristic 

 red algal flora is that of the bays and swamp man- 

 groves associated with Ulvaceae and blue-green 

 algae. 



Alabama's short coastline is phycologically 

 little known. There seems to be some growth of 

 Polysiphonia where it can become attached. 

 Sargassum, apparently the pelagic gulfweed, is 

 washed ashore in the Mobile area. More con- 

 spicuous on docks, walls, and such constructions 

 are growths of Enter omorpha, Rhizoclonium, and 

 blue-green algae, but there is very little natural 

 opportunity for coarser algae, and these forms 

 adapted to mud are the most widespread. 



Mississippi is in the same unreported condition. 

 There is much shoal water off shore. The coast 

 is guarded hj a line of sandy islands, and itself is 

 of sand and mud with some swamp areas ap- 

 proaching the shoreline to the west. The flora 

 reported is limited to observations about Biloxi, 

 Ocean Springs, and Bay St. Louis. The flora is 

 much the same as in Alabama and restricted by 

 the same factors except that we have no reports 

 of Sargassum, though doubtless gales can throw 

 gulfweed ashore upon the outer islands. 



In fact, the general limitation of the algal vege- 

 tation of the north and northwest sector has now 

 been completed. The prevalence of muddy shores 

 will explain the dominance of a flora composed of 

 Rhizoclonium, Vaucheria, and numerous Myxo- 

 phyceae. For a long distance to the west this is 

 seldom relieved by sandy beaches. Occasional 

 accumulations of shells permit the appearance of 

 Enteromorpha and Ulva which can also grow on 

 exposed roots and tree balks projecting from the 

 mud. The exposed black mangrove roots permit 

 the Bostrychia-Caloglossa vegetation to appear, 

 often with elements from the last-named mud and 

 shell flora. All these also appear on wharves and 

 stone jetties but with almost none of the larger 

 types added that flourish in hke situations to 

 the east. 



Louisiana has a highly dissected coastline with 

 swampy land almost everywhere descending to 

 the sea. Off the coast between the Sabine and 

 Atchafalaya Rivers just inside the 183-meter line, 

 Trask, Phleger, and Stetson (1947) report flat- 

 topped hills which rise to within 18 meters of the 

 surface, and which in 18 to 36 meters of water 

 support a dominating flora of Lithothamnion balls 



