224 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



study of the causes of these outbreaks was ham- 

 pered by the lack of previous work in the area. 

 As a consequence, the Marine Laboratory of the 

 University of Miami and the Fish and WikUife 

 Service of the United States Department of the 

 Interior initiated a study of the local plankton in 

 order to gain some information regarding the 

 causes of such plankton blooms. In the course of 

 these studies some insight was gained of the nor- 

 mal dinoflagellate plankton along the west coast 

 of Florida. 



Davis (1950) reported upon a number of plank- 

 ton samples collected there in 1947 and 1948. 

 He listed 15 species of dinoflagellates. 



He stated that the plankton of the west coast 

 of Florida is markedly different from that of the 

 east coast of Florida. Species found only on the 

 west coast included the dinoflagellates, G. hrevis 

 and Noctiluca scintillans Macartney, which were 

 found both inshore and offshore. In addition, 

 a number of plankters were found only in the 

 open waters of the Gulf. These included Cerato- 

 corys horrida Stein. 



Some species were found only in open waters 

 but on both coasts. This group consisted of 

 Ceratium candelabrum (Ehr.) Stein, Pyrocystis fu- 

 sijormis W. Thomson, and P. noctiluca Murray. 

 Occasionally, the open water species were found 

 inshore. Davis interpreted this as indicating an 

 admixture of open water with the inshore water. 

 Davis and Williams (1950) listed seven species 

 from brackish water in mangrove areas of southern 

 Florida. 



King (1950) listed 19 species of dinoflagellates 

 from the west coast of Florida in a series of samples 

 extending from inshore bays to a distance of 120 

 miles offshore and collected over a period of 10 

 months in 1949. About 10 of these species were 

 not listed by Davis or Davis and Williams. 



Additional species have been found by John 

 Howell, biologist. Fish and Wildlife Service (un- 

 published data), along the west coast of Florida. 

 Ceratium pentagonum Gourret occurred only at 

 stations more than 30 miles offshore. A species 

 of Pyrocystis (Gymnodinium) was present only 

 ofl^shore except in one sample. In a study of 

 samples collected throughout the year Howell 

 found the most commonly occurring species of 

 dinoflagellates to be Ceratium furca (Ehr.) Dujar- 

 din and C. tripos (O. F. Muller) Nitzsch. Next in 

 order of occurrence were C. macroceros (Ehr.) 



Vanhoffen, C.Jusus (Ehr.) Dujardin, C. trichoceros 

 (Ehr.) Kofoid, C. massilliense (Gour.) Jorgensen 

 Peridinium depressum Bailey, and Dinophysis 

 caudata Saville-Kent. All of these appear to 

 occur inshore as well as in the offshore waters of 

 the Gulf. However, a more intensive study of 

 the distribution of dinoflagellates along the coast 

 may bring out more zonation than is at present 

 apparent. The situation is complicated by the 

 fact that typical open Gulf water with high salin- 

 ity, low nutrient content, etc., sometimes extends 

 up to the beach and, indeed, is carried into the 

 bays by tidal action. 



Howell found 11 species not reported by Davis 

 or King. In addition to those listed above, 

 there were 4 species of Ceratium: C. carriense 

 Gourret, C. horridum Gran., C. Jalcatum (Kof.) 

 Jorgensen, C. praelongum (Lem.) Kofoid. The 

 last-named was found only once and is typical of 

 a large number of very rare species which may be 

 expected to be found occasionally in the open 

 Gulf waters if any extensive investigation of 

 these waters is made. 



Other rare species found by Howell were Pyro- 

 cystis hamulus Cleve, Pyrophacus horologicum 

 Stein, Amphisolenia sp., Goniodoma sp., and 

 Ornithocercus quadratus Schiitt. In a laboratory 

 culture of Florida west coast water Oxyrrhis 

 marina Dujardin flourished, and a large population 

 developed. 



Despite the richness of the dinoflagellate fauna 

 in the Gulf, the actual concentration in terms 

 of populations is normally very low. The con- 

 centration of dinoflagellates in numbers of cells 

 per liter of sea water is usually less than 50 in 

 the waters along the west coast of Florida. Yet, 

 under unusual conditions which are still not clearly 

 understood, a particular species may increase to 

 enormous concentrations and cause serious dis- 

 ruption of the normal biological balance in the 

 area involved. 



Thus, in the Florida red tide of 1946 and 1947 

 the concentrations of Gymnodinium hrevis Davis 

 reached 60 million cells per liter (Davis 1948). 

 These enormous concentrations cause the water 

 to turn color, usually a brownish red, producing 

 what is commonly called "red water" or "red 

 tide." ' Such concentrations of dinoflaggeUates 

 are frequently accompanied by the death of fish 



' Red tide in the Gulf of Mexico waters is discussed in an article by R. 

 Lasker and F. O. Walton Smith pp. 173-176. 



