Phycological Research 2004; 52: 419–428 Free-living dinoflagellates in the southern Gulf of Mexico: Report of data (1979–2002) Sergio Licea,* María Eugenia Zamudio, Ruth Luna and Jesús Soto Instituto de Ciencias del Mary Limnología, Universidad Nacional Autónoma de México Apartado postal 70–305 México 04510 D. F., México SUMMARY The present study is a report of data of planktonic dinoflagellates which includes a list of 252 species, with 10 985 entries in the southern Gulf of Mexico along with information concerning their occurrence. Material for the present study consists of water and net samples obtained during 11 cruises collected at 608 sites between June 1979 and December 2002. Ceratium (47 spp.), Protoperidinium (28 spp.), Dinophysis (26 spp.), Oxytoxum (19 spp.) and Prorocentrum (15 spp.) were the most diverse genera. The most common species found are Ceratium breve, Ceratium contortum, Ceratium furca, Ceratium furca var. eugranum, Ceratium fusus. Ceratium fusus var. seta, Ceratium kofoidii, Ceratium macroceros, Ceratium massiliense, Ceratium pentagonum, Ceratium teres, Ceratium trichoceros, Ceratium tripos, Dinophysis caudata, Ornithocercus magnificus, Podolampas palmipes, Prorocentrum compressum, Prorocentrum gracile, Prorocentrum micans, Protoperidinium divergens and Pyrophacus steinii. Thirteen species are potential toxin producers, among which Karenia brevis was responsible for fish mass mortalities. Other toxic species such as Amphidinium carterae, Dinophysis acuta, Dinophysis caudata, Dinophysis fortii, Dinophysis mitra, Dinophysis rotundata, Dinophysis tripos, Prorocentrum mexicanum, Prorocentrum micans and Prorocentrum minimum were present mostly in net samples. The non-toxic species Ceratium furca, Pyrodinium bahamense var. bahamense, Scrippsiella trochoidea and Gonyaulax polygramma were found in blooms during the summer. Qualitative data show that dinoflagellates occurred mostly during July and August, associated with hydrographic conditions. A checklist of the species and their occurrence are given. Key words: database, check list, dinoflagellates, Gulf of Mexico, toxic species. Balech (1967a,b), Norris and Berner (1970), Steidinger and Williams (1970) and Steidinger (1971). Toxic and harmful species have recently received recognition as a result of the increase of poisoning events in this northern area (Steidinger et al. 1967, 1978; Williams & Ingle 1972; Roberts 1979; Steidinger & Baden 1984; Tester et al. 1991). In the southern region, earlier plankton investigations were carried out during the Soviet and Soviet-Cuban expeditions in the 1960s– 1980s (Khromov 1965; Bogdanov et al. 1968; Roujiyaynen et al. 1968; Zernova 1969, 1970, 1974, 1982; Bessonov et al. 1971; de la Cruz 1971;Krylov 1974; Vinogradova 1976; Zernova & Zhitina 1985). However, in most of these studies, dinoflagellates are only mentioned without details concerning species distribution. Although some investigations on phytoplankton on the shelf of the southern Gulf of Mexico have been conducted at the Institute of Marine Science and Limnology (Santoyo & Signoret 1973, 1975; Licea 1977; Licea & Santoyo 1991), knowledge of dinoflagellates in this region is still scanty. Several harmful species have recently been observed in great numbers by Gómez-Aguirre and Licea (1998) and Licea et al. (2003), but since there has been no consistent assessment and inventory of them, the present paper seeks to investigate the frequency of species and their distribution based on a taxonomic database obtained by the authors. STUDY AREA The study area, located in the southern Gulf of Mexico (Fig. 1), has a predominantly cyclonic circulation, mainly associated with the Yucatan Canal waters (Nowlin 1972; Merrel & Morrison). Monreal-Gómez and Salas de León (1985, 1990) confirmed the presence of cyclonic gyres in a westerly direction that persists in the whole region from February until March and tends to vanish in April. In May the gyre disappears, and the circulation changes from east to west. The cyclonic INTRODUCTION There are few records of dinoflagellate taxonomy and distribution in the southern Gulf of Mexico and contiguous waters. Early investigations were made in the northern gulf, mainly by Graham (1954), Curl (1959), *To whom correspondence should be addressed. Email: licea@mar.icmyl.unam.mx Communicating editor: K. Matsuoka Received 1 January 2004; accepted 13 July 2004. 420 S. Licea et al. Fig. 1. Location of sampling stations in the southern Gulf of Mexico (608 sites). Region-I corresponds to the south-western coast; Region-II belonging to the Bay of Campeche; and Region-III, is situated on the Yucatan shelf. gyre sets in August and September throughout the whole region and lasts until December Hydrographic conditions in the south-west Gulf of Mexico are highly influenced by the Loop Current and the Loop Current rings, as well as by the occurrence of winter storms between October and February (Hulburt & Thompson 1980) whose winds contribute to the cooling and mixing of the surface water column in this region. In addition, the dominant cyclonic circulation and riverfronts create quite a dynamic system, which gives this region unique ecologic conditions. Some particularly important rivers, such as the Coatzacoalcos and the Grijalva-Usumacinta RiverSystem, represent approximately one-third of all fluvial discharges onto the Mexican coast in the southern gulf (Tamayo 1990). There are two coastal lagoons that stand out for their estuarine outwelling to the coast: the Terminos and Tamiahua. The Yucatan Shelf is highly influenced by the upwelling that is north of Cape Catoche (Cochrane 1969; Merino 1997). Another significant feature is the shelf width around the peninsula, which extends seaward for over 260 km: this makes it the widest continental shelf in the Caribbean region. In contrast, in the Caribbean margin, the shelf is very narrow (3 km wide), which means water upwells onto this shelf and remains trapped within its euphotic zone for long periods; this might very well increase the fertilizing potential in this area (Furnas & Smayda 1987). One part of the upwelled waters flows toward the west, leaving the shelf near the Alacranes Reef, while the other part moves toward the coast, forming a cyclonic circulation to the north of Cape Catoche. Another peculiar feature is the absence of rivers along the Yucatan coast (Merino & Otero 1991); however, ground water discharge induces negligible salinity variations (Merino et al. 1990). MATERIALS AND METHODS The phytoplankton community in the Gulf of Mexico has been sampled during long-term oceanographic surveys (projects: PROGMEX, OGMEX and SGM). For the present study, 11 cruises were selected. Surveys were carried out on board the R/V JUSTO SIERRA between July 1979 and December 2002. The stations occupied during these cruises are shown in Figure 1 (608 sites were sampled). For practical purposes the region surveyed was divided into three regions. Water samples were taken in at least one-third of the region by a conductivity, temperature and depth recorder (CTD) Neil Brown with a rosette of Niskin bottles and Dinoflagellates in the Gulf of Mexico Table 1. 421 Common species for each region in the southern Gulf of Mexico Region-I Occurrence Region-II Occurrence Ceratium breve Ceratium macroceros Ceratium tripos Gyrodinium fusiforme Oxytoxum gracile Pyrophacus steinii 196 192 149 126 125 194 Ceratium candelabrum 75 Ceratium carriense 83 Ceratium contortum 134 Ceratium contrarium 103 Ceratium pentagonum var. tenerum 100 Ceratocorys horrida 128 Ornithocercus magnificus 164 Ornithocercus steinii 106 Podolampas bipes 102 Region-III Occurrence Amphidinium acutissimum Ceratium furca Ceratium horridum Dinophysis mitra Lingulodinium polyedrum Oxytoxum parvum Prorocentrum aporum Prorocentrum mexicanum Prorocentrum micans Prorocentrum sigmoides Prorocentrum grande Protoperidinium mediterraneum 32 154 128 30 44 36 23 94 139 32 104 126 Occurrence corresponds to the number of stations where each species was found. were fixed in Lugol’s solution for analysis in an inverted microscope. Cell counts were made following the Utermöhl method (Hasle 1978). Vertical net tows within 10 m beneath the surface were made at each station with a 30 and 45 µm mesh net and were preserved with 2% buffered formalin. Water mounts by using Trypan blue (= diamine blue 3B) were examined to obtain information on plate patterns to aid species identification. Material has been deposited in the collection MEXU-UNAM at the Institute of Marine Science and Limnology (ICMYL). In some cases subsamples rinsed of salt were mounted directly on aluminum stubs for scanning electron microscopy (SEM) for detail identification. Electron microscopy was carried out using a SEM model JSM5410LV. Species frequency was counted using a database on 11 oceanographic cruises between 1979 and 2002. Species with their nomenclatural authorities (Table 2) are arranged alphabetically in each order, according to the classification of Crétinnot-Dinet et al. (1993). The occurrence data have also been deposited in a database designed by the National Commission of Knowledge and Use of Diversity using Biotica version 4.1 (Fideicomiso Fondo para la Biodiversidad, CONABIO 2003), which is in active use for further projects. Although interpretation of the data is based on or derived from the tables, knowledge of hitherto unpublished data has also been applied. RESULTS Table 1 shows that each region in the southern gulf has its typical species. As can be seen, region-III had the highest diversity; in contrast, region-I had fewer characteristic species; although, the composition of these contrasting species could be related to the hydrographical conditions, or influenced by other factors. Figures 2–22 illustrate the most common and potentially toxic species. Table 2 shows a list of 252 free-living dinoflagellates, of which the most common genus was Ceratium with the species Ceratium breve, Ceratium contortum, Ceratium furca var. furca, Ceratium furca var. eugranum, Ceratium fusus var. fusus, Ceratium fusus var. seta, Ceratium kofoidii, Ceratium macroceros, Ceratium massiliense, Ceratium pentagonum, Ceratium teres, Ceratium trichoceros and C. tripos. Of these, C. furca and C. fusus had blooms in summer 1987 and early autumn 2000, respectively, in region-II. Other frequent species were Dinophysis caudata var. caudata, Ornithocercus magnificus, Podolampas palmipes, Protoperidinium divergens, Pyrophacus steinii, Prorocentrum gracile, Prorocentrum micans, and Prorocentrum compressum, all being the most widely distributed species in the area. Because of the use of preserved material, there are few records of unarmoured species; however, the detection of Karenia brevis, Amphidinium carterae, among others, is significant since these species are potentially toxic. The genus Ceratium registered 49 species and 21 infraspecific taxa representing 25.8% of the total species considered in the database. Its ubiquitous presence throughout the year makes this genus important not only for its wide distribution but for its relative abundance. The high frequency of C. furca var. furca, particularly in summer, is an interesting feature, since this species was found to be the most common in the southern gulf. The presence of K. brevis is particularly significant since this species is a neurotoxic shellfish poisoning producer. It was found in 35 localities in late summer and autumn in regions I and II. Quantitative data show that the maximum cell concentration of K. brevis occurred during October 1998 along the shelf of region-II, which coincided with red tide events, with fish mass mortalities having densities up to 13.9 × 106 cells/L. The first bloom was observed along the southwestern shelf during the summer of 1979, and was also associated with fish mortality, according to local coast guard reports. Other toxic species observed were Dinophysis acuta var. acuta, Dinophysis caudata, Dinophysis fortii, Dinophysis mitra, Dinophysis rapa, Dinophysis rotundata 422 S. Licea et al. Figs 2–22. 2. Ceratium furca var. eugrammun, dorsal view. 3. Ceratium fusus var. fusus, dorsal view. 4. Ceratium trichoceros, ventral view. 5. Ceratium teres, dorsal view. 6. Ceratium pentagonum, ventral view. 7. Ceratium kofoidii, dorsal view. 8. Ceratium furca var. furca, ventral view. 9. Ceratium breve var. breve, ventral view. 10. Ceratium massiliense, dorsal view. 11. Ornithocercus magnificus, right lateral view. 12. Ceratium fusus var. seta, ventral view. 13. Dinophysis caudata var. caudata, right lateral view. 14. Ceratium macroceros, ventral view. 15. Protoperidinium divergens, ventral view. 16. Podolampas palmipes, ventral view. 17. Pyrophacus steinii, antapical view. 18. Prorocentrum gracile. 19. Ceratium contortum var. contortum, vental view. 20. Prorocentrum micans. 21. Prorocentrum compressum. 22. Ceratium tripos var. tripos, ventral view. Scales: Figs 13,15,22,23 = 5 µm; Figs 4,8,7,17,18,20 = 10 µm; Figs 5,6–10,11,14,19 = 20 µm; Fig. 21 = 40 µm; Figs 16,24 = 50 µm; Fig. 12 = 100 µm. Dinoflagellates in the Gulf of Mexico Table 2. Taxa 423 Table 2. List of taxa and their occurrence† Occurrence† Actiniscales Sournia, 1984 Actiniscaceae Kützing, 1844 Actiniscus pentasterias Ehrenberg, 1854 Dinophysiales Lindemann, 1928 Citharistaceae Kofoid et Skogsberg, 1928 Citharistes apsteinii Schütt, 1895 Citharistes regius Stein, 1883 Dinophysiaceae Stein, 1883 Amphisolenia asymmetrica Kofoid, 1907 Amphisolenia bidentata Schröder, 1900 Amphisolenia bifurcata Murray et Whitting, 1899 Amphisolenia cf. elongata Kofoid et Skogsberg, 1928 Amphisolenia globifera Stein, 1883 Amphisolenia schroederi Kofoid, 1907 Dinophysis acuta Ehrenberg, 1839 Dinophysis argus (Stein) Abé, 1967 Dinophysis caudata var. caudata Saville Kent, 1881 Dinophysis caudata var. abbreviata Jörgensen, 1923 Dinophysis caudata var. pedunculata (Schmidt) Schröder, 1906 Dinophysis circumsutum (Karsten) Balech, l967 Dinophysis cuneus (Schütt) Abé, 1967 Dinophysis diegensis Kofoid, 1907 Dinophysis doryphora (Stein) Abé, 1967 Dinophysis exigua Kofoid et Skogsberg, 1928 Dinohysis fortii Pavillard, 1923 Dinophysis hastata Stein, 1883 Dinophysis hindmarchii (Murray et Whitting) Balech, 1967 Dinophysis laevis Cleparède et Lachmann, 1859 Dinophysis mitra (Schütt) Abé, 1967 Dinophysis operculoides (Schütt) Balech, 1967 Dinophysis ovata Cleparède et Lachmann, 1859 Dinophysis parvula (Schütt) Balech, 1967 Dinophysis pusilla Jörgensen, 1923 Dinophysis rapa (Stein) Abé, 1967 Dinophysis rotundata Cleparède et Lachmann, 1859 Dinophysis schroederi Pavillard, 1909 Dinophysis schuettii Murray et Whitting, 1899 Dinophysis sphaerica Stein Dinophysis tripos Gourret, 1883 Dinophysis whittingae Balech, 1967 Heteroschisma inaequale Kofoid et Skogsberg, 1928 Heteroschisma cf. subantartica Balech, 1971 Histioneis crateriformis Stein, 1883 Histioneis hippoperoides Kofoid et Michener, 1911 Histioneis inclinata Kofoid et Michener, 1911 Histioneis jorgensenii Schiller, 1928 Histioneis pulchra Kofoid, 1907 Histioneis rotundata Kofoid et Michener, 1911 Histioneis striata Kofoid et Michener, 1911 Metaphalacroma skogsbergi Tai, 1934 Ornithocercus heteroporus Kofoid, 1907 Ornithocercus magnificus Stein, 1883 Ornithocercus quadratus Schütt, 1900 Ornithocercus splendidus Schütt, 1893 Ornithocercus steinii Schütt, 1900 Ornithocercus thumii (Schmidt) Kofoid et Skogsberg, 1928 Triposolenia depressa Kofoid, 1906 Triposolenia intermedia Kofoid et Skogsberg, 1928 Oxyphysaceae Sournia, 1984 Oxyphysis oxytoxoides Kofoid, 1926 Gymnodiniales Lemmermann, 1910 Akashiwo sanguinea (Hirasaka) G. Hansen et Moestrup, 2000 18 1 3 2 124 38 4 18 1 11 2 185 27 99 2 22 7 8 2 2 76 6 4 33 2 2 6 7 44 11 5 60 2 3 1 1 1 2 18 3 6 1 3 28 11 18 184 86 30 107 96 1 3 4 5 Taxa List of taxa and their occurrence† (continued ) Occurrence† Gymnodiniaceae Lankester, 1885 Amphidinium acutissimum Schiller, 1937 Amphidinium acutum Lohmann, 1920 Amphidinium carterae Hulburt, 1957 Amphidinium extensum Wulff, 1916 Amphidinium globosum Schröder, 1911 Amphidinium operculatum Cleparède et Lechmann, 1858–1859 Amphidinium schroderi Schiller, 1928 Amphidinium sphenoides Wulff, 1916 Balechina coerulea (Dogiel) Taylor, 1976 Gymnodinium grammaticum (Pouchet) Kofoid et Swezy, 1921 Gymnodinium marinum Seville-Kent, 1880–1882 Gyrodinium falcatum sensu Kofoid et Swezy, 1921 Gyrodinium fusiforme Kofoid et Swezy, 1921 Karenia brevis (Davis) G. Hansen et Moestrup, 2000 Noctilucales Haeckel, 1894 Kofoidiniaceae Taylor 1976 Kofoidinium pavillardii J. Cachon et M. Cachon, 1967 Kofoidinium velleloides Pavillard, 1928 Noctilucaceae Kent, 1881 Pronoctiluca pelagica Fabre-Domergue, 1889 Oxyrrhinales Sournia, 1984 Oxyrrhinaceae Sournia, 1984 Oxyrrhis marina Dujardin, 1841 Peridiniales Haeckel, 1894 Ceratiaceae Kofoid, 1907 Ceratium arietinum var. arietinum Cleve, 1900 Ceratium arietinum var. gracilentum (Jörgensen) Sournia, 1966 Ceratium azoricum Cleve, 1900 Ceratium belone Cleve, 1900 Ceratium bigelowi Kofoid, 1907 Ceratium breve var. breve (Ostenfeld et Schmidt) Schröder, 1906 Ceratium breve var. parallelum (Schmidt) Jörgensen, 1911 Ceratium candelabrum var. candelabrum (Ehrenberg) Stein, 1883 Ceratium candelabrum var. depressum (Pouchet) Jörgensen, 1920 Ceratium carriense var. carriense Gourret, 1883 Ceratium carriense var. volans (Cleve) Jörgensen, 1911 Ceratium cephalotum (Lemmermann) Jörgensen, 1911 Ceratium concilians Jörgensen, 1920 Ceratium contortum var. contortum (Gourret) Cleve, 1900 Ceratium contortum var. karsteinii (Pavillard) Sournia, 1966 Ceratium contortum var. robustum (Karsten) Sournia, 1966 Ceratium contrarium (Gourret) Pavillard, 1905 Ceratium declinatum (Karsten) Jörgensen, 1911 Ceratium deflexum (Kofoid) Jörgensen, 1911 Ceratium digitatum Schütt, 1895 Ceratium euarcuatum Jörgensen, 1920 Ceratium extensum (Gourret) Cleve, 1900 Ceratium falcatiforme Jörgensen, 1920 Ceratium falcatum (Kofoid) Jörgensen, 1920 Ceratium furca var. furca (Ehrenberg) Cleparède et Lechmann 1859 Ceratium furca var. eugrammum (Ehrenberg) Schiller, 1937 32 33 17 7 11 9 7 19 38 1 1 36 126 35 13 9 37 22 75 28 20 27 7 231 80 77 31 89 29 9 8 149 122 47 122 26 44 13 34 129 38 49 160 326 424 Table 2. Taxa S. Licea et al. List of taxa and their occurrence† (continued) Table 2. Occurrence† Ceratium fusus var. fusus (Ehrenberg) Dujardin, 1841 Ceratium fusus var. seta (Ehrenberg) Sournia, 1966 Ceratium geniculatum (Lemmermann) Cleve, 1901 Ceratium gibberum var. gibberum Gourret, 1883 Ceratium gibberum var. dispar (Pouchet) Sournia, 1966 Ceratium gravidum Gourret, 1883 Ceratium hexacanthum f. hexacanthum Gourret, 1883 Ceratium hexacanthum f. spirale (Kofoid) Schiller, 1937 Ceratium hircus var. horridum Schröder, 1909 Ceratium horridum (Cleve) Gran, 1902 var. horridum Ceratium horridum var. molle (Kofoid) Jörgensen, 1911 Ceratium incisum (Karsten) Jörgensen, 1911 Ceratium inflatum (Kofoid) Jörgensen, 1911 Ceratium kofoidii Jörgensen, 1911 Ceratium limulus Gourret, 1883 Ceratium lineatum (Ehrenberg) Cleve, 1899 Ceratium longirostrum Gourret, 1883 Ceratium longissimum (Schröder) Kofoid, 1907 Ceratium lunula (Schimper) Jörgensen, 1911 Ceratium macroceros var. macroceros (Ehrenberg) Vanhöffen, 1897 Ceratium macroceros var. gallicum (Kofoid) Sournia, 1966 Ceratium massiliense (Gourret) Jörgensen, 1911 Ceratium minutum Jörgensen, 1920 Ceratium paradoxides Cleve, 1900 Ceratium pentagonum var. pentagonum Gourret, 1883 Ceratium pentagonum var. tenerum Jörgensen, 1920 Ceratium platycorne Daday, 1888 Ceratium praelongum (Lemmermann) Kofoid, 1907 Ceratium ranipes Cleve, 1900 Ceratium setaceum Jörgensen, 1911 Ceratium symmetricum var. symmetricum Pavillard, 1905 Ceratium symmetricum var. coarctatum (Pavillard) Graham et Bronikowsky, 1944 Ceratium tenue var. tenue Ostenfeld et Schmidt, 1901 Ceratium tenue var. buceros Balech, 1988 Ceratium tenue ver. tenuissimum (Kofoid) Graham et Bronikovsky, 1944 Ceratium teres Kofoid, 1907 Ceratium trichoceros (Ehrenberg) Kofoid, 1908 Ceratium tripos var. tripos (O. F. Müller) Nitzsch, 1817 Ceratium tripos var. atlanticus (Ostenfeld) Paulsen, 1907 Ceratium tripos var. neglectum (Ostenfeld) Paulsen, 1907 Ceratium tripos var. pulchellum (Schröder) López, 1955 Ceratium vultur f. vultur Cleve, 1900 Ceratium vultur f. japonicum (Schröder) Wood, 1954 Ceratium vultur f. recurvum (Jörgensen) Schiller, 1937 Ceratium vultur f. sumatranum (Karsten) Sournia, 1966 Ceratocorythaceae Lindemann, 1928 Ceratocorys armata (Schütt) Kofoid, 1910 Ceratocorys horrida Stein, 1883 255 254 4 12 11 9 104 9 87 147 6 3 16 142 17 81 44 13 27 229 97 223 14 3 218 100 1 8 20 4 83 51 95 55 20 240 245 186 12 40 19 61 17 3 9 24 140 Taxa List of taxa and their occurrence† (continued ) Occurrence† Cladopyxidaceae Stein emend. Balech, 1913 Cladopyxis brachiolata Stein, 1883 Cladopyxis hemibrachiata Balech, 1964 Paleophalacroma unicinctum Schiller, 1928 Goniodoma sphaericum Murray et Whitting, 1899 Triadinium polyedricum (Pouchet) Dodge, 1981 Pyrodinium bahamense Plate, 1906 var. bahamense Gonyaulacaceae Lindemann, 1928 Gonyaulax birostris Stein, 1883 Gonyaulax ceratocoroides (Murray et Whitting) Kofoid, 1910 Gonyaulax fusiformis Graham, 1942 Gonyaulax fragilis (Schütt) Kofoid, 1911 Gonyaulax pacifica Kofoid, 1907 Gonyaulax polygramma Stein, 1883 Gonyaulax spinifera (Cleparède et Lachmann) Diesing, 1866 Gonyaulax striata Manguin, 1922 Lingulodinium polyedrum (Stein) Dodge, 1989 Peridiniella danica (Paulsen) Okolodkov et Dodge, 1995 Peridiniella sphaeroidea Kofoid et Michener, 1911 Protoceratium spinulosum (Murray et Whitting) Schiller, 1937 Heterodiniaceae Lindemann, 1928 Heterodinium agassizii Kofoid, 1907 Heterodinium dispar Kofoid et Adams, 1933 Heterodinium scrippsii Kofoid, 1906 Heterodinium whittingae Kofoid, 1906 Oxytoxaceae Lindemann, 1928 Corythodinium constrictum (Stein) Taylor, 1976 Corythodinium tesselatum (Stein) Loeblich et Loeblich III, 1966 Oxytoxum adriaticum Schiller, 1937 Oxytoxum caudatum Schiller, 1937 Oxytoxum crassum Schiller, 1937 Oxytoxum elegans Pavillard, 1916 Oxytoxum elongatum Wood, 1962 Oxytoxum globosum Schiller, 1937 Oxytoxum gracile Schiller, 1937 Oxytoxum laticeps Schiller, 1937 Oxytoxum longiceps Schiller, 1937 Oxytoxum mediterraneum Schiller, 1937 Oxytoxum milneri Murray et Whitting, 1899 Oxytoxum ovale Schiller, 1937 Oxytoxum pachyderme Schiller, 1937 Oxytoxum parvum Schiller, 1937 Oxytoxum sceptrum (Stein) Schröder, 1900 Oxytoxum scolopax Stein, 1883 Oxytoxum sphaeroideum Stein, 1883 Oxytoxum turbo Kofoid, 1907 Oxytoxum variabile Schiller, 1937 Schuettiella mitra (Schütt) Balech, 1988 Peridiniaceae Ehrenberg, 1828 Diplopsalopsis globula Abé, 1941 Ensiculifera angulata Balech, 1988 Ensiculifera mexicana Balech, 1967 Protoperidinium abei (Paulsen) Balech, 1974 Protoperidinium brochii (Kofoid et Swezy) Balech, 1974 Protoperidinium cassum (Balech) Balech, 1974 Protoperidinium conicum (Gran) Balech, 1974 Protoperidinium crassipes (Kofoid) Balech, 1974 Protoperidinium depresum (Bailey) Balech, 1974 Protoperidinium divergens (Ehrenberg) Balech, 1974 Protoperidinium elegans (Cleve) Balech, 1974 26 18 8 3 6 14 39 5 33 2 35 132 6 6 45 8 1 8 1 1 3 1 19 16 4 11 9 46 1 20 125 67 7 20 10 25 1 36 28 103 1 28 5 13 5 1 4 1 1 26 64 9 14 202 48 Dinoflagellates in the Gulf of Mexico Table 2. 425 List of taxa and their occurrence† (continued) Taxa Occurrence† Protoperidinium fartum Balech, 1979 Protoperidinium grande (Kofoid) Balech, 1974 Protoperidinium jorgenseni Balech, 1971 Protoperidinium longipes (Karsten) Balech, 1974 Protoperidinium mediterraneum (Kofoid) Balech, 1974 Protoperidinium nipponicum (Abé) Balech, 1974 Protoperidinium oblongum (Aurivillus) Park et Dodge, 1976 Protoperidinium oceanicum (Vanhöffen) Balech, 1974 Protoperidinium oviforme (Dangeard) Balech, 1974 Protoperidinium ovum (Schiller) Balech, 1974 Protoperidinium pallidum var. daedalum Balech, 1978 Protoperidinium pellucidum var. stellatum Balech, 1978 Protoperidinium pentagonum (Gran) Balech, 1974 Protoperidinium poucheti (Kofoid et Michener) Taylor et Balech, 1988 Protoperidinium punctulatum (Paulsen) Balech, 1974 Protoperidinium cf. rectum (Kofoid) Balech, 1974 Protoperidinium subsphaericum (Balech) Balech, 1974 Protoperidinium tuba (Schiller) Balech, 1974 Protoperidinium venustum (Matzenauer) Balech, 1974 Protoperidinium vulgare Balech, 1978 Scrippsiella trochoidea (Stein) Fine et Loeblich III, 1976 Podolampadaceae Lindemann, 1928 Blepharocysta splendor-maris (Ehrenberg) Ehrenberg, 1873 Podolampas bipes Stein, 1883 Podolampas elegans Schütt, 1895 Podolampas palmipes Stein, 1883 Podolampas reticulata Kofoid, 1907 Podolampas spinifera Okamura, 1912 Pyrophacus horologium Stein, 1383 Pyrophacus steinii (Stein) Wall et Dale, 1971 Pyrophacus vancanpoae (Rossignol) Wall et Dale, 1972 Peridiniales incertae sedis Spiraulax kofoidii Grabam, 1942 Prorocentrales Lemmermann, 1910 Prorocentraceae Stein, 1883 Prorocentrum aporum (Schiller) Dodge, 1975 Prorocentrum balticum (Lohmann) Loeblich, 1970 Prorocentrum compressum (Bailey), Abé 1967 Prorocentrum cordatum (Ostenfeld), Dodge 1976 Prorocentrum dentatum, Stein 1883 Prorocentrum gibbosum (Schiller) Schiller, 1933 Prorocentrum gracile Schütt, 1895 Prorocentrum cf. lima (Ehrenberg) Dodge, 1975 Prorocentrum mexicanum Osorio-Tafall, 1942 Prorocentrum micans Ehrenberg, 1833 Prorocentrum minimum (Pavillard) Schiller, 1933 Prorocentrum rostratum Stein, 1883 Prorocentrum sigmoides Böhm, 1933 Prorocentrum triestinum Schiller, 1918 Pyrocystales Apstein, 1909 Pyrocystaceae (Schütt) Lemmermann, 1899 Dissodinium elegans (Pavillard) Matzenauer, 1933 Pyrocystis fusiformis Wyviile-Thomson, 1885 Pyrocystis humulus Cleve, 1900 Pyrocystis lunula (Schütt) Schütt, 1896 Pyrocystis obtusa Pavillard, 1931 Pyrocystis robusta Kofoid, 1907 † Number of sites where species were found. 1 120 1 35 125 6 37 97 1 30 3 1 78 1 2 4 1 68 5 3 10 13 102 65 192 14 92 81 133 18 and Dinophysis tripos, all of which widely distributed, although in small numbers. A. carterae has been noted to produce toxic substances (Steidinger 1993). Prorocentrum cf. lima was found in 32 localities in the region-II (Bay of Campeche). A. carterae, D. caudata, D. fortii, D. tripos, D. mitra and D. rotundata were present mostly in net samples. Based on the analysis of water samples, Amphidinium carterae were found to have a brief blooming period in the region-III (2 × 104 cells l–1). P. micans and D. caudata had fluctuations between >103 and <104 cells/L in March 2000. Pyrodinium bahamense var. bahamense had values of <105 cells/L, mostly at inlets of some coastal lagoons. Occurrence data show that Prorocentrum mexicanum and D. tripos are species widely distributed in small numbers. Prorocentrum minimum, D. acuta and D. mitra were occasionally found only in net samples. P. micans showed its maximum frequency during summer and autumn. A red tide of Scrippsiella trochoidea was found in concentrations of about 300 000 cells/L north-east of Cape Catoche on the Yucatan Shelf. This bloom caused a brown-greenish water discoloration in early summer (July–August), representing 99.6% of the total phytoplankton population (Licea unpubl. data 1998). The potentially harmful species C. furca var. furca, P. bahamense var. bahamense, S. trochoidea and Gonyaulax polygramma were found forming blooms during summer. In all cases every species was widely distributed, with the exception of S. trochoidea, which bloomed at only 7 stations located east of region-III, where a regular upwelling occurs. DISCUSSION 6 23 29 168 1 18 1 160 32 100 143 10 2 34 4 34 39 4 20 47 83 Our results agree with the considerable constancy in the dinoflagellate species composition found in the Caribbean Sea (Balech 1967a; Wood 1968, 1969; Zernova 1969, 1970, 1974) and the Straits of Florida (Steidinger & Williams 1970). The latter author explains this similarity on the basis of the fact that a great part of the waters of Florida are derived from the Caribbean Sea through the Yucatan Channel, with only a small contribution from the Gulf of Mexico. The small differences found in species composition are probably a result of regional hydrographic conditions that occur, particularly in region-II. D. acuta, Heteroschisma cf. subantartica, Amphidinium acutissimum, A. globosum and Prorocentrum cf. lima, which were found in that region, are reported for the first time for the Gulf of Mexico. Data suggest that species distribution is mainly associated with local hydrographic conditions and species requirements. According to the distribution patterns of Ceratium arietinum, Ceratium azoricum, C. contortum, Ceratium euarcuatum, Ceratium tenue, 426 Ornithocercus quadratus, Oxytoxum sceptrum and Podolampas spinifera, these species were found close to the limit of a hyaline front located in the northern coast of the Tamiahua lagoon (Region-I), where several rivers discharge and nutrients were relatively high, as compared with the adjacent area. In contrast, the same species were absent at salinities below 32 PSU and because of oligotrophic conditions (Estradas-Romero 2004). In addition, this region was characterized by the presence of anticyclonic gyres that drift in from the Loop Current (Vidal et al. 1992), which indicates a lack of nutrients. The same species were present at the western part of region-II near the shelf where the discharge of rivers was evident. These facts, combined with littoral circulation associated with cyclonic gyres drifting from a branch of the Loop Current (Monreal & Salas de León 1990), created contrasting hydrographical conditions that might or might not support the survival of species, therefore affecting their distribution. The same group of species occurred simultaneously along the shelf of Yucatan, associated with the upwelled water described by Merino (1997) at the eastern region-III. In contrast, the eastern part of region-II has no rivers, but it does have a wide shelf and high temperature and salinity (Alatorre et al. 1987), which are advantageous conditions for the settlement of blooms of Oxyrrhis marina and P. bahamense. Therefore, it can be concluded that region-II is a transition between region-I and region-III. In the early summer at the eastern region-III (Fig. 1), a water discoloration by S. trochoidea was observed, apparently associated with the upwelling that occurs in the north of Cape Catoche, suggesting that nutrients contribute to the bloom settlement of this species. However, the presence of many cysts (not counted) during this time indicates the beginning of the development of the first two of four blooming stages of algae, described by Steidinger (1983). Therefore, the blooming in question manifests itself more prominently, followed by the third and fourth stages of the development of this species, when water discoloration is visible; then it moves and is scattered over the Yucatan Shelf. The dominance of dinoflagellates during summer shows that it is precisely at this time of the year when the most appropriate conditions exist in the Gulf of Mexico. ACKNOWLEDGMENTS Funds for this research were provided by the Institute of Marine Science and Limnology (ICMYL-UNAM). We are grateful to National Commission for the Knowledge and Use of Diversity for financial support for 2 years (grants: FB683/S088 and A0012/2002). We extend our deep appreciation to the crew members of the RV JUSTO SIERRA and the participating scientists in the PROGMEX, OGMEX and SGM cruises for their invaluable support, to Yuri Okolodkov for some species S. Licea et al. identification, to Joseph Doshner for reading and commenting on the English and to Jorge Sepulveda for scanning electron microscopy technical assistance. REFERENCES Alatorre, M. A., Ruiz, F. and Salas de León, D. 1987. Efecto Del Paso de Frentes Fríos Atmosféricos Sobre la Bahía de Campeche. In Gonzàlez, J. F., Medina, M. and Martínez, M. (Eds) Memoria Reunión Anual 1987. Unión Geofísica Mexicana, México, pp. 186–93. Balech, E. 1967a. Dinoflagellates and tintinnids in the northeastern Gulf of Mexico. Bull. Mart. Sci. 17: 280–98. Balech, E. 1967b. Dinoflagelados nuevos o interesantes del Golfo de México y Caribe. 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