Phytoplankton abundance and distribution on the Yucatan shelf (June 1979 and April 1983)

Licea Sergio; Luna Ruth; Okolodkov Yuri B.; Cortés-Altamirano Roberto

Sergio Licea1, Ruth Luna1, Yuri B. Okolodkov2, Roberto Cortés-Altamirano3

1 Instituto de Ciencias del Mar y Limnología (ICMyL), Universidad Nacional

Autónoma de México (UNAM), A. P. 70-305, 04510, México, D. F., México

2 Instituto de Ciencias Marinas y Pesquerías, Universidad Veracruzana, Calle Hidalgo

617, Col. Río Jamapa, Boca del Río, 94290, Veracruz, México

3 Estación Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad

Nacional Autónoma de México, A. P. 811, 82204, Mazatlán, Sinaloa, México Correspondence to: Yuri B. Okolodkov, [email protected]

Abstract. Chlorophyll-л concentration and phytoplankton abundance data obtained during two cruises (April 1983 and June 1979) were used to study phytoplankton horizontal and vertical distributions in the waters of the Yucatan shelf. Water-bottle samples were taken to 200 m depth at 60 stations. The maximum mean (from different depths per station) phytoplankton abundance (734000 cells/l in April and 632900 cells/l in June) and chlorophyll concentration (1.63 mg/m3 in April and 0.60 mg/m3 in June) occurred near the region of Cape Catoche (approximately at 22°15'N and 87°45'W), where upwelling occurs regularly. Along the vertical profile, in April chlorophyll ranged between 0.05 and 1.73 mg/m3; in general, the highest values were observed at the 2 m depth (1.73 mg/m3) to the 25 m depth (up to 1.50 mg/m3). On the basis of the chlorophyll content, phytoplankton abundance and species composition distribution, three regions were distinguished on the Yucatan shelf: 1) the upwelling region located to the north of Cape Catoche; 2) the region of possible upwellings, with one area located along the coast between Río Lagartos and Progreso and with another located at the central edge zone of the shelf; 3) and the transitional zone that includes most of the central and western parts of the study area. The conclusions of this study support those based on the Soviet-Cuban plankton surveys of the 1960s-1980s.

Keywords: abundance, chlorophyll, distribution, Gulf of Mexico, microalgae, phytoplankton, species composition, upwelling, Yucatan.

Численность и распределение фитопланктона на шельфе Юкатана (июнь 1979 г. и апрель 1983 г.)

Серхио Лисеа1, Рут Луна1, Ю. Б. Околодков2, Роберто Кортес-Альтамирано3 1 Институт морских наук и лимнологии, Национальный автономный университет Мехико, A. P. 70-305, 04510, Мехико, Мексика

2 Институт морских наук и рыболовства, Университет Веракрус, 94290,

Веракрус, Мексика

3 Институт морских наук и лимнологии, Национальный автономный университет

Мехико, A. P. 811, 82204, Масатлан, Синалоа, Мексика Автор для переписки: Ю. Б. Околодков, [email protected]

Резюме. Для изучения горизонтального и вертикального распределения фитопланктона на шельфе Юкатана были использованы данные по концентрации хлорофилла-я и численности фитопланктона во время двух океанографических экспедиций (ранняя и поздняя весна: апрель 1983 г. и июнь 1979 г.). Батоме-трические пробы были отобраны на 60 станциях с глубин 2, 10, 25, 50, 75, 100, 150 и 200 м. Хлорофилл был определен флуорометрическим методом, численность — методом Утермеля, виды были определены с использованием фазово-контрастной микроскопии и окрашивания трипановым синим. Максимальная численность фитопланктона (734 тыс. кл./л в апреле и 632.9 тыс. кл./л в июне) и более высокие концентрации хлорофилла (0.60-1.63 мг/м3 в апреле и 0.30-0.60 мг/м3 в июне) были отмечены вблизи мыса Каточе (приблизительно 22°15'N и 87°45'W), где регулярно происходит апвеллинг. Вдоль вертикального профиля в апреле содержание хлорофилла было 0.05-1.73 мг/м3; в целом, наиболее высокие величины были отмечены от поверхности (1.73 мг/м3) до глубины 25 м (до 1.50 мг/м3). На основе различий в распределении содержания хлорофилла, численности фитопланктона и видового состава на шельфе Юкатана были выделены три района: 1) район апвеллинга, расположенный к северу от мыса Ка-точе; 2) район вероятных апвеллингов с одним участком, находящимся вдоль побережья между Рио Лагартос у Прогресо, и другим, расположенным в центре краевой зоны шельфа; 3) переходная зона, включающая в себя центральную и западную части района исследований. Выводы настоящей работы подтверждают результаты, полученные на основе материалов советско-кубинских экспедиций 1960-1980 гг.

Ключевые слова: численность, хлорофилл, распределение, Мексиканский залив, микроводоросли, фитопланктон, видовой состав, апвеллинг, Юкатан.

Introduction

The Yucatan shelf is a striking environment in terms of its oceano-graphic biogeochemical processes. This ecosystem is highly influenced by the upwelling north of Cape Catoche and in other areas on the Yucatan shelf (Cochrane, 1966, 1968, 1969; Bulanienkov, García-Díaz, 1975; Berberian, Starr, 1978; Ruiz, 1979; Flores-Tellez, Villa-Aguilar, 1984; Espinosa, 1989; Merino, 1997). Common foci of most of the cited investigations have been the biological and chemical processes in the region. Another significant feature is the shelf width around the peninsula, which extends seaward for over 260 km, making it the widest continental shelf in the Caribbean region. In contrast, in the Caribbean margin the shelf is very narrow (3 km wide). This causes water to be upwelled onto this shelf and remain trapped within the euphotic zone for long periods, which could increase the fertilizing potential in this area (Furnas, Smay-da, 1987).

The Yucatan upwelling water has a temperature-salinity signature in the range of 16-20 °C (with the isotherm of 22.5 °C as the limiting boundary of upwelling influence) and 36.1-36.5, respectively, and high

concentrations of nitrates (8 to 14 ^mol/l) reaching 17 ^mol/l near the sea bottom, phosphates (1.2 to 1.7 ^mol/l) and silicates (4.5 to 7.3 ^mol/l). Therefore, it has a high fertilization potential during the period from March to September (Merino, 1992, 1997; Mariño-Tapia et al., 2014; Reyes-Mendoza et al., 2016). This water, originating at about 220-250 m depth in the Yucatan Channel, rises into the euphotic zone and moves over the shelf to the west, forming a subsurface dome (Merino, 1997). Consequently, a two-layered structure occurs over the Yucatan shelf during spring and summer: the Caribbean surface waters and the lower up-welled waters, both separated by strong gradients of temperature, density and nutrient concentrations. One part of the upwelled waters flows toward the west, leaving the shelf near Alacranes Reef, while the other part moves toward the coast, forming a cyclonic circulation to the north of Cape Catoche. Easterly winds and the characteristics of the Yucatan Current strongly influence the upwelling in the Cape Catoche region (En-ríquez, Mariño-Tapia, 2014). The velocity of the Yucatan Current entering the Gulf of Mexico from the Caribbean Sea is between 1 and 2 m/sec; it is a strong, permanent jet, generally found in the western part of the channel, with a nucleus 50-100 km wide that follows the topography of the slope into the Gulf of Mexico, becoming the Loop Current (Badan et al., 2005). It has been hypothesized that the Yucatan Current is stopped during autumn and winter (from October to March) when northerly storms dominate the dynamics of the Yucatan shelf, due to an increased sea level over the Yucatan shelf (Mariño-Tapia et al., 2014; Reyes-Mendoza et al., 2016).

Another peculiar feature is the absence of rivers along the Yucatan coast (Merino, Otero, 1991); furthermore, ground water discharge induces negligible salinity variations (Merino et al., 1990).

Until recently our knowledge of the phytoplankton in the Yucatan shelf was scarce (Fukase, 1967; El-Sayed et al., 1972; Hulburt, Corwin, 1972; Luna, 1981; Torres-Galván, 1986). Recently some checklists of phytoplankton species (including those for the whole Gulf of Mexico), new records and investigations on pelagic harmful algal blooms or species have been published (Licea et al., 2004a, b, 2011, 2016; Krayesky et al., 2009; Steidinger et al., 2009; Aké-Castillo et al., 2012; Merino-Virgilio et al., 2012, 2013, 2014a, b; Barón-Campis et al., 2014; Okolodkov et al., 2014; Aké-Castillo, Poot-Delgado, 2016).

Earlier large-scale investigations on plankton and productivity in the Gulf of Mexico and the Bank of Campeche were performed during the Soviet and Soviet-Cuban expeditions during the 1960s-1980s (Belousov et al., 1966; Bogdanov et al., 1968; Roujiyaynen et al., 1968; Zernova,

1969, 1970, 1974, 1982; Bessonov et al., 1971; Bessonov, González, 1971; Cruz, 1971; Krylov, 1974; Vinogradova, 1976; Zernova, Zhitina, 1985; López-Baluja et al., 1992). A brief critical analysis of these studies is given by Okolodkov (2003). The comparison of these data with those obtained during the PROGMEX-I and ONJUKO cruises is of limited value because the Russian papers contain no data on chlorophyll-a (Chl-a). However, the cited publications discuss in detail the hydrology of the study region, the species composition of phytoplankton and their temporal succession in the zone of upwelling, phytoplankton abundance and partial contributions of the major taxonomic groups.

In this study we describe the distributions of Chl-a concentration and phytoplankton abundance in June 1979 and April 1983. The comparison of these data with data from previous investigations allowed us to recognize some temporal changes in phytoplankton abundance in two different periods that correspond to the dry season (April) and the beginning of the rainy season (June). Of particular interest were the patches of phytoplank-ton abundance and species composition near Cape Catoche that are likely associated with upwelling.

Material and methods

The data obtained during two cruises were used: ONJUKO (June 7-12, 1979) onboard the R/V «ONJUKO» and PROGMEX-I (April 9-16, 1983) onboard the R/V «Justo Sierra» (Fig. 1). In general, oceanograph-ic transects were located perpendicular to the coast across the continental shelf. For the ONJUKO cruise, sometimes integrated water samples (taken from various depths — 2, 10, 25, 50, 75, 100, 150 and 200 m, and mixed before the laboratory analyses) were used both for measuring Chl-a and for counting algal cells. Mean values were calculated from the surface to the bottom or to the 100 m depth. A conventional Carl Zeiss Photomicroscope supplied with the phase contrast 40*/0.65 objective (total microscope magnification up to 400*) was used in combination with Trypan Blue (Lebour, 1925; Taylor, 1978) to identify dinoflagellate species; one or two drops of a 0.2 % stain water solution was added to water mounts.

During the PROGMEX-I cruise, water samples were obtained with Niskin bottles mounted on a rosette sampler attached to a CTD system. At each station samples were taken from eight depths: subsurface (2 m), 10, 25, 50, 75, 100, 150 and 200 m, depending on the depth of the sampling site. Samples for phytoplankton counts were taken in 200 ml dark plastic bottles and preserved with stock Lugol's solution with a few drops of 40 % formalin added. Shortly after collection, 100 ml of water were

24° N R J8n

Fig. 1. Location of sampling sites on the Yucatan shelf. Straight lines show the positions of the five selected transects referred to in the text.

settled in a combined chamber and examined using the Utermohl technique and an inverted microscope (Hasle, 1978). Many organisms could not be classified at the level of genus or species and were referred to as «naked phytoflagellates» and «unidentified». A species was considered dominant when its abundance was higher than 10 % of the total phyto-plankton abundance and subdominant when its abundance varied between 5 and 10 %.

Chl-a concentration was measured fluorometrically after filtering 250 ml of water through 45 mm GF/F filters and storing immediately at -20 °C (Yentsch, Menzel, 1963). Laboratory procedure involved Chl-a extraction in 90 % acetone before measurements in a Turner Fluorometer (Turner Designs, San Jose, CA, USA).

Results

Chl-a concentrations and phytoplankton abundances are shown in Figures 2-5. Data from the 0NJUK0-09-79 and PROGMEX-I cruises are treated separately.

ONJUKO-09-79 cruise (June 1979)

Chlorophyll-«

The mean (from different depths) values of Chl-a concentrations (Fig. 2A) were generally within a small range; however, a region north of Cape Catoche in the eastern portion of the Yucatan shelf (stations 23 to 29) showed the highest values (between 0.30 and 0.60 mg/m3 of Chl-a). Intermediate values of 0.30 mg/m3 were found to the north of Río Lagartos (station 17) and at the northwest boundary of the Yucatan shelf (station 13). Most of the western region showed values <0.20 mg/m3.

Vertical distribution of Chl-a concentration showed high values (0.30 to 0.70 mg/m3) at 10 m to the north of Cape Catoche and at the northwest boundary of the Yucatan shelf (up to 1.0 mg/m3) (Figs. 3A-D). High values (>0.80 mg/m3) were also recorded at 30 m toward the eastern coastal region above the shelf.

Phytoplankton abundance and species composition

The horizontal distribution of mean (from different depths) values of the total phytoplankton abundance shows a clear gradient from east to west along the Yucatan shelf (Fig. 2C). The highest values of 160100 and 632900 cells/l occurred in the region surrounding Cape Catoche. The lowest values (<10000 cells/l) occurred at all stations located in the western region. Intermediate values (<100000 cells/l) were recorded between these two regions (stations 16 to 20 and 23 to 25).

Based on the net samples, a total of 86 phytoplankton species were identified, of which diatoms were represented by 67 % of the total number of phytoplankton species. Dinoflagellates represented 21 %, and the remaining 12 % were coccolithophorids, cyanobacteria and unidentified nanoflagellates. Several unidentified naked phytoflagellates were widely distributed, dominating the phytoplankton community with low abundances (between 1000 and 10000 cells/l) in the western region at 16 stations.

The most common planktonic diatom species are listed in the Table. Among toxigenic species, only Pseudo-nitzschia pungens (Grunow ex Cleve) Hasle that causes amnesic shellfish poisoning (Bates et al., 1989) was found. Among dinoflagellates, Gymnodinium spp. reached 28 % of the total phytoplankton abundance at station 8 with 1246 cells/l. Proro-centrum micans Ehrenb., Amphidinium acutissimum J. Schiller, A. glo-bosum Schröd., Kapelodinium vestifici (F. Schütt) Boutrup, Moestrup et Daugbjerg, Protoperidinium sp. and Oxytoxum sp. were subdominant at some sites. Coccolithophorids were represented by four species, of which Rhabdosphaera sp. reached an abundance of 250 cells/l at station 14. Cy-anobacteria (three species) were present in low abundances.

Fig. 2. The regional distribution of mean Chl-a concentration and phytoplankton abundance during the ONJUKO and PROGMEX-I cruises. A — Chl-a distribution during the survey of June 1979; shaded area indicates the maximum abundance (>0.3 mg/m3). B — Chl-a distribution during the survey of April 1983; shaded area indicates the maximum abundance (>0.3 mg/m3). C — Phytoplank-ton abundance during the June survey; shaded area indicates the maximum abundance (>200 x 103 cells/l). D — Phytoplankton abundance during the April survey; shaded area indicates the maximum abundance (>200 x 103 cells/l). Mean values were calculated from the surface to the bottom or to the 100 m depth. Dots indicate the position

of sampling stations.

Table

The most common planktonic diatom species during the ONJUKO-09-79 cruise

Массовые виды планктонных диатомовых во время экспедиции ONJUKO-09-79

Species Relative abundance Stations

Pseudo-nitzschia pungens d 16, 24, 26-29

Skeletonema costatum d 27-29

Chaetoceros affinis d 16, 24, 26

C. messanensis sd 7, 11, 12

C. constrictus sd 10

C. lorenzianus sd 18, 27

C. teres sd 13

C. dichaeta sd 16, 18

Nitzschia longissima sd 8

Guinardia striata sd 16

Pseudosolenia calcar-avis sd 17

Leptocilyndrus danicus sd 17

Note. d - dominant, sd - subdominant.

Based on the Chl-a values, phytoplankton abundance and species composition, three regions can be distinguished on the Yucatan shelf. Region I, located to the north of Cape Catoche, is characterized by blooming Pseudo-nitzschia pungens, Skeletonema costatum (Grev.) Cleve, Chae-toceros lorenzianus Grunow, C. affinis Lauder and Thalassiosira sp. This region had the highest values of cell numbers and Chl-a in the study area and its effect reached stations 24, 26 and 28. Mean cell numbers ranged between 97400 and 632900 cells/l. Mean Chl-a values were between 0.40 and 0.61mg/m3. Region II, located along the coast between Rio Lagartos and Progreso (stations 16 to 18), was characterized by the dominance of Guinardia striata (Stolterf.) Hasle, Pseudosolenia calcar-avis (M. Schul-tze) Sundstrom, Chaetoceros affinis, Leptocylindrus danicus Cleve and Pseudo-nitzschia pungens. This region had mean Chl-a values between 0.19 and 0.30 mg/m3. Cell abundances were between 25800 and 133340 cells/l. Region III, located westward of the Yucatan shelf, is a transitional zone between regions I and II. It was characterized by low phytoplankton abundance, the dominance of Chaetoceros affinis, C. messanensis Castrac., Hemiaulus membranaceus Cleve, H. hauckii Grunow and the presence of several unidentified naked phytoflagellate species. Mean cell numbers were between 9050 and 30750 cells/l, and Chl-a values ranged from 0.07 to 0.23 mg/m3.

PROGMEX-I cruise (April 1983)

Chlorophyll-«

Mean Chl-a values were between 0.05 and 1.63 mg/m3. High concentrations of Chl-a occurred in the Cape Catoche area with values between 0.60 and 1.63 mg/m3. Low values (0.05 mg/m3) were recorded in the Yucatan Channel. Intermediate values between 0.10 and 0.40 mg/m3 occurred toward the northern and western regions (Fig. 2B).

In the vertical profile Chl-a ranged between 0.05 and 1.73 mg/m3. In general, the highest values were found from the subsurface layer (1.73 mg/m3) to the 25 m depth (up to 1.50 mg/m3) in the area surrounding Cape Catoche. In the northern and western regions, Chl-a values were between 0.07 and 0.40 mg/m3 (Figs. 4A-D).

Phytoplankton abundance and species composition

The highest mean values of the total phytoplankton abundance were found near Cape Catoche (stations 63, 65, 66, 70, 72, 76 and 80). The minimum value was 137000 cells/l at station 63, and the maximum reached 734000 cells/l at station 73. The lowest values occurred in the Yucatan Channel at stations 77 to 79 and 81 to 88 (Fig. 2D). The vertical profiles showed the maximum cell abundances (200000 to 600000 cells/l) between the surface and 75 m depth along transects C and D (Fig. 5).

A total of 175 taxa were identified based mainly on the net samples. Of these, Chaetoceros Ehrenb. was the most diverse genus with 30 species, followed by Ceratium Schrank (9 species), Oxytoxum F. Stein (8 species) and Nitzschia Hassall (7 species). Dinoflagellates were represented by 44 species, mostly the thecate forms. Other groups were silico-flagellates, coccolithophorids, cyanobacteria, chlorophytes and unidentified naked phytoflagellates.

Discussion

Phytoplankton and upwelling

The northern region of Cape Catoche has been characterized as a region of upwelling whose maximum intensity occurs during spring and summer (Cochrane, 1966; Bessonov et al., 1971; Ruiz-Renteria, 1979; Merino, 1997; Reyes-Mendoza et al., 2015). The highest Chl-a values (up to 1.73 mg/m3) and phytoplankton abundance (up to 734000 cells/l) recorded in April (PROGMEX-I) make this region one of the most productive in the Bank of Campeche in terms of primary production. A similar situation was previously noted by Bogdanov et al. (1968), Khromov (1965) and Cruz (1971), based on high concentrations of dissolved oxygen, seston and plankton biomass. On the inner shelf north of the Yucatan Peninsula, Zavala-Hidalgo et al. (2006) reported higher Chl-a con-

Fig. 3. The regional distribution of Chl-a concentration from the surface to the 30 m depth during the survey of June 1979; shaded area shows the maximum Chl-a values (>0.3 mg/m3). A — Surface (2 m). B — 10 m. C — 20 m. D — 30 m. Dots indicate the position of sampling stations.

Fig. 4. The regional distribution of Chl-a concentration from the surface to the 34 m depth during the survey of April 1983; shaded area shows the maximum Chl-a values (> 0.6 mg/m3). A — 2 m. B — 10 m. C — 25 m. D — 34 m. Dots indicate the position of sampling stations.

Fig. 5. Vertical distribution of phytoplankton abundance (cells per litre x 103) along five selected transects during the surveys of June 1979 and April 1983 (for location, see Fig. 1): A — transect A, B — transect B, C — transect C, D — transect D, E — transect F. Dots show the position of sampling stations. Light shading shows the maximum phytoplankton abundance (>200 x

103 cells/l).

centrations (derived from SeaWiFS) between July and November. In both spring and summer the influence of upwelling above the northern Yucatan shelf is obvious. However, in spring the area with high Chl-a content and abundance of phytoplankton is smaller than in summer, and it does not spread to the west of Rio Lagartos (Figs 2B, D, 4A-D). In summer the Chl-a values are lower than in spring, but the area occupied by the waters characterized by values higher than 0.3 mg/m3 is much more extensive, spreading out to the west of Progreso.

Associated with high phytoplankton production in the region of Cape Catoche, intense growth of the diatoms Pseudo-nitzschia pungens (a potentially toxic species that causes amnesic shellfish poisoning; Bates et al., 1989), Skeletonema costatum, Chaetoceros affinis, C. messanensis, Pseu-dosolenia calcar-avis, Guinardia striata, Hemiaulus membranaceus and H. hauckii was observed. Such growth rates require a high nutrient supply. Smayda (1967) found that S. costatum and G. striata require high nutrient concentrations for their growth under laboratory conditions. In contrast, in the offshore areas, the dominance of dinoflagellates and naked phyto-flagellates indicates oligotrophic conditions. Teixeira (1963) found a similar situation in the oligotrophic waters in the Sargasso Sea as well as in other tropical oceanic waters. According to El-Sayed et al. (1972), Smayda (1976) and Merino (1997), most of the Bank of Campeche is oligotrophic.

In ageing waters upwelled in the northern part of the Yucatan shelf and moving westward above the shelf, the following temporal succession of species and the replacement of smaller-sized algae by larger-sized species was observed: Skeletonema costatum, Chaetoceros compressus Lauder, Guinardia striata, Thalassiosira subtilis (Ostenf.) Gran, Thalassionema nitzschioides (Grunow) Mereschk. and Prorocentrum scutellum Schrod. (Zernova, 1969, 1974; Zernova, Zhitina, 1985). The high concentration of phosphates appears to be the main reason for the mass development of small-sized diatoms in the zone of upwelling near the eastern margin of the Yucatan shelf (Zernova, 1969, 1982; Merino, 1997). In March — April 1965, in the area above the northern and western Yucatan shelf, diatoms were the dominant taxonomic group, contributing 50 % to more than 90 % of the total phytoplankton abundance (Zernova, 1970, 1982; Lopez et al., 1992). Depletion of nutrients downstream of the upwelling zone and diminishing phosphate concentrations from the Yucatan Peninsula offshore and along the transect through the Yucatan Channel resulted in changes in species composition from diatoms to dinoflagellates or cyanobacteria as dominant major taxonomic groups.

The phytoplankton development in relation to upwelling studied above the northern Yucatan shelf in July 2-25, 1970 (Vinogradova, 1976)

showed that at the later stage, cold upwelled waters rich in nutrients spread onto the shelf. Apart from planktonic diatoms, which were the main component of phytoplankton blooms in the zone of upwelling in the study area, benthic diatoms and abundant detritus could be also found in the water column. As suggested, the high concentration of detritus was due to bottom vegetation and wind. In some cases, a high amount of detritus in the surface and near-bottom layers can be related to phytoplankton developed during the most active phase of upwelling. Thus, the Chl-a data obtained from the northern Yucatan shelf should be referred as not only due to living planktonic algal cells but also to decaying phytoplankton cells and to detritus of bottom macrophyte origin.

On the Bank of Campeche the intensity of the upwelling depends on the intensity of the Yucatan Current, which varies between 0.8 and 1.2 knots, increasing in summer (Vasiliev, Torin, 1965). Our data support the previously published results: on the Bank of Campeche the area enriched by nutrients is 2 to 3 times larger in summer than in winter (Bessonov et al, 1971). Favourable conditions for phytoplankton development that permanently exist on the Bank of Campeche are not only because of the upwelling produced by the transversal circulation within the Yucatan Current but also due to the local closed circulation within the bank (Zernova, 1970). According to this author, on the Bank of Campeche the maximum abundance was observed in April and the maximum biomass in August. Our data are not sufficient to confirm or to contradict this observation. However, it should be noted that the maximum mean Chl-a values calculated from the surface to the sea bottom or down to the 100 m depth were observed in April 1983 (dry season), and in June 1979 (rainy season) they were noticeably lower (Figs. 2B, A).

The eastern part of the Bank of Campeche was reported as an area where an increased number of species was observed — 100 to 174 species per station (Zernova, Zhitina, 1985). However, a greater degree of dominance of smaller-sized diatom species in this region at the early stage of upwelling results in a low diversity index (Zernova, 1974).

On the whole, the abundance and biomass of phytoplankton in the southern Gulf of Mexico is comparable to those near the southwestern coast of Africa, in the zone of upwelling, known for its high productivity (Zernova, 1974). The neritic zone in the southern Gulf of Mexico can be characterized as productive (Zernova, 1969). Contrary to that, Vinogradova (1976) did not consider the waters of the Bank of Campeche productive. In this region intense but short-term algal blooms can be observed in the neritic zone during upwelling. Pelagic fish assemblages were found in the eastern part of the Bank of Campeche in summer-

autumn (Sokolova, 1965), which was obviously related to higher zooplankton biomass during this period (Sánchez-Velasco, Flores-Coto, 1994).

According to the results obtained during the Soviet-Cuban expedition in the period of 25 March — 23 April 1965, the character of the horizontal distribution of the total phytoplankton biomass in the southern Gulf of Mexico was similar to that of phytoplankton abundance (Zernova, 1974). It was concluded that the total phytoplankton abundance and its distribution were determined mainly by diatoms, both in the shelf zone and the zones of upwellings in offshore areas. It was also noted that in the zone of upwelling above the eastern part of the Bank of Campeche, the panthalassic (those that show no preference for neritic or oceanic zones) and neritic species reached their maximum values in terms of abundance (Zernova, 1974; Zernova, Zhitina, 1985); this was confirmed by the results of the present study. In the Gulf of Mexico and the Yucatan Channel, the panthalassic species play a much more important role than the neritic and oceanic ones (Krylov, 1974; Zernova, Zhitina, 1985).

Regionalization

Based on the results obtained, three regions on the Yucatan shelf were distinguished: 1) the eastern region located to the north of Cape Catoche, in the eastern portion of the Yucatan shelf, characterized by the highest phytoplankton biomass as a result of upwelling and dominated by diatom species; 2) the region of possible upwellings, with one area located near the coast between Río Lagartos and Progreso (stations 16 to 18) and with another located at the central edge zone of the shelf, both being characterized by their relatively high biomass, low species richness, abundant diatoms and by few phytoflagellates (stations 3, 5, 12-14); and 3) the transitional zone that includes most of the central and western parts of the study area and is characterized by a mixed phytoplankton population of oceanic and neritic origins, dominated by dinoflagellates and naked phytoflagellates, with few diatoms.

Concluding remarks

To evaluate the annual production and the mean productivity of phytoplankton in the study region, data on periodicity of upwellings are needed. As is known, upwellings determine the seasonal changes in phy-toplankton development in the study region and are mainly determined by the hydrological regime in the Yucatan Channel area. The intensification of the Yucatan Current, which occurs mainly in summer and autumn, results in a more intense upwelling above the Yucatan shelf, which in turn is responsible for high biological production (Bessonov et al., 1971).

The existence of the subsurface countercurrent reported by Bulanien-kov, García (1973) and confirmed by Merino (1997) also suggests a close relation between this countercurrent and the upwelling process, indicating the expected effects of such upwelling along the eastern Yucatan slope. Data on phytoplankton abundance presented here support Merino's suggestion that the countercurrent may be formed by upwelled water that sinks as it flows along the slope.

The lack of data on nutrients precludes a more refined analysis of the phytoplankton growth during our surveys. However, by analyzing the data of other authors obtained from the same region (El-Sayed, 1972; Furnas, Smayda, 1987; Merino, 1997), it is possible to deduce that the phytoplankton abundance primarily reflects the nutrient concentrations in the study region, especially to the north of Cape Catoche.

Acknowledgements

We are indebted to the ICMyL-UNAM for logistic and financial support. Thanks are also due to the students of the Phytoplankton Laboratory of ICMyL and the officers and the crew of both the R/V «ONJUKO» and the R/V «Justo Sierra». Ranulfo Rodríguez and Boris Okolodkov assisted in graph production. Joseph Doshner and Marcia M. Gowing (University of California at Santa Cruz, California, USA) kindly improved the style. The two anonymous reviewers are thanked for their valuable critical comments and corrections.

References

Aké-Castillo J. A., Okolodkov Y. B., Espinosa-Matías S., Merino-Virgilio F. del C., Herre-ra-Silveira J. A., Ector L. 2012. Cyclotella marina (Tanimura, Nagumo et Kato) Aké-Castillo, Okolodkov et Ector comb. et stat. nov. (Thalassiosiraceae): a bloom-forming diatom in the southeastern Gulf of Mexico. Nova Hedwigia Beih. 141: 263-274. Aké-Castillo J. A., Poot-Delgado C. A. 2016. FAN en el Golfo de México: panorama general sobre eventos y especies. Florecimientos algales nocivos en México. CICESE, Ensenada, México: 298-307. Badan A., Candela J., Sheinbaum J., Ochoa J. 2005. Upper-layer circulation in the approaches to Yucatan Channel. Circulation in the Gulf of Mexico. Observations and models. AGU Books Board, Geophysical Monograph 161. Washington: 57-69. Bates S. S., Bird C. J., de Freitas A. S. W., Foxall R., Gilgan M., Hanic L. A., Johnson G. R., McCulloch A. W., Odense P., Pocklington R., Quilliam M. A., Sim P. G., Smith J. C. 1989. Pennate diatom Nitzschia pungens as the primary source of domoic acid, a toxin in shellfish from eastern Prince Edward Island, Canada. Ca-nad. J. Fish. Aquat. Sci. 46: 1203-1215. Belousov I. M., Ivanov Y. A., Pasternak S. A., Rass T. S., Rossov V. V. Oceanographic research by the Soviet-Cuban marine expedition. Okeanologiya. 6(2): 312-320. (In Russ.).

Berberian G. A., Starr R. B. 1978. The circulation between the Cayman Sea and the Gulf of Mexico as deducted from nutrient distributions. CICAR-II Symp. Progress in Marine Research in the Caribbean and Adjacent Regions. FAO Fisheries Report 200 (Suppl.). Rome: 255-266.

Bessonov N. M., Elizarov E. A., Gonzalez O. 1971. The main features of formation of oceanological conditions on the Bank of Campeche in relation to the distribution and concentration of commercial organisms. Soviet-Cuban Fishery Research (VNIRO-CIP), 3. Moscow: 14-32. (In Russ.).

Bessonov N. M., González O. 1971. About the causes of changes in productivity of waters in the Gulf of Mexico. Soviet-Cuban Fishery Research (VNIRO-CIP), 3. Moscow: 54-63. (In Russ.).

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Bogdanov D. V., Sokolov V. A., Khromov N. S. 1968. Regions of high biological and commercial productivity in the Gulf of Mexico and the Caribbean Sea. Okeanolo-giya. 8(3): 466-478. (In Russ.).

Bulanienkov S. K., García-Díaz C. 1975. Influencia de los procesos atmosféricos en el afloramiento del Banco de Campeche. Rev. Invest. INP. 1(2): 99-140.

Cochrane J. D. 1966. The Yucatan Current, upwelling off Northeastern Yucatan, and currents and waters of Western Equatorial Atlantic. Oceanography of the Gulf of Mexico. Progress Rep. TAMURef. No. 66-23T: 14-32.

Cochrane J. D. 1968. Currents and waters of the eastern Gulf of Mexico and western Caribbean, of the western tropical Atlantic Ocean, and of the eastern tropical Pacific Ocean. Dep. Oceanogr. Meteorol., Texas A&M Univ. Ref. 68-8T: 19-28 (unpublished report).

Cochrane J. D. 1969. Water and circulation on Bank of Campeche in May. Bull. Jap. Soc. Fish. Oceanogr. Spec. No. (Prof. Uda's Commemorative Papers): 123-128.

Cruz A. 1971. Estudios de plancton en el Banco de Campeche. Coloquio sobre investigaciones y recursos del mar Caribe y regiones adyacentes. UNESCO: 375-383.

El-Sayed S. Z., Sackett W. M., Jeffrey L. M., Fredericks A. D., Saunders R. P., Conger P. S., Fryxell G. A., Steidinger K. A., Earl S. A. 1972. Chemistry, primary productivity and benthic algae of the Gulf of Mexico. Amer. Geogr. Soc. Ser. Mar. Environm. 22: 1-29.

Enríquez C. E., Mariño-Tapia I. 2014. Mechanisms driving a coastal dynamic upwelling. Proc. Physics of Estuaries and Coastal Seas (PECS) Conf., Porto de Galinhas, Pernambruco, Brazil, 19-24 October 2014: 5 p.

Enríquez C. E., Mariño-Tapia I., Herrera-Silveira J. A. 2010. Dispersion in the Yucatan coastal zone: Implications for red tide events. Continental Shelf Res. 30: 127-137.

Espinosa L. T. 1989. Biomasa fitoplanctónica y afloramiento en el Caribe mexicano y la porción oriental del Banco de Campeche. Tesis de Licenciatura. ENEP-Iztacala, UNAM, México, D.F., México: 121 p.

Flores-Tellez L., Villa-Aguilar V. 1984. Estimación de la productividad primaria en la plataforma de la Península de Yucatán (julio de 1984). Invest. Ocean. F Q. (Secretaría de Marina, México). 3(3): 156-194.

Fukase S. 1967. Distribution of diatoms in relation to hydrographical conditions in the Gulf of Mexico in the late summer of1965. Unpub. Rep. Texas A&M Univ. College Station: 45 p.

Furnas M. J., Smayda T. J. 1987. Inputs of subthermocline waters and nitrate onto the Bank of Campeche. Continental Shelf Res. 7(2): 161-175.

Hasle G. R. 1978. The inverted-microscope method. Phytoplankton manual. Monographs on Oceanographic Methodology. Vol. 6. UNESCO, Paris: 88-96.

Hulburt E. M., Corwin N. 1972. A note on the phytoplankton distribution in the offshore water of the eastern and central Gulf of Mexico. Caribbean J. Sci. 12: 29-38.

Khromov N. S. 1965. Distribution of plankton in the Gulf of Mexico and some features of the seasonal dynamics. Soviet-Cuban Fishery Research (VNIRO-CIP). Vol. 2. Moscow: 47-69. (In Russ.).

Krayesky D. M., Meave del Castillo E., Zamudio E., Norris J. N., Fredericq S. 2009. Diatoms (Bacillariophyta) of the Gulf of Mexico. Gulf of Mexico origin, waters, and biota. Vol. 1. Biodiversity. Harte Research Institute for Gulf of Mexico Studies Ser. Texas A&M Univ. Press, Corpus Christi (TX): 155-185.

Krylov V. V. 1974. On planktonic biocoenoses in the Bank of Campeche area. Soviet-Cuban Fishery Research. Vol. 4. Moscow: 94-116. (In Russ.).

Lebour M. 1925. The dinoflagellates of northern seas. The Marine Biological Association of the United Kingdom, Plymouth: 250 p.

Licea S., Zamudio-Resendiz M. E., Luna R., Soto J. 2004a. Free-living dinoflagellates in the southern Gulf of Mexico: report of data (1979-2002). Phycol. Res. 52: 419-423.

Licea S., Zamudio M. E., Luna R., Okolodkov Y. B., Gómez-Aguirre S. 2004b. Toxic and harmful dinoflagellates in the southern Gulf of Mexico. Harmful Algae 2002. Xth Intern. Conf., St. Pete Beach, Florida, USA, October 21-25, 2002. Florida Fish and Wildlife Conservation Commission, Florida Institute of Oceanography, and Intergovernmental Oceanographic Commission of UNESCO: 380-382.

Licea S., Zamudio M. E., Moreno-Ruiz J. L., Luna R. 2011. A suggested local regions in the Southern Gulf of Mexico using a diatom database (1979-2002) and oceanic hidrographic features. J. Environm. Biol. 32: 443-453.

Licea S., Moreno-Ruiz J. L., Luna R. 2016. Checklist of diatoms (Bacillariophyceae) from the southern Gulf of Mexico: data-base (1979-2010) and new records. J. Biodivers. Endang. Spec. 4: 174. doi: 10.4172/2332-2543.1000174

López-Baluja L., Zernova V. V., Semina H. J. 1992. Fitoplankton prikubinskikh vod i Meksikanskogo zaliva [Phytoplankton of Cuban waters and the Gulf of Mexico]. Moscow: 214 p. (In Russ.).

Luna R. 1981. Algunos aspectos del fitoplancton de la plataforma continental de Yucatán (7-12 de junio, 1979). Tesis de Licenciatura. Fac. Ci., UNAM, México, D. F., México: 18 p.

Mariño-Tapia I., Enríquez C. E., Reyes-Mendoza O., Herrera-Silveira J. 2014. On the dynamics of upwelling events in the Yucatan Shelf using in situ observations. Proc. 17th Physics of Estuaries and Coastal Seas (PECS) Conf., Porto de Galinhas, Per-nambruco, Brazil, 19-24 October 2014: 5 p.

Merino M. 1992. Afloramiento en la Plataforma de Yucatán: estructura y fertilización. Doct. Diss. Unidad Acad. Ciclos Prof. Posgrado Colegio Cienc. Humanidades, UNAM, México, D. F., México: 285 p.

Merino M. 1997. Upwelling on the Yucatan Shelf: hydrographic evidence. J. Mar. Systems. 13: 101-121.

Merino M., Otero L. 1991. Atlas ambiental costero, Puerto Morelos-Quintana Roo. Centro de Investigaciones de Quintana Roo, Chetumal, Quintana Roo, México: 80 p.

Merino M., Czitrom S., Jordan E., Martín E., Thomé E., Moreno O. 1990. Hydrology and rain flushing of the Nichupté Lagoon System, Cancum, México. Estuarine Coastal Shelf Sci. 30: 223-237.

Merino-Virgilio F. del C., Herrera-Silveira J. A., Okolodkov Y. B., Steidinger K. A. 2012. Karenia blooms in Gulf of Mexico. Harmful Algae News. 46: 8.

Merino-Virgilio F. del C., Okolodkov Y. B., Aguilar-Trujillo A. C., Herrera-Silvei-ra J. A. 2013. Phytoplankton of the northern coastal and shelf waters of the Yucatan Peninsula, southeastern Gulf of Mexico, Mexico. Check List. 9(4): 771-779.

Merino-Virgilio F. del C., Okolodkov Y. B., Aguilar-Trujillo A. C., Osorio-Moreno I., Herrera-Silveira J. A.. 2014a. Florecimientos algales nocivos en las aguas costeras del norte de Yucatán (2001-2013). Golfo de México. Contaminación, impacto ambiental, diagnóstico y tendencias. 3a ed. UAC, UNAM-ICMYL, CINVESTAV-Unidad Mérida: 161-180.

Merino-Virgilio F. del C., Okolodkov Y. B., Aguilar-Trujillo A. C., Osorio-Moreno I., Ector L., Herrera-Silveira J. A. 2014b. Florecimientos de Cylindrotheca closterium (Bacillariophyceae) en el norte de Yucatán (2001-2014). Res. XXI Congr. Nac. Ci. Tecn. Mar, Isla Cozumel, Quintana Roo, México, 8 al 11 de octubre de 2014: 10 p.

Núñez-Vázquez E. J., Ramírez-Camarena C., Poot-Delgado C. A., Almazán-Becerril A., Aké-Castillo J. A., Pérez-Morales A., Hernández-Sandoval F. E., Fernández-Herrera L. J., Heredia-Tapia A., Band-Schmidt C., Bustillos-Guzmán J., López-Cortés D. J., Domínguez-Solis G., Ley-Martínez T. C., Cauich-Sánchez Y. R., Barra-González L. A. 2016. Toxinas marinas en el Golfo de México: orígenes e impactos. Florecimientos algales nocivos en México. CICESE, Ensenada, México: 308-321.

Okolodkov Y. B. 2003. A review of Russian plankton research in the Gulf of Mexico and the Caribbean Sea in the 1960-1980s. Hidrobiológica. 13(3): 207-221.

Okolodkov Y. B., Merino-Virgilio F. del C., Aguilar-Trujillo A. C., Osorio-Moreno I., Herrera-Silveira J. A. 2014. The genus Scrippsiella (Dinoflagellata) in coastal waters of the northern Yucatan Peninsula, SE Gulf of Mexico. Bol. Soc. Mex. Ficol. Soc. Ficol. Amér. Lat. Caribe. 4: 21-32.

Reyes-Mendoza O., Mariño-Tapia I., Herrera-Silveira J., Ruiz-Martínez G., Enríquez C., Largier J. L. 2016. The effects of wind on upwelling off Cabo Catoche. J. Coastal Res. 32(3): 638-650.

Roujiyaynen M. I., Georgieva L. V., Senichkina L. G. 1968. Composition, quantitative development and distribution of phytoplankton in the Central-American seas. Studies on the Central-American seas. Vol. 2. Kiev: 14-39. (In Russ.).

Ruíz-Rentería F. G. 1979. Upwelling north of the Yucatan Peninsula. M. Sci. Thesis. Dept. Oceanography, Texas A&M Univ., Texas: 85 p.

Sánchez-Velasco L., Flores-Coto C. 1994. Larval assemblages at the Yucatan shelf and the Mexican Caribbean Sea during the upwelling period (spring, 1985). Ciencia Marina. 58(4): 289-297.

Smayda T. J. 1976. Plankton processes in mid-Atlantic near-shore and shelf waters and energy-related activities. Effects of energy-related activities on the Atlantic Continental Shelf Proc. Conf. Brookhaven National Laboratory. BNL: 70-94.

Sokolova L. B. 1965. Distribution and biological characteristics of main commercial fishes at the Bank of Campeche. Soviet-Cuban Fishery Research (VNIRO-CIP). Moscow. (In Russ.; cited after Bessonov, González, 1971).

Steidinger K. A., Faust A. M., Hernández-Becerril D. U. 2009. Dinoflagellates (Di-noflagellata) of the Gulf of Mexico. Gulf of Mexico origin, waters, and biota. Vol. 1. Biodiversity. Harte Research Institute for Gulf of Mexico Studies Ser. Texas A&M Univ. Press, Corpus Christi (TX): 131-154.

Taylor F. J. R. 1978. Dinoflagellates. Phytoplankton manual. Monographs on Oceanographic Methodology. Vol. 6. UNESCO, Paris: 143-147.

Teixeira C. 1963. Relative rates of photosynthesis and standing stock of net phytoplankton and nannoplankton. Bol. Inst. Oceanogr. (Sao Paulo). 13: 53-60.

Torres-Galván J. P. 1986. Acerca de la distribución vertical del fitoplancton frente a Cabo Catoche: un ciclo nictemeral en abril de 1983. Tesis de Licenciatura. Fac. Ci., UNAM, México, D.F., México: 51 p.

Vasiliev G. D., Torin Y. A. 1965. Oceanographic and commercial-biological characteristics of the Gulf of Mexico and the Caribbean Sea. Soviet-Cuban fishery research (VNIRO-CIP). Vol. 1. Moscow: 241-266. (In Russ.).

Vinogradova L. A. 1976. Influence of upwelling on the development of phytoplankton in the area of the Bank of Campeche. TrudyAtlantNIRO. 63: 81-89. (In Russ.).

Yentsch C. S., Menzel D. W. 1963. A method for the determination of phytoplankton chlorophyll-a and phaeophytin by fluorescence. Deep-Sea Res. 10: 221-231.

Zavala-Hidalgo J., Gallegos-García A., Martínez-López B., Morey S. L., O'Brien J. J. 2006. Seasonal upwelling on the western and southern shelves of the Gulf of Mexico. Ocean Dynamics. 56: 333-338.

Zernova V. V. 1969. The horizontal distribution of phytoplankton in the Gulf of Mexico. Okeanologiya. 9(4): 695-706. (In Russ.).

Zernova V. V. 1970. About planktonic algae of the Gulf of Mexico and the Caribbean Sea. Okeanologicheskie issledovaniya. 20: 69-104. (In Russ.).

Zernova V. V. 1974. Species structure of the phytocene in the southern Gulf of Mexico. Soviet-Cuban Fishery Research (VNIRO-CIP). Vol. 4. Moscow: 117-131. (In Russ.).

Zernova V. V. 1982. On the dependence of the quantitative development of phytoplankton on the abiotic factors in the Gulf of Mexico. Trudy Inst. Okeanol. Akad. Nauk SSSR. 114: 60-72. (In Russ.).

Zernova V. V., Zhitina L. S. 1985. About the phytoplankton community of the American Mediterranean Sea. Issledovaniya okeanicheskogo fitoplanktona [Studies on the oceanic phytoplankton]. Moscow: 27-36. (In Russ.).

Литература

Aké-Castillo J. A., Okolodkov Y. B., Espinosa-Matías S., Merino-Virgilio F. del C., Herrera-Silveira J. A., Ector L. 2012. Cyclotella marina (Tanimura, Nagumo et Kato) Aké-Castillo, Okolodkov et Ector comb. et stat. nov. (Thalassiosiraceae): a bloom-forming diatom in the southeastern Gulf of Mexico. Nova Hedwigia Beih. 141: 263-274.

Aké-Castillo J. A., Poot-Delgado C. A. 2016. FAN en el Golfo de México: panorama general sobre eventos y especies. Florecimientos algales nocivos en México. CICESE, Ensenada, México: 298-307.

Badan A., Candela J., Sheinbaum J., Ochoa J. 2005. Upper-layer circulation in the approaches to Yucatan Channel. Circulation in the Gulf of Mexico. Observations and models. AGU Books Board, Geophysical Monograph 161. Washington: 57-69.

Bates S. S., Bird C. J., de Freitas A. S. W., Foxall R., Gilgan M., Hanic L. A., Johnson G. R., McCulloch A. W., Odense P., Pocklington R., Quilliam M. A., Sim P. G., Smith J. C. 1989. Pennate diatom Nitzschia pungens as the primary source of domoic acid, a toxin in shellfish from eastern Prince Edward Island, Canada. Ca-nad. J. Fish. Aquat. Sci. 46: 1203-1215.

[Belousov et al.] Белоусов И. М., Иванов Ю. А., Пастернак С. А., Расс Т. С., Россов В. В. 1966. Океанологические исследования Советско-кубинской морской экспедиции. Океанология. 6(2): 312-320.

Berberian G. A., Starr R. B. 1978. The circulation between the Cayman Sea and the Gulf of Mexico as deducted from nutrient distributions. CICAR-II Symp. Progress in Marine Research in the Caribbean and Adjacent Regions. FAO Fisheries Report 200 (Suppl.). Rome: 255-266.

[Bessonov et al.] Бессонов Н. М., Елизаров Е. А., Гонсалес О. 1971. Основные черты формирования океанологических условий на банке Кампече в связи с распределением и концентрацией промысловых организмов. Советско-кубинские рыбохозяйственные исследования (ВНИРО-ЦРИ), 3. М.: 14-32.

[Bessonov, González] Бессонов Н. М., Гонсалес О. 1971. О причинах изменений продуктивности вод Мексиканского залива. Советско-кубинские рыбохозяй-ственные исследования (ВНИРО-ЦРИ), 3. М.: 54-63.

[Bogdanov et al.] Богданов Д. В., Соколов В. А., Хромов Н. С. 1968. Районы высокой биологической продуктивности в Мексиканском заливе и Карибском море. Океанология. 8(3): 466-478.

Bulanienkov S. K., García-Díaz C. 1975. Influencia de los procesos atmosféricos en el afloramiento del Banco de Campeche. Rev. Invest. INP. 1(2): 99-140.

Cochrane J. D. 1966. The Yucatan Current, upwelling off Northeastern Yucatan, and currents and waters of Western Equatorial Atlantic. Oceanography of the Gulf of Mexico. Progress Rep. TAMURef. No. 66-23T: 14-32.

Cochrane J. D. 1968. Currents and waters of the eastern Gulf of Mexico and western Caribbean, of the western tropical Atlantic Ocean, and of the eastern tropical Pacific Ocean. Dep. Oceanogr. Meteorol., Texas A&M Univ. Ref. 68-8T (unpublished report): 19-28.

Cochrane J. D. 1969. Water and circulation on Bank of Campeche in May. Bull. Jap. Soc. Fish. Oceanogr. Spec. No. (Prof. Uda's Commemorative Papers): 123-128.

Cruz A. 1971. Estudios de plancton en el Banco de Campeche. Coloquio sobre investigaciones y recursos del mar Caribe y regiones adyacentes. UNESCO: 375-383.

El-Sayed S. Z., Sackett W. M., Jeffrey L. M., Fredericks A. D., Saunders R. P., Conger P. S., Fryxell G. A., Steidinger K. A., Earl S. A. 1972. Chemistry, primary productivity and benthic algae of the Gulf of Mexico. Amer. Geogr. Soc. Ser. Mar. Environm. 22: 1-29.

Enríquez C. E., Mariño-Tapia I. 2014. Mechanisms driving a coastal dynamic upwelling. Proc. Physics of Estuaries and Coastal Seas (PECS) Conf., Porto de Galinhas, Pernambruco, Brazil, 19-24 October 2014: 5 p.

Enríquez C. E., Mariño-Tapia I., Herrera-Silveira J. A. 2010. Dispersion in the Yucatan coastal zone: Implications for red tide events. Continental Shelf Res. 30: 127-137.

Espinosa L. T. 1989. Biomasa fitoplanctónica y afloramiento en el Caribe mexicano y la porción oriental del Banco de Campeche. Tesis de Licenciatura. ENEP-Iztacala, UNAM, México, D. F., México: 121 p.

Flores-Tellez L., Villa-Aguilar V. 1984. Estimación de la productividad primaria en la plataforma de la Península de Yucatán (julio de 1984). Invest. Ocean. F Q. (Secretaría de Marina, México). 3(3): 156-194.

Fukase S. 1967. Distribution of diatoms in relation to hydrographical conditions in the Gulf of Mexico in the late summer of 1965. Unpub. Rep. Texas A&M University College Station: 45 p.

Furnas M. J., Smayda T. J. 1987. Inputs of subthermocline waters and nitrate onto the Bank of Campeche. Continental Shelf Res. 7(2): 161-175.

Hasle G. R. 1978. The inverted-microscope method. Phytoplankton manual. Monographs on Oceanographic Methodology. Vol. 6. UNESCO, Paris: 88-96.

Hulburt E. M., Corwin N. 1972. A note on the phytoplankton distribution in the offshore water of the eastern and central Gulf of Mexico. Caribbean J. Sci. 12: 29-38.

[Khromov] Хромов Н. С. 1965. Распределение планктона в Мексиканском заливе и некоторые черты его сезонной динамики. Советско-кубинские рыбохозяй-ственные исследования (ВНИРО-ЦРИ). Т. 2. М.: 47-69.

Krayesky D. M., Meave del Castillo E., Zamudio E., Norris J. N., Fredericq S. 2009. Diatoms (Bacillariophyta) of the Gulf of Mexico. Gulf of Mexico origin, waters, and biota. Vol. 1. Biodiversity. Harte Research Institute for Gulf of Mexico Studies Ser. Texas A&M Univ. Press, Corpus Christi (TX): 155-185.

[Krylov] Крылов В. В. 1974. О планктонных биоценозах в районе банки Кампече. Советско-кубuнскue рыбохозяйственные исследования (ВНИРО-ЦРИ). Т. 4. М.: 94-116.

Lebour M. 1925. The dinoflagellates of northern seas. The Marine Biological Association of the United Kingdom, Plymouth: 250 p.

Licea S., Zamudio-Resendiz M. E., Luna R., Soto J. 2004a. Free-living dinoflagellates in the southern Gulf of Mexico: report of data (1979-2002). Phycol. Res. 52: 419-423.

Licea S., Zamudio M. E., Luna R., Okolodkov Y. B., Gómez-Aguirre S. 2004b. Toxic and harmful dinoflagellates in the southern Gulf of Mexico. Harmful Algae 2002. Xth Intern. Conf, St. Pete Beach, Florida, USA, October 21-25, 2002. Florida Fish and Wildlife Conservation Commission, Florida Institute of Oceanography, and Intergovernmental Oceanographic Commission of UNESCO: 380-382.

Lice S., Zamudio M. E., Moreno-Ruiz J. L., Luna R. 2011. A suggested local regions in the Southern Gulf of Mexico using a diatom database (1979-2002) and oceanic hidrographic features. J. Environm. Biol. 32: 443-453.

Licea S., Moreno-Ruiz J. L., Luna R. 2016. Checklist of diatoms (Bacillariophyceae) from the southern Gulf of Mexico: data-base (1979-2010) and new records. J. Biodivers. Endang. Spec. 4: 174. doi: 10.4172/2332-2543.1000174

[López-Baluja et al.] Лопес-Балуха Л., Зернова В. В., Сёмина Г. И. 1992. Фитопланктон прикубинских вод и Мексиканского залива. М.: 214 c.