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New records of planktonic dinoflagellates (Dinophyceae) from the Mexican Pacific Ocean

Authors:
  • Instituto de Ciencias del Mar y Limnología, UNAM, México

Abstract

Phytoplankton samples were taken during several oceanographic cruises in the Mexican Pacific Ocean (1998–2000), following three different protocols of collection and analysis, and from the material we report six new records of planktonic dinoflagellates in the region. Two species, Asterodinium spinosum and Brachydinium capitatum, are unarmored, another species, Actiniscus pentasterias, has internal siliceous skeletons, whereas Thoracosphaera heimii usually develops a calcareous coccoid vegetative stage. Calciodinellum operosum produces calcareous cysts that were also found in this study, and Achradina pulchra has an internal skeleton of organic material. Three species, A. spinosum, B. capitatum and C. operosum, were represented by very few specimens, whereas all others were more frequent. Brief descriptions and illustrations of these species by light and scanning electron microscopy are provided. The methods and techniques to study this group have been diverse and useful in finding a greater diversity. The world distribution of the species recorded here is revised.
Botanica Marina 47 (2004): 417–423 2004 by Walter de Gruyter Berlin New York. DOI 10.1515/BOT.2004.051
New records of planktonic dinoflagellates (Dinophyceae)
from the Mexican Pacific Ocean
David U. Herna´ ndez-Becerril* and Ernesto
Bravo-Sierra
Laboratorio de Diversidad y Ecologı´a del Fitoplancton
Marino, Instituto de Ciencias del Mar y Limnologı´a,
Universidad Nacional Auto´ noma de Me´ xico (UNAM),
Apdo. postal 70-305, Me´ xico, D.F. 04510 Mexico,
e-mail: dhernand@mar.icmyl.unam.mx
*Corresponding author
Abstract
Phytoplankton samples were taken during several ocean-
ographic cruises in the Mexican Pacific Ocean
(1998–2000), following three different protocols of collec-
tion and analysis, and from the material we report six new
records of planktonic dinoflagellates in the region. Two
species, Asterodinium spinosum and Brachydinium capi-
tatum, are unarmored, another species, Actiniscus pen-
tasterias, has internal siliceous skeletons, whereas
Thoracosphaera heimii usually develops a calcareous
coccoid vegetative stage. Calciodinellum operosum pro-
duces calcareous cysts that were also found in this
study, and Achradina pulchra has an internal skeleton of
organic material. Three species, A. spinosum,B. capita-
tum and C. operosum, were represented by very few
specimens, whereas all others were more frequent. Brief
descriptions and illustrations of these species by light
and scanning electron microscopy are provided. The
methods and techniques to study this group have been
diverse and useful in finding a greater diversity. The world
distribution of the species recorded here is revised.
Keywords: dinoflagellates; Mexican Pacific Ocean; new
records; phytoplankton.
Introduction
Dinoflagellates (Class Dinophyceae) belong to a very
diverse and heterogeneous microalgal group, which is
very important in the marine phytoplankton. These algae
(together with diatoms), contribute significantly to both
the biomass and productivity of coastal pelagic systems.
The number of extant species of marine phytoplankton
is around 1880 (Sournia 1986, Sournia et al. 1991) or
approximately 2000 (Taylor 1987, Steidinger and Tangen
1997).
In the Mexican Pacific Ocean, dinoflagellates have
been studied from floristic and taxonomic points of view,
beginning with early work of Kofoid (1907); subsequently,
in adjacent waters Kofoid studied and described many
dinoflagellates. Later, Allen (1941) recorded the plank-
tonic dinoflagellates from southern California. There are
further reports from Osorio-Tafall (1942), Herna´ ndez-
Becerril (1988a,b,c, 1989, 1991, 1992) and Licea et al.
(1995), who carried out studies in more tropical waters
(i.e., Gulf of California, Acapulco, Gulf of Tehuantepec).
These studies have concentrated mostly on the
armored (or thecate) fraction of dinoflagellates, whose
external structures preserve well using even collection
methods such as nets or bottles and routine preserva-
tives (Lugol’s solution or formalin). The unarmored (or
naked) dinoflagellates have been less studied, and their
contribution to phytoplankton productivity may have
been underestimated. Other dinoflagellates with internal
skeletons or producing calcareous stages have not been
reported in Mexican waters so far, although a recent
paper contributed to our knowledge of dinoflagellate
cysts in the Gulf of California (Mexican Pacific Ocean)
(Morquecho and Lechuga-Deve´ ze 2003).
Despite continuing investigations of phytoplankton col-
lected off the Mexican Pacific coast, important areas still
remain unstudied, among them the so-called Tropical
Mexican Pacific Ocean, which may prove to be species-
rich. Our analysis of phytoplankton, obtained and studied
following different protocols, from various oceanographic
cruises carried out recently off the Pacific coast of Mex-
ico, has revealed several interesting dinoflagellate spe-
cies that are new records for the country.
Materials and methods
Between 1998 and 2000 samples were taken following
three different protocols:
1. Samples collected off the coast of Michoacan (9–10
April, 1999) by net (54 mm mesh), in vertical hauls
from 100 m to surface, fixed with 4% formalin (Table
1, Figure 1). Some forms smaller than the net mesh
size were found, probably because of clogging of the
net.
2. Bottle samples (generally 5 l) were taken off the coast
of Baja California (5–14 December, 1998), at surface
(1–1.5 m), and filtered (filters 1.2 mm) by gravity (Table
1, Figure 1). Before the complete filtration, 10–20 ml
of the concentrated material were divided into: (a) a
reference sample fixed with Lugol’s solution and glu-
taraldehyde (Østergaard 1998), (b) material for obser-
vation in vivo by light microscopy, and (c) an inoculum
for establishing culture-isolations of single cells by the
dilution method (Throndsen 1997).
3. Bottle samples (4 l) were taken from several fixed
stations off the coast of Baja California (20 March–1
April, 1998) and the Gulf of Tehuantepec (8–15 April,
2000), at three different depths (5, 25, 50 m), and were
filtered (filters 0.45 mm) with a vacuum pump
418 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Table 1 New records of dinoflagellates from the Mexican Pacific Ocean, with locations (Figure 1) and study protocols used.
Species Localities Protocol
Achradina pulchra Lohmann 4 Tehuantepec 3
Actiniscus pentasterias (Ehrenberg) Ehrenberg 1, 2, 4 BC and Tehuantepec 1, 3
Asterodinium spinosum Sournia 3 Michoacan 1
Brachydinium capitatum Taylor 2 BC 2
Calciodinellum operosum Deflandre emend. Montresor 4 Tehuantepec 3
Thoracosphaera heimii (Lohmann) Kamptner 1, 2, 4 BC and Tehuantepec 3
BCsBaja California.
(Bollmann et al. 2002), and then were rinsed with dis-
tilled water (Table 1, Figure 1).
Material was studied directly from the net samples, the
filtered and fixed samples, and the filters by light micro-
scopy (LM) in fresh mounts. Observations by scanning
electron microscopy (SEM) were also made, using mate-
rial treated conventionally (mounted, air-dried and coated
with gold). A Zeiss (Mexico City, Mexico) Axiolab light
microscope (bright field and phase contrast, with
attached camera -Contax 167 MT wTokyo, Japanx) and a
JEOL 1200 EX scanning electron microscope (Tokyo,
Japan) were used for our observations.
Terminology and systematics follow recent proposals
by Fensome et al. (1993) and Steidinger and Tangen
(1997).
Results
We identified 6 species of dinoflagellates, which are brief-
ly described and illustrated by LM and/or SEM. Some
relevant references are annotated for each species and
conspicuous synonyms are also provided. Table 1 pro-
vides the complete species list.
Systematic account of Actiniscus pentasterias
(Ehrenberg) Ehrenberg (Figures 2–4)
Division Dinoflagellata (Bu¨ tschli) Fensome et al.; Subdi-
vision Dinokaryota Fensome et al.; Class Dinophyceae
Pascher; Subclass Gymnodiniphycidae Fensome et al.;
Order Gymnodiniales Apstein; Suborder Actiniscineae
(Sournia) Fensome et al.
Family Actiniscaceae Ku¨ tzing; Genus Actiniscus
Ehrenberg; Actiniscus pentasterias (Ehrenberg) Ehren-
berg. – Schiller 1937, p. 2, figs 1 a–d (as Gymnaster pen-
tasterias Schu¨ tt); Bursa 1969, p. 412, figs 1– 14;
Steidinger and Williams 1970, p. 42, pl. 1, figs 1a–b; Orr
and Conley 1976, p. 92, pl. 1, figs 1–11, pl. 2, figs 1–6;
Balech 1988, p. 199, pl. 82, figs 22, 23; Larsen and Sour-
nia 1991, p. 320, fig. 21.30; Hansen and Larsen 1992, p.
90, figs. 4.46 a–c; Hansen 1993, p. 486, figs 1–5; Stei-
dinger and Tangen 1997, p. 428, pl. 24; Konovalova
1998, p. 81, figs 19.6 a–v; Be´ rard-Therriault et al. 1999,
p. 163, pl. 81 e–g, i.
The specimens encountered here agree well with all
previous descriptions. Whole cells were undetected and
only specimens showing the internal, siliceous skeleton
were found. Many authors have confirmed absence of
chloroplasts in this species (Larsen and Sournia 1991,
Hansen 1993). Dimensions: maximum diameter of skel-
etons ranged between 23–28 mm.
Distribution: specimens were found at various loca-
tions, including the coasts of Baja California and the Gulf
of Tehuantepec (localities 1, 2, 4; Figure 1). The species
was relatively frequent, hence we suggest that its distri-
bution is wide in the Mexican Pacific Ocean.
Systematic account of Achradina pulchra Lohmann
(Figures 5–8)
Order Ptychodiscales Fensome et al.; Family Amphitho-
laceae Poche; Genus Achradina Lohmann; Achradina
pulchra Lohmann. – Schiller 1937, p. 5, figs 2 a– c; Nival
1969, p. 126, figs 1–11, pl. 1, figs 1–10, pl. 2, figs 1–12;
Larsen and Sournia 1991, p. 314, fig. 21.28; Konovalova
1998, p. 82, figs 19.5 a–b.
Specimens found had no cytoplasm. The internal skel-
etons have a general oblong shape, with a constriction
in the middle. Most of the skeleton is run by longitudinal
ridges formed by large granule-like structures, and also
has a complex pattern of smaller granules in a zig-zag
pattern. The apical hemisphere has a pointed crest which
is smooth, with four slit-like openings radiating to the
margin. Below this crest, there are two larger, ovoid
openings. The antapical end presents a hexagonal or
heptagonal pattern of granules, which are larger at the
angles and center of this pattern. The dorsal view shows
an archeopyle, a large opening. This species is consid-
ered to be non-photosynthetic. Dimensions: total length
29–36.5 mm, width 18–21 mm.
Distribution: many specimens of this species were
detected in the Gulf of Tehuantepec (locality 4; Figure 1).
Systematic account of Asterodinium spinosum
Sournia (Figure 9)
Family Brachidiniaceae Sournia; Genus Asterodinium
Sournia; Asterodinium spinosum Sournia. – Sournia
1972, p. 152, fig. 5; Abboud-Abi-Saab 1989, p. 12, fig.
5a; Go´ mez and Claustre 2003, fig. 2 a (as Asterodinium
gracile Sournia).
The cells are solitary and delicate, of small size. The
shape is star-like, with the body very reduced and with
five straight or slightly curved arms or processes. The
apical arm is longer, straight and truncate, the lateral
arms are thin and delicate, with pointed ends, whereas
the posterior arms are slightly shorter and more robust:
the left posterior arm bears the prominent nucleus. The
cingulum is inconspicuous. There are several oblong and
discoid chloroplasts throughout the cell. Dimensions:
total length 22–24 mm, width (maximum separation of
lateral arms) 26–28 mm, length of apical arm 11.5 mm.
D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico 419
Figure 1 Map of the Mexican Pacific Ocean showing sampling locations.
1sBaja California (Ensenada), 2sBaja California (Bahia Magdalena), 3sMichoacan (La´ zaro Cardenas), 4sGulf of Tehuantepec.
Figures 2–4 Actiniscus pentasterias: LM, SEM.
(2) Apical view of a typical internal skeleton with 5 arms and ornamentation in ridges, SEM. (3) Another internal skeleton of a specimen,
LM. (4) Two skeletons in apical and lateral view showing surface morphology, SEM. Scale barss5mm (Figures 2, 4); 15 mm (Figure
3).
Distribution: species occurring on the coasts of
Michoacan (locality 3; Figure 1), with only two specimens
found.
Systematic account of Brachydinium capitatum
Taylor (Figures 10, 11)
Genus Brachydinium Taylor; Brachydinium capitatum
Taylor. – Taylor 1963, p. 75, pl. VIII, figs 1–3; Le´ ger 1972,
p. 29, fig.14; Sournia 1972, p. 152, figs 2, 6; Sournia et
al. 1979, p. 193, fig. 39; Abboud-Abi-Saab 1989, p. 12,
fig. 4b; Steidinger and Tangen 1997, p. 428, pl. 24.
The cells appeared solitary, delicate, of medium size.
The cells are asymmetric, with no general shape, four
relatively long, curved or more straight arms (or process-
es), which arise from the body. There is an apical pro-
tuberance, eccentric, slightly displaced to the right, and
an indentation is present between the two lateral arms
and this protuberance; this indentation represents the
cingulum. The lateral arms are longer than the posterior
arms, tapering toward the tip, which is pointed. The pos-
terior arms are almost symmetric, with the right slightly
shorter than the left. The nucleus is parietal, displaced to
the right of the body. Numerous chloroplasts throughout
the cell. Dimensions: total length 48–50 mm, width (max-
imum separation of lateral arms) 107–110 mm, maximum
length of posterior arms 37 mm.
Distribution: species found in Baja California (locality
2; Figure 1), very rare.
Systematic account of Calciodinellum operosum
Deflandre emend. Montresor (Figure 12)
Subclass Peridiniphycidae Fensome et al.; Order
Peridiniales Haeckel; Suborder Peridiniineae; Family
Peridiniaceae Ehrenberg; Subfamily Calciodinelloideae
Fensome et al.; Genus Calciodinellum Deflandre; Calcio-
dinellum operosum Deflandre emend. Montresor. – Mon-
tresor et al. 1997, p. 123, figs 10–13, 19; Williams et al.
1998, p. 86; D’Onofrio et al. 1999, p. 1066, figs 14–16;
Sgrosso et al. 2001, p. 81.
In our samples only calcareous cysts were encoun-
tered. The cysts show an arrangement of paraplates and
a conspicuous apical pore. There are four paraplates sur-
420 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Figures 5–8 Achradina pulchra: SEM.
(5) Ventral view of an internal skeleton showing surface ornamentation and the apical crest with four openings. (6) Dorsal view of
another specimen, with the archeopyle. (7) Antapical view of a specimen. (8) Apical view of the skeleton, showing the apical crest.
Scale bars5mm.
rounding the apical pore. Other specimens showed well-
developed paratabulation ridges. The surface of the
cysts appears granular and has scattered pores. Vege-
tative cells are photosynthetic. Dimensions: diameter
29–34 mm.
Distribution: very few cysts found in the Gulf of
Tehuantepec (locality 4; Figure 1).
Systematic account of Thoracosphaera heimii
(Lohmann) Kamptner (Figure 13)
Subclass Prorocentrophycidae Fensome et al.; Order
Thoracosphaerales Tangen; Family Thoracosphaeraceae
Schiller; Genus Thoracosphaera Kamptner; Thoraco-
sphaera heimii (Lohmann) Kamptner. Synonym: Syraco-
sphaera heimii Lohmann. – Inouye and Pienaar 1982, p.
64, figs 1, 2, 24; Tangen et al. 1982, p. 195, pl. I, figs
1–6; Fensome et al. 1993, p. 168, fig. 171; Steidinger and
Tangen, 1997, p. 549; Williams et al. 1998, p. 160.
This species has a particular vegetative form, which is
predominantly a coccoid, calcareous stage, for some
time considered to be a coccolithophorid (Tangen et al.
1982). The cells are spherical and relatively small, with a
large and conspicuous aperture. The surface of the wall
is irregular, covered with granules and perforated by
small pores. The planospore is non-thecate and a Gym-
nodinium-like cell. All live stages possess chloroplasts
(Inouye and Pienaar 1982, Tangen et al. 1982). Dimen-
sions: diameter 10–12 mm, aperture 3–4 mm.
Distribution: occurred in a relatively common manner
in Baja California and the Gulf of Tehuantepec (localities
1, 2, 4; Figure 1).
Discussion
Diversity of planktonic dinoflagellates from the Mexican
Pacific Ocean may be considered relatively high: recent
reviews indicate an approximate number of 350 taxa
(Herna´ ndez-Becerril 2003), and for only the Order Dino-
physiales, the number of taxa is 90 (Herna´ ndez-Becerril
et al. 2003). However, unarmored or naked planktonic
dinoflagellates have generally been underestimated,
ignored or little studied in Mexican waters. This could be
mainly due to the methods traditionally used for collect-
ing and studying dinoflagellates, which deteriorate the
unarmored fraction. Bottle samples, fixed with Lugol’s
solution preserve relatively well most naked dinoflagel-
lates, and concentrated samples from passive filtration
(this study, protocol 2) are ideal for studying naked forms
D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico 421
Figures 9–11 Asterodinium spinosum and Brachydinium capitatum:LM.
(9) A. spinosum, a complete cell in dorsal view, showing the typical star-like shape of the cell, phase contrast. (10, 11) B. capitatum,
a cell in dorsal view, showing four processes and numerous chloroplasts, bright field. (11) Same cell, phase contrast. Scale bars10 mm
(Figure 9); 20 mm (Figures 10, 11).
Figures 12–13 Calciodinellum operosum and Thoracosphaera heimii: SEM.
(12) C. operosum, apical view of a cyst with the apical pore and apical plates. (13) T. heimii, a complete coccoid cell, showing large
aperture and surface granulation. Scale bars5mm.
in vivo, to cultivate them, or to preserve them with a mix-
ture of Lugol’s solution and glutaraldehyde. We found
one unarmored new record, Brachydinium capitatum
(Table 1) following this method, and we are still working
with naked forms that have been cultivated.
There are four possible explanations for finding new
records of planktonic dinoflagellates in the Mexican
Pacific Ocean: (1) some areas still remain unstudied, par-
ticularly in the Tropics, (2) the methods traditionally used
to collect and study phytoplankton have underestimated
the diversity of certain forms, especially the naked frac-
tion, (3) the routine analyses have been made by poorly
trained personnel, who have misidentified or ignored
some species difficult to recognize (due to their size or
shape) or who lack literature to identify species, and (4)
there have been introductions of exotic species into the
area.
Introduction of planktonic species into the Mexican
Pacific waters may only be speculated upon, for medium
to long-term studies or monitoring do not exist for most
regions. However, this fact has been discussed in the
context of increasing events of harmful microalgal
blooms (Hallegraeff 1998).
World distribution of the species recorded here indi-
cates that Achradina pulchra,Actiniscus pentasterias and
Thoracosphaera heimii are forms very widely distributed
in temperate to tropical regions. They may be referred
to as ‘‘cosmopolitan’’, with no certainty of their habitat:
oceanic or neritic, although they appear more in coastal
waters. All locations where we found them are coastal.
The distribution of Calciodinellum operosum is not well
known and it was only detected at the calcareous cyst
stage. It is likely that further collections and studies in
Mexican waters will find the vegetative cell, too.
Actiniscus pentasterias has a considerable fossil rec-
ord (Williams et al. 1998) and all other species found here
with a calcareous external/internal structure have also
been recorded from fossil material (Fensome et al. 1993).
This species is well represented in world waters, and it
may also be considered to be ‘‘cosmopolitan’’.
Two genera of the Family Brachydiniaceae, Asterodi-
nium and Brachydinium, were recently recorded for the
first time from the subtropical (Philippine Sea, Sulu and
East China Seas) and equatorial western Pacific Ocean
(Go´ mez et al. 2003). The species we report herein for the
Mexican Pacific Ocean belong to those genera: Astero-
dinium spinosum and Brachydinium capitatum. There-
fore, we confirm that the two genera are more widely
distributed than previously thought, as they were origi-
nally described for Indian Ocean waters (Taylor 1963,
422 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Sournia 1972), and then the species Brachydinium capi-
tatum,Asterodinium gracile Sournia and Asterodinium
libanum Abboud-Abi Saab were reported for the Medi-
terranean Sea (Le´ ger 1972, Go´ mez and Claustre 2003,
respectively). The presence of Asterodinium species may
well be favored by the progressive warming of the Med-
iterranean Sea (Go´ mez and Claustre 2003). The two spe-
cies are unquestionably tropical forms, probably also
neritic, although Sournia et al. (1979) found the species
in a supposedly colder area, still in the Indian Ocean.
Acknowledgements
We are grateful to Drs V. Arenas, C. Robinson, A. Carranza, Ma.
L. Machaı´n for inviting us to participate in the oceanographic
cruises where material was obtained for this study (cruises SIM-
SUP XIV, XVI, SEDIMENTO III and PACMEX III), and to the crew
of R/V ‘‘El Puma’’. F.I. Barbosa collected samples on one cruise,
Y. Hornelas and J. Sepu´ lveda provided assistance with SEM.
Drs M. Faust and D. Marino sent us relevant literature.
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Received 2 December, 2003; accepted 5 August, 2004
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... These morphological differences were based on preserved specimens usually collected during research cruises (e.g. Gómez 2003Gómez , 2006Gómez , 2011Hernandez-Becerril & Bravo-Sierra 2004). ...
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Resumen: Antecedentes y Objetivos: El orden Gymnodiniales está compuesto por 11 familias, 63 géneros y 641 especies taxonómicamente válidas. Estos dinoflagelados se caracterizan por presentar una pared celular muy frágil. Además, algunas especies pueden llegar a producir potentes toxinas e incluso tienen la capacidad para formar grandes florecimientos. Los estudios enfocados en conocer la diversidad de este grupo, en el caso de las costas del Pacífico Mexicano, siguen siendo limitados, a pesar de la importancia económica, social y ecológica de estos microorganismos. Por lo tanto, el objetivo de este estudio fue realizar un listado florístico a partir de una revi-sión bibliográfica, que integre únicamente a los registros respaldados por micrografías, para conocer la diversidad de dinoflagelados atecados del orden Gymnodiniales presentes en el Pacífico Mexicano, con énfasis en aquellos formadores de florecimientos algales nocivos. Métodos: La búsqueda de información se realizó en publicaciones (artículos y capítulos de libros), desde el primer registro (1943) hasta la actualidad (noviembre 2022). Cada registro fue confirmado únicamente mediante la existencia de micrografías ópticas y de electrónicas de barrido. Resultados clave: El Pacífico Mexicano está conformado por 11 estados costeros, donde actualmente se tiene reportada la presencia de 10 familias, 31 géneros y 103 especies (16% del total de las registradas a nivel mundial) para el orden Gymnodiniales. De las 11 familias que conforman a este orden, la familia Gymnodiniaceae agru-pó 29% del total de especies registradas para el Pacífico Mexicano, donde los géneros Gymnodinium y Gyrodinium presentaron el mayor número de especies. Conclusiones: La evidencia presentada en este estudio demostró que existe una baja diversidad para este orden en el Pacífico Mexicano, por lo que es necesario imple-mentar un mayor esfuerzo de muestreo, además de incursionar en diferentes herramientas moleculares que permitan obtener una mejor aproximación a la diversidad alfa en las costas mexicanas. Palabras clave: FAN, Gymnodiniaceae, Gymnodinium, Gyrodinium, herramientas moleculares. Abstract: Background and Aims: The order Gymnodiniales is composed of 11 families, 63 genera and 641 taxonomically valid species. These dinoflagellates are characterized by having a very fragile cell wall. In addition, some species can produce phycotoxins and form dense blooms. In the case of the Mexican Pacific coast, studies focused on knowing the diversity of this group are still limited, despite the economic, social, and ecological importance of these microorganisms. Therefore, the objective of this study was to make a floristic list from a bibliographical review, integrating only the records supported by micrographs, to know the diversity of athecate dinoflagellates of the order Gymnodiniales present in the Mexican Pacific Ocean, with emphasis on those that form harmful algal blooms. Methods: The search for information was carried out in publications (articles and book chapters), from the first record (1943) to the present (November 2022). Each record was confirmed only by the existence of optical and scanning electron micrographs. Key results: The Mexican Pacific is made up of 11 coastal states, where the presence of 10 families, 31 genera and 103 species (which represents 16% of the total number of species recorded worldwide) is currently reported for the order Gymnodiniales. Of the 11 families that make up this order, the Gymnodiniaceae family grouped 29% of the total number of species recorded for the Mexican Pacific, where the genera Gymnodinium and Gyrodinium presented the largest number of species. Conclusions: The evidence presented in this study showed that there is a low diversity for this order in the Mexican Pacific, so it is necessary to implement a greater sampling effort, in addition to venturing into different molecular tools that allow obtaining a better approximation of the diversity in the Mexican coasts.
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We present the inventory of the planktonic algal flora of the Bahia de Acapulco and surrounding marine area, studied through a decade, including an intensive bimonthly sampling study using plankton net, bottle method and the observation of live samples, from February 2010 to February 2011. It recognized 641 taxa, corresponding to eight algal divisions. The most diverse groups were Dinophyta and Bacillariophyta with 347 and 274 taxa, respectively. Photographs of 131 taxa are presented, corresponding to 38 new records for the Mexican Pacific, 34 taxa were not identified at species level, and 59 taxa represent some taxonomic or ecological interest. Species accumulation curves allow to recognize that the species richness observed in the present study represents a good approximation of the planktonic algal flora from the Bahia de Acapulco. However, more detailed studies over phytoflagellates and picoplankton are necessary. A biological characterization of the phytoplankton community was made according to organization level, type of nutrition, life form, potential harmfulness or toxicity, origin (freshwater, brackish or marine), affinity (neritic or oceanic) and distribution (cosmopolitan, cold-temperate or subtropical-tropical). It recognized the common species of the bay and those that have produced blooms. The high species richness of planktonic algal flora observed in Acapulco may reflect a variable trophic status throughout the year, with nutrient limitation at certain times, condition which agrees with the symbiotic relationships found among phaeosomes (cyanophytes), dinoflagellates and diatoms. However, some species indicative of pollution such as Euglena pascheri, Phaeocystis sp. and the presence of the consortium Leptocilindrus mediterraneus (diatom)-Solenicola setigera (protozoan), show that some times the concentrations of nutrients and organic matter can be high. The typical form of "amphitheater" that characterizes the bay causes that, during the rainy season, the system receives an input of large amounts of waste and sewage from the surrounding densely populated hills. However, Acapulco Bay seems to have a high resilience, probably as a result of a conjugated role between ocean currents (which produce a washing effect of the anthropogen pollution) and the purification produced by the functional diversity of the phytoplankton community.
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Athecate dinoflagellates have been poorly studied in the plankton of Mexican marine waters, mainly because of their fragility, as they may become deformed using nets and strong fixatives. However, their biodiversity and ecological role might be important in the planktonic realm. As part of routine phytoplankton monitoring in the Chiapas coasts, Mexico, in the southern Mexican Pacific, samples were obtained during 2009 by net (20 mu m mesh) in vertical hauls (up to 15 m), fixed with Lugol's solution and studied by light microscope (bright field and phase contrast). Athecate dinoflagellates species were identified using morphological characters such as shape and size, nucleus position, chloroplasts number and position, and particular characters ('arms', 'carina', etc.). Twenty-seven species were documented to be present in the study area, with 3 species considered to be new records for the Mexican Pacific Ocean: Cochlodinium pulchellum, Karenia bicuneiformis (= K. bidigitata) and K. papilionacea. Few species studied here have historically been reported as 'bloom-forming' species in other parts of the Mexican Pacific. It is clear that more studies should be systematically done to assess the present biodiversity of these dinoflagellates groups in Mexican waters.