www.elsevier.com/locate/hal

Harmful Algae 6 (2007) 93–103

The genus Pseudo-nitzschia (Bacillariophyceae) in continental

shelf waters of Argentina (Southwestern Atlantic Ocean, 38–558S)

Gaston O. Almandoz a,b,*, Martha E. Ferrario a,b, Gustavo A. Ferreyra c,Irene R. Schloss c,b, Jose L. Esteves d, Flavio E. Paparazzo d

a Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentinab CONICET, Argentina

c Instituto Antartico Argentino, Cerrito 1248, 1010 Ciudad de Buenos Aires, Argentinad CENPAT-CONICET, Bv. Brown 3000, 9120 Puerto Madryn, Argentina

Received 13 March 2006; received in revised form 4 July 2006; accepted 17 July 2006

Abstract

The distribution pattern of Pseudo-nitzschia species, associated phytoplankton flora and its relationships with main environ-

mental factors were studied for the first time in continental shelf surface waters of the Argentine Sea (Southwestern Atlantic Ocean,

38–558S). Both qualitative and quantitative samples, collected during summer and fall 2003, were examined using light and

scanning electron microscopy. Results indicated that the genus Pseudo-nitzschia has a wide distribution along the studied area. It

was present at low densities, with infrequent peak abundances and appeared most frequently as a minor component of the diatom

populations that typically develop on the continental shelf of the Argentine Sea. Moreover, phytoplankton communities were

numerically dominated by unidentified phytoflagellates (�5 mm) throughout almost all samples analyzed. Eight Pseudo-nitzschia

species were identified in our study: P. australis, P. fraudulenta, P. heimii, P. lineola, P. pungens, P. cf. subcurvata, P. turgidula and

P. turgiduloides. Of these, P. heimii, P. lineola and P. turgiduloides are new records for the Argentine Sea. Their presence in the area

is attributable to the influence of southerly cold water masses. Spatial and temporal variations of the environmental parameters

recorded in the study area generally determined the distribution of Pseudo-nitzschia species. P. pungens and P. australis were widely

distributed and reached high densities, especially in waters with elevated temperatures and salinities (around 15 8C, 33.8 psu) and

low nutrients concentrations. On the other hand, P. heimii, P. lineola, P. turgidula and P. turgiduloides showed a more restricted

distribution, with lower densities in relatively cold, less saline (8 8C, 32.45 psu) and nutrient-rich waters. From the Pseudo-nitzschia

species found throughout this survey, P. australis, P. fraudulenta, P. pungens and P. turgidula are known as domoic acid (DA)

producers around the world, but there is little information on the potential toxicity of these species in Argentina.

# 2006 Elsevier B.V. All rights reserved.

Keywords: Argentine sea; Diatoms; Distribution; Phytoplankton; Pseudo-nitzschia

* Corresponding autor at: Facultad de Ciencias Naturales y Museo,

Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La

Plata, Argentina. Tel.: +54 221 4257744; fax: +54 221 4257527.

E-mail address: galmandoz@fcnym.unlp.edu.ar

(G.O. Almandoz).

1568-9883/$ – see front matter # 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.hal.2006.07.003

1. Introduction

The diatom genus Pseudo-nitzschia was originally

proposed by Peragallo (Peragallo and Peragallo, 1897–

1908). Later, it was reduced to a section of the genus

Nitzschia (Hustedt, 1958) and again has been recently

recognized as a distinct genus by Hasle (1994).

Compared to Nitzschia, one of the closely related

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–10394

Fig. 1. Map of the study area showing the location of sampling

transects and stations. Transect 1 was tracked from 7 to 10 February

2003 and transect 2 from 15 to 19 May 2003.

genus with several hundred species (Mann, 1986),

Pseudo-nitzschia is a relatively small genus containing

about 30 species, some of them recently described

(Lundholm and Moestrup, 2002; Priisholm et al., 2002;

Lundholm et al., 2002, 2003). This genus occurs in

marine planktonic habitats and has a worldwide

distribution, including polar waters (Hasle and Medlin,

1990; Hasle and Syvertsen, 1997; Hasle, 2002).

From the discovery that several Pseudo-nitzschia

species are implicated in domoic acid (DA) outbreaks

(Bates et al., 1989), the genus has received more attention

and several studies on its taxonomy and eco-toxicology

have been conducted around the world (e.g. Orsini et al.,

2002; Lundholm et al., 2003, 2004; Cerino et al., 2005;

Fehling et al., 2005). DA is a neurotoxin that can be

transferred along the marine food web via feeding mainly

by shellfish. This can provoke amnesic shellfish

poisoning, which can have lethal effects in sea birds,

marine mammals and humans (Bates, 2000; Fehling

et al., 2004).

Harmful dinoflagellate events with significant eco-

nomical impacts and human casualties have been

observed along the Argentine Sea since the 1980s

(Carreto et al., 1981, 1985; Vecchio et al., 1986). The first

DA record for the Argentine Sea, although without

negative health consequences, was registered in July

2000 in Mar del Plata. The toxin was detected in

plankton, mussels and anchovy stomachs, during a bloom

of Pseudo-nitzschia australis (Negri et al., 2004).

Most of the early records of Pseudo-nitzschia species

in Argentinean waters correspond to works dealing with

general phytoplankton composition (Balech, 1971;

Carreto et al., 1974; Verona et al., 1974; Lange, 1985).

Nevertheless, P. australis was described as a new species

by Frenguelli (1939) based on material from San Matıas

Gulf, Argentina. More recent studies focused on Pseudo-

nitzschia species were conducted using both light and

electron microscopy (Negri and Inza, 1998; Ferrario

et al., 1999, 2002; Sastre et al., 2001). The latter

nowadays considered essential for a reliable identifica-

tion at the specific level (Fryxell and Hasle, 2003).

However, most of these studies were restricted to coastal

and space-limited areas, thus limiting the available

information on the occurrence of Pseudo-nitzschia

species in Argentinean shelf waters.

The continental shelf of Argentina has an extension

of about 106 km2, where the main source of the water

masses is the subantarctic water flowing from the

northern Drake Passage (Acha et al., 2004; Bianchi

et al., 2005). Access to an extensive and complete

sampling gave us the opportunity to obtain original

field information on the presence of Pseudo-nitzschia

spp. in a region with an extensive shoreline and a

considerable shellfish fishing industry. The main goal of

this research was to study the distribution pattern of

Pseudo-nitzschia species, associated phytoplankton

flora and its relationships with main environmental

factors in continental shelf surface waters of the

Argentine Sea.

2. Materials and methods

The continental shelf waters of the Argentine Sea

were sampled during summer and autumn 2003,

onboard the icebreaker A.R.A ‘‘Almirante Irizar’’ in

the frame of an Argentinean–French cooperative

research (‘‘ARGAU’’; Balestrini et al., 2000).

Samples were taken at 49 stations along 2 north–south

transects located approximately between 38–558S and

57–688W (Fig. 1). Transect 1 was tracked from 7 to 10

February 2003 and transect 2 from 15 to 19 May 2003.

Samples were collected at 9 m depth using a

continuous seawater pumping system (Balestrini

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103 95

et al., 2000). Water temperature and salinity were

measured continuously with Sea-Bird SB 38 and 37

sensors, respectively. For chlorophyll a determination,

2–4 l of seawater were filtered onto GF/F filters and

frozen at �20 8C until analysis. Ninety percentage of

acetone pigment extracts were read in a Beckman DU

650 spectrophotometer, and corrected for phaeopig-

ments. Concentrations were calculated following

Strickland and Parsons (1972). Duplicate samples for

nitrate, nitrite, phosphate and silicate were taken from

the continuous seawater pumping system, kept frozen

(�20 8C) until analysis. Nitrate, nitrite and silicate were

measured with an automatic analyzer (Autonalyzer

Technicon II1), while phosphate was determined

manually, following methods proposed by Strickland

and Parsons (1972).

At each station, both qualitative and quantitative

samples were taken for phytoplankton analyses.

Qualitative samples were collected by filtering seawater

from the continuous system through a 20 mm mesh net,

whereas quantitative samples were collected in 250 ml

bottles. All samples were fixed with Lugol’s iodine

solution and kept in dark conditions at room tempera-

ture until analysis.

For species identification, net samples were cleaned

(Hasle and Fryxell, 1970) and dried onto cover glasses

for mounting in Naphrax for light microscopy (LM) and

onto stubs shadowed with gold-palladium for scanning

electron microscopy (SEM), according to Ferrario et al.

(1995). Observations were made with a phase contrast

Wild M20 microscope (equipped with an attached

camera) and a Jeol JSM-6360 LV (SEM). Species

identifications were confirmed by SEM studies, except

for P. subcurvata, which is called P. cf. subcurvata. In

order to avoid species misinterpretation during quanti-

fication, cell counts were always done after qualitative

analyses.

For quantitative estimations, cells were enumerated

with an Iroscope SI-PH inverted microscope according

Table 1

Minimum (min), mean and maximum (max) values of temperature, salinity, n

chlorophyll a (chl a) recorded during the sampling period in the Argentine

Date Temperature (8C) Salinity (psu) NO3� (mM) N

Summer 2003

Min 9.7 32.64 0.00 0

Mean 14.1 33.27 1.16 0

Max 22.5 33.92 6.06 0

Autumn 2003

Min 8.0 32.45 0.00 0

Mean 12.4 33.40 4.16 0

Max 15.9 34.05 13.48 0

to the procedures described by Utermohl (1958). During

cell counting, since flagellates generally loose their

flagella by the addition of fixatives, unidentified

phytoflagellates and round-shaped organisms with or

without flagella, were included in a single group as

‘‘phytoflagellates’’ and classified according to their

size.

3. Results

3.1. Environmental conditions

Temperature shows a marked latitudinal gradient

along the Patagonian coast (see Acha et al., 2004),

sharply decreasing southwards. Salinity in the coastal

most areas is heavily influenced by freshwater runoff

from various rivers, and increases offshore. Moreover,

in the southernmost stations, the influence of the cold

and saline subantarctic waters can be seen on the

Patagonian Shelf (Acha et al., 2004). On average, higher

temperatures and lower salinities were detected in

summer (Table 1). Nutrient distribution did not show

such a clear latitudinal pattern, although higher

concentrations were typically found in relation with

oceanographic fronts (data not shown). Average

nutrient concentrations were higher during autumn

transect (Table 1).

Highest chl a concentrations measured during

summer and autumn were 19 and 4.8 mg m�3

respectively (Table 1). They were found near 528Sand 418S, respectively, and associated with diatom

blooms. As described by Schloss et al. (in press), sectors

of maximum concentration of chl a were generally

located in the stratified side of the tidal fronts of Valdes

peninsula (428S), San Jorge Gulf (close to 468S), its

southern tip (Blanco Cape) and Grande Bay (close to

528S). Other high values were observed near De los

Estados Island (�558S) and south of Mar del Plata

(�398S).

itrate (NO3�), nitrite (NO2

�), phosphate (PO4BB), silicate (SiO3 ) and

Sea

O2� (mM) PO4

BB (mM) SiO3 (mM) chl a (mg m�3)

.00 0.33 0.00 0.32

.07 0.63 1.36 3.51

.28 0.90 3.38 19.22

.00 0.43 0.00 0.11

.18 0.78 2.03 1.59

.71 1.24 4.85 4.81

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–10396

Fig. 2. Light (LM) and scanning electron (SEM) micrographs of Pseudo-nitzschia species first reported in Argentinean waters. (1–4) P. heimii: (1–3)

SEM, internal valve views showing the cell shape, apical and central part details; (4) LM, colony in girdle view. (5–8) P. lineola: (5–7) SEM, internal

valve views showing the cell shape, apical and central part details; (8) LM, colony in girdle view. (9–12) P. turgiduloides: (9–11) SEM, internal valve

views showing the cell shape, apical and central part details; (12) LM, colony in girdle view.

3.2. Phytoplankton composition, abundance and

distribution

Unidentified tiny phytoflagellates (�5 mm) numeri-

cally dominated phytoplankton assemblages throughout

both transects and usually exceeded 70% of total cells.

During summer, its densities ranged between 0.18 � 106

and 5 � 106 cells l�1, with an average of 1.15 � 106

cells l�1 and the highest abundance recorded at 508400S.

During autumn, densities varied from 0.15 � 106 to

2.9 � 106 cells l�1, with an average of 0.55 � 106

cells l�1and the maximum located close to 488S.

Table 2

Number of stations where Pseudo-nitzschia species were recorded during

Date P. australis P. fraudulenta P. heimii P. line

Summer 2003 (N = 26) 6 0 0 0

Autumn 2003 (N = 23) 10 2 2 7

Total (N = 49) 16 2 2 7

Cryptophytes (8.5%), unidentified phytoflagellates

of 6–15 mm (6.4%), diatoms (6.3%), dinoflagellates

(2.1%), prasinophytes (1.4%) and silicoflagellates

(<0.1%) followed the small phytoflagellates in order

of decreasing mean relative abundance for both transects.

Diatom densities showed great variability among

summer samples. Total diatom abundances ranged from

80 (�448S) to 3 � 106 cells l�1 (�528S) where an

exceptional bloom of Chaetoceros debilis was observed.

The net summer diatom assemblage was dominated

(present in more than 80% of total samples) by Ditylum

brightwellii, Paralia sulcata, Chaetoceros decipiens,

the sampling period in the Argentine Sea

ola P. pungens P. cf. subcurvata P. turgidula P. turgiduloides

21 7 0 7

11 2 4 17

32 9 4 24

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103 97

Pleurosigma sp., Thalassionema nitzschioides, Bacter-

iastrum delicatulum, Coscinodiscus jonesianus, Psam-

modictyon panduriforme and Raphoneis amphiceros.

Throughout the autumn, diatom densities varied from

9.5 � 102 to 1.45 � 105 cells l�1. Autumn maximum

was recorded close to 388S and was mainly composed of

C. debilis, Thalassiosira mala, Rhizosolenia pungens,

Fig. 3. Distribution patterns of Pseudo-nitzschia speci

Leptocylindrus minimus, Meuniera membranacea,

Chaetoceros decipiens and Guinardia delicatula. The

most frequent diatom species in net autumn samples were

Actinoptychus senarius, P. sulcata, Pleurosigma sp., P.

panduriforme, Thalassionema nitzschioides, R. amphi-

ceros, Asterionellopsis glacialis, Hyalodiscus radiatus

and Delphineis minutissima. Typical cold water species

es in surface shelf waters of the Argentine Sea.

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–10398

such as Chaetoceros dichaeta, Dactyliosolen antarcticus,

Thalassiosira gracilis and Corethron pennatum mainly

collected south of 498S, were particularly common along

this transect.

3.3. Occurrence of Pseudo-nitzschia spp.

The genus Pseudo-nitzschia showed a wide dis-

tribution along the studied area, being present in 90% of

the examined stations. However, Pseudo-nitzschia spp.

Table 3

Minimum (min), mean and maximum (max) values of temperature, salinity,

in which Pseudo-nitzschia species were recorded in the Argentine Sea

Temperature (8C) Salinity (psu) NO3� (m

P. australis

N 16 16 15

Min 9.7 32.6 0.000

Mean 12.7 33.4 2.398

Max 15.9 34.1 7.049

P. fraudulenta

N 2 2 2

Min 12.8 33.4 1.040

Mean 13.1 33.4 1.217

Max 13.4 33.4 1.395

P. heimii

N 2 2 2

Min 8.0 32.5 8.255

Mean 8.5 32.6 10.649

Max 9.0 32.8 13.044

P. lineola

N 7 7 7

Min 8.0 32.5 1.040

Mean 10.3 33.1 7.566

Max 13.4 33.4 13.476

P. pungens

N 32 32 31

Min 9.7 32.6 0.000

Mean 14.4 33.4 1.296

Max 22.5 34.1 7.049

P. cf. subcurvata

N 9 9 9

Min 8.0 32.5 0.022

Mean 13.7 33.2 1.639

Max 20.9 33.7 8.255

P. turgidula

N 5 5 5

Min 8.0 32.5 7.829

Mean 9.1 33.0 9.877

Max 9.6 33.3 13.476

P. turgiduloides

N 24 24 24

Min 8.0 32.5 0.000

Mean 12.3 33.3 3.943

Max 18.3 34.1 13.476

were usually present at low densities, ranging from 10

to 6.1 � 104 cells l�1 (average 3.3 � 103 cells l�1) and

accounting from 0.1 to 50% of total diatom densities,

with an average contribution of 4.3% (N: 27). In many

cases the genus was just recorded in concentrated

qualitative samples (N: 17).

Eight Pseudo-nitzschia species were identified in our

study: P. australis, P. fraudulenta, P. heimii, P. lineola,

P. pungens, P. cf. subcurvata, P. turgidula and P.

turgiduloides, of which P. heimii, P. lineola and P.

nitrate (NO3�), nitrite (NO2

�), phosphate (PO4BB) and silicate (SiO3 )

M) NO2� (mM) PO4

BB (mM) SiO3 (mM)

15 16 16

0.000 0.438 0.000

0.089 0.687 1.171

0.186 1.134 4.850

2 2 2

0.472 0.689 1.582

0.589 0.719 1.902

0.706 0.749 2.222

2 2 2

0.052 1.029 2.817

0.294 1.134 3.218

0.536 1.240 3.620

7 7 7

0.052 0.679 1.010

0.296 0.923 2.300

0.706 1.240 3.620

31 32 32

0.000 0.425 0.000

0.112 0.679 1.449

0.706 1.134 4.850

9 9 9

0.000 0.476 0.000

0.183 0.683 1.653

0.706 1.029 3.620

5 5 5

0.026 0.840 1.811

0.151 0.992 2.621

0.536 1.235 3.620

24 24 24

0.000 0.332 0.000

0.123 0.706 1.831

0.706 1.240 4.444

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103 99

turgiduloides are new records for the Argentine Sea

(Fig. 2). Most of the morphological characters of the

Pseudo-nitzschia species observed fitted their descrip-

tions provided by Hasle (1964, 1965) and Ferrario et al.

(2002). Small and delicate specimens, either solitary

cells or grouped in stepped curved colonies resembling

P. subcurvata, were tentatively called P. cf. subcurvata.

The most commonly occurring species recorded were

P. pungens, P. turgiduloides and P. australis, present

respectively in 65, 49 and 33% of all samples examined.

An overview of each species presence is shown in

Table 2. The spatial and temporal distribution and

abundance of the Pseudo-nitzschia species is presented in

Fig. 3. Table 3 shows a summary of temperature, salinity

and nutrient values at which Pseudo-nitzschia species

were recorded during our study.

P. australis was discontinuously distributed from

388290S to 548260S (Fig. 3). Throughout summer, its

presence was restricted southward 518S where a

maximum of 6.1 � 104 cells l�1 was recorded close

to 528S (Table 4) during the mentioned C. debilis

bloom. During autumn, P. australis was recorded north-

ward 488180S. Relative high densities (up to 2–

3 � 103 cells l�1) were registered approximately

between 38 and 418S, at temperatures between 15.0

and 15.9 8C, salinities from 33.64 to 34.05 psu, nitrates

(0.00–0.11 mM), nitrites (0.04–0.18 mM), phosphates

(0.46–0.63 mM) and silicates (0.00–3.22 mM).

P. fraudulenta was just recorded in autumn between

438S and 458S (Fig. 3), but was present only in

Table 4

Environmental conditions recorded during peak abundances of Pseudo-nit

Argentine Sea

Date P. australis P. fraudulenta P. heimii P. line

Summer 2003

Abundance (cells l�1) 61111 n/d n/d n/d

Latitude (8S) 51842 – – –

Temperature (8C) 10.7 n/d n/d n/d

–Salinity (psu) 33.08 n/d n/d n/d

–NO3� (mM) 0.55 n/d n/d n/d

NO2� (mM) 0.00 n/d n/d n/d

PO4BB (mM) 0.44 n/d n/d n/d

SiO3 (mM) 0.00 n/d n/d n/d

Autumn 2003

Abundance (cells l�1) 2778 n/d 10 110

Latitude (8S) 38829 – 52819 52819

Temperature (8C) 15.2 n/d 8.0 8.0

Salinity (psu) 33.74 n/d 32.45 32.45

NO3� (mM) 0.11 n/d 8.26 8.26

NO2� (mM) 0.08 n/d 0.54 0.54

PO4BB (mM) 0.63 n/d 1.03 1.03

SiO3 (mM) 0.81 n/d 3.62 3.62

concentrated qualitative samples, never in the quanti-

tative ones.

P. heimii was recorded in autumn from 518350S to

528190S (Fig. 3). Its highest density (10 cells l�1) was

registered at 528190S (Table 4).

P. lineola was recorded in autumn between 438S and

538S (Fig. 3). Its highest density (110 cells l�1) was

reached at 528190S (Table 4).

P. pungens was recorded from 388290S to 548260S(Fig. 3). Throughout summer, it was widely distributed,

being present in 81% of total samples, but usually in

concentrations lower than 100 cells l�1. During autumn

its presence was restricted northward 488S, reaching the

highest abundances between approximately 38–418Swith a maximum of 4.2 � 103 cells l�1 (Table 4).

P. cf. subcurvata was recorded between 408200S and

548260S (Fig. 3). During summer reached high densities

(up to 6.6 � 103 cells l�1) especially between 458S and

548S whereas in autumn was poorly registered from

about 438S to 528S. Its highest density was reached in

summer, near 548S (Table 4).

P. turgidula was recorded in autumn between

approximately 498S and 528S (Fig. 3). The highest

density (20 cells l�1) was registered at 528190S (Table 4).

P. turgiduloides was recorded from 388470S to

528190S (Fig. 3). During summer, it was rarely detected

just in net samples from 438210S to 518420S. Through-

out autumn, it was the most common species recorded,

being present in 79% of all samples analyzed but

usually at concentrations lower than 100 cells l�1. It

zschia spp. reached throughout summer and autumn transects in the

ola P. pungens P. cf. subcurvata P. turgidula P. turgiduloides

926 6667 n/d n/d

47842 54826 – –

12.6 9.8 n/d n/d

32.91 32.64 n/d n/d

2.50 3.15 n/d n/d

0.28 0.16 n/d n/d

0.85 0.59 n/d n/d

2.07 0.00 n/d n/d

4167 40 20 130

41834 52819 52819 52819

15.4 8.0 8.0 8.0

33.83 32.45 32.45 32.45

0.00 8.26 8.26 8.26

0.18 0.54 0.54 0.54

0.75 1.03 1.03 1.03

0.40 3.62 3.62 3.62

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103100

was distributed from 388470S to 528190S but highest

Pseudo-nitzschia turgiduloides densities were found

southward 428S, with a maximum of 130 cells l�1

recorded near 528S (Table 4).

4. Discussion and conclusions

Phytoplankton communities were numerically domi-

nated by unidentified phytoflagellates (�5 mm) through-

out almost all samples, which is in accordance with

previous surveys conducted in the area (Carreto et al.,

2003). In particular, the genus Pseudo-nitzschia appeared

most frequently as a minor component of diatom

populations that typically develop at the continental

shelf of the Argentine Sea.

We found the genus Pseudo-nitzschia widely dis-

tributed in surface shelf waters of the Argentine Sea,

being present in 90% of all samples analyzed. Cell

densities were generally low (<103 cells l�1) and often

undetectable in quantitative samples, with infrequent

peak abundances. Although distribution data on Pseudo-

nitzschia spp. for this vast area are sparse, our results

agree with those of Lange (1985) who found Pseudo-

nitzschia spp. widely distributed between 388S and 398Sduring the same seasons. Similar results were also found

by Negri and Inza (1998) in shelf waters between 358Sand 398S. However, these authors mention a sporadic cell

maximum of P. turgidula, which reached bloom

concentrations (>106 cells l�1). Unlike low densities

recorded in shelf waters, higher densities with peak

abundances up to 6 � 106 cells l�1 have been frequently

recorded for coastal and enclosed areas in the Argentine

Sea (Sastre et al., 2001).

The specific richness of the genus Pseudo-nitzschia

in the Argentine Sea was higher than that reported by

Odebrecht et al. (2001) for adjacent shelf surface waters

of Southern Brazil (32–348S).

We found a total of eight species, P. australis, P.

fraudulenta, P. heimii, P. lineola, P. pungens, P. cf.

subcurvata, P. turgidula and P. turgiduloides, from which

P. heimii, P. lineola and P. turgiduloides are first reported

in Argentina. P. australis was found throughout both

seasons, irregularly covering an ample zone of the

Argentine Sea and showing a strong seasonality in its

distribution patterns (Fig. 3). During summer, it was

restricted to the southernmost areas (51–558S), where

low cell concentrations were observed, except for a peak

abundance (6.1 � 104 cells l�1) recorded close to 528S(Fig. 3). This peak was the highest abundance reached by

a Pseudo-nitzschia species throughout our survey and the

highest abundance recorded for P. australis in Argen-

tinean waters (Negri and Inza, 1998; Sastre et al., 2001;

Negri et al., 2004). During autumn, P. australis was

principally found in the northernmost samples (�38–

428S) and generally at high densities (Fig. 3).

P. pungens was the most commonly recorded Pseudo-

nitzschia spp., present in 65% of all samples examined.

This result coincides with other observations in northern

Argentinean shelf waters (Lange, 1985; Negri and Inza,

1998). Moreover, P. pungens was widely distributed,

extending southward as far as 548260S (Fig. 3). This

record, compared to those reported by Hasle (2002),

represents the southernmost record for P. pungens,

transcending that of Rivera (1985) for Chilean coasts

(498520S) in the Pacific Ocean. P. pungens was present in

almost all samples analyzed during summer, whereas its

distribution was restricted to the northern area during

autumn (Fig. 3).

P. fraudulenta and P. cf. subcurvata did not show

clear distribution patterns. Our results, in agreement

with previous studies (Lange, 1985; Negri and Inza,

1998; Sastre, pers. com.), indicate that P. fraudulenta is

an uncommon species in the Argentine Sea. Conversely,

P. cf. subcurvata showed a widespread distribution,

reaching high densities in summer. Historically, P.

subcurvata has been considered to be restricted to

southern cold waters (Hasle and Syvertsen, 1997), and it

has recently been found north of the Polar Front in

Drake Passage (Ferrario and Licea, 2006).

P. heimii, P. lineola, P. turgidula and P. turgidu-

loides were mainly recorded in southerly autumn

samples, characterized by colder, less saline and

nutrient-rich waters. In addition, they were frequently

associated with typical cold water species such as C.

dichaeta, D. antarcticus, T. gracilis and C. pennatum

(Hasle and Syvertsen, 1997), suggesting the influence

of southerly cold water masses. These four Pseudo-

nitzschia species are a common phytoplankton com-

ponent in subantarctic and Antarctic waters (Manguin,

1960; Hasle, 1965; Ferrario et al., 2004; Fiala et al.,

2004). Furthermore, P. turgiduloides is considered to

be restricted to southern cold water regions (Hasle and

Syvertsen, 1997). The presence of Antarctic species in

this area has been seen previously in sediments between

358S and 508S, indicating the northward displacement

of Antarctic-source water masses, which are char-

acterized by high nutrient content and low salinity

(Romero and Hensen, 2002).

In conclusion, spatial and temporal variations of the

environmental parameters recorded in the study area

determined the distribution of Pseudo-nitzschia species.

In this sense, except for P. fraudulenta and P. cf.

subcurvata, two groups can be distinguished according

to their distributional patterns. The first group including

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103 101

P. pungens and P. australis has a widespread distribu-

tion and reaches high densities, especially in waters

with elevated temperatures and salinities, and low

nutrient concentrations. In contrast, the other group,

including P. heimii, P. lineola, P. turgidula and P.

turgiduloides shows a more restricted distribution, with

lower densities in relatively cold, less saline and

nutrient-rich waters (Fig. 3 and Table 4).

Other Peudo-nitzschia species have been recorded

previously in the Argentine Sea: P. multiseries, P. seriata,

P. pseudodelicatissima, P. delicatissima and P. aff.

cuspidata (see summary in Ferrario and Galvan, 1989;

Ferrario et al., 2002). Except for the presence of P.

multiseries, these other species require further ultra-

structural analyses to confirm their identification and

presence in Argentinean waters. A particular case is P.

seriata, which is thought to be confined to the Northern

hemisphere (Fryxell and Hasle, 2003). Both previous

SEM studies in the area and the present field study failed

to identify P. seriata in Argentinean waters. Therefore,

we support the hypothesis of Ferrario et al. (2002), who

considered the records of P. seriata in Argentinean waters

to be a misidentification. Furthermore, we suggest that

these early records should have been referred to as P.

australis, a species similar when observed at LM, and

which has been repeatedly mentioned in this area since its

original description in Argentinean waters (Frenguelli,

1939; Hasle, 1965; Lange, 1985; Negri and Inza, 1998;

Ferrario et al., 1999; Sastre et al., 2001; Negri et al.,

2004). A different case is the record of P. pseudodeli-

catissima, whose identity has been recently reexamined,

allowing the description of two new species: P. calliantha

and P. caciantha (Lundholm et al., 2003). Based on this, it

was corroborated that specimens thought to be P.

pseudodelicatissima in Ferrario et al. (1999, 2002)

correspond to P. calliantha. Therefore, the presence of P.

pseudodelicatissima in Argentinean waters is not yet

confirmed.

From the eight Pseudo-nitzschia species found

throughout this survey, P. australis, P. fraudulenta, P.

pungens and P. turgidula are known to be potential DA

producers (Fryxell and Hasle, 2003; Cerino et al.,

2005). Moreover, P. australis has been indicated as a

DA producer in Argentinean waters (Negri et al., 2004).

Conversely, available information on the potential

toxicity of typical cold water species such as P. heimii,

P. lineola, P. subcurvata and P. turgiduloides is scarce,

and therefore further investigations are required on the

potential development of new toxic species.

Although much work is still necessary to understand

the mechanisms underlying their population dynamics,

the present study is the first assessment of the

distribution patterns of Pseudo-nitzschia species along

a vast area of Argentinean continental shelf.

Acknowledgments

We wish to thank technical personnel from the

Instituto Antartico Argentino (IAA), the Servicio de

Hidrografıa Naval and the crew of A.R.A. ‘‘Almirante

Irizar’’ for their support during sampling. Thanks are also

due to P. Sarmiento from the MEB service, Museo de La

Plata and two anonymous reviewers for their suggestions.

This survey was supported from the IAA, the Consejo

Nacional de Investigaciones Cientıficas y Tecnicas

(CONICET) PIP-5603 to M. Ferrario, PEI-2001, CON-

ICET, and PICTO 6524/1108/03-ANPCyT 01-11563 to

I. Schloss. G.O. Almandoz work was supported by a

doctoral fellowship of the CONICET, Argentina.

References

Acha, E.M., Mianzan, H.M., Guerrero, R.A., Favero, M., Bava, J.,

2004. Marine fronts at the continental shelves of austral South

America. Physical and ecological processes. J. Mar. Syst. 44, 83–

105.

Balech, E., 1971. Microplancton de la campana oceanografica Pro-

ductividad III. Rev. Mus. Arg. Cs. Nat. ‘‘Bernardino Rivadavia’’ e

Inst. Nac. Invest. Cs. Hidrobiologıa 3 (1), 1–202.

Balestrini, C.F., Poisson, A.R., Ferreyra, G.A., Ferrario, M.E.,

Schauer, B., Schloss, I.R., Molina, D.A., Sala, H., Bianchi,

A.A., Ruiz-Pino, D., Piola, A.R., Saraceno, M., 2000. Project

‘‘ARGAU’’. Preliminary data-report I/B A.R.A. Almte. Irızar,

Cruise ARGAU ZERO. Instituto Antartico Argentino, Contribu-

cion 529, 1–30.

Bates, S.S., 2000. Domoic acid-producing diatoms: another genus

added! J. Phycol. 36, 978–983.

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., Pock-

lington, R., Quilliam, M.A., Sim, P.G., Smith, J.C., Subba Rao,

D.V., Todd, E.C.D., Walter, J.A., Wright, J.L.C., 1989. Pennate

diatom Nitzschia pungens as the primary source of domoic acid, a

toxin in shellfish from Eastern Prince Edward Island, Canada. Can.

J. Fish. Aquat. Sci. 46, 1203–1215.

Bianchi, A.A., Bianucci, L., Piola, A.R., Ruiz-Pino, D., Schloss, I.R.,

Poisson, A., Balestrini, C.F., 2005. Vertical stratification and air-

sea CO2 fluxes in the Patagonian shelf. J. Geophys. Res. 110,

C07003 doi:10.1029/2004JC002488.

Carreto, J.I., Verona, C.A., Casal, A.B., Laborde, M.A., 1974. Fito-

plancton, pigmentos y condiciones ecologicas del Golfo San

Matıas III. Comision de Investigaciones Cientıficas de la Prov,

de Buenos Aires Contrib. 237. Inst. Biol. Mar. de Mar del Plata.

Informe 10, 49–76.

Carreto, J.I., Lasta, M., Negri, R.M., Benavides, H.R., 1981. Los

fenomenos de marea roja y toxicidad de moluscos bivalvos en el

Mar Argentino. Contr. INIDEP 399, 1–55.

Carreto, J.I., Negri, R.M., Benavides, H.R., Akselman, R., 1985. Toxic

dinoflagellates blooms in the Argentine Sea. In: Anderson, D.M.,

White, A.W., Baden, D.G. (Eds.), Toxic Dinoflagellates. Elsevier,

New York, pp. 147–152.

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103102

Carreto, J.I., Montoya, N.G., Benavides, H.R., Guerrero, R., Carignan,

M.O., 2003. Characterization of spring phytoplankton commu-

nities in the Rıo de La Plata maritime front using pigment

signatures and cell microscopy. Mar. Biol. 143, 1013–1027.

Cerino, F., Orsini, L., Sarno, D., Dell’Aversano, C., Tartaglione, L.,

Zingone, A., 2005. The alternation of different morphotypes in the

seasonal cycle of the toxic diatom Pseudo-nitzschia galaxiae.

Harmful Algae 4, 33–48.

Fehling, J., Green, D.H., Davidson, K., Bolch, C.J., Bates, S.S., 2004.

Domoic acid production by Pseudo-nitzschia seriata (Bacillario-

phyceae) in Scottish waters. J. Phycol. 40, 622–630.

Fehling, J., Davidson, K., Bates, S.S., 2005. Growth dynamics of non-

toxic Pseudo-nitzschia delicatissima and toxic P. seriata (Bacil-

lariophyceae) under simulated spring and summer photoperiods.

Harmful Algae 4, 763–769.

Ferrario, M.E., Galvan, N., 1989. Catalogo de las diatomeas marinas

citadas entre los 368 y los 608S con especial referencia en el Mar

Argentino. Direccion Nacional del Antartico. Inst. Ant. Arg. Publ.

20, 1–327.

Ferrario, M.E., Licea, S., 2006. Species of the genus Pseudo-nitzschia

Peragallo in Antarctic waters: morphology and distribution. In:

Crawford, R.M., Moss, B., Mann, D.G., Preisig, H.R. (Eds.),

Microalgal Biology, Evolution and Ecology. Volume dedicated

to Professor Frank E. Round. Nov. Hed. Beih. 130, 1–16.

Ferrario, M.E., Sar, E.A., Sala, S., 1995. Metodologıa basica para el

estudio del fitoplancton con espacial referencia a las diatomeas. In:

Alveal, K., Ferrario, M.E., Oliveira, E.C., Sar, E.A. (Eds.),Manual

de Metodos Ficologicos. Universidad de Concepcion, Editora A.

Pinto, Chile, pp. 1–23.

Ferrario, M.E., Sar, E.A., Castanos, C., Hinz, F., 1999. Potentially

toxic species of the diatom genus Pseudo-nitzschia in Argentinian

coastal waters. Nova Hedwigia 68 (1/2), 131–147.

Ferrario, M.E., Sar, E.A., Sala, S., 2002. Diatomeas Potencialmente

Toxigenicas del Cono Sur Americano. In: Sar, E.A., Ferrario,

M.E., Reguera, B. (Eds.), Floraciones de Algas Nocivas en el

Cono Sur Americano. Instituto Espanol Ocenografico de Madrid,

Espana, pp. 167–194.

Ferrario, M.E., Licea, S., Balestrini, C.F., Ferreyra, G.A., 2004.

Species of Pseudo-nitzschia in the Drake Passage (548–618S to

468–648W). Harmful Algae 2002. In: Steidinguer, K.A.,

Landsberg, J.H., Tomas, C.R., Vargo, G.A. (Eds.), Florida

Fish and Wildlife Conservation Commission. Florida Institute

of Oceanography, and Intergovernmental Oceanographic Com-

mission of UNESCO, St. Petesbourg, Florida, USA, pp. 434–

436.

Fiala, M., Kopczynska, E., Oriol, L., Machado, M., 2004. Phyto-

plankton variability in the Crozet Basin frontal zone (Southwest

Indian Ocean) during austral summer. J. Mar. Syst. 50, 243–261.

Frenguelli, J., 1939. XV Contribucion al conocimiento de las diato-

meas argentinas. Diatomeas del Golfo San Matıas (Rıo Negro).

Rev. Mus. La Plata (n.s.) 2, 201–226 Bot.

Fryxell, G.A., Hasle, G.R., 2003. Taxonomy of harmful diatoms. In:

Hallegraeff, G.M., Anderson, D.M., Cembella, A.D. (Eds.), Man-

ual on Harmful Marine Microalgae. Monographs on Oceano-

graphic Methodology. UNESCO Publishing, France, pp. 465–

509.

Hasle, G.R., 1964. Nitzschia and Fragilariopsis species studied in the

light and electron microscopes. Part I. Some marine species of the

groups Nitzschiella and Lanceolatae. Skr. Nor. Vidensk-Akad.

Oslo Part I. Mat-Naturvidensk. Kl. 16, 1–48.

Hasle, G.R., 1965. Nitzschia and Fragilariopsis species studied in the

light and electron microscopes. Part II. The group Pseudo-

nitzschia. Skr. Nor. Vidensk-Akad. Oslo Part I. Mat-Naturvidensk.

Kl 18, 1–45.

Hasle, G.R., 1994. Pseudo-nitzschia as a genus distinct from Nitzschia

(Bacillariophyceae): nomenclatural history, morphology and dis-

tribution. J. Phycol. 30, 1036–1039.

Hasle, G.R., 2002. Are most of the domoic-acid producing species of

the diatom genus Pseudo-nitzschia cosmopolites? Harmful Algae

1, 137–146.

Hasle, G.R., Fryxell, G.A., 1970. Diatoms: cleaning and mounting for

light and electron microscopy. Trans. Am. Microsc. Soc. 89, 468–

474.

Hasle, G.R., Medlin, L.K., 1990. Family Bacillariaceae: the genus

Nitzschia section Pseudonitzschia. In: Medlin, L.K., Priddle, J.

(Eds.), Polar Marine Diatoms. British Antarctic Survey. Natural

Environment Research Council, Cambridge, pp. 169–176.

Hasle, G.R., Syvertsen, E.E., 1997. Marine Diatoms. In: Tomas, C.R.

(Ed.), Identifying Marine Phytoplankton. Academic Press, San

Diego, pp. 5–385.

Hustedt, F., 1958. Diatomeen aus der Antarktis und dem Sudatlantik.

Deutsche antarktische Expedition 1938/39 2, 103–191.

Lange, C., 1985. Spatial and seasonal variations of diatom assem-

blages off the Argentinian coast (South Western Atlantic). Ocea-

nol. Acta 8 (3), 361–370.

Lundholm, N., Moestrup, Ø, 2002. The marine diatom Pseudo-

nitzschia galaxiae sp. nov (Bacillariophyceae): morphology and

phylogenetic relationships. Phycologia 41 (6), 594–605.

Lundholm, N., Hasle, G.R., Fryxell, G.A., Hargraves, P.E., 2002.

Morphology, phylogeny and taxonomy of species within the

Pseudo-nitzschia americana complex (Bacillariophyceae) with

descriptions of two new species. Pseudo-nitzschia brasiliana

and Pseudo-nitzschia linea. Phycologia 41 (5), 480–497.

Lundholm, N., Moestrup, Ø, Hasle, G.R., Hoef-Edmen, K., 2003. A

study of the P. pseudodelicatissima/cuspidata complex (Bacillar-

iophyceae): what is Pseudo-nitzschia pseudodelicatissima? J.

Phycol. 39, 797–813.

Lundholm, N., Hansen, P.J., Kotaki, Y., 2004. Effect of pH on growth

and domoic acid production by potentially toxic diatoms of the

genera Pseudo-nitzschia and Nitzschia. Mar. Ecol. Prog. Ser. 273,

1–15.

Manguin, E., 1960. Les diatomees de la Terre Adelie. Campagne du

‘‘Commandant Charcot’’ 1949–1950. Ann. Sci. Nat. Bot. Biol 12,

223–363.

Mann, D.G., 1986. Nitzschia subgenus Nitzschia (notes for a mono-

graph of the Bacillariaceae (2). In: Ricard, M. (Ed.), Proceedings

of the Eight International Symposium, Koeltz, Koenigstein, pp.

215–226.

Negri, R.M., Inza, D., 1998. Some potentially toxic species of Pseudo-

nitzschia in the Argentine Sea (358–398S). Harmful algae. In:

Reguera, B., Blanco, J., Fernandez, M.L., Wyatt, T. (Eds.), Pro-

ceedings of the VIII International Conference on Harmful Algae.

Xunta de Galicia and IOC of UNESCO Publishers, Vigo, pp. 84–

85.

Negri, R.M., Montoya, N., Carreto, J.I., Akselman, R., Inza, D., 2004.

Pseudo-nitzschia australis, Mytilus edulis, Engraulis anchoita,

and Domoic Acid in the Argentine Sea. In: Steidinguer, K.A.,

Landsberg, J.H., Tomas, C.R., Vargo, G.A. (Eds.), Harmful Algae

2002. Florida Fish and Wildlife Conservation Comission, Florida

Institute of Oceanography, and Intergovernamental Oceano-

graphic Comission of UNESCO, St. Petesbourg, Florida, USA,

pp. 139–141.

Odebrecht, C., Ferrario, M.E., Ciotti, A.M., Kitzmann, D., Odete,

M., Moreira, P., Hinz, F., 2001. The distribution of the diatom

G.O. Almandoz et al. / Harmful Algae 6 (2007) 93–103 103

Pseudo-nitzschia off Southern Brazil and relationships with ocea-

nographic conditions. In: Hallegraeff, G.M.,Blackburn, S.I.,Bolch,

C.J., Lewis, R.J. (Eds.), Harmful algal blooms 2000. Intergoverna-

mental Oceanographic Commission of UNESCO, 2001, Paris, pp.

42–45.

Orsini, L., Sarno, D., Procaccini, G., Poletti, R., Dahlmann, J.,

Montresor, M., 2002. Toxic Pseudo-nitzschia multistriata (Bacil-

lariophyceae) from the Gulf of Naples: morphology, toxin analysis

and phylogenetic relationships with other Pseudo-nitzschia spe-

cies. Eur. J. Phycol. 37, 247–257.

Peragallo, H., Peragallo, M., 1897–1908. Diatomees marines de

France et des districts maritimes voisin. Micrographe-Editeur,

Grez sur Loing. (S.-et-M.).

Priisholm, K., Moestrup, Ø., Lundholm, N., 2002. Taxonomic notes

on the marine diatom genus Pseudo-nitzschia in the Andamian Sea

near the island of Phuket, Thailand, with a description of Pseudo-

nitzschia micropora sp. nov. Diatom Res. 17, 153–175.

Rivera, P., 1985. Las especies del genero Nitzschia Hassall, seccion

Pseudo-nitzschia (Bacillariophyceae), en las aguas marinas chi-

lenas. Gayana Bol. 42, 9–38.

Romero, O., Hensen, C., 2002. Oceanographic control of biogenic

opal and diatoms in surface sediments of the Southwestern

Atlantic. Mar. Geol. 186, 263–280.

Sastre, A., Santinelli, N., Esteves, J., Ferrario, M., 2001. Aspectos

ecologicos de especies de Pseudo-nitzschia en aguas costeras

patagonicas (Argentina). In: Alveal, K., Antezana, T. (Eds.),

Sustentabilidad de la biodiversidad. Universidad de Concepcion,

Concepcion, pp. 217–235.

Schloss, I.R., Ferreyra, G.A., Ferrario, M.E., Almandoz, G.O.,

Codina, R., Bianchi, A.A., Balestrini, C.F., Ochoa, H.A., Ruiz

Pino, D., Poisson, A., in press. Role of plankton communities in

the sea–air variation of pCO2 in the SWAtlantic Ocean. Mar. Ecol.

Prog. Ser.

Strickland, J.D.H., Parsons, T.R., 1972. A Practical Handbook of

Seawater Analysis, 2nd ed. J. Fish. Res. Bd. Canada 167, 311

pp.

Utermohl, H., 1958. Zur vervollkommnung der quantitativen phy-

toplankton-methodik. Mitt. Int. Ver. Theor. Angew. Limnol. 9, 1–

38.

Vecchio, J., Tartaglione, J., Orozco, J., Gomez, O., Grikman, G., 1986.

Intoxicacion por V.P.M. (Marea Roja). Medicina 6, 705–707.

Verona, C.A., Carreto, J.I., Hinojal, A., 1974. Fitoplancton, pigmen-

tos y condiciones ecologicas del Golfo San Matıas II. Comision

de Investigaciones Cientıficas de la Prov, de Buenos Aires.

Contrib. 236. Inst. Biol. Mar. de Mar del Plata. Informe 10,

23–49.