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1
~_________________________________________________O_C_E_A_N_O_L_O_G_IC_A__A_C_T_A_,_19_8_7_'_N_O_S_P~~r-____
Observations on blooms
of Mesodinium rubrum
in the upwelling 'area off Ecuador
Ciliates
Red tide
Upwelling
Nutrient distribution
Phytoplankton distribution
Ciliés
Eaux rouges
Upwelling
Répartition des sels nutritifs
Répartition du phytoplancton
Roberto JIMENEZ, Pablo INTRIAGO
Instituto Nacional de Pesca, Casilla 5918, Guayaquil, Ecuador.
Received 24/7/85, in revised form 24/2/87, accepted 3/3i87.
ABSTRACT
During January 1984, sorne upwelling water was found in the euphotic zone along the
coast of Ecuador from 1°20'S to 2°30'S.
This water was characterized by a relatively low surface temperature of 23°C and the
presence of Mesodinium rubrum. The concentration of chlorophyll a was between
0.50 and 1.37 mg/m3• Levels of phosphate, nitrate, ammonia and silicate fluctuated
between < 0.03 to 0.35 I-Lg-at P04-P/I, 0.6 to 3.5 I-Lg-at NOTN/I, 1.0 to 6.0 I-Lg-at
NH4-N/l, and 4.0 to 10.3 I-Lg-at Si0 4-SiIl respectively.
In February-March of the same year, a large scale " red tide " bloom of M. rubrum
developed, with dense patches, covering an area of one hundred square miles,
though the organism was spread over more than two hundred miles along the coast.
The maximum number of cells was 7.6 x 106 cells/l within and 100 x 103 cells/l
outside the patches. The sea surface tempe rature was 26°C. The concentration of
chlorophyll a varied between 0.5 and 140 mg/m3• Nutrient content was similar to that
of the previous month. Large concentrations of diatoms and dinoflagellates were
most abundant concentrations of up to 600 X 103 cells/l and 400 x 103 cells/l
respectively. Microflagellates were an important component of the phytoplankton
community, with concentrations of 100 x 103 cells/l extending along the coast from
0° to 3°20'S.
Oceanol. Acta, 1987. Proceedings International Symposium on Equatorial Vertical
Motion, Paris, 6-10 May 1985, 145-154.
RÉSUMÉ
'1
i
l.
I
Observations de la floraison de Mesodinium rubrum dans la zone
d'upwelling au large de l'Equateur
Au cours du mois de janvier 1984, une eau d'origine profonde a été découverte dans
la zone euphotique qui longe les côtes de l'Equateur, entre 1°20'S et 2°30'S de
latitude.
Cette eau se caractérisait, en surface, par une température relativement basse de
23°C et par la présence de Mesodinium rubrum. La concentration de chlorophylle a
se situait entre 0,50 et 1,37 mg/m3• Les taux de phosphates, nitrates, ammonium, et
silicates variaient respectivement entre < 0,03 et 0,35 I-Lg-at P0 4-P/I, 0,6 et 3,5 I-Lg-at
NOTN/I, 1,0 et 6,0 I-Lg-at NH4-N/I, 4,0 et 10,3 I-Lg-at Si0 4-SiIl.
En février-mars de la même année, un phénomène de marée rouge à M. rubrum de ,.
grande ampleur se développa, avec des taches compactes couvrant une surface de
cent milles carrés, alors que le phénomène s'étalait sur plus de 200 milles le long de. la
côte. Le nombre maximum des cellules dans les bancs était de 7,6 x 106 cellules/l, et
en dehors de ceux-ci, de 100 x 103 cellule sil. La température à la surface de la mer
était de 26°C. La concentration de chlorophylle a variait entre 0,5 et 1,40 mg/m3 • Le
contenu en sels nutritifs était presque identique à celui du mois précédent. On trouva
également une grande concentration de diatomées et dinoflagellés, dont les maxima
étaient respectivement de 600 x 103 cellules/l et 400 x 103 cellules/l. Les microflagel-
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145
l
R. JIMÉNEZ, P. INTRIAGO
lés constituaient une part importante du phytoplancton, avec une concentration de
100 x 103 cellules/l, s'étendant le long de la côte entre 0° et 3°20'S de latitude.
La distribution et l'abondance des espèces de phytoplancton furent enregistrées en
janvier, et février/mars 1984.
Oceanol. Acta, 1987. Proceedings International Symposium on Equatorial Vertieal
Motion, Paris, 6-10 May 1985, 145-154.
months of August 1980 and February-March and
August 1981. The range of chlorophyll a was between
2.97 and 49.97 mglm3 in the red tideformations. The
maximum cellular concentration of 14.75 x 106 cells/l
was recorded in nutrient-rieh water. The minimum
concentration (8.2 x 104 cells/l) was recorded in the
outer part of the Gulf of Guayaquil, although the high
values of phosphate, silicate and ammonium mentioned by Arcos (1982) could suggest upwelling deep
water and the development of a red tide associated
with a rieh diatom flora of small cells of Thalassiosira
sp. following such upwelling.
Cucalan (1984) described the oceanographie characteristies and water masses during these years and
pointed out that the relatively cold, saline and
nutrient-rieh water found in the southern side of the
Equatorial Front (South of 2°S) during winter is
associated with upwelling of Equatorial Subsurface
Water (ESSW) related to the Equatorial Undercurrent (Cromwell Current). The distribution of water
properties at this time agrees weil with earlier observations in that the Undercurrent extends as far east as
82°W off Ecuador. The fact that the Undercurrent
was observed during both periods, February-March
(summer) and August (winter) 1981 seems to indicate
that the blooms of M. rubrum found du ring these
times were associated with upwelling conditions.
These important observations explain to sorne extent
the physieal-chemieal properties related to the upwelling process off Ecuador, and its effects on the
biologieal productivity along the coast in 1981 and
1984. In early 1985, a red tide of M. rubrum was seen
around the Galapagos Islands (Intriago, pers. comm.)
and in the Gulf of Guayaquil. This observation
suggests that M. rubrum is an important component
of phytoplankton related to a high biologieal productivity in the sea.
Recent records of M. rubrum blooms in the eastern
Pacifie have been reported by Ochoa and Gamez
(1981) during October-November 1977 and Santander
and Ochoa (1982) along the Peruvian coast during
1980 and 1981. Avaria (1982) registered red tides
caused by M. rubrum during 1975, 1977, 1978 and
1980 along the Chilean coasts and Jiménez (1982)
found red tides of the same organism during 1973,
1980 and 1981 off the coast of Ecuador.
This paper describes sorne observations of M. rubrum
and phytoplankton in terms of numerieal abundance
and horizontal distribution in relation to water discoloration, temperature, salinity and concentrations of.
phosphate, nitrate, ammonium, silicate and chlorophyll a, along the coast of Ecuador during January,
February and March 1984.
INTRODUCTION
Mesodinium rubrum Lohmann is a holotriehous ciliate
responsible for nontoxie red tides in every major
ocean. This ciliate always contains chloroplasts and
mitochondria (Taylor et al., 1971). Regardless of their
origin, the chloroplasts retain the characteristies of
phytoplankton. Ryther (1967), Barber et al. (1969)
and Jiménez (1974) measured chlorophyll a and c in
M. rubrum. Ryther (1967) and Barber et al. (1969)
measured light-stimulated 14C-uptake, Margalef
(1956) found higher O 2 concentrations within patches
of Mesodinium blooms than outside them. Packard et
al. (1978), reviewing the existing information on this
ciliate, pointed out that the distribution of M. rubrum,
although widespread, appears to be confined to bays
and fjords or to upwelling areas in coastal waters.
When sighted the organism has also been identified as
Halteria rubra (Lohmann, 1908) or Cyclotrichium
meunieri (Powers, 1932). The name of H. rubra was
discontinued soon after 1911 (Hamburger, Buddenbrock, 1911), but the confusion between M. rubrum
and C. meunieri was dispelled only recently by
Fenchel (1968) and Taylor et al. (1971) who conclude
that the organisms are conspecifie and recommend the
use of the taxonomieally correct name Mesodinium
rubrum. Most authors noted the extreme fragility of
the organism, finding it diffieult to preserve, or to
observe alive. A detailed description of the organism
is found in Powers (1932), Bary and Stuckey (1950)
and Fenchel (1968). Its tolerance of variations in
temperature and salinity is exceptional : blooms have
been found in waters ranging in salinity and temperature from 4 to 35 and 2°C to 20°C (Taylor et al.,
1971). In blooms recorded along the coast of Ecuador,
the temperature fluctuated between 21.2°C and
28.0°C (Arcos, 1982). Ryther (1967) Barber et al.
(1969) and Jiménez (1974) found M. rubrum blooms
at the northern boundary of the Humboldt coastal
current. Ryther (1967) found a bloom in a small
upwelling area where the density of the seawater and
the nutrient concentration were higher than in adjacent oligotrophie seawater. The two blooms described
by Barber et al. (1969) in February 1968, and Jiménez
(1974) in May 1973, were less closely associated with
freshly upwelling seawater and were located offshore
in the Gulf of Guayaquil. The red tides reported in
May 1973, were related to high chlorophyll a concentration up to 93 mglm3 and a primary production of
3.7 g C/m3 • Jiménez (1978) also found M. rubrum in
May 1973, 300 miles from the coast in an area
associated with the equatorial upwelling east of the
Galapagos Islands. Arcos (1982) found M. rubrum
blooming along the coast of Ecuador during the
146
1
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M. RUBRUM BLOOMS IN THE UPWELLING OFF ECUADOR
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plankton counts were taken with a Niskin bottle. The
cells were preserved with Lugol (KI saturated with 1),
iodine without sodium acetate, and counted after
sedimentation. The total cell counts were carried out
in a l'cm2 chamber bottom, which was scanned under
high magnification (400 x) with a Zeiss inverted
microscope. Sorne seawater samples were collected
with Niskin bottles at 10 m intervals from the surface
(1 m) to 300 m depth. Measurements of salinity,
temperature, oxygen, phosphate, nitrate, silicate and
ammonium were made in sorne stations. Nutrient and
chlorophyll a concentrations were determined by the
methods outlined in Strickland and Parsons (1972).
Oxygen was estimated by the method of Carpenter
(1965).
MATE RIALS AND METHODS
Samples were taken in the course of two croises
carried out in Ecuadorian coastal waters during the
first quarter of 1984. The first croise was made from
12-27 January, and the second between 19 Febroary
and 4 March. The stations occupied are indicated in
Figure 1. Surface seawater samples (l-m) for phyto83°
82°
81°
~
..
&
0
0
~
0
1
1
~
CJ
«"'l'
•
00
-
~./
0
1
RESULTS
0
January 1984
During the first croise (Fig. 2 A), hydrographic observations at 81°W showed near-surface stratification
between 0 and 20 m depth. A vertical section at 81°W
showed cold water (15°C) reaching the shallow layers,
with the presence of warm water (26°C) at the
surface, overriding the upwelled water, particularly
between lOS and 2°1O'S.
In the area, a front was evident as a narrow band, with
a tempe rature gradient between 23°C and 26°C
(Fig. 3 A) and a salinity gradient from 33.2 to 34.0
(Fig. 3 B). North of this area, the temperature was
around 27°C and the salinity 32.5. Southwards in the
Gulf of Guayaquil, the temperature was between
25°C and 27°C and the salinity from 33.2 to 33.5. The
low salinity values show the influence of fresh ronoff
20
~
e•• ~""~
0-'---- -0-0--0 •
.
o·
0 • •
Gull of 0 ·0.0--.
GuayaqUil 0
0
o
000 ••
o. ••
•
January
February-March
Nutrients in February-March
Figure 1
Station locations for BI! Tohalli in January and February-March
1984; cross sections oftemperature in January and February-March,
nutrients in February-March.
om_
10
10
20
30
40
50
10~
80
80
90
100
81°05'
100 L-..=_-""":........_ _
81° 00'
w_
A
82°
Figure 2 (A)
Vertical temperature section along 81°W in January 1984.
81°35'W
B
Figure 2 (S)
Vertical temperature section between 82°W and 81°W in FebruaryMarch 1984.
+------------------------------------------------------~
147
R. JIMÉNEZ. P. INTRIAGO
water from the Guayas river. Nitrate also indicated
upwelling off the central coast of Ecuador (Fig. 3 C)
between lOS and 2°lO'S, with values ranging from 0.6
to 3.5 fLg-at NOTN/L At the northern end of the
front, the lowest value of 0.1 fLg-at NOTN/l was
detected, while to the south in the Gulf of Guayaquil,
concentrations varied between 0.2 and 0.5 fLg-at N0 3-
shallow mixed layer was still near the surface. The
15°C and 18°C isotherms at lOS to 2°S were deeper
than in the previous cruise, the first being close to
80 m depth, and the second at around 20 m. Most of
the red tide patches of M. rubrum were detected in
this area.
In the horizontal distribution of temperature
(Fig. 4 A), the highest temperatures of 28°C were
recorded to the north and to the south of this area.
Salinity also showed a similar pattern (Fig. 4 B) with
an advection of surface water of 34 from offshore, off
the central coast of Ecuador. Salinity values between
33.2 and 33.5 were observed in the northern and
southern parts of this area.
An oxygen content of between 5.2 mil and 6.7 mIlI at
the surface was associated with M. rubrum blooms.
There were also relatively high concentrations of
oxygen in the subsurface layers, between 0.2 mIlI and
NIL
f,
Chlorophyll a did not exhibit any correlation with the
above-mentioned features (Fig. 3 D), although the
highest values up to 1.0 mglm3 were registered
between lOS and 3°30'S. To the north, chlorophyll
values were between 0.4 and 0.5 mglm3 •
February-~arch
1984
In the second cruise, low winds allowed surface
heating and strengthened stratification; the surface
temperature was up to 27°C Fig. 2 B) although a
'femperature
Salinity
Nitrate
Chlorophyll
.; 0.5
0.5
"
'b'~
t?
.; 0.5
A
B
C
D
Figure 3 (A)
Horizontal distribution of: A) temperature oC; B) salinity; C)nitrate I1g-at NOrN/l; D) chlorophyll a mg/m3 in January 1984.
800
820
810
800
82°
80°
80°
82°
r-~------~------~~---r------~--------~--~------r-------~--~-------,--------~Io
Temperature
Salinity
Nitrate
(
\ 5 <0.5
33.5
Chlorophyll
0
~
/0'5~~ t?
.; 0.5
B
aO)
D
Figure 4 (A)
Horizontal distribution of: A) temperature oC; B) salinity; C) nitrate I1g-at NOrN/l; D)chlorophyll a mg/m3 in February-March 1984.
148
~
___________________________________________________________M_'_R_U_B_R_UM
__B_LO_O_M_S__
IN_T_H_E_U_P_W_E_LL_IN_G__
O_FF_E_C_U_A_DO_R________
plankton bloom not only of M. rubrum, but also of
associated diatoms. In addition, the presence of
ammonium with values between 2.0 and 6.0 flg-at
NH4- Nil within the patches (Fig. 6) favoured t~
growth of phytoplankton cells. A relatively high value
of 1.0 flg-at NH4-NIl was observed at 100 m depth at
81°W, probably due to the excretion of zooplankton
organisms.
Concentrations of phosphate in the surface layers
decreased from the coast towards the open ocean
(Fig. 7). Values in the coastal waters were between
0,3 and 0.6 flg-at P0 4-P/I ; offshore, they were around
0.1 flg-at P0 4-P/1. At 30 m depth, the concentration
was 0.5 flg-at P0 4-P/I although sorne higher values,
between 0.8 and 1.0 J,Lg-at P0 4-P/I, were observed in
the vertical sections of certain stations. Cucal6n
(1984) found in October 1983 high values of phosphate, probably taken up by the flowering of diatoms
developed prior to our croise of FebroaF-y-March
0.3 mUI around 90 m depth, possibly related to the
water mass associated with the extension of the
Equatorial Undercurrent.
In the surface layer of the water off the central coast,
nitrate maintained concentrations siIililar to those
observed during the previous croise (Fig. 4 C), with
values ranging between 1.5 and 2.0 J,Lg-at NOT NIl.
Lower concentrations were recorded to the north and
south of this area, except off Cabo Pasado where a
nitrate value of 0.8 flg-at NOTN/I was found next to a
patch of water discolored by M. rubrum. At 10 m
depth, from the coast to 60 miles offshore (Fig. 5), the
concentration of nitrate was 5 flg-at N0 3-NIl. A high
concentration of 10 flg-at NOT Nil was found at 30 m
depth in the northern part of the area ; in the southern
part this value was observed at 20 m depth. Between
81°W and 82°W the value of 10 flg-at NOTN/I was
recorded around 10 m depth. The high nitrate concentration in the euphotic zone supported a rich phyto-
'60
10,_ _~
80
90
60
10
80
90
Figure 5
Spatial distribution of nitrate ILg-at NOrN/l between 82°W and
8rW.
lor--..:::::::::::......----....
20
30
2°40'5.
0
m,
40
10
50
20
60
30
10
40
80
50
90
60
10
80
Figure 6
Spatial distribution of ammonium ILg-at NH.N/l between 82"W and
8l oW.
90
82°
149
1
bL
~
"L____R,_J_IM_É_N_E_Z,_P_,_IN_T_R_IA_G_O_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
10
20
30
40
50
60
70
80
Figure 7
Spatial distribution of phosphate (fLg-at PO.PII) between
82"W and 810W,
90
o~-----
___
10
20
30
40
10
50
60
70
80
90
100
82°
Figure 8
Spatial distribution of silicate (fLg-at SiO.Sill) between
82"W and 810W,
1984, where blooms of M. rubrum were found instead.
According to Vaas (1968), this organism is not found
were recorded along the coast, with the exception of
the outer part of the Gulf of Guayaquil where
0.2 mg/m 3 was recorded.
in association with important phosphate uptake. In a
manner similar to phosphate, silicate concentration
diminished from the coast to offshore (Fig. 8). The
highest value (30 ILg-at Si04-Si/I) was found close to
the coast, and related to upwelling processes. The
lowest values, between 5.0 and 10 ILg-at Si0 4-Si/l,
were detected offshore at 82°W and northward. In
the water column, the concentration of silicate was
between 15 and 20 ILg-at Si0 4-Si/l, showing sorne
vertical advection close to the coast. Major concentrations of diatoms in the surface water were found
together with high values of silicate.
The surface distribution of chlorophyll a exhibited the
highest values within the red-tide patches (Fig. 4 D),
reaching a maximum of 140 mg/m3 • In areas where
the organism was abundant, chlorophyll a was above
3.0 mg/m3 • Higher concentrations than 2.0 mg/m3
Phytoplankton
In January M. rubrum was present in small patches
with concentrations of less than 10 cells/ml (Fig. 9 A),
located close to the same areas where the FebruaryMarch blooms were observed. Diatoms were in relatively low numbers along the coast (Fig. 9 B) except
north of Puerto L6pez where a concentration of 80
cells/ml dominated by Rhizosolenia stolterfothii, R.
delicatula, R. styliformis and Nitzschia delicatissima
was found. Fewer dia toms were registered at the
northem and southem ends of this area ; possibly as a
result of the decay of a diatom bloom which may have
occurred in October 1983, when nutrient-rich waters
were detected in association with the formation of the
Equatorial Front (CucaI6n, 1984). On the other hand,
150
i
l
-r-----------------------------------------------------M. RUBRUM BLOOMS IN THE UPWELLING OFF ECUADOR
w
81 0
M. rubrum
80 0
80 0
81 0
Coccolithophorids
Diatoms
810
Microflagel!ates
/
1
Cbo.Pasad
/
tI"~~~~DOR ,.
~
((.2
A
D
10
Monta
10
E
Figure 9
Horizontal distribution and concentration of phytoplankton in January 1984.
81 0
W
M. rubrum
Diatoms
Coccolithophorids
A
Figure 10
Horizontal distribution and concentration of phytoplankton in February-March 1984 (cells/ml).
small patches of diatoms were observed in the Gulf of
Guayaquil with 20 cells/ml, dominated by R. stolterforthii, R. delicatula and R. styliformis.
/
. Dinoflagelattes were more abundant in the coastal
water (Fig. 9 C) with concentrations around 10
cells/ml. Sorne small patches (from 40 to 100 cells/ml)
were detected in other areas dominated by small
Gymnodinium sp., Prorocentrum spp. and Oxytoxum
spp.
The coccolithophorids in January showed low values
of 1 celllmi offshore (Fig. 9 D) ; inshore, sorne patches
with cell concentrations between 20 and 80 cells/mi
were registered. The major concentrations were in the
areas where nutrient-rich waters were observed. The
most common species were Emiliania huxleyi,
Oolithotus fragilis and Gephyrocapsa oceanica.
The distribution and abundance of microflagellates
(Fig. 9 E) were similar to those of the coccolithophorids. Values of 1 celllmi to 10 cells/mi were found
offshore. High concentrations of up to 100 cells/ml,
were recorded in sorne areas close to the coast,
particularly from 1°S to 3°S.
In February-March, M. rubrum was blooming in a red
tide formation (Fig. 10 A). Dense patches with cell \.
numbers ranging from 670 to 7,600 cells/mi were
found along the coast. Four of the major patches were
observed in the area 1°S and 2°1O'S and another off
Cabo Pasado, the large st patch being sorne 4 miles in
length. The dense bloom dominated by M. rubrum
covered an area of one hundred square miles, though
the organism extended over more than two hundred
miles along the coast. Lower cell densities were seen
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151
R. JIMÉNEZ, P. INTRIAGO
1
1
:
in the open ocean west of 81°30'W, with concentrations between 1 and 10 cells/ml.
Concentrations of diatoms were up to 600 cells/ml,
especially in areas where M. rubrum was also present
(Fig. 10 B). Large densities of Thalassiosira sp. were
recorded as well as Nitzschia delicatissima with cellular
côncentrations of up to 100 cells/ml, Thalassiotrix
mediterranea with 40 cells/ml and Chaetoceros curvisetus with 120 cells/ml. To the north and south much
lower concentrations of diatoms were recorded, especially south and west of the Gulf of Guayaquil, where
cell concentration was between 10 and 20 cells/ml ; in
the inner part of the Gulf, higher concentrations of
diatoms were recorded, dominated by N. delicatissima
(200 cells/ml), Chaetoceros curvisetus (96 cells/ml),
Ch. pendu lus (96 cells/ml) and Ch. similis. Lesser
concentrations of Rhizosolenia stolterfothii, Leptocylindrus danicus were recorded.
Total dinoflagellate populations were more abundant
than in the previous month (Fig. 10 C). The maximum
number of cells ranged from 100 to 400 cells/ml. They
were also present in areas where M. rubrum developed. Large concentrations of small Gymnodinium sp.
were registered, as well as Mesodinium, with densities
between 100 and 400 cells/ml, Dinophysis caudata
with 20 cells/ml and Heterocapsa triquetra with 10
cells/ml. The lowest concentrations, from 1 to 10
cells/ml, were observed in the open ocean. The most
common dinoflagellates, although in lesser densities,
were Protoperidinium minusculum, Prorocentrum
micans and Oxytoxum spp., Gonyaulax polygrama
were restricted to the north in the warmer waters.
The distribution of coccolithophorids did not show a
particular pattern (Fig. 10 D). The highest concentrations, between 20 and 100 cells/ml, were found from
lOS to the south, inc1uding the inshore waters of the
Gulf of Guayaquil, dominated by Emiliania huxleyi
and Oolithotus fragilis with densities up to 100 cells/ml
and Gephyrocapsa oceanica with 16 cells/ml. Lower
densities were registered offshore in the Gulf of
Guayaquil and north of lOS. Lesser densities were
observed of Umbilicosphaera sibogae, Calyptrosphaera oblonga, Helicosphaera carte ri, Discosphaera
tubifera, Coronosphaera sp. Syracosphaera sp.
Microflagellates (Fig. 10 E) were an important
component of the phytoplankton community. The
concentrations along the coast and west of 81°W were
usually around 100 cells/ml, but the highest densities
were detected to the north of Salinas, with cell
concentrations around 600 cells/ml. In the Gulf of
Guayaquil, cell concentrations reached 400 cells/ml.
The lowest concentrations were registered at 82°W
northward. The blue-green algae Trichodesmium sp.
was present in sorne localities but the highest densities
were of 25 filaments/ml.
nutrient-rich subtropical surface waters (STSW) in the
upper 70 m from the Humboldt Current, which, at
that time, was found as far north at 2°S, and Tropical
Surface waters (TSW) north of 1°30'S extending
down to 30 m depth. The transition zone between
these two water masses formed the Equatorial Front
at that time. Meanwhile in February-March 1984,
Cucal6n (1984) described two water masses in the
upper 300 m. At the surface TSW covered the entire
area extending down to 20 m depth; below this,
Equatorial Subsurface Water (ESSW) was situated
with concentrations increasing downward to reach its
core concentrations (;;.: 90%) at about 150-300 m
depth. Cucal6n suggests that the surface warming was
associated with a seasonal strengthening of the local
surface circulation possibly associated with an advection southward of TSW from the Panama Bight. From
this observation it is possible to deduce that the
nutrient-rich waters in February-March 1984 were
related to the presence of ESSW associated with the
eastward transport of the Equatorial Undercurrent.
Although M. rubrum is related to strong upwelling
areas like Baja California, Peru and elsewhere, it is
evident that the presence of M. rubrum off Ecuador is
related to a less intense but a more constant upwelling
processes as was observed from the data of nutrient
levels; bloom conditions can, however, persist for
longer periods ; a red tide of M. rubrum was reported
as existing until August 1984.
In February-March 1984, the upwelling was weak or
relaxed with a strongly stratified near-surface water
column and low current velocities, between 0.2 and
1.1 knot. M. rubrum may bloom through a combination of its autotrophic capacity and its mobility, by
exploiting both the nutrient-rich waters below the
pycnoc1ine and the euphotic zone above it ; observations here agree quite well with one of the suggestions
made by Packard et al. (1978) for the hypothetical
sequential development of various states of an upwelling system in which blooms of M. rubrum may
develop. During February-March, concentrations of
3.0 mg/m3 to 140 mg/m3 of chlorophyll a were found
in the major areas of the patches of M. rubrum,
although chlorophyll a concentrations around
1.0 mg/m3 were recorded along the coast. The occurrence of nitrate and chlorophyll in the surface waters
shows that the spatial distribution of the phytoplankton biomass in this ecosystem is determined by
the convective supply of new nutrients to the surface
layer. A progressive decrease in phytoplankton biomass was recorded off the Gulf of Guayaquil, where
the mixed layer deepened and the nitrate at the
surface were less than 0.2 f-Lg-at N0 3-N/I as well as
north of lOS, although in sorne areas relatively high
nitrate and chlorophyll a concentrations were observed. The difference in the nitrate concentration in the
water column between January and February-March
1984 shows that the processes which normally keep
the surface layer rich in nutrients were stronger in
January, when values between 0.6 to 3.5 f-Lg-at NOT
Nil were recorded between lOS and 2°10'S at 81°W.
North and south of this area, low values were detected
at the surface, although in the Gulf of Guayaquil
patches of 0.5 to 0.9 f-Lg-at NOrN/1 were also observed. In February-March, the nutrient-rich surface
layer was reduced, but the surface layer was not
DISCUSSION
Cucal6n (1984) has pointed out that in October 1983,
three months before our first cruise in January 1984,
the surface distribution of nutrients showed a significant increase in the levels of phosphate (0.8 f-Lg-at/l),
nitrate (4 f-Lg-atll) and nitrite (0.2 f-Lg-at/l) south of 2°S
at about 82°W. This area of higher nutrient concentrations was associated with the presence of cold and
152
~ iF;~E:,:~~:'< :
j.-.. ,'
_,e,,, ..
1
M. RUBRUM BLOOMS IN THE UPWELLING OFF ECJAQGJil ;';::S
-.~------------------------------------------------------------------------------------~;~~~~~~~'-----
l
2°30'S (Arcos, 1982). These months were coincident
with important spawning of small pelagie fishes,
mainly Scomber japonicus, Sardinops sagax and Etrumeus teres, were Mesodinium was present (Garcia,
1983). The survival success of the larval stages of
these species might be related to stability in the
surface layer as weIl as adequate food density associated with the Mesodinium bloom. Further information
on the distribution and abundance of eggs of small
pelagie fishes in Febroary-March 1984 suggests that
spawning areas were coincident with the region where
Mesodinium was present; although larvae were also
in highest concentration in this region, lesser densities
were reported in the Gulf of Guayaquil (Garcia, pers.
comm.).
During El Nino of 1982-1983, M. rubrum was not
present off Ecuador and poor spawning §uccess of
small pelagie fishes was reported (GarcIa, 1983).
Recently in the inner part of the Gulf of Guayaquil a
red-tide of M. rubrum was reported (August, 1984),
anchovy larvae being observed feeding at the borders
of these patches.
From the above findings, we may conclude, in summary, that:
1) Phytoplankton cells of M. rubrum from water and
net samples collected during routine croises were
destroyed by the formalin solution used as a preservative. This might be the reason why M. rubrum,
although a common organism in eastern Pacifie
waters, is not usually mentioned in the phytoplankton
list compiled from the data of oceanographie croises.
Lugol solution without acid would appear to be a
better preservative of this ciliate.
2) Recent records of M. rubrum blooms along the
coastal waters of Ecuador suggest that the presence of
this organism was associated with upwelling conditions
related to the Equatorial Undercurrent. During " El
Nino" 1982-1983, neither red tide formations nor
upwelling conditions were found off Ecuador.
3) M. rubrum presence was probably related to
continuaI, but less intense upwelling processes.
Blooms could persist for long periods of time, the
autotrophie and mobility capacities of the organisms
making the nutrients of the photie zone and below it
available to them.
4) During the last 20 years, heavy blooms of M.
rubrum have been reported along the coast of Ecuador, in the estuary of the Gulf of Guayaquil and off
the Galapagos Islands. Sometimes, as in 1981 and
1984, blooms along the coast spread over a distance of
more than two hundred miles. In recent years,
important blooms have been registered in Perovian
and Chilean waters.
5) M. rubrum may play an important role in marine
food chains, since a number of different species of
zooplankton and fish larvae have been seen feeding at
the borders of the red tide formations. To substantiate
its potential importance to upwelling ecosystems such
as that of the eastern Pacifie region, more effQrt
should be devoted to understanding physiology, biochemistry and ecology of M. rubrum.
depleted of nitrate and concentrations over 5 !Lg-at
NOTNII were around the 10 m depth between 81°W
and 82°W from the coast to 60 miles offshore.
The relation between phytoplankton growth and
ambientnutrient concentration is complex. Nitrate,
silicate and phosphate, the major inorganie nutrient
anions, covary in the upper 100 m of the eastern
equatorial Pacifie. Sometimes nitrate is used as an
index of the nutrient abundance of all the major
nutrient anions (Barber, Chavez, 1983). Hart (1934)
observed red-water blooms of M. rubrum in a rieh
assemblage of diatoms and copepods along the Atlantie coast of South Afriea and noted that rotifers were
feeding on the ciliates. Further evidence of the role of
M. rubrum in marine food chains was cited by
Clemens (1935) who observed red crystalline styles in
clams and oysters following blooms of M. rubrum
along the eastern shore of Vancouver Island.
Rassmussen (1973) mentioned that the mysids, Praunus flexuosus and P. inermis, have been se en feeding
at the borders of the red clouds of the M. rubrum
blooms. Striekland et al. (1969) found two distinct
conditions in March-April 1966 in Perovian coastal
waters. In one, concentrations of surface and nearsurface nutrients were high, nitrate concentrations
often exceeding 10 !Lg-at NOT Nil, but there was
relatively little phytoplankton in the water, with
chiorophyll a less than 2 mglm3 ; this was called
" blue" water. At the other extreme, the water
contained less nutrient at the surface and was
" brown ", with phytoplankton present in bloom
proportions and chlorophyll a concentration exceeding
5 mglm3 , often reaching more thant 10 mglm3 • Striekland et al. (1969) suggest that the anchovy must seek
out or feed mainly in "brown" water patches.
Although M. rubrum was not reported in the list of
phytoplankton recorded in the" brown " waters, this
might be because formalin was used as a preservative
and the cells thus destroyed ; we can assume that M.
rubrum was indeed associated with this kind of water.
Beers et al. (1971) in June 1969 found M. rubrum in
plankton populations in aIl the stations studied off the
coast of Pero, although they did not observe the
" brown" and "blue" waters. Ware et al. (1981)
working on first-feeding Perovian anchoveta larvae,
found that Actinocyclus, Mesodinium and Gymnodinium were the main components in the diet.
Recently Harrison and Platt (1982) have studied
production and nutrient characteristies of sorne
" brown " and" blue " water patches investigated off
Pero in November 1977. Although M. rubrum was
found in a " red water" patch, it was not mentioned
as an organism causing this discoloration, probably
because mieroscopie analysis of the phytoplankton
was made on formalin fixed samples. Nevertheless,
the existing information confirms not only the important role of M. rubrum in the productivity of the
coastal zone but also provides evidence that M.
rubrum could be an important component in the food
consumption of zooplankton and other organisms.
During Febroary-March 1981, blooms of M. rubrum
were found along the coast of Ecuador from 0° to
153
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R. JIMÉNEZ, P. INTRIAGO
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This volume is the Special I$sue nO 6 published by Oceanologica Acta.
Special issues have been dedicated to :
• N° 1: Geology of continental margins
Géologie des marges continentales
Colloqll;.e C3
Proceedings of the 26th International Geological Congress, Paris, 7-17 July, 1980.
• N° 2: Geology of Oceans
Géologie des océans
Colloque C4
Proceedings of the 26th International Geological Congress, Paris, 7-17 July, 1980.
• N° 3: Coastal lagoons
Les lagunes côtières
Proceedings of the International Symposium on coastal lagoons, Bordeaux, France, 814 September, 1981.
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Fluctuation et succession dans les écosystèmes marins
Proceedings of the 17th European Symposium on Marine Biology, Brest, France, September
27-0ctober 1, 1982.
• N° 5: CYAMAZ cruise 1982
Campagne CYAMAZ 1982
Submersible Cyana studies of the Mazagan Escarpment (Moroccan continental margin),
September 15-0ctober 15, 1982.
• N° 6: Vertical motion in the equatorial upper ocean
Proceedings of the International Symposium on Vertical Motion in the Equatorial Upper
Ocean and its Effects upon Living Resources and the Atmosphere, Paris, 6-10 May 1985.
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