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Seasonal absolute acoustic intensity, atmospheric forcing and currents ina tropical coral reef system

José de Jesús Salas Pérez a,b,c, f,*, David Salas-Monreal c, María Adela Monreal-Gómez d,Mayra Lorena Riveron-Enzastiga e, Carme Llasat b

a Facultad de Ciencias Biológicas y Agropecuarias, Universidad Veracruzana, Campus Tuxpan, Km. 7.5 Carretera Tuxpan-Tampico, Tuxpan de Rodríguez Cano-Veracruz,

CP. 92780, Mexicob Facultad de Física, Universidad de Barcelona, Av. Diagonal 647, CP. 08028, Barcelona, Spainc Instituto de Ciencias Marinas y Pesquerías, Universidad Veracruzana, Campus Veracruz, Hidalgo 617, Col. Río Jamapa, Bocal del Río-Veracruz, CP. 94290, Mexicod Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Cd. Universitaria, 04510, México D.F, Mexicoe Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Cd. Universitaria, 04510, México D.F, MexicofObservatori de L’Ebre (Universitat Ramon Llull - CSIC), Horta Alta, 38, 43520, Roquetes (Tarragona), Spain

a r t i c l e i n f o

Article history:

Received 12 July 2011

Accepted 10 January 2012

Available online 20 January 2012

Keywords:

Gulf of Mexico

Parque Nacional Sistema Arrecifal

Veracruzano

plankton variation

seasonal current

wind induced current

Gyre of Campeche Bay

a b s t r a c t

The seasonal patterns of marine circulation and biovolume were obtained from time-series measure-

ments carried out in the “Parque Nacional Sistema Arrecifal Veracruzano” (PNSAV), located in the

western continental shelf of the Gulf of Mexico, from June 2008 to September 2009. Two mechanisms

were depicted as the responsible for the current pattern observed in the PNSAV and not only one as

suggested in large-scale studies. The first mechanism is the wind generated currents. This mechanism by

itself is responsible for up to 78% of total variation of the seasonal circulation in the PNSAV as estimated

with the first mode of the EOF’s (Empirical Orthogonal Functions), which was correlated (Normalized

Lagged Correlation) with the north-south wind component. Therefore, the wind and the first mode were

highly correlated for most of the year (r > 0.7). The second mode was attributed to the low frequency

current, associated to the meso-scale circulation of the Gulf of Mexico, owing to the cyclonic eddy of the

Campeche Bay. Both mechanisms were mostly observed throughout the year. Nevertheless, the cyclonic

eddy of the Campeche Bay (meso-scale) was the first responsible for the current fluctuations observed

during the summer of 2008 and 2009. The absolute acoustic intensity (plankton biovolumes) was highly

correlated to currents, showing high spatial variability, attributed to advection produced by the meso-

scale circulation and to river discharges, but also by eddy diffusion produced by atmospheric and

coastal water fronts.

! 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The understanding of the seasonal current pattern in shallow

areas is crucial to predict planktonic and organic matter concen-

tration (Lennert-Cody and Franks, 1999; Salas-Monreal et al., 2009;

Zavala-Sansón and Provenzale, 2009), hydraulic controls (Falter

and Sansone, 2000) and lee wave generation (Salas-Monreal and

Valle-Levinson, 2009). Studies using long-term data sets to

describe the variability of currents have been carried out in the

Central Great Barrier Reef, with corals of fringing and barrier reefs

and atolls (Wolanski and Pickard, 1985), in the Caribbean Reef

with fringing reefs (Coronado et al., 2007), among others. The

“Parque Nacional Sistema Arrecifal Veracruzano” (PNSAV) (Fig. 1a)

is formed by a 20e45 m depth platform coral reef types (Krutak

et al., 1980) protected by the cape of Anton Lizardo in the southern

end and by the port of Veracruz in the northern end (Fig. 1b);

those characteristics suggest frictional dynamics (Salas-Monreal

et al., 2009).

The study area located in the northern PNSAV (Fig. 1c) is char-

acterized by the influence of diurnal tides (Salas-Pérez et al., 2008)

with a coral reef area covering close to 19 km2. The depth of coral

reefs varies from 20 to 45 mwith shallow reef lagoons of about 2 m

depth and variable coral reef length extensions from 0.3 to 3.2 km

(Salas-Pérez and Granados-Barba, 2008). Those characteristics

suggest that the Gulf of Mexico (large-scale) current pattern

(Zavala-Hidalgo et al., 2003; Salas-Pérez and Granados-Barba,

* Corresponding author. Facultad de Ciencias Biológicas y Agropecuarias, Uni-

versidad Veracruzana, Campus Tuxpan, Km. 7.5 Carretera Tuxpan-Tampico, Tuxpan

de Rodríguez Cano-Veracruz, CP. 92780, Mexico.

E-mail address: [email protected] (J. de Jesús Salas Pérez).

Contents lists available at SciVerse ScienceDirect

Estuarine, Coastal and Shelf Science

journal homepage: www.elsevier .com/locate/ecss

0272-7714/$ e see front matter ! 2012 Elsevier Ltd. All rights reserved.

doi:10.1016/j.ecss.2012.01.002

Estuarine, Coastal and Shelf Science 100 (2012) 102e112


2008) and the meso-scale currents of the Campeche Bay (Monreal-

Gómez et al., 2004; Vázquez de la Cerda et al., 2005; Salas-Pérez

and Granados-Barba, 2008) should be locally modified by the

presence of the coral reefs and islands (Salas-Monreal et al., 2009)

and wind stress (Salas-Pérez et al., 2007; Salas-Pérez and

Granados-Barba, 2008). Even though the PNSAV is located off the

Port of Veracruz (Fig. 1), one of the oldest cities in America (1519),

there is still no continuous long-term data studies in order to

elucidate the seasonal and inter-annual signals (Salas-Perez and

Granados-Barba, 2008). Thus, the seasonal current pattern of the

PNSAV remains unknown.

Coastal seasonal currents in the PNSAV must be strongly

correlated to the seasonal large-scale circulation of the Gulf of

Mexico, as reported with data set of AVHRR and CZCS (Coastal Zone

Color Scanner) images, surface drifters and from model outputs

(Biggs and Müller-Karger, 1994; Boicourt et al., 1998; Lugo-

Fernández et al., 2001; Zavala-Hidalgo et al., 2003). Those studies

agree on the seasonal reversal of the current on the western

continental shelf of the Gulf of Mexico. During the spring-summer

season the current flows toward the north while during the

autumn-winter season these current flows toward the south.

Model studies at coastal scale using a hydrodynamic-barotropic

two-dimensional explicit numerical model, forced with constant

and uniform winds of 15 m s!1 and 35 m s!1, had also suggested

that winds blowing from the N, NW and W directions induce

southward currents, while winds blowing from the NE, E, SE, S

induces northward currents. In both cases the current directionwas

modulated by the complex bathymetry (Caballero-Rosas, 1990). A

recent study carried out with observations during the summer of

2007, showed a cyclonic-anticyclonic pair of gyres between the two

groups of coral colonies in the PNSAV, produced by shear velocity

owing to the cape of Anton Lizardo, located in the southern area of

the PNSAV (Salas-Monreal et al., 2009). However, all the previous

studies were carried out at basin scale (>100 km), or describing

only one season (<8 days), making them inaccurate to describe the

seasonal current pattern in the PNSAV.

Large and coastal scale numerical studies (Caballero-Rosas,1990;

Zavala-Hidalgo et al., 2003) differ in the current pattern of the

PNSAV. The difference can be attributed to the modulation of the

complex bathymetry owing to the presence of coral reefs and islands

(Caballero-Rosas, 1990; Salas-Pérez and Granados-Barba, 2008;

Salas-Pérez et al., 2008; Salas-Monreal et al., 2009). These charac-

teristics are the ones that had lead some studies to the conclusion

that local wind and the irregular bathymetries dominate the local

circulation (Caballero-Rosas,1990; Salas-Monreal et al., 2009). Other

studies suggested that on thewestern continental shelf of the Gulf of

Mexico the coastal circulation patterns should be related to large

scale and meso-scale circulation (Monreal-Gómez et al., 1994; Biggs

and Müller-Karger, 1994; Vidal et al., 1994; Boicourt et al., 1998;

Lugo-Fernández et al., 2001; Zavala-Hidalgo et al., 2003; Vázquez

de la Cerda et al., 2005) rather than local wind and topographic

controls (Salas-Pérez et al., 2007; Salas-Pérez and Granados-Barba,

2008; Salas-Monreal et al., 2009). However, most of these studies

were obtained from model outputs at large-scale or at coastal scale

during a short period of time (<8 days). Thus, this is the first study

regarding current andwind velocity data, withyear-long time series,

in order to elucidate the seasonal current pattern in a shallow coral

reef system located in the western Gulf of Mexico (PNSAV).

Fig. 1. a) Location of the “Parque Nacional Sistema Arrecifal Veracruzano” (PNSAV) in the Western continental shelf of Gulf of Mexico. b) Amplification of the northern area of the

PNSAV, and weather station location. c) Moorings location at Blanquilla reef (BB), Anegada de Adentro reef (AA), Isla de Sacrificios (IS), and Isla Verde (IV). Bathymetric contours at

5 m interval.

J. de Jesús Salas Pérez et al. / Estuarine, Coastal and Shelf Science 100 (2012) 102e112 103


2. Material and methods

Correlations and Empirical Orthogonal Function analysis were

performed in order to analyze the effect of thewind on the seasonal

current pattern. The correlations (Normalized Lagged Correlation)

between the current components and the wind and between the

modes of the EOF’s (Empirical Orthogonal Functions) with the NeS

wind component were carried out in order to obtain their depen-

dence and phase according to Emery and Thomson (2001).

However, the biovolumes were also calculated in order to depict

the possible relation between the seasonal biovolume with the

current variability within the northern coral reef area. Since the

PNSAV is a shallow water system it could be assumed that atmo-

spheric storms will have a major influence on current variability

and on biovolume variability owing to mixing process.

One year-long of absolute acoustic intensity data of the ADCP

(dB) converted to backscatter intensity and water velocity data

throughout the entire water columnwere recorded from June 2008

to September 2009. The ADCP data had a vertical blanking distance

of 0.75 m from the surface and 1 m at the bottom. Water velocities

and the backscatter intensity were registered using four Acoustic

Doppler Current Profilers (ADCP) moored at about 20 m depth

(Fig. 1c). The ADCPs recorded the water velocity at depth intervals

of 2 m every 15 min. The ADCPs were strategically deployed at the

reefs ends of the PNSAV (Fig. 1c) under the hypothesis that seasonal

circulation around the PNSAV is governed by wind patterns and

modulated by coastal topography, which in turn should influence

plankton biovolumes. However, the seasonal wind-driven current

should also be affected by the presence of coral reefs and islands.

The four year-long data series were recorded by two Nortek

Aquadop 400 kHz ADCPs deployed in the leeward side of Blanquilla

(BB) and Anegada de Adentro (AA) (Fig. 1c) and two Nortek Aqua-

dop 1 MHz ADCPs deployed in the southward side of Isla Verde (IV)

and in the northern side of Isla de Sacrificios (IS) (Fig. 1c).

One year-long time series of wind velocity were recorded every

hour from a weather station (19" 12.550 N; 96" 7.680 W) located

approximately 4 km southward from the moorings (Fig. 1b). The

weather station was located at a height of 10 m in a flat area where

the wind velocity is expected to represent the wind over the

studied area. A spectral analysis was carried out to determine the

spectral energy and main periods of the hourly wind velocity and

the water velocities (not showed here). On the other hand, the

backscatter intensity, the vertically averaged velocity profiles and

the Empirical Orthogonal Functions (EOF’s) time series were

filtered using a lowpass filter with 26 h (Salas-Pérez et al., 2008) in

order to obtain the subtidal biovolumes and seasonal currents

fluctuations. Progressive vectors diagrams of the currents were

computed at a sampling interval of 1 h. No previous filters were

applied to the original data. JASON-1/-2, TOPEX, ERS-2, ENVISAT

and GFO Sea Height Anomaly (SHA) data available from the NOAA

on a near-real time basis with a 2-day average delay were used to

show geostrophic currents maps of the Campeche Bay, where the

study area is located.

3. Results and discussions

3.1. Biovolumes

The absolute acoustic intensity (dB) obtained from the back-

scatter intensity of the ADCP (Holliday and Pieper, 1980; Ressler,

2002) was used to estimate plankton biovolumes (Fig. 2) There is

a possibility for an overestimation of the biovolumes owing to

sediment transport throughout the river discharge during the rainy

season. The overestimation was also suggested during the winter

(cold atmospheric front). However the overestimation was only

suggested during storm events (low frequency) and not during the

entire season. There was a time lag of 5 h between the wind gust

events and the biovolume maximum value for each atmospheric

storm. However, using the high frequency data series, the correla-

tion between the wind gust and the biovolume maximum values

during the winter were lower (r < 0.43). The absolute acoustic

intensity (dB) during the four moorings showed different seasonal

behavior. The moorings at (AA) and (BB) (Fig. 2a, b) had higher

values and particularly (AA) and (IV) had a larger seasonal variation

throughout the entire year (Fig. 2a, d). While the mooring at Isla de

Sacrificios (IS) (Fig. 2c) had higher values during winter, when the

northerly wind mix the entire water column, bringing nutrients to

the surface and from the La Antigua River located northward from

the study area (Salas-Pérez and Granados-Barba, 2008; Salas-Pérez

and Arenas-Fuentes, 2011). While during the summer, the values

were lower than during the winter, because the less energetic

southerly winds (Fig. 3a) did not mix the entire water column. For

the southern mooring (IV) (Fig. 2d), the absolute acoustic intensity

shows the lowest values during winter, since the (IV) mooring is

free of the influence of the northern Rivers and protected from the

northerly winds by the reef (Fig. 1). However during the summer

season, its values increases owing to the influence of the southerly

winds and the Jamapa and Papaloapan Rivers discharges (Salas-

Pérez and Granados-Barba, 2008), those rivers are located south-

ward from the mooring station, bringing nutrients to the area. All

the biovolumes series have a high correlation (>0.6) during most of

the year, however, during the winter the correlation between (AA)

and (IV) was lower (<0.5) than for the other series (>0.5).

Fig. 2. The vertically averaged absolute acoustic intensity (dB) at a) Anegada de

Adentro (AA), b) Blanquilla (BB), c) Isla de Sacrificios (IS), and d) Isla Verde (IV), from

July 22, 2008 to September 22, 2009. The black like represents the subtidal biovolume.

J. de Jesús Salas Pérez et al. / Estuarine, Coastal and Shelf Science 100 (2012) 102e112104


As a first approximation the seaward moorings seems to have

a similar pattern at high frequencies (from September to November

of 2008 and from May to September of 2009), both series had

similar correlation (0.78) and reported the highest values (close to

85 dB), while the other two series show a different pattern. At low

frequencies the correlation between the seaward moorings was of

0.56. Themain difference in the correlation values was attributed to

wind effect. Wind gust produce different responses at low

frequencies at each mooring. Therefore at high frequencies the

series seem to be influenced by different factors. All of them seem

to be influenced by the wind during the winter (r > 0.62) (Salas-

Perez and Arenas-Fuentes, 2011). The association between the

wind driving currents and the dispersion of plankton organisms

was also described in shallow water like in the Great Barrier Reef

(Wolankski and Pickard, 1985) where most of the variance of the

current, with periods <20 days, was associated to wind-driven

circulation, which disperse planktonic organisms over the Great

Barrier Reef (Wolanski and Pickard, 1985). However, owing to the

correlation between the wind and the biovolumes there should be

a second factor responsible for current variations. This factor should

not only be the influence of the river discharges since it affects the

four moorings and not only the once closer to the coast. During the

summer the Jamapa and Papaloapan Rivers affect the landward

moorings (Isla de Sacrificios and Isla Verde) (Fig. 2c, d). However, in

general the stations seem to have a similar behavior (high values

during the summer), implying that another factor should influence

themooring areas. This factorwas attributed to advection produced

by large-scale (wind induced currents) and meso-scale circulation

(Monreal-Gómez et al., 2004; Salas-Pérez and Granados-Barba,

2008; Salas-Pérez and Arenas-Fuentes, 2011). Thus, the patchi-

ness of plankton are advectedwind induced currents and themeso-

scale circulation but it is also influenced by random mixing

processes owing to eddy diffusion, produced in the frontal zone of

river and coastal waters, and mixing owing to tides and atmo-

spheric fronts.

3.2. Seasonal winds

Since the winds may play a significant forcing mechanism to

generate currents along to the Western Continental Shelf of the

Gulf of Mexico (Salas-Pérez and Granados-Barba, 2008), where the

PNSAV is located and they are related to the high absolute acoustic

intensity values observed in the PNSAV, a spectral analysis of the

hourly wind velocity was carried out in order to obtain the main

frequencies of the wind and any possible influence over the

seasonal currents. The main periods of energy obtained by an

annual spectral analysis of the hourly wind velocity was the

diurnal signal (23.67 h) with a peak of energy of 6.4 $ 106

(m2s!2cph!1) and two energy peaks of about 5.43 $ 106

(m2s!2cph!1) and 2.54 $ 106 (m2s!2cph!1) corresponding to

periods of approximately 6 and 11 days, respectively. Finally, there

is a peak of energy of about 6.06 $ 106 (m2s!2cph!1) as important

as the diurnal signal with a period of about 40 days (Fig. 3b)

implying that the wind had a strong nearly monthly signal (40

days) over the study area, which could be associated to Atmo-

spheric Angular Momentum oscillation at different latitudes

(Magaña, 1993). The spectral analysis depicted the atmospheric

diurnal signal (23.67 h) and the meso-scale signal (6 and 11 days)

within the area, which are the main frequencies associated to

current velocities. The nearly monthly signal was also observed

with the absolute acoustic intensity signal of the backscatter (a 40

day signal obtained with a spectral analysis).

The wind induced currents in the continental shelf of the Gulf of

Mexico have been noticeably established on the basis of several

data sets (Biggs and Müller-Karger, 1994; Boicourt et al., 1998) and

from numerical models (Lugo-Fernández et al., 2001; Zavala-

Hidalgo et al., 2003). On the western continental shelf of the gulf,

the current patterns described in previous studies had a southward

component direction during the autumn and winter season, and

a northward component direction during the spring and summer.

The wind presented in a stick plot diagram during summer of 2008

PowerSpectra(m/s)cph

2-1

Time (day)

7

6

5

4

3

2

1

0

106

160 140 120 100 80 60 40 20 0

b

-5

0

5

10

S N J M M J S

Windvelocity(ms)-1

2008 2009

O D F A J AA

Summer Autumn Winter Spring Summer

a

Fig. 3. Wind from the weather station indicated in Fig. 1: a) Stick plot diagram of the daily winds (m s!1) from July 22, 2008 to September 22, 2009 in meteorological convention,

and b) Spectra of the hourly wind velocity, showing the main energetic components of the wind series.



and spring-summer of 2009 shows the southeasterly winds (winds

blowing from the southeast in meteorological convention) domi-

nance (Fig. 3a), and not southward (steered by the mountain range

which border the gulf in this area) as Gutierrez de Velasco and

Winant (1996) reported. The reversals of the winds blowing from

the north to the south from autumn 2008 to spring 2009 occurred

at short periods of time, <6 days (Fig. 3a), mainly attributed to the

development of atmospheric fronts over the area (Gutierrez de

Velasco and Winant, 1996; Salas-Pérez and Arenas-Fuentes, 2011).

In all cases, the wind and currents were out of phase by approxi-

mately 5.5 h and the magnitude of the currents induced by the

wind was higher than 15 cm s!1 on average. The winds reversal is

not typically observed during summer, this feature has only been

reported during spring (Zavala-Hidalgo et al., 2003) (Fig. 3a). In

contrast, during some periods of time during the autumn and

winter seasons, the wind had a northerly direction, with magni-

tudes below 10 m s!1 (Fig. 3a). These winds were observed at

frequencies of about 40,11, 6 and 1 days. During the summer season

of 2009 the southeasterly (winds blowing from the southeast in

meteorological convention) winds were predominant, which is the

typical direction observed during this season (Fig. 3a). The wind

direction has two predominant directions, from northeast and from

southeast (Fig. 3a). Since the PNSAV is a shallow area it may be

assumed that the current and the winds should move in the same

direction (frictional dynamics), however owing to the abrupt

bathymetric changes of the area and the influence of the meso-

scale circulation of the western Gulf of Mexico (Monreal-Gómez

et al., 2004; Boicourt et al., 1998) the currents (Fig. 4) did not

necessary flow in the same direction as the wind (Fig. 3a), sug-

gesting that the wind induced current may be modified by local

bathymetry and by the meso-scale circulation.

3.3. Vertically averaged currents

In order to elucidate the vertically averaged velocity through the

reefs at each mooring, a stick diagram of the vertically averaged

current was analyzed (Fig. 4). In the mooring located at AA, the

currents had in general magnitudes of 30 cm s!1 (Fig. 4a). It may be

assumed that this mooring should have the highest velocities

because it is located in the most exposed (northeastern) part of the

sampling area. For the mooring located at BB reef the maximum

currents took place between November 2008 and January 2009,

with velocities higher than 40 cm s!1 (Fig. 4b). However during the

remaining period themagnitudes were of approximately 20 cm s!1.

The strong current velocities located at this mooring were mostly

attributed to its location, since it is located in the northernmost part

of the sampling area exposed to the most energetic winds. The

magnitudes for the mooring located off BB reef, were not as strong

as for the one located off Anegada de Adentro (AA) owing to the

shallowness of the surrounding area. The AA reef is an extended

shallow reef when compared to the relatively short and deep BB

reef. As for the case of AA (Fig. 4a), the mooring located in IV (Fig. 1)

also had a southeastward predominant direction (Fig. 4d). The

maximum currents were of 30 cm s!1 with larger peaks reaching

values close to 55 cm s!1. The apparent paradox, southeastward

current direction with northeasterly, northerly and northwesterly

winds (Fig. 4b, c, d) was mainly attributed to the presence of the

northern reef (AA) and the coastal area which rectify the flow

toward the southeast. When the vectors were aligned with the

bathymetric contours the rectification could be generated by fric-

tion, and when the vectors are perpendicular to the isobaths the

currents could be rectified by potential vorticity, which could be

added to the flow of the Campeche Bay gyre. However, with the

data obtained at moored stations it is difficult to distinguish which

of the mechanism (friction or potential vorticity) is the responsible

of this flow.

Almost all the moorings were highly correlated among them,

however, the correlation of the vertically averaged speed between

AA and IS (0.87) were slightly higher than the correlation between

BB and IV (0.81). Once the currents were correlated by component

(u,v) its correlation increased. The correlation for the v (north-

south) component was always higher than 0.82, while the corre-

lation for the u (east-west) component ranged between 0.78 and

0.85. This was mainly attributed to the local bathymetry and the

presence of islands, which rectify the flow. The v component was

highly correlated among stations owing to the meso-scale wind

characteristics of the area. While the u component was more

influenced by the local bathymetry, since the reefs located closer to

the coast are protected by the seaward reefs (Fig. 1), producing

cyclonic and anticyclonic eddies (Salas-Monreal et al., 2009).

Therefore, the local bathymetry and the shallowness of the area

(bottom and lateral friction), modulate the wind induced currents.

Current observations analyzed in this study showed a strong

correlation with the different periods of wind oscillation, which

fluctuate from 1 day to approximately 40 days. These fluctuations

have a strong relevance in the low frequency of the current rever-

sals among seasons. Even though the fluctuation of the wind

direction and the vertically averaged mean current velocity were

correlated during most of the seasons (autumn 2008 and winter-

spring 2009) as previously described in several studies at large

and coastal scale (Caballero-Rosas, 1990; Zavala-Hidalgo et al.,

2003; Salas-Pérez et al., 2007; Salas-Monreal et al., 2009), this

study showed variations on their spatial structure. It is important to

emphasize that the vertically averaged mean current velocity

showed in Fig. 4 during the spring and summer season of 2009, did

not always shows a northward component as predicted by large

and coastal scale studies (Caballero-Rosas, 1990; Zavala-Hidalgo

Currentvelocity(cms)

-40

-20

0

20

IV

-20

0

20

AA

-60

-40

-20

0

20

BB

-60

-40

-20

0

20

-80

IS

Sep Nov Jan Mar May Jul Sep

2008 2009

-60

a

b

c

d

Fig. 4. Stick plot diagram of the vertically averaged currents (cm s!1) at a)Anegada de

Adentro (AA), b) Blanquilla (BB), c) Isla de Sacrificios (IS), and d) Isla Verde (IV), from

July 22, 2008 to September 22, 2009.



et al., 2003; Salas-Pérez et al., 2007; Salas-Pérez and Granados-

Barba, 2008; Salas-Monreal et al., 2009). During these seasons

the flow had a predominant southwestward and northwestward

direction. Those features imply that even though current velocities

had a strong large-scale component, coastal bathymetry is

responsible for the current rectification either by friction or

potential vorticity (Salas-Monreal et al., 2009).

The vertically averaged mean currents were computed with

their respective standard deviation ellipses for each mooring

(Fig. 5). The coastal currents of the area should be generated by the

seasonal wind patterns previously described, but influenced by

local bathymetry because the current vectors were mostly aligned

with the bathymetric contours (Falter and Sansone, 2000). The

current velocities observed during the summer season of 2008 at

30

2040

50

10

20

30 40

19.20

19.25

Latitude

10

10

10

10

10 cm s-1

a

30

2040

50

10

20

30 40

10

10

10

10

b

30

2040

50

10

20

30 40

10

10

10

10

c

30

2040

50

10

20

30 40

10

10

10

10

d

30

2040

50

10

20

30 40

-96.10 -96.05-96.15

Longitude10

10

10

10

e

19.20

19.25

Latitude

19.20

19.25

Latitude

-96.10 -96.05-96.15

Longitude

BB AA

ISIV

Fig. 5. Vertically averaged mean currents with their respective standard deviation ellipses for the different seasons, computed with one day time interval between observations. a)

Summer 2008. b) Autumn 2008. c) Winter 2008e2009. d) Spring 2009. e) Summer 2009.

Table 1

Summary of the correlation (r) and phase (q) analysis, between the seasonal winds and the vertically averagedmean current components (u,v) of eachmooring. Positive phase

means wind lags current event.

Mooring Summer 2008 Autumn 2008 Winter 2008e2009 Spring 2009 Summer 2009

Variable Variable Variable Variable Variable

r q r q r q r q r q

BB u 0.62 !192 0.60 !52 0.40 !110 0.36 24 0.66 !67

v 0.37 !198 0.39 60 0.40 !170 0.63 77 0.39 !61

AA u 0.38 !80 0.40 70 0.61 209 0.38 72 0.64 !68

v 0.39 !18 0.62 75 0.39 215 0.63 76 0.41 !63

IV u 0.70 !40 0.40 !519 0.62 208 0.35 47 0.67 !68

v 0.29 !41 0.63 76 0.39 215 0.62 78 0.59 !284

IS u 0.61 !257 0.59 52 0.61 209 0.35 48 0.31 !24.5

v 0.63 !315 0.63 !512 0.39 71 0.61 76 0.58 !283



the moorings (AA), (IS), (IV), during the winter at moorings (AA)

and (IS) and during the summer of 2009 at moorings (AA) and (IV)

showed magnitudes below 15 cm s!1, with a southwestward

component. It means that the flow is not in geostrophic balance

since the velocity vectors point in a transversal direction to the

bathymetry. Thus, the flow is ageostrophic (Fig. 5a, c, e).

During autumn 2008 and winter 2008 and 2009 (Fig. 5b and c),

the seasonal variability represented by the standard deviation

ellipses increased their major axis and the mean current magni-

tudes (>10 cm s!1). This feature is attributed to the generation of

atmospheric frontal system (northerly winds), with velocities

above 15 m s!1 (Salas-Pérez and Arenas-Fuentes, 2011). The verti-

cally averaged mean currents velocity during the spring season of

2009 was mainly oriented in a northwestward direction, with

magnitudes below 15 cm s!1 (Fig. 5d).

In general, the correlation of the seasonal wind patterns with

the seasonal vertically averaged mean currents, with predominant

southwestward and westward component for the current were

lower than 0.62 (Fig. 5e). It means that the Ekman transport is not

the major responsible of the southwestward and westward flow of

the current, the variability is then explained with the meso-scale

flow of the gyre of Campeche Bay (Monreal-Gómez et al., 2004;

Vázquez de la Cerda et al., 2005) and by flow rectification (poten-

tial vorticity) in the study area under the presence of reefs and

islands (Salas-Monreal et al., 2009).

The seasonal wind and the vertically averaged mean currents

were correlated to quantify their degree of dependence and phase

between both data sets. This analysis showed correlation values

higher than 0.5 for the u (east-west) component of the current,

while the phase indicate that seasonal currents are in general wind

generated, however during some periods of time the low correla-

tion between the current velocities and the wind (Table 1) sug-

gested the influence of other mechanisms (such as the gyre of

Campeche Bay and current rectification by potential vorticity) that

Fig. 6. Distribution of the annual total variance obtained with the Empirical Orthogonal Functions (EOF) for the yearly time series, mode 1 and 2 at Anegada de Adentro (AA),

Blanquilla (BB), Isla de Sacrificios (IS), and Isla Verde (IV), from July 22, 2008 to September 22, 2009. The first mode, associated with the wind induced current, is represented in the

left panels, and the influence of the meso-scale circulation or second mode is represented in right panels.

Table 2

Analysis of correlation between the first two modes of the EOF’s (Empirical Orthogonal Functions) with the NeS component of the wind. Symbol M1vsV indicates correlation

between Mode 1 and NeS component of the wind, and M2vsV indicates correlation between Mode 2 and NeS component of the wind.

Mooring season Mooring BB M1vsV/M2vsV Mooring AA M1vsV/M2vsV Mooring IV M1vsV/M2vsV Mooring IS M1vsV/M2vsV

Summer 2008 0.59/0.12 0.52/0.46 0.58/0.24 0.51/!0.24

Fall 2008 0.71/0.30 0.77/!0.24 0.74/0.30 0.78/0.19

Winter 2008e2009 0.76/0.16 0.73/0.26 0.78/0.25 0.76/!0.19

Spring 2009 0.73/!0.10 0.76/!0.19 0.73/0.13 0.74/!0.14

Summer 2009 0.55/0.22 0.51/0.19 0.52/0.33 0.67/!0.23



should modulate the current velocities. Furthermore in some

specific cases, the north-south wind component (v) had a lower

correlation with the measured currents than the east-west (u)

component (Table 1).

In order to elucidate the different forcing mechanism of the

area, an Empirical Orthogonal Function analysis of the filtered time

series were analyzed (Fig. 6), as observed in the distribution of the

total variance of the annual series there are two modes which

explains the variability of the currents in the PNSAV. Those modes

were attributed to the wind induced current in the PNSAV (because

of the previous correlation made between the first mode and the

NeS component of the wind, Table 2), and with the meso-scale

circulation associated to the large-scale circulation of the Gulf of

Mexico (this association was performed with maps of geostrophic

sea level anomalies and with the knowledge of the area), respec-

tively. The contributions of the diurnal tidal currents were not

analyzed since the aim of this study focuses on the seasonal

current.

During the summer season the distribution of the first mode

when compared to other seasons where lower (Fig. 6), this is

mainly attributed to the less energetic southerly winds, which had

a lower influence over the water column when compared to the

energetic northerly winds. In addition, the first mode (wind

induced currents) of the northerly moorings was reduced, since

Fig. 7. Progressive vector diagrams of the vertically averaged currents at the different seasons. a) Summer 2008. b) Autumn 2008. c) Winter 2008e2009. d) Spring 2009. e) Summer

2009. The initial position is marked by the name of the moorings. In summer of 2008, the scheme for BB was plotted at different scale.



they are protected from the southerly winds owing to the presence

of the southerly reefs (Fig. 1). While for the southerly moorings the

first mode increases due to their location.

3.4. Progresive vectors

The vertically averaged current velocity was influenced by wind

events associated with temporal fluctuations from diurnal to about

40 days period (Fig. 3b). Hence, an analysis employing the

progressive vector diagrams technique is presented to illustrate this

behavior. Fig. 7 shows the progressive vectors calculated from the

subtidal data set. In general two main features were observed:

Inertial oscillations with radius of hundred of meters along the

progressive vector diagrams and the random reversals of the flow

observed at periods of few days, in almost all seasons. The

progressive vector diagrams agree with the main direction of the

vertically averaged mean currents velocity described in Fig. 5 and

with the correlation analysis. However, during specific periods of

time the values of the correlation between the vertically averaged

current and the wind velocity (Table 1) were below what could be

expected according to frictional dynamics, where the wind and the

water velocity should have the same direction owing to the shal-

lowness of the system. The inertial oscillations inferred from the

progressive vectors also suggested that the system should not have

strong frictional dynamics as could be the case for shallow systems.

This is inferred since the progressive vectors did not follow strait

lines as would be the case of strong frictional dynamic systems. The

inertial oscillations have previously been described in a shallow

system in the southern Gulf of Mexico (Expósito-Díaz et al., 2009).

Therefore, two mechanisms were suggested from the Empirical

Orthogonal Function (EOF) analysis, the wind induced currents and

the meso-scale circulationwithin the Bay of Campeche (advection),

represented by a meso-scale cyclonic structure (Monreal-Gómez

and Salas de León, 1990; Vidal et al., 1994; Monreal-Gómez et al.,

2004; Vázquez de la Cerda et al., 2005). The Campeche Bay has

a cyclonic circulation, which has been described from observational

data (Vazquez de la Cerda et al., 2005) and from numerical model

studies (Monreal-Gómez and Salas de León,1990), the cyclonic gyre

start its development on the Campeche Bank, and shift westward

from August to December. This type of circulation affects the costal

circulation of the PNSAV inducing a southward flow pattern in the

study area.

The coastal area of thewestern Gulf of Mexico, where the PNSAV

is located has influence of the cyclonic eddy during the summer

season of 2008 and 2009 (Fig. 8). This eddy varies its size along the

seasons. In the southern Gulf of Mexico the current speed oscillates

Fig. 8. Altimeter maps of geostrophic anomaly current (NRL-NOAA Stennis Space Center), for the Campeche Bay, where the study area is located. a) 22 July, 2008. b) 03 August,

2008. c) 22 September, 2008. d) 22 July, 2009. e) 03 August, 2009. f) 22 September, 2009.



from low values during July to higher values during September

(Fig. 8a, b, c). Current direction associated to the eddy had

a southward predominant component, in the area where the

PNSAV is located, with an intensification of its magnitude from July

to September (Fig. 8). Thus, the current velocity observed in the

PNSAV should be associated to the wind induced currents and by

the meso-scale circulation induced by the cyclonic eddy (advec-

tion), mostly during the summer season, when the flow is ageo-

strophic. It is confirmed that the effect of wind velocity in the

northern PNSAV circulation modulate the distribution of bio-

volumes, since it mix the entire water column and bring nutrients

from the different river discharges (Alongi, 1990; Grimes and

Finucane, 1991; Salas-Pérez and Arenas-Fuentes, 2011). This

phenomenon is similar to the one observed in the Catalan Sea

located in the northwestern Mediterranean sea, where a shallow

coastal haline front produced by the Rhone River increases the

biovolume of the area (Sabatés, 1990).

The influence of the meso-scale circulation generate a second

maximum in the biovolumes time series, mainly attributed to the

intrusion of the high nutrient water from the southwestern Gulf of

Mexico. The interaction of the cyclonic eddy in the western Gulf of

Mexico with eddies detached from the Loop current, constituted

a source of exchange of chlorophyll, nutrients, phytoplankton and

zooplankton, between the open-sea (Gulf of Mexico) and the

coastal waters, but mostly from the coastal area to the open sea

(Biggs and Müller-Karger, 1994; Toner et al., 2003), particularly in

the outer boundaries of the eddies, with a jet stream varying in

magnitude and size, located in the Campeche Bay (Salas-Pérez and

Granados-Barba, 2008). But also, the interaction of the river

discharges with the meso-scale circulation generates a local

circulation in the PNSAV, which might be an efficient mechanism

for the exchange of physical and biogeochemical properties

between the open-sea and the coastal area as reported for the

planktonic communities in the southern Gulf of Mexico (Salas de

León et al., 1998).

Finally, with the data analyzed of this study there was no

evidence of upwelling owing to the association between the coral

reefs bathymetry and the flow induced by the meso-scale cyclonic

gyre of the Campeche Bay (Zavala-Sansón and Provenzale, 2009). At

coastal scale, water mixed by wind effect bringing nutrients to the

entirewater columnwhich increase the plankton biovolumes of the

study area. The current profiles analyzed in this study, did not

showed signals associated to internal or lee waves, which produce

plankton patchiness peaks, mostly because of the location of the

moorings (Lennert-Cody and Franks, 1999; Salas-Monreal and

Valle-Levinson, 2009).

4. Conclusions

The seasonal patterns of marine circulation and biovolume

were obtained from the year-long in-situ time-series measure-

ments in the Parque Nacional Sistema Arrecifal Veracruzano

(PNSAV), located in the western continental shelf of the Gulf of

Mexico. Two mechanisms were depicted as the responsible for the

current pattern observed in the PNSAV and not only one as sug-

gested with large and coastal scale models. The first mechanism is

the wind generated currents (friction) responsible for up to 78% of

total variation of the seasonal circulation in the PNSAV throughout

the entire year. The second mechanism is the low frequency

current associated to the large-scale circulation of the Gulf of

Mexico, owing to the meso-scale circulation of the Bay of Cam-

peche. The cyclonic eddy of the Campeche Bay was responsible for

the current fluctuations analyzed during the summer of 2008 and

2009, which induce the ageostrophic mean current flow. The

absolute acoustic intensity (plankton biovolumes) was highly

correlated to wind induced currents and it was also associated

with the position of the meso-scale gyre of Campeche Bay. The

biovolume showed its maximum value during the summer

with high spatial variability between time series, mainly attrib-

uted to advection produced by meso-scale circulation and river

discharges, but also by eddy diffusion produced by atmospheric

and coastal water fronts.

Acknowledgments

The financial support of the SEP-CONACYT (Mexico) grants

59882 and 78773 is gratefully acknowledge. Jorge Castro-Sánchez

improved the quality of the figures. The authors want to thank two

anonymous reviewers for their helpful comments that have

improved the context and presentation of the paper.

References

Alongi, D.M., 1990. The ecology of tropical soft-bottom benthic ecosystems.Oceanogr. Marine Biology Annual Review 28, 381e496.

Biggs, D.C., Müller-Karger, F.E., 1994. Ship and satellite observations of chlorophyllstocks in interacting cyclone-anticyclone eddy pairs in the western gulf ofMexico. Journal of Geophysical Research C99, 7371e7384.

Boicourt, W.C., Wiseman Jr., W.J., Valle-Levinson, A., Atkinson, L.P., 1998. Continentalshelf of the southeastern United States and the Gulf of Mexico: the shadow ofthe western boundary current. In: Robinson, A.R., Brink, K.H. (Eds.), The Sea, vol.11. John Wiley, Hoboken, NJ-USA, pp. 135e182.

Caballero-Rosas, A., 1990. Modelación hidrodinámica numérica de la circulación porviento en la zona costera del Puerto de Veracruz y sus proximidades. Masterthesis, Univ. Veracruzana, México.

Coronado, C.J., Candela, J., Iglesias-Prieto, R., Sheinbaum, J., López, M., Ocampo-Torres, F.J., 2007. On the circulation in the Puerto Morelos fringing reef lagoon.Coral Reefs 26, 149e163.

Emery, W.J., Thomson, R.E., 2001. Data Analysis Methods in Physical Oceanography,second and revised ed. Elsevier, Amsterdam, p. 346.

Expósito-Díaz, G., Salas-de-León, D.A., Monreal-Gómez, M.A., Salas-Monreal, D.,Vázquez-Gutiérrez, F., 2009. Inertial currents in the southern Gulf of Mexico.Ciencias Marinas 35 (3), 287e296.

Falter, J.L., Sansone, F.J., 2000. Hydraulic control of pore water geochemistry withinthe oxic-suboxic zone of a permeable sediment. Limnology Oceanography 45(3), 550e557.

Grimes, C.B., Finucane, J.H., 1991. Spatial distribution and abundance of larval andjuvenile fish, chlorophyll and macrozooplankton around the Mississippi Riverdischarge plume, and the role of the plume in fish recruitment. Marine EcologyProgress Series 75, 109e119.

Gutiérrez de Velasco, G., Winant, C.D., 1996. Seasonal patterns of wind stress andwind stress curl over the Gulf of México. Journal of Geophysical Research 101,18127e18140.

Holliday, D.V., Pieper, R.E., 1980. Volume scattering strengths and zooplanktondistributions at acoustic frequencies between 0.5 and 3 MHz. Journal of theAcoustic Society of America 67, 135e145.

Krutak, P.R., Rickles, S.E., Gío-Argáez, R., 1980. Modern Ostracod Species Diversity,Dominance and Biofacies Patterns Veracruz-Anton Lizardo Reefs, México, vol. 7.Anales del Instituto de Ciencias del Mar y Limnología, pp. 181e198.

Lennert-Cody, C.E., Franks, P.J.S., 1999. Plankton patchiness in high- frequencyinternal waves. Marine Ecology Progress Series 186, 59e66.

Lugo-Fernández, A., Desalrzes, K.J., Price, J.M., Boland, G.S., Morin, M.V., 2001.Inferring probable dispersal of Flower Garden Banks coral larvae (Gulf ofMexico) using observed and simulated drifter trajectories. Continental ShelfResearch 21, 47e67.

Magaña, V., 1993. The 40- and 50- day oscillations in atmospheric angularmomentum at various latitudes. Journal of Geophysical Research 98 (D6),10441e10450.

Monreal-Gómez, M.A., Salas-de-León, D.A., Velasco-Mendoza, H., 2004. La hidro-dinámica del Golfo de México: diagnostico ambiental del Golfo de México. In:Caso, M., Pisanty, I., Ezcurra, E. (Eds.), Instituto Nacional de Ecología, vol 1.SEMARNAT, México, pp. 47e68 (In Spanish).

Monreal-Gómez, M.A., Salas-de-León, D.A., 1990. Simulación de la circulación de labahía de Campeche. Geofisica International 29, 101e111.

Ressler, P.H., 2002. Acoustic backscatter measurements with a 153 kHz ADCP in thenortheastern Gulf of Mexico: determination of dominant zooplankton andmicronekton scatterers. Deep-Sea Research 49, 2035e2051.

Sabatés, A., 1990. Changes in the heterogeneity of meso-scale distribution patternsof larval fish associate with a shallow coastal haline front. Estuarine. Coastal andShelf Science 30, 131e140.

Salas de León, D., Monreal-Gómez, M.A., San Vicente-Añorve, L., Flores-Coto, C.,1998. Influence de la circulation à long terme sur la répartition des organismeszooplanctoniques dans la Baie de Campeche, Mexique. Oceanologica Acta 21,87e93.



Salas-Monreal, D., Salas-de-León, D.A., Monreal-Gómez, M.A.,RiveróneEnzástiga, M.L., 2009. Current rectification in a tropical coral reefsystem. Coral Reefs 28 (4), 871e879.

Salas-Monreal, D., Valle-Levinson, A., 2009. Continuously stratified flow dynamicsover a hollow. Journal of Geophysical Research 114, C03021. doi:10.1029/2007JC004648.

Salas-Pérez, J.J., Arenas-Fuentes, V., 2011. Winter water mass of the Veracruz reefsystem. Atmosfera 24 (2), 221e231.

Salas-Pérez, J.J., Granados-Barba, A., 2008. Oceanographic characterization of theVeracruz reef system. Atmosfera 21 (3), 281e301.

Salas-Pérez, J.J., Salas-Monreal, D., Arenas-Fuentes, V., Salas-de-León, D.A., Riveron-Enzástiga, M.L., 2008. Tidal characteristics at the Veracruz reef system (Westerngulf of Mexico). Ciencias Marinas 34 (4), 467e478.

Salas-Pérez, J.J., Vargas-Hernández, J.M., Arenas-Fuentes, V., Balderas-Cruz, P., 2007.In: Granados-Barba, A., Abarca-Arenas, L., Vargas-Hernández, J.M. (Eds.),Trayectoria de masas de agua en los sistemas arrecífales de Veracruz y modelosnuméricos: Circulación de verano: Investigaciones Científicas en el SistemaArrecifal Veracruzano. EPOMEX-UAC, México, pp. 17e26 (In Spanish).

Toner, M., Kirwan, A., Poje, A., Kantha, L., Müller-Karger, F., Jones, C., 2003.Chlorophyll dispersal by eddy-eddy interactions in the Gulf of México. Journalof Geophysical Research 108, 18127e18140.

Vázquez de la Cerda, A.M., Reid, R.O., DiMarco, S.F., Jochens, A.E., 2005. Bay ofCampeche circulation an update: circulation of the gulf of México: observationsand models. In: Sturges, W.E., Lugo-Fernández, A. (Eds.), GeophysicalMonograph Series, vol. 161. American Geophysical Union, USA, pp. 279e293.

Vidal, M.V.V., Hernández, A.F., Meza, E., Pérez-Molero, J.M., 1994. Baroclinicflows, transports, and kinematic properties in a cyclonic-anticyclonic-cyclonic ring triad in the Gulf of Mexico. Journal of Geophysical ResearchC99, 7571e7597.

Wolanski, E., Pickard, G.L., 1985. Long-term observations of currents on the centralGreat Barrier Reef continental shelf. Coral Reefs 4, 47e57.

Zavala-Hidalgo, J., Morey, S.L., O’Brien, J.J., 2003. Seasonal circulation on the westernshelf of the Gulf of México using a high resolution numerical model. Journal ofGeophysical Research C108, 1e19.

Zavala-Sansón, L., Provenzale, A., 2009. The effects of abrupt topography onplankton dynamics. Theoritical Population Biology 76 (4), 258e267.


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