Jane L. Guentzel Enrique Portilla-Ochoa
Alejandro Ortega-Argueta Blanca E. Cortina-Julio
Edward O. Keith
THE ALVARADO LAGOON – ENVIRONMENT,IMPACT, AND CONSERVATION
In: "Lagoons: Biology, Management and Environmental Impact”
Editor: Adam G. Friedman
ISBN: 978-1-61761-738-6 2011
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In: Lagoons: Biology, Management and Environmental Impact ISBN: 978-1-61761-738-6
Editor: Adam G. Friedman, pp. 397-415 © 2011 Nova Science Publishers, Inc.
Chapter 14
THE ALVARADO LAGOON – ENVIRONMENT,
IMPACT, AND CONSERVATION
Jane L. Guentzel1*
, Enrique Portilla-Ochoa2,
Alejandro Ortega-Argueta2,3
, Blanca E. Cortina-Julio2
and Edward O. Keith 4**
1Department of Marine Science, Coastal Carolina University, Conway, SC, USA
2 Investigaciones Biologicas, Universidad Veracruzana, Xalapa, Ver., Mexico 3 Ambiente y Sustentabilidad, Instituto de Ecología, Xalapa, Ver., Mexico
4 Oceanographic Center, Nova Southeastern University, Ft. Lauderdale, FL , USA
ABSTRACT
The Alvarado Lagoon System (ALS) in south-central Veracruz State, Mexico, is a
mangrove dominated coastal wetland formed by the confluence of the Acula, Blanco,
Limon and Papaloapan rivers. The ALS has a maximum width of 4.5 km, a mean surface
area of 62 km2, and is connected to the Camaronera Lagoon by a narrow channel and to
the Gulf of Mexico (GOM) via a 0.4 km wide sea channel. Water samples were collected
during the wet (September 2005) and dry (March 2003 and 2005) seasons. Salinity
ranged from 1-25.5 psu and pH was slightly alkaline (7.6-8.6). Levels of total organic
carbon (TOC), total mercury (Hg), and total suspended solids (TSS) ranged from 3.9-20.9
mg C/L, 0.92-26.1 ng Hg/L, and 1-39.2 mg TSS/L, respectively. The strong correlation
(R2=0.71; P=0.001) between total mercury and TSS in the water column suggests that
particulate matter is a carrier phase for mercury within the Alvarado and Camaronera
Lagoons.
The ALS is one of the most productive estuarine-lagoon systems in the Mexican
GOM. Model studies suggest that primary production by sea grasses provides more
energy input to the ecosystem than detritus, which is contrary to most other Mexican
GOM lagoons and estuaries. In 2004 the ALS was nominated Ramsar site no. 1355
because of its important biodiversity, ecological attributes, and high resource production.
* Corresponding authors: Email: [email protected]
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Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
398
Over 100 fish species have been collected from the ALS, representing four ecological
guilds: marine stenohaline, marine euryhaline, estuarine, and freshwater fishes. These
assemblages have not experienced significant changes over the past 40 years, but there
has been a recent decline in diversity. Antillean manatees (Trichechus manatus manatus)
historically have occurred in the ALS but were reduced in the 1970s and 1980s by
hunting and are now considered endangered. The rescue of 6 orphan calves between 1998
and 2000 suggests that manatees are reinhabiting the ALS as a result of conservation
measures. Manatees are most commonly sighted in the Alvarado Lagoon, Acula River
and adjacent lagoons, and are rarely sighted in the Limon River and adjacent lagoons. To
protect the manatees and their habitat an educational program was developed in 1998 and
an assessment of their current status and critical habitat in the ALS was conducted. Our
manatee conservation efforts were recognized in 2001 when September 7th was officially
declared the ―National Day of the Manatee‖ in Mexico. Almost 350 species of birds
occur in the ALS, including the Mexican Duck (Anas diazi), which is undergoing a slow
but marked decline due to habitat destruction and overhunting. The largest threats to the
ALS include unsustainable sugar cane cultivation, cattle-ranching, coastal urban
development, oil and gas exploration and exploitation, water pollution by urban waste
and agricultural runoff, and increases in port and tourism industries. Despite the
establishment of government policy and measures to protect the coastal wetlands of ALS,
the identified threats continue to menace the important biodiversity and human well-
being of the region.
INTRODUCTION
The Alvarado Lagoon System (ALS) in south-central Veracruz state (Figure 1), Mexico,
is a large mangrove dominated coastal wetland located 70 km southeast of the Port of
Veracruz. It has a total area of 2800 km2 of which 258 km
2 are covered by water. The
Alvarado Lagoon (AL) is a shallow system (average depth 1.5 m) connected to the
Camaronera Lagoon by a narrow channel and to the Gulf of Mexico (GOM) via a 0.4 km
wide sea channel [Moran-Silva et al., 2005, Cruz-Escalona et al., 2007]. The AL has a
maximum width of 4.5 km and a mean surface area of 62 km2. The ALS is mainly formed by
the Alvarado, Buen Pais, Camaronera and Tlalixcoyan lagoons, but it is also associated with a
great number of smaller aquatic bodies, flood zones, and parts of the Acula, Blanco, Limon
and Papaloapan rivers. The Papaloapan River extends through the states of Oaxaca, Puebla
and Veracruz and traverses a distance of 445 km, passing through the city of Tlacotalpan and
finally emptying into the AL. The Papaloapan drainage basin covers an area of approximately
39,200 km2.
The ALS is one of the most productive estuarine-lagoon systems in the Mexican GOM
[Cruz-Escalona et al. 2007]. It is characterized by a large diversity of interactions with its
adjacent systems, particularly an extensive marsh, which contributes greatly to its biological
productivity. Seasonal changes are well pronounced and are mainly influenced by the
precipitation-drought regime conditions associated with its ecosystem. The ALS has three
separate zones based on physicochemical characteristics; Camaronera Lagoon, Buen Pais
Lagoon and the urban zone of Alvarado Lagoon, and the river zone of Alvarado Lagoon
[Moran-Silva et al., 2005].
Model studies suggest that primary production by sea grasses provides more energy input
to the ecosystem than detritus, which is the opposite of most other Mexican GOM lagoons
The Alvarado Lagoon – Environment, Impact, and Conservation
399
and estuaries. This may be a consequence of relatively rapid flushing (50 x 109 m
3 of water
each year), a short water exchange time (0.5 days), mangrove deforestation, and overfishing
[Cruz-Escalona et al., 2007]. The increase of anthropogenic activities in the surrounding
terrestrial areas coupled with limited waste management planning have contributed to both
local and regional deterioration of the hydrological characteristics of the ALS [Cruz-Escalona
et al., 2007].
Figure 1. Satellite photograph of the Alvarado Lagoon System showing the major lagoons and rivers of
the area. Image courtesy of the Consejo de Desarrollo del Papaloapan (CODEPAP, 2003), Xalapa, Ver.,
Mexico
ENVIRONMENT AND IMPACT
Mercury and Other Water Quality Parameters
We collected sediment, fish, and unfiltered water samples from the Alvarado Lagoon,
Lagoon Camaronera, and the Gulf of Mexico during the wet (September 2005) and dry
(March 2003 and 2005) seasons (Table 1). Water column pH values were slightly alkaline
(7.6-8.6) and the salinity ranged from 1-25.5 psu. Precipitation amounts for the dry season
months of March 2003 and March 2005 were 0.23 cm, and 2.79 cm, respectively, and the wet
season month of September 2005 was 272 cm. Salinity in the ALS was inversely correlated
with rainfall, with highest levels occurring in the dry season samples (March 2003 and 2005)
and lowest levels occurring in the wet season samples (September 2005) (Table 2). Our
salinity values are similar to the salinity ranges (1-14 psu) reported for the lagoon during the
2000-2001 wet, dry, and storm seasons [Moran-Silva et al., 2005]. Levels of nitrate (NO3-N
mg/L) during the 2000-2001 season ranged from 0.03-0.14 mg N/L [Moran-Silva et al.,
2005]. Our values for nitrate (NO3-N mg/L) during the 2003 dry season ranged from 0.73-2.3
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
400
mg NO3-N/L. These values are slightly higher than the 2000-2001 values and may be
indicative of increasing anthropogenic stressors within the lagoon system. Estuaries are
considered at medium risk for eutrophication when nitrate values range from 0.1-1 mg N/L
and high euthrophic risk when the values are greater than 1 mg N/L [Bricker et al., 1999]. It
has been noted that nutrient levels within the lagoon can vary seasonally and spatially as a
result of river discharge, rainfall, resuspension of sediments, and biological activity [Moran-
Silva, et al. 2005]. Concentrations of total inorganic carbon (TIC) ranged from 14.4-22.1 mg
C/L and did not vary seasonally. Levels of total organic carbon (TOC) ranged from 3.9-20.9
mg C/L, with the highest concentrations observed during the rainy season (Table 2).
Total mercury and total suspended solids (TSS) ranged from 0.92-26.1 ng Hg/L and 1-
39.2 mg TSS/L, respectively (Table 2). The strong correlation (R2=0.71; P=0.001) between
total mercury and TSS in the water column suggests that particulate matter is a carrier phase
for mercury within the Alvarado and Camaronera lagoons. A more comprehensive study of
the Alvarado Lagoon, and the Limon, Acula, Blanco, and Papaloapan rivers conducted during
the March 2003 and 2005 dry seasons and the September 2005 wet season found that mercury
concentrations were significantly correlated with total suspended solids in the water column
(R2=0.82; P<0.001) [Guentzel et al., 2007]. The mercury concentrations in the Alvarado
Lagoon, and the Blanco, Acula, and Limon rivers during the March 2003 and 2005 dry
seasons (0.9-4.9 ng Hg/L) were similar to the September 2005 wet season (1.9-4.9 ng Hg/L),
with higher Hg levels associated with higher levels of TSS. Water samples collected from the
Papaloapan River were higher in Hg (10.9-12.7 ng (Hg/L) and TSS (89.1-154.7 mg TSS/L)
during the September 2005 wet season than the March 2003 and 2005 dry seasons (0.9-2.7 ng
Hg/L; 4.8-39.7 mg TSS/L). The sites from the Papaloapan River were sampled within 12
hours of a nighttime rainfall (15cm) event during the September 2005 wet season. The
elevated Hg concentrations from this site during the wet season are likely a result of increased
particulate matter transport within the river during high flow conditions and or input of
dissolved and particulate Hg from precipitation [Guentzel et al., 2007]. A Mercury Deposition
Network (MDN) monitoring site (HD01) within this region reported a rainfall Hg
concentration of 11.4 ng Hg/L during the time period that the samples were collected from the
Papaloapan River [Mercury Deposition Network]. The water column values that we observed
for total Hg (0.92-26.1 ng/L) are below the US EPA ambient surface water quality criteria for
freshwater (0.77-1.4 µg/L) and saltwater (0.94-1.8 µg/L) (US EPA, 2006) and the Mexican
marine aquatic life criteria of 0.02 µg/L [Jimenez et al., 1999].
Table 1. Station identifications and locations for
mercury and other water quality parameters
Latitude Longitude
Station Identification (N) (W)
Alvarado Lagoon I 18 46.132 095 47.333
T 18 45.955 095 48.607
BB 18 44.995 095 44.966
Lagoon Camaronera DD 18 51.178 095 54.654
EE 18 51.589 095 55.187
FF 18 51.716 095 54.412
Gulf of Mexico AA 18 48.422 095 44.420
Table 2. Water quality parameters measured during the March 2003 and 2005
dry season and the September 2005 wet season
, Month Station Salinity
(psu)
Nitrate
NO3-N
(mg/L)
pH Total
Inorganic
Carbon
(mg C/L)
Total
Organic
Carbon
(mg C/L)
Total
Suspended
Solids
(mg/L)
Total
Mercury
(ng/L)
Alvarado Lagoon March 2003 I 9.9 2.3±0.9 8.1 14.9±4.2 5.4±2.1a 9.1±4.5a 0.92±0.05a
March 2003 T 9.8 1.35 8.0 14.4 4.7a 1a 1.78a
March 2003 BB 6.7 1.51 7.9 14.7 3.9a 14.1a 2.67a
March 2005 T 12.9 - 8.1 22.1±0.16 9.5±0.98a 9.1±5.6a 0.92±0.03a
September 2005 T 1 - 7.6 16.7 20.9a 25a 3.8a
Lagoon Camaronera March 2003 DD 14.5 0.86 8.2 17.2 7.3 39.2 26.1
EE 14 1.08 8.2 17.6 7.8 18.6 5.2
FF 13.8 0.75 8.3 17.9 7.6 20.5 10.3
Gulf of Mexico March 2003 AA 25.5 0.73±0.8 8.6 16.4±0.47 6.5±0.04a 1.13a 1.27±0.01a
The values for March 2003 stations I and AA, and March 2005 station T represent the mean and standard deviation of 2 replicate field samples. ―a‖ denotes that
the total organic carbon, total suspended solids and total mercury data for the Alvarado Lagoon and Gulf of Mexico are taken from Guentzel et al., 2007. ―-
― denotes that there is no data for this parameter.
Table 3. Mercury concentrations in fish, crab, shrimp, and squid and log bioconcentration
(BCF) factors from the Alvarado Lagoon system
n Total Hg (ug Hg/g-wet) Log BCF
March March September March March September
2003 2005 2005 2003 2005 2005
Brown Shrimp (Peneus aztecus)* 20, 20, 20 0.008±0.001 0.065±0.01 0.008±0.001 3.6 4.6 3.6
Bay Squid (Lolliguncula brevis)* 3 0.024±0.002 4.2
Blue Crab (Callinectes rathbunae)* 3 0.026±0.002 4.2
White Mullet (Mugil curema)* 2 0.057±0.026 5.6
Sheepshead (Archosargus
probatocephalus)*
1 0.082 4.7
Big Mouth Sleeper (Gobimorus dormitor)* 2 0.106±0.02 4.8
Fat Snook (Centropomus parallelus)* 2 0.152±0.034 4.9
Spine Snook (Centropomus ensiferus)* 1 0.184 5.1
Striped Moharra (Eugerres plumeri)* 1, 2 0.35 0.301±0.117 5.3 5.3
Catfish (Bagre marina)* 1 0.291 5.3
*The data for mercury concentration is taken from Guentzel et al., 2007. The log BCF is calculated as Log 10([Hg in tissue]/[Hg in water]). The average water
concentration of Hg was 1.6 ng/L. n=the number of samples.
The Alvarado Lagoon – Environment, Impact, and Conservation
403
We collected sediment from the lagoons and nearby rivers within the ALS. Total mercury
at station T in the AL ranged from 13-22 ng Hg/g-wet and the %C and %N ranged from 0.23-
0.77% and 0.31-0.37%, respectively. Total Hg from sediments in the adjacent rivers (Acula,
Limon, Blanco, and Papaloapan) ranged from 10-78 ng Hg/g wet and the %C and %N ranged
from 05-8.9% and 0.31-0.9%, respectively. There was a moderate correlation (R2=0.435,
p=0.020) between the total Hg and % carbon in the sediments from the ALS [Guentzel et al.,
2007]. The total Hg values for the sediment we collected are below the threshold effects level
of 130 ng Hg/g dry for marine sediments [Buchman 1999] and are within the US EPA
background sediment criteria of 0-300 ng Hg/g dry (US EPA 1997). Aquatic biota that
represent ~87% of the annual catch from the ALS [Cruz-Escalona et al., 2007] were collected
and analyzed for total Hg (Table 3). The total Hg concentration in the invertebrate species
(shrimp, squid, crab) ranged from 0.008-0.026 μg Hg/g wet and the vertebrate species ranged
from 0.082-0.35 μg Hg/g wet. The levels of Hg in the piscivorous and omnivorous fish
(catfish, moharra) are at or slightly above the recommended consumption level of 0.3 μg Hg/g
wet [NAS, 2000].
The log bioconcentration factors for total Hg in the organisms we collected ranged from
3.9-5.3, with no observable seasonal difference (Table 3). Activities such as biomass burning
for land clearing, mangrove deforestation, and urbanization are known stressors to the ALS.
These activities are also associated with increased mercury mobilization in aquatic and
terrestrial environments, which can result in an increase in the bioaccumulation of mercury in
biota from these systems [Friedli et al., 2003; Porvari et al., 2003; Munthe et al., 2007]. There
are a large number of indigenous riverbank communities within the ALS that rely on fishing
for comestible and economic subsistence. Reported total Hg levels in hair samples from
individuals that reside and consume fish from within the ALS ranged from 0.10-3.36 µg Hg/g
(n=47) [Guentzel et al., 2007]. Of these values, 58% are above the recommended
consumption limit of 0.1 µg Hg/kg body/day which corresponds to a hair level of 1.0 µg Hg/g
[NAS, 2000]. Anthropogenic activities that mobilize Hg could result in an increase in the
mercury content of the fish and seafood from the ALS which may ultimately lead to increased
body burdens of mercury in the indigenous peoples that reside in this region.
Vegetation
The ALS features representative and diverse ecosystems of Mexico´s Gulf coastal plain,
such as coastal dunes, reed beds of Cyperus spp., cattail Typha spp., palm forests of Sabal
mexicana, Scheelea liebmannii, and Acrocomia mexicana, oak forest of Quercus oleoides;
apompales (Pachira aquatica), and a large mangrove forest dominated by Avicenia
germinans, Laguncularia racemosa, and Rhizophora mangle [Vazques-Torres, 1998]. There
are 15 distinguishable landscape units (LU) in the area [Portilla-Ochoa et al., 1998 and Silva-
López and Portilla-Ochoa 1998]. The LU were first differentiated as areas disturbed by
agricultural activities, areas disturbed by cattle ranching, and areas where human intervention
is not yet considerable, such that natural vegetation remains the dominant landscape element.
Each LU was described in terms of land use, seasonal flooding, vegetation cover (i.e. primary
and secondary), predominant exploitation systems, the physical medium (i.e. substrate origin
and soil type), hydrologic characteristics, and other data (e.g. human settlements, main roads,
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
404
and observations on deforestation, urban and rural infrastructure, and industrial development)
[Silva-López and Portilla-Ochoa 1998 ].
Fish
There are 107 fish species that have been collected in the ALS which represent four
ecological guilds: marine stenohaline, marine euryhaline, estuarine, and freshwater fishes.
Fish assemblages of the Alvarado Lagoon Estuary have not experienced significant changes
over 40 years, but there may have been a decline in fish biodiversity during that period
[Chávez-López et al., 2005a]. A comprehensive study of Mayan cichlids conducted in the
ALS, by Chavez-Lopez et al., 2005b, reports that there are three genera and seven species of
cichlids (Cichlidae) with the Mayan cichlid (Cichlasoma urophthalmus) being the species
with the highest abundance. The Mayan cichlid is distributed throughout southeastern Mexico
where it inhabits rivers and coastal lagoons. In the ALS it is distributed towards the north in
Camaronera Lagoon. The Mayan cichlid inhabits oligohaline to mesohaline sites that are well
oxygenated and contain submerged vegetation and deep transparent water. The major
abundance and biomass of this species was obtained during December to February. The diet
of Mayan cichlids is primarily herbivorous and consists mainly of plant detrital material and
algae. There are two size classes that occur during the dry and rainy seasons which
correspond to young of the year and reproductive fish. There is only one modal size class of
fish between 60–100 mm during the stormy season. Although individuals with developed
gonads are found throughout the year, the most reproductive adults are found between April
and December. The highest gonadosomatic index (GSI) values occurred during the May
through July time period of peak reproductive activity [Chávez-López et al., 2005b]. Other
families with numerous species reported within the ALS include the Eleotridae and the
Gobiidae, and the species with the highest abundance and biomass were Gambusia affinis,
Petenia splendida, Cathoropus melanopus, Diapterus auratus, and Bathygobius soporator
[Shareet et al., 2009].
A study by Pelaez-Rodriguez et al., (2005) examined the diet of demersal piscivorous
fishes captured as bycatch by the commercial shrimping fleet just ouside of the ALS . Nine
collections distributed throughout the stormy, wet, and dry seasons from November 1993 to
January 1995 yielded a total of 646 fishes which represented 10 families and 14 species.
44.9% of these collections had empty digestive tracts and were excluded from the study. The
most abundant species of dermersal predators found were Trichiurus lepturus and Synodus
foetens. Differences in food consumption of the seven most abundant predators were
observed among the 3 seasons. The greatest variety of prey (20 species) occurred during the
stormy season and the lowest variety (nine species) occurred during the dry season. Prey type
and location of prey within the water column helped to determine the classification of five
distinct trophic guilds based on an overall index of relative importance of prey. The
occurrence of these different trophic guilds may contribute to decreased competition for food
resources on the continental shelf off of Alvarado lagoon [Peláez-Rodríguez et al., 2005].
The Alvarado Lagoon – Environment, Impact, and Conservation
405
River Otters
A study of the neotropical river otter (Lontra longicaudis annectens) and its habitat based
on personal observations and the information provided by fishermen of the ALS, yielded
three observations of adult otters hunting and eating in lagoons and rivers, together with
records of otter tracks and feces. In addition, an adult otter skin was found in a fisherman‘s
house in November 2002, where residents of the ALS said the otter was killed that year. All
of these records were collected in three of the most conserved LU of the system, which
include an area of 607 km2, encompassing more than 22.7 % of the total area of the ALS
[Silva-López, 2009]. These observations and records, along with comments made by other
Alvarado fishermen, suggest the neotropical river otter occupies the ALS year-round, and
emphasizes the need to conduct more detailed surveys and studies to determine the present
status and ecology of the ―perro de agua‖ (as it is locally known) and its habitat [Silva-López,
2009].
Manatees
Antillean manatees (Trichechus manatus manatus) have historically occurred in the ALS,
representing one of the most important areas for manatees in the southern GOM.
Overexploitation reduced their numbers in the 1970s and 1980s and they are now considered
endangered throughout their range in Mexico. However, the rescue of six orphan calves
suggests that manatees may be increasing in the ALS. Historically, the Antillean manatee was
found from northern Veracruz state along the west coast of the GOM to the eastern coast of
the Yucatan peninsula and the Mexico-Belize border [Lluch, 1965, Lefebvre et al., 2001,
Morales-Vela et al., 2005]. However; hunting, water quality degradation, and the destruction
of breeding habitat has caused a decline in the number of manatees [Campbell and Gicca,
1978, Colmenero and Hoz, 1986].
There is little information regarding the life history of manatees in the state of Veracruz.
It is not known if they migrate, as the Florida subspecies (Trichechus manatus latirostris)
does in the United States [Deutsch et al., 2003], or whether they are year-round residents of
their local habitat, as is typical of Antillean manatees in the Yucatan Peninsula of Mexico and
in Belize [Morales-Vela et al., 2000, Self-Sullivan et al., 2003]. Movements of Antillean
manatees in Chetumal Bay, on the east coast of the Yucatan Peninsula, do not appear to be
influenced by cloudiness, atmospheric pressure, or temperature, in contrast to the Florida
manatee that migrates seasonally in response to intra-annual changes in water temperature
[Axis-Arroyo et al., 1998, Deutsch et al., 2003]. However, movements of Antillean manatees
in Chetumal Bay were moderately associated with water salinity (as in Florida), depth and
group structure [Axis-Arroyo et al., 1998]. Manatees in Florida seem to prefer areas with
access to freshwater that they require for osmoregulation. The salinity in the waters of the
ALS decreases with distance from the ocean, and the potential influence of this salinity
gradient on the movements of manatees in the ALS is unknown. Manatees in Nicaragua
undergo seasonal migrations, and their daily movements appear to be influenced by tides,
which may also influence water salinity [Jimenez, 2002]. In the ALS fishermen have reported
that manatees were quite common in the region in the mid-1900s. Even though large scale
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
406
hunting of manatees was not practiced in ALS, the sale of meat in the town market of
Alvarado during the 1970‘s was common [Ortega-Argueta, 1999], and poaching continues to
be an important threat to the species. Studies conducted in the mid 1980s reported the
disappearance of manatees from the ALS [Colmenero, 1984]. Nevertheless, recent reports
from local residents of the ALS, and the incidental capture of manatee calves, have confirmed
their continued occurrence in the Alvarado region [Ortega-Argueta, 1999; Portilla-Ochoa et
al., 1999]. A recent study assessing manatee distribution and habitat utilization found that
manatees could potentially be found in 3150 km2 of lowlands and wetlands in the ALS
(Figure 2) [Ortega-Argueta, 2002]. Habitats selected by manatees include estuaries, mangrove
wetlands and unpopulated areas. The marine zone appears not to be utilized permanently by
manatees, although they may move locally between rivers along the coast through the marine
zone. Threats to the manatees in the ALS include the clearing of land for sugar cane
cultivation, cattle-ranching, coastal urban development, mangrove deforestation, increases in
port and tourism industries in the coastal zone, water pollution, and oil and gas exploration
and exploitation [Ortega-Argueta, 1999, 2002].
Rodriguez-Ibañez [2004] investigated the knowledge, use, and cultural traditions of the
inhabitants of the ALS with respect to the Antillean manatee using oral interviews. She found
a large number of correlations between the inhabitants‘ oral history knowledge of manatee
movements and habitat use with current scientific knowledge as determined by a review of
the literature. Additionally, many inhabitants knew a lot about the hunting, butchering, and
preparing of manatee meat for human consumption. Such hunting has reduced the manatee
population in the ALS to very low levels [Ortega-Argueta et al., 2003].
Figure 2. Classification of manatee habitat within the Alvarado Lagoon System (from Ortega-Argueta,
2002). Most of the best habitat lies in the lagoons along the Limon river and in lagoons between the
Limon and Acula rivers. The Papaloapan river is not good manatee habitat due to its rapid current and
channelizing with dikes that prevent animals from entering and leaving the river easily.
The Alvarado Lagoon – Environment, Impact, and Conservation
407
During several interview surveys conducted with local inhabitants and fishermen,
besides boat and airplane surveys in 2000, 2005 and 2006 it was revealed that manatees are
common in the ALS around the year [Ortega-Argueta, 2002, Portilla-Ochoa et al., 2006,
2007, Keith et al., 2009]. Manatees are most commonly sighted in the Acula River and
adjacent lagoons, and are rarely sighted in the Limon River and adjacent lagoons (Figure 3).
Most of the interviewees reported that manatees are not as abundant now as compared to
three decades ago, but their numbers have increased in the past few years (Figure 4). Most of
the sightings are of adult animals, although females and calves are infrequently seen (Figure
5). Most sightings occur in the rainy season (Figure 6), and most sightings are unique in the
sense that an animal is usually only seen once, rather than frequently or repeatedly (Figure 6).
Respondents thought that manatees predominantly feed on marsh plants and water hyacinth,
with ―grasses‖ and other emergent plants also being important in the diet (Figure 7). A recent
survey of the ALS using visual, acoustic, and side-scan sonar methods estimated the
abundance of manatees in the ALS at 0.93 manatees/ha ± 0.39 (95% CI) [Serrano-Solis,
N.D.].
Figure 3. Locations of manatee sightings (from both vessels and aircraft), interviews and evidence of
manatee butchering (from Ortega-Argueta, 2002).
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
408
Figure 4. Increase in the number of manatee sightings over the past decade as determined by interviews
with residents of the ALS. Most of the interviewees reported that manatees are not as abundant now as
compared to three decades ago, but their numbers have increased recently. This increment in
observations may reflect a recovery of the manatee population; a more dedicated monitoring effort; or
an increase of the appeal of the species as results of the education and awareness campaigns.
Figure 5. Age-class of manatees sighted in the ALS as determined by interviews with residents. Most of
the sightings are of adult animals, although females and calves are infrequently seen
Figure 6. Seasonality and frequency of manatee sightings in the ALS as determined by interviews with
the residents. Most of the sightings occur in the rainy season and most sightings are unique in the sense
that an animal is usually only seen once, rather than frequently or repeatedly
The Alvarado Lagoon – Environment, Impact, and Conservation
409
Figure 7. Foods of manatees as reported by residents of the ALS. Respondents thought that manatees
predominantly ate marsh plants and water hyacinth, with ―grasses‖ and other things also being
important in the diet
We also found that the inhabitants of the ALS maximized their use of the manatees killed
in the distant past, including the medicinal use of powdered manatee bones and manatee fat,
and the use of manatee bones and teeth in the production of artifacts. This suggests that
manatees played a significant role in the culture of these riverbank communities in the past. A
majority of those interviewed (82%) said they were interested in protecting animals liberated
near their homes in the ALS. However, several respondents expressed concern that neighbors
would kill released animals and/or that hunting would continue because of lack of
enforcement of the laws [Portilla-Ochoa et al., 2006, 2007, Keith et al., 2009]. Manatee
poaching continues in many areas despite official protection. This illegal activity is still
practiced for a number of reasons: tradition; an appreciation of manatee meat, which is
considered a delicacy; ignorance of national laws and sanctions in force to protect the
manatee, and limited inspection and vigilance by Mexican environmental and regulatory
authorities (Ortega-Argueta, 1999).
CONSERVATION
The coastal wetland lagoon system of Alvarado is one of the most productive such
systems in Veracruz and the third largest wetland in Mexico. A total 350 species of birds have
been registered in the ALS, including the Mexican Duck (Anas diazi), which is undergoing a
slow but marked decline due to habitat destruction and overhunting. The ALS has been
considered a high priority region for conservation [Arriaga-Cabrera et al., 1998; CONABIO,
1998; Dugan, 1993], including recognition by the North American Wetlands Conservation
Council (NWCCA), the International Council for Bird Preservation-Mexico Chapter
(CIPAMEX), and Mexico‘s Commission on Biodiversity (CONABIO). Notable, too, are the
threats, including agricultural encroachment and increasing levels of contamination from
urban wastewater and pesticides. A newly funded program will enable the municipality of
Alvarado and Pronatura Veracruz (local NGO) to strengthen the environmental education
program in Alvarado schools; teach sustainable management techniques to local communities
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
410
and train them to be conservation promoters; and develop wetland-conservation outreach
materials for use by local authorities. A conservation easement will be pursued at a site of
high importance to wetland-associated birds. Partners will work to reduce the effects of cattle
ranching on wetland resources and will continue monitoring resident and migratory birds in
the area. These activities will be coordinated with the newly formed Veracruz State
Committee for Conservation of Wetlands.
One of the most important achievements of our conservation activities in Veracruz was
the nomination of Alvarado lagoon system as a Ramsar Site. On February 4th
, 2004, the ALS
was designated Ramsar Site No. 1355 through the efforts of the Institute for Biological
Research (IBR) at the University of Veracruz, and other organizations such as the North
American Wetlands Conservation Council. The area encompasses 2671 km2 that includes
most of our proposed critical manatee habitats and other areas that are crucial to manatee
survival. The ecological description of the site mentions the region‘s importance to this
endangered species. The IBR is taking further actions with the collaboration of local
authorities in order to assure the implementation of protective measures and to establish a
Regional Management Plan for the area. Further information on the ALS Ramsar Site can be
found on the following web page: http://www.ramsar.org/wwd2004_rpt_mexico1.htm.
After several workshops involving specialists and governmental agencies, including the
―Technical Advisory Subcommittee for Manatee Recovery in Mexico‖, it was concluded that
in order to protect the manatees in the ALS from continued poaching, the primary mortality
factor, an education and awareness program should be developed throughout the ALS.
Additional components included an assessment of the current status of manatees in the ALS
and the identification of critical manatee habitats within the ALS [Ortega-Argueta, 1999,
2002, Portilla-Ochoa et al., 2002]. These efforts led to the preparation of a ―Regional Manatee
Recovery Plan in the Wetlands of Alvarado, Veracruz, Mexico‖ [Ortega-Argueta et al., 2001,
2002, 2003], and culminated in 2001 when September 7th
was officially declared the
―National Day of the Manatee‖ in Mexico. With the potential for the release of rehabilitated
manatees from the Veracruz Aquarium into the ALS, there is need for continued educational
and informational campaigns to further educate the local community about the need to protect
and conserve manatees and their habitat. Over the intervening years our educational,
conservation, and outreach activities have continued, including informative workshops for
children and adults in the communities within and surrounding the ALS, boat surveys of the
ALS for manatees, interviews with fishermen and others familiar with the ALS and putative
manatee habitats there, and continued celebration of the ―National Day of the Manatee‖
[Ortega-Argueta et al., 2001, 2002, 2003, Portilla-Ochoa et al., 2002,].
The rescue of orphan manatees in the ALS suggested that the population of manatees
might be rebounding, and this has motivated the conservation and education efforts of the
past decade [Ortega-Argueta et al., 2002, 2003]. During this period, six orphan manatees have
been rescued from the ALS and transported to the Veracruz Aquarium in the city of Veracruz,
Mexico. A seventh animal was rescued but subsequently died from a gunshot wound. As the
captive population in the aquarium has grown, they have constructed a new, larger, manatee
pool and viewing area, sufficient to support 4-6 manatees. The possibility that more orphan
manatee calves may be encountered in the future has raised the concern that the aquarium will
no longer be able to continue to accept new orphans without some mechanism to decrease the
total number of animals being cared for there. The ability to release some animals will
increase the Aquarium‘s capability to foster new orphans if and when they should be found.
The Alvarado Lagoon – Environment, Impact, and Conservation
411
Rehabilitation strategies and sites for release are being discussed in the Manatee Advisory
Committee.
An agency of the government of the state of Veracruz, the ―Papaloapan Development
Council‖ (Consejo de Desarrollo del Papaloapan, CODEPAP) has recently constructed two
concrete-lined tanks suitable for manatee husbandry along the banks of the Acula River in the
central ALS. These tanks were designed and constructed to facilitate the reintroduction of
captive manatees into the ALS. Plans are currently underway to transfer some of the manatees
from the Veracruz Aquarium to these tanks and to begin their transition to a free-ranging
existence. Once the manatees have become accustomed to feeding on the native vegetation,
and have been weaned from their dependence on humans, it is anticipated that they will be
released into an enclosure along the bank of the Acula River, and eventually into their native
habitat. Such husbandry constitutes an opportunity to rehabilitate and release individuals of
one of the most threatened species in Mexico.
CONCLUSION
The Alvarado Lagoon System is a mangrove dominated coastal wetland formed by the
confluence of the Acula, Blanco, Limon and Papaloapan rivers. The ALS is one of the most
productive estuary-lagoon systems in the Mexican GOM. It has a total area of 2800 km2 of
which 258 km2 are covered by water with an average depth of 1.5 m. Vegetation of the ALS
includes diverse ecosystems representative of Mexico´s Gulf coastal plain. Salinity in the
ALS was inversely correlated with rainfall, with highest levels occurring in the dry season
samples (March 2003 and 2005) and lowest levels occurring in the wet season samples
(September 2005). Concentrations of total inorganic carbon did not vary seasonally, while
levels of total organic carbon were higher during the rainy season. A strong correlation
between total mercury and total suspended solids in the water column suggests that
particulate matter may be a carrier phase for mercury within this lagoon system.
Historically, Antillean manatees were found in the ALS and along the west coast of the
Gulf of Mexico to the eastern coast of the Yucatan peninsula and the Mexico-Belize border.
However, hunting, water quality degradation, and the destruction of breeding habitat has
caused a decline in the number of manatees and they are now considered endangered
throughout their range in Mexico. Manatee habitat in the ALS includes estuaries, mangrove
wetlands and unpopulated regions, with a total potential area of 3150 km2.
Interviews with the inhabitants of the ALS reveal important correlations between their
oral history knowledge of manatees with current scientific knowledge. They also knew a lot
about the hunting, butchering, and preparing of manatee meat for human consumption. The
inhabitants maximized their use of the manatee carcass, including the medicinal use of
powdered manatee bones and manatee fat, and the use of manatee bones and teeth in the
artisanal production of artifacts, suggesting that manatees played a significant role in their
culture in the past.
A majority of those interviewed said they were interested in protecting manatees, but
several expressed concern that hunting would continue because of lack of enforcement of the
laws. Manatee poaching continues for a number of reasons including tradition; an
Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al.
412
appreciation of manatee meat that is considered a delicacy; ignorance of national laws and,
and limited vigilance by Mexican environmental and regulatory authorities.
In 2001, September 7th
was officially declared the ―National Day of the Manatee‖ in
Mexico. Our educational and informational campaigns have continued in order to educate the
local communities about the need to protect and conserve manatees and their habitat. In 2004,
the ALS was designated Ramsar Site No. 1355 and a ―Regional Manatee Recovery Plan in
the Wetlands of Alvarado‖ was prepared. Over the past decade, six orphan manatees have
been rescued from the ALS and transported to the Veracruz Aquarium in the city of Veracruz.
Two concrete-lined tanks suitable for manatee husbandry have recently been constructed
along the banks of the Acula River in the central ALS. These tanks were designed and
constructed to facilitate the reintroduction of captive manatees into the ALS. Such efforts
constitute an important opportunity to rescue, rehabilitate, and release individuals of one of
the most threatened species in Mexico.
Continuing threats to the ALS include increasing anthropogenic activities both within the
lagoon system and in its surrounding terrestrial areas. Limited waste management planning
and practices have contributed to deterioration of its hydrological characteristics. Overfishing,
manatee poaching, and loss of habitat have lead to a significant deterioration in the quality of
ecosystem services provided by the ALS. Despite the establishment of government policy and
measures to protect the coastal wetlands of ALS, the identified threats continue to menace the
important biodiversity and human well-being of the region.
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