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THE ALVARADO LAGOON – ENVIRONMENT, IMPACT, AND CONSERVATION Jane L. Guentzel Enrique Portilla-Ochoa Alejandro Ortega-Argueta Blanca E. Cortina-Julio Edward O. Keith

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In: "Lagoons: Biology, Management and Environmental Impact” Editor: Adam G. Friedman ISBN: 978-1-61761-738-6 2011

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. The license for this PDF is unlimited except that no part of this digital document may be reproduced, stored in a retrieval system or transmitted commercially in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.

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** 1

Department 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] [email protected]

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Jane L. Guentzel, Enrique Portilla, Alejandro Ortega-Argueta et al. 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 wellbeing 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 km2 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

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and estuaries. This may be a consequence of relatively rapid flushing (50 x 109 m3 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

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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 [MoranSilva, 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 139.2 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