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| The Alvarado Lagoon – Environment, Impact, and Conservation pp. 397-416 |
$100.00 |
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Authors: (Jane L. Guentzel, Enrique Portilla, Alejandro Ortega, Blanca Cortina Julio, Edward O. Keith, Department of Marine Science, Coastal Carolina University, Conway, South Carolina, USA, and others)
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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. 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. |
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