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Litter falls and their contributions to soil nutriments were measured in five distinct facies of a mangrove in French Guyana. These facies were characterized by their distance from the sea, their floral composition (Laguncularia racemosa (L.), Avicennia germinans (L.) Stearn, Rhizophora spp.), and their structural features. Data were analyzed according to facies and to species for litters, as well as to seasons for the nutriments. This mangrove produced respectively 8.8 and 8.7 t·ha–1·year–1 of litter at the pioneer and senescent stages submitted to strong environmental constraint and 12.5 and 12.6 t·ha–1·year–1 for young and mature stages where developmental conditions are optimum. Nitrogen and carbon inputs were estimated to 1.3 × 10–2 and 6.4 t·ha–1·year–1, respectively. Litter appeared rich in phosphorous, corresponding with the high concentrations characterizing the sediments. For a given species, magnesium and calcium concentrations were constant between facies, whereas potassium and sodium concentrations varied according to the distance from the sea. Differences were perceived between species for all nutriments except sodium. Results are discussed in relation with the ecophysiological characteristics of the mangrove trees and the specific sedimentology of Guyana coast and are replaced in the perspective of an improved knowledge of the carbon and mineral balances in tropical coastal ecosystems.Key words: mangrove, French Guyana, litter, carbon balance, mineral nutriments, spatial variations.[Journal translation]

West Nile virus ecology has yet to be rigorously investigated in the Caribbean Basin. We identified a transmission focus in Puerto Barrios, Guatemala, and established systematic monitoring of avian abundance and infection, seroconversions in domestic poultry, and viral infections in mosquitoes. West Nile virus transmission was detected annually between May and October from 2005 to 2008. High temperature and low rainfall enhanced the probability of chicken seroconversions, which occurred in both urban and rural sites. West Nile virus was isolated from Culex quinquefasciatus and to a lesser extent, from Culex mollis/Culex inflictus, but not from the most abundant Culex mosquito, Culex nigripalpus. A calculation that combined avian abundance, seroprevalence, and vertebrate reservoir competence suggested that great-tailed grackle (Quiscalus mexicanus) is the major amplifying host in this ecosystem. West Nile virus transmission reached moderate levels in sentinel chickens during 2007, but less than that observed during outbreaks of human disease attributed to West Nile virus in the United States.

The role wild bird species play in the transmission and ecology of avian influenza virus (AIV) is well established; however, there are significant gaps in our understanding of the worldwide distribution of these viruses, specifically about the prevalence and/or significance of AIV in Central and South America. As part of an assessment of the ecology of AIV in Guatemala, we conducted active surveillance in wild birds on the Pacific and Atlantic coasts. Cloacal and tracheal swab samples taken from resident and migratory wild birds were collected from February 2007 to January 2010.1913 samples were collected and virus was detected by real time RT-PCR (rRT-PCR) in 28 swab samples from ducks (Anas discors). Virus isolation was attempted for these positive samples, and 15 isolates were obtained from the migratory duck species Blue-winged teal. The subtypes identified included H7N9, H11N2, H3N8, H5N3, H8N4, and H5N4. Phylogenetic analysis of the viral sequences revealed that AIV isolates are highly similar to viruses from the North American lineage suggesting that bird migration dictates the ecology of these viruses in the Guatemalan bird population.