RESUMO
Eutrophication is a global problem causing the reduction of water quality and the loss of ecosystem goods and services. The lakes of the "Lagunas de Montebello" National Park (LMNP), Chiapas, Mexico, not only represent unique and beautiful natural scenic sites in southern Mexico but are also a national protected area and RAMSAR site. Unfortunately, some of these lakes started showing eutrophication signs since 2003. Anthropogenic activities (e.g., land-use change from forested to agricultural and urban development) are leading to water quality and trophic state alterations of the lakes of the LMNP. This study shows the results of a coupled limnological characterization and high-throughput sequencing of the V4 hypervariable region of the 16S rRNA gene to analyze the microbial composition of the water column in a set of oligotrophic and eutrophic lakes. Chlorophyll a (Chl-a) was the main environmental parameter correlated with the trophic conditions of the lakes. Although the microbial diversity was similar, the microbial composition changed significantly from oligo to eutrophic lakes. Proteobacteria, Firmicutes, and Cyanobacteria were the main components of oligotrophic lakes, and Cyanobacteria, Proteobacteria, and Bacteroidetes of eutrophic lakes. While Acinetobacter (Proteobacteria) and Cyanobium (a unicellular cyanobacterium) dominated in oligotrophic lakes, the filamentous, bloom-forming, and toxin-producing cyanobacteria Planktothrix was the dominant genus in eutrophic lakes. High-throughput sequencing allowed the detection of changes in the composition of the microbial component in oligotrophic lakes, suggesting a shift towards eutrophication, highlighting the relevance of sensitive monitoring protocols of these ecosystems to implement remediation programs for eutrophicated lakes and conservation strategies for those yet pristine.
Assuntos
Cianobactérias , Lagos , Lagos/análise , Ecossistema , Clorofila A , México , RNA Ribossômico 16S/genética , Parques Recreativos , Cianobactérias/genéticaRESUMO
Baird's tapir (Tapirus bairdii) is the largest native terrestrial mammal in the Neotropics, which is endangered primarily as a consequence of habitat loss and overhunting. Baird's tapir is predominantly nocturnal and exists at low densities which complicates field studies. Baird's tapir is a large-bodied herbivore that plays a key role in maintaining healthy tropical forests through seed dispersal in its feces. Studies of gut microbiome are essential and valuable to assess the health status of the host and the interaction with the environment. In this study, we collected fresh fecal samples of T. bairdii to analyze its gut microbiome during the rainy and dry seasons in the Calakmul region, which is a critical rainforest conservation area in Mexico. The results of a high-throughput 16S rDNA gene sequencing approach suggest that the fecal microbiome of Baird's tapir has no significant differences in composition among seasons. The most common phyla were Firmicutes, Bacteroidetes, Proteobacteria, Kiritimatiellaeota, and Spirochaetes. This study suggests that the stability of the fecal microbiome is related to similar feeding strategies throughout the year, and emphasizes the value of tapir in seed dispersal (and associated microbes) to the well-conserved forests of the Greater Calakmul region as biodiversity hotspots for conservation.
Assuntos
Microbiota , Perissodáctilos , Animais , Fezes , Florestas , MéxicoRESUMO
Microbialites are highly diverse microbial communities that represent modern examples of the oldest life forms, stromatolites (dated >3.7 Ga). Bacalar Lagoon, in Mexico, harbors the largest freshwater microbialite occurrences of the world; yet diverse anthropogenic activities are changing the oligotrophic conditions of the lagoon. The objective of this work was to perform a spatial exploration of the microbialites of Bacalar Lagoon, analyze their prokaryote diversity, following a high throughput sequencing approach of the V4 region of the 16S rDNA, and correlate to the environmental parameters that influence the structure of these communities. The results indicate the presence of microbialites throughout the periphery of the lagoon. The microbiome of the microbialites is composed primarily of Proteobacteria (40-80%), Cyanobacteria (1-11%), Bacteroidetes (7-8%), Chloroflexi (8-14%), Firmicutes (1-23%), Planctomycetes (1-8%), and Verrucomicrobia (1-4%). Phylogenetic distance analyses suggests two distinct groups of microbialites associated with regions in the lagoon that have differences in their environmental parameters, including soluble reactive silicate (in the north), bicarbonates and available forms of nitrogen (ammonium, nitrates and nitrites) (in the south). These microbialite groups had differences in their microbiome composition associated to strong anthropogenic pressure on water quality (agriculture, landfill leachate, lack of water treatment infrastructure and intensive tourism), which were related to a loss of microbial diversity.