Raygoza-Alcantar, L.N.; Vázquez, G., and Rodríguez-Zaragoza, F.A., 0000. Spatiotemporal relationship between diatom diversity and environmental gradients at La Mancha coastal lagoon (Veracruz, Mexico).

This study analyzed the composition and distribution of diatoms in the La Mancha tropical coastal lagoon, Veracruz, Mexico, under different environmental conditions. Water samples were collected from the surface and bottom of the lagoon at five sites during the “nortes” (cold winter fronts), dry, and rainy seasons. The physical and chemical variables of the lagoon water were also analyzed. Diatom taxa were identified and quantified. Sixty-five taxa were determined and classified according to functional groups. Sites 1 and 2 were considered potential sources of nutrients and folin phenol active substances (FPAS). In addition, two horizontal gradients were observed. The first concerned nutrient concentration, which increased in the area of the mouth of the Caño Grande River and decreased towards the bar. The second was a salinity gradient characterized by high values in the area of the bar and decreasing values towards the river mouth. Diatom richness and diversity were higher in the areas influenced by the opening of the bar and the Caño Grande River discharges in the “nortes” season. Diatom composition varied across seasons, sites, and depth levels; functional groups only varied between sites (p ≤ 0.05). A redundancy analysis recorded the species that responded to the salinity and temperature gradients, including Paralia sulcata, Odontella spp., and Grammatophora oceanica. The species that responded to high nutrient concentrations, total phosphorus, and transparency were Aulacoseira granulata, Stephanocyclus meneghinianus, Ulnaria ulna, Gyrosigma acuminatum, Navicula subrhynchocephala, and Amphipleura pellucida in different seasons in the area close to the river mouth and mangrove swamp. The correlation between diatom density and FPAS indicates that Psammodictyon constrictum and Amphiprora pseudoduplex have optimal growth when the FPAS concentration increases.

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