ABSTRACT
The tropical karstic lakes on the Mexican Caribbean Sea coast are numerous. However, there is an enormous gap of knowledge about their limnological conditions and micro-algae communities. In the present study, surface water samples were collected monthly from November 2007 to September 2008 to provide taxonomical composition and biovolume of planktonic cyanobacteria of the lake Lagartos from State of Quintana Roo, Mexico. Water temperature, pH, conductivity, salinity, soluble reactive phosphorus (SRP), dissolved inorganic nitrogen (DIN), and soluble reactive silica (SRSi) levels were also analyzed. A total of 22 species were identified. Chroococcales and Oscillatoriales dominated the phytoplankton assemblages during the study period. Chroococcus pulcherrimus, Coelosphaerium confertum, Cyanodyction iac, Phormidium pachydermaticum and Planktolyngbya contorta were recorded for the first time in Mexico. A surplus of DIN (mean value of 42.7µM) and low concentrations of SRP (mean value of 1.0µM) promoted the enhanced growth and bloom formation of cyanobacteria. The mean biovolume was 3.22X10(8)µm³/mL, and two biovolume peaks were observed; the first was dominated by Microcystis panniformis in November 2007 (7.40X10(8)µm³/mL), and the second was dominated by Oscillatoria princeps in April 2008 (6.55X10(8)µm³/mL). Water quality data, nitrates enrichment, and trophic state based on biovolume, indicated that Lagartos is a hyposaline, secondarily phosphorus-limited, and eutrophic lake, where the cyanobacteria flora was composed mainly by non-heterocystous groups.
Los lagos cársticos tropicales en la costa del Caribe mexicano son numerosos. Sin embargo, existe un enorme desconocimiento acerca de sus condiciones limnológicas y de las comunidades de microalgas que se desarrollan en ellos. El objetivo del presente estudio fue estudiar las condiciones limnológicas en las que crecen las poblaciones de cianobacterias planctónicas del lago Lagartos, Quintana Roo, México. Las recolectas se realizaron de forma mensual entre noviembre 2007 y septiembre 2008. Las especies fueron identificadas y su biovolumen determinado. Se midieron in situ la temperatura del agua, pH, conductividad y salinidad. También, se analizaron las concentraciones de fósforo reactivo soluble (SRP), nitrógeno inorgánico disuelto (DIN) y sílice reactivo soluble (SRSi). Se identificaron 22 especies de cianobacterias. Chroococcus pulcherrimus, Coelosphaerium confertum, Cyanodyction iac, Phormidium pachydermaticum y Planktolyngbya contorta fueron nuevos registros para México. Un exceso de DIN (valor promedio de 42.7µM) y bajas concentraciones de PRS (valor promedio de 1.0µM) promovieron la proliferación de cianobacterias. El biovolumen presentó dos picos: el primero en noviembre 2007, dominado por Microcystis panniformis (7.40X10(8)µm³/mL) y el segundo en abril 2008, representado por Oscillatoria princeps (6.55X10(8)µm³/mL). Los datos de calidad del agua, el enriquecimiento por nitratos y el estado trófico basado en el biovolumen, indican que Lagartos es un lago hiposalino, eutrófico, con limitación secundaria por fósforo, donde los crecimientos masivos de cianobacterias sin heterocitos fueron recurrentes.
Subject(s)
Biomass , Cyanobacteria/classification , Environmental Monitoring , Lakes/microbiology , Plankton/classification , Lakes/chemistry , Mexico , Population Density , SeasonsABSTRACT
We studied the zooplankton community composition at different depths (2, 4, 8, 12 and 20 m) of Valle de Bravo, a drinking water reservoir in central Mexico during December 2005 to November 2006.Temperature, dissolved oxygen, pH and chlorophyll a were measured simultaneously. While physicochemical values were similar to those found in previous studies, total zooplankton abundance was higher (mean 847 ind. l-1), doubling the mean abundance found in the previous year. Nevertheless, Zooplankton remained dominated by the rotifer genera Keratella, Polyarthra and Trichocerca, which constituted nearly 80% of the total numerical abundances. We encountered 23 rotifer species of which 5 of them (Lepadella rhomboides, Cephalodella catellina, Trichocerca elongata, T. porcellus and Dicranophorus forcipatus) were recorded for the first time from this reservoir. Shannon Wiener diversity index showed that the annual mean species diversity index was similar at depths of 2, 4 and 8 m, but were reduced at 12 and 20 m. Regardless of depth, the highest diversity value of 1.82 was observed during January, while the lowest (0.07) during March. Principal component analysis showed that temperature, dissolved oxygen, water column depth and chlorophyll a have combined effects on the abundance of dominant rotifer species. The highest rotifer density was observed in April (>1600 individuals l-1), while the lowest was recorded during January (<50 ind. l-1). During the study period, the most abundant rotifer species were Keratella chochlearis, Polyarthra vulgaris, Trichocecra elongata and Anuraeopsis fissa.