Las cianobacterias planctónicas del lago tropical cárstico Lagartos de la Península de Yucatán, México. 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 µm 3 /mL, and two biovolume peaks were observed; the first was dominated by Microcystis panniformis in November 2007 (7.40X10 8 µm 3 /mL), and the second was dominated by Oscillatoria princeps in April 2008 (6.55X10 8 µm 3 /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. Rev. Biol. Trop. 61 (2): 971-979. Epub 2013 June 01.
In 2010, we surveyed 42 sampling locations at 11 sites along the Mexican part of the Mesoamerican Reef System, including eight protected natural areas of the coastal state of Quintana Roo, to determine the richness of benthic-epiphytic dinoflagellates in the area. At each site, the host macroalgae of the genera Dictyota, Halimeda, Laurencia, Sargassum, and Stypopodium were manually collected. A total of 383 samples were analyzed microscopically using transmitted light, epifluorescence with calcofluor staining, and scanning electron microscopy. A total of 24 dinoflagellate species distributed among the genera Amphidinium, Bysmatrum, Coolia, Gambierdiscus, Ostreopsis, Prorocentrum, Plagiodinium, and Sinophysis were identified. Prorocentrum is the most diverse genus in the benthic-epiphytic environment with 13 species. This work also includes 15 new records of species from the Mexican Caribbean.
Vinasses are one of the main wastes generated from the mezcal industry in Mexico. Due to their high organic matter content and low pH, vinasses have negative environmental impacts if discharged without any treatment. An alternative treatment of vinasses is their use in microbial fuel cells (MFC) for organic matter removal and electricity production. In this paper, the performance of a MFC using vinasses is analyzed. Different organic matter concentrations in terms of chemical oxygen demand (COD) were tested and compared regarding power density, internal resistance, and voltage production. The results demonstrated that the highest COD tested resulted in a poor MFC performance. When using vinasses in MFC for 10 days, COD of 6000 mg/L generated 80.64 W/m 3 and when using vinasses with a COD of 17 143 mg/L, the power density dropped to 5.13 W/m 3 . Further tests of COD performance in MFC were made with 10 640 and 6760 mg/L for 68 days. It was demonstrated that a COD of 10 604 mg/L only produced 0.61 V, while a COD of 6760 mg/L reached 0.81 V. Regarding the organic matter removal, the highest COD removed (92 %) was obtained when using vinasses with a COD of 10 604 mg/L. By operating the cell with 6000 mg/L, COD removal was 83 % and with 17 143 mg/L, 49 %. To achieve a better MFC performance, the organic matter content in the electrolyte should not exceed 6000 mg/L so that the MFC does not achieve a saturated state that hinders the oxidation mechanisms and thus electricity production and COD removal.Palabras clave: Agave, demanda química de oxígeno, remoción de materia orgánica, producción de electricidad RESUMENLas vinazas son uno de los principales residuos generados por la industria del mezcal en México. Debido a su alto contenido de materia orgánica y bajo pH, las vinazas tienen impactos ambientales negativos si se descargan sin tratamiento alguno. Un tratamiento alternativo de las vinazas es su utilización en celdas de combustible microbianas (CCM) M. López Velarde Santos et al. 522 para la disminución de materia orgánica y la producción de electricidad. En este trabajo se analiza el rendimiento de una CCM operada con vinazas. Diferentes concentraciones de materia orgánica en términos de demanda química de oxígeno (DQO) se utilizaron y compararon con respecto a la densidad de potencia, resistencia interna y la producción de voltaje. Los resultados demostraron que la DQO más alta, dio como resultado un pobre rendimiento de la CCM. Al utilizar las vinazas en la CCM durante 10 días, una DQO de 6000 mg/L generó 80.64 W/m 3 y utilizando las vinazas con una DQO de 17 143 mg/L, la densidad de potencia se redujo a 5.13 W/m 3 . Otras pruebas de rendimiento de la DQO en la CCM se llevaron a cabo por 68 días con DQO de 10 640 y 6760 mg/L. Se demostró que una DQO de 10 604 mg/L sólo produjo 0.61 V, mientras que una DQO de 6760 mg/L alcanzó 0.81 V. En cuanto a la remoción de materia orgánica, la mayor remoción de DQO (92 %) se obtuvo utilizando vinazas en la CCM con 10 604 mg/L de DQO. Utilizando una DQO de 6000 mg/L,...
Cenotes (sink holes) are karstic formations characteristic of the Yucatán Peninsula and are the main source of fresh water in the region. Because of their tropical location, they receive high levels of solar radiation and are exposed to high temperatures. However, the effect of these global-change-related variables on phytoplankton in cenotes is unknown. We carried out experiments with phytoplankton communities collected from 2 cenotes differing in their penetration of solar radiation (Leona Vicario [LV]: turbid, Las Mojarras [LM]: clear) to assess the combined effect of solar ultraviolet radiation (UVR; 280-400 nm) and increased temperature on their photosystem (PS) II photochemistry. We exposed samples in microcosms to solar radiation (with and without UVR) and 2 temperatures (ambient = 25°C and increased by 3°C) and analyzed photochemical performance over daily cycles. A significant antagonistic interaction between UVR and temperature in LV caused a combined inhibition of the effective photochemical quantum yield (Φ PSII) that was smaller (63%) than the sum of the 2 individual effects of UVR and temperature (116%). In contrast, a significant synergistic interaction between UVR and temperature in LM caused the combined inhibition of Φ PSII (172%) to be higher than the sum of the individual effects of the 2 variables (134%). Differences in the size distribution and taxonomic composition of the phytoplankton communities, with smaller cells in LV than in LM, seem to account for much of the variability in responses to UVR and increased temperature between the 2 communities. Our results suggest that phytoplankton communities from clear cenotes will be more affected by the combined effects of solar UVR and increased temperature that those from turbid cenotes.
In petroleum exploration drilling cuttings are generated, which are toxic residues that contain significant amounts of oil. The oil levels within the cuttings are a risk for marine and terrestrial environments. This study was carried out to investigate the removal of total petroleum hydrocarbons (TPH) in perforation cuttings (OBDC) by a washing process in which humic acids (HA) were used as surfactants. The cuttings contained 114 372 mg/kg of TPH, which were washed with HA solutions, resulting in 80 % removal of OBDC contaminants, applying a washing an additional water rinse. The process effectiveness was found strongly dependent on the HA solution concentration, the highest removal rates were attained using solutions in the range of 2500 to 3000 mg/L, and lower concentrations yielded removal rates lower than 70 %. Comparing the use of HA versus synthetic surfactants, such as sodium dodecyl sulfate (SDS) and tween-20 (TW20), both resulted in lower removal efficiency than HA. An additional advantage of HA is that it is a natural material, therefore there is no risk of toxic side effects that occur with synthetic surfactants.Palabras clave: TPH, surfactantes, ácidos húmicos, proceso de lavado RESUMENEn la exploración petrolera se generan recortes de perforación, los cuales son residuos tóxicos que contienen cantidades significativas de aceites. Los niveles de aceite en los recortes representan un riesgo para los ambientes marinos y terrestres. Este estudio se llevó a cabo para investigar la remoción de hidrocarburos totales de petróleo (TPH) en recortes de perforación (OBDC) mediante un proceso de lavado en el que se utilizaron ácidos húmicos (HA) como tensoactivos. Los recortes contenían inicialmente 114 372 mg/kg de TPH, los cuales fueron lavados con soluciones de HA, obteniéndose una remoción del 80 % utilizando un proceso de lavado y posterior enjuague con
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