Seasonal Responses of Phyloplankton Productivity to Water-Quality Variations in a Coastal Karst Ecosystem of the Yucatan Peninsula

Dzilam Lagoon (DL) is a shallow, semienclosed, coastal ecosystem located on the north coast of the Yucatan Peninsula. With 9.4 km3 surface area, this system is influenced by groundwater (GD) supply and inorganic nutrients drained from the nearby mangrove. DL is highly preserved and provides a unique site to address the seasonal responses of phytoplankton production to environmental variability in a karstic and pristine scenario. Twelve monthly sampling trips were undertaken during Sep. 1998–Aug. 1999 to record in situ physicochemical parameters and collect water for inorganic nutrients, chlorophyll a (Chl a), and phytoplankton production at seven stations plus one GD. Highest Chl a concentrations were determined at the innermost points of the lagoon, whereas primary production peaked at brackish zones. The average net primary production in DL (80 g C m-3 yr-1) is lower than that reported for other coastal lagoons of the Yucatan Peninsula. Differences in the physical setting and disturbance extent between DL and those ecosystems are discussed as the context underlying their distinct production levels

Methane fluxes from tropical coastal lagoons surrounded by mangroves, Yucatán, Mexico

Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentrations (up to 8378 nM) were measured in a polluted canal associated with Terminos Lagoon. In Chelem Lagoon, methane concentrations were typically lower, except in the polluted harbor area (1796 nM). In the relatively pristine Celestún Lagoon, surface water methane concentrations ranged from 41 to 2551 nM. Methane concentrations were negatively correlated with salinity in Celestún, while in Chelem and Terminos high methane concentrations were associated with areas of known pollution inputs, irrespective of salinity. The diffusive methane flux from surface lagoon water to the atmosphere ranged from 0.0023 to 15 mmol CH4 m-2 d-1. Flux chamber measurements revealed that direct methane release as ebullition was up to 3 orders of magnitude greater than measured diffusive flux. Coastal mangrove lagoons may therefore be an important natural source of methane to the atmosphere despite their relatively high salinity. Pollution inputs are likely to substantially enhance this flux. Additional statistically rigorous data collected globally are needed to better consider methane fluxes from mangrove-surrounded coastal areas in response to sea level changes and anthropogenic pollution in order to refine projections of future atmospheric methane budgets

Hydrodynamic Variability in a Microtidal Coastal Bay Geographically Susceptible to North East Trade Winds

The ecological integrity and overall health conditions of natural coastal systems are largely based upon the balance among physical processes. The objective of this study was to assess the effects of tides and winds on the water level variability, circulation patterns, and turnover time in Bahia de la Ascension (BA), a shallow, tropical coastal bay in the Mexican Caribbean prone to the influence of Trade winds due to its geographical location. The analysis of the hydrodynamics of BA using a 2D numerical model indicates that the tidal flow in the inlets and central basin of the bay vary by tidal phase. An averaged seawater inflow through the south inlet and outflow through the north inlet is observed for every simulated case, while peak instantaneous current velocities are evident in the northern entrance. Winds play a dominant role in the water turnover from the system’s interior to the main bay. The model shows an average turnover time of 45 days for the whole bay, with shorter turnover when Trade winds impart stress along the main northeast–southwest axis in the bay. Since the tidal signal is attenuated in the southwest endpoint of the bay, the relevance of winds in the transport phenomena was considered fundamental to preserve the ecological heterogeneity of BA

Perception of physicians about medical education received during their Nephrology residency

Introduction: In Peru there are different hospitals and university programs for training of specialists in nephrology. Objective: To assess the perception of physicians who attend such programs. Methods: We carried out a descriptive cross-sectional national-level study in physicians who were in the last two years of nephrology training during February 2012 and who had graduated from it in 2010 and 2011. A self-applied questionnaire was developed along with the Peruvian Society of Nephrology based on international standards. The questionnaire evaluated: mentoring, clinical training, procedures, external rotations, research and global perception. Results: Forty doctors were surveyed nationwide. 82.5% had tutors, 22.5% of them said their support was poor. A 27.5% described their theoretical formation as deficient. The practical training was perceived as acceptable globally; however, improvements in training on peritoneal dialysis and reading kidney transplant biopsies are necessary. A 90% have national external rotations and 65% reported to have an international rotation. In the assessment of research, 77.5% thought this is deficient. In addition, 82.5% believed that residency should last four years. However, 60% reported that their residency training was good. There is a decrease in the positive perception of the aspects studied among residents regarding graduates. Conclusion: The overall perception of nephrology residency training was considered good; however, areas of tutoring, and academic and research activities on average were deficient.Revisión por pare

Eutrofización costera en la Península de Yucatán

28 páginas, 12 figuras, 2 tablas.-- Artículo incluido en el Cap.IV: Manejo de la Zona Costera del Golfo de México.El financiamiento ha provenido del CONACYT (PO20COOR; 4147PT; 32356T; SISIERRA-2000-07-06-15), CONABIO (B019; M011; S004) y CINVESTAV-IPN Unidad Merida.Peer reviewe

Fotopletismografía laparoscópica: Nueva técnica mínimamente invasiva y estudios experimentales iniciales

In the endoscopic procedures there is not possible to use the sense of touch for the detection of weak palpitations as in open surgery, neither to directly evaluate the oxygenation and perfusion of intra-corporeal organs and tissues. Here, we present the initial results after the application of laparoscopic photoplethysmography, a novel technique developed by our group, which allows obtaining specific clinical parameters and overcome the cited drawbacks. From the photoplethysmograpic signals of different wavelengths recorded in intra-abdominal organs and territories of animal models, their pulse values and oxygenation related quotients have been derived. © Sociedad Española de Óptica.Este trabajo ha sido financiado por el proyecto PI 04/0715 del Fondo de Investigaciones Sanitarias. Agradecemos la colaboración prestada durante el estudio experimental por Dr. José Carlos Manuel Palazuelos, Dr. Juan Carlos González Cueli y las diplomadas en Enfermería del CENDOS. Parte de los resultados aquí expuestos han sido presentados oralmente en el Congreso de la Sociedad Española de Laparoscopia (SECLA 2009) celebrado en Santander en mayo de 2009. SMLS está contratada por el Programa I3P con financiación del Fondo Social Europeo.Peer Reviewe

Evaluating the capacity of species distribution modeling to predict the geographic distribution of the mangrove community in Mexico

This work is licensed under a Creative Commons Attribution 4.0 International License.Mangroves are highly productive ecosystems that provide important environmental services, but have been impacted massively in recent years by human activities. Studies of mangroves have focused on their ecology and function at local or landscape scales, but little has been done to understand their broader distributional patterns or the environmental factors that determine those distributions. Species distribution models (SDMs), have been used to estimate potential distributions of hundreds of species, yet no SDM studies to date have assessed mangrove community distributions in Mexico (the country with the fourth largest extent of this ecosystem). We used maximum entropy approaches to model environmental suitability for mangrove species distributions in the country, and to identify the environmental factors most important in determining those distributions. We also evaluated whether this modeling approach is adequate to estimate mangrove distribution as a community across Mexico. Best models were selected based on statistical significance (AUC ratio), predictive performance (omission error of 5%), and model complexity (Akaike criterion); after this evaluation, only one model per species met the three evaluation criteria. Environmental variable sets that included distance to coast yielded significantly better models; variables with strongest contributions included elevation, temperature of the coldest month, and organic carbon content of soil. Based on our results, we conclude that SDMs can be used to map mangrove communities in Mexico, but that results can be improved at local scales with inclusion of local variables (salinity, hydroperiod and microtopography), field validations, and remote sensing data.National Council for Science and Technology in Mexico (N°275430

Los peces como indicador de restauración de áreas de manglar en la costa norte de Yucatán

ResumenLos manglares son reconocidos por los servicios ecológicos que proveen a muchas especies de peces. Estudios previos sobre restauración ecológica han pasado por alto estas funciones, generalmente enfocándose a la restauración de cobertura vegetal. El objetivo fue determinar las funciones de los manglares como zonas de refugio y alimentación para peces, evaluando la composición y abundancia en sitios con diferente tiempo de restauración. Se realizaron 2 muestreos en 4 sitios de manglar en restauración en Yucatán —Celestún 1, Celestún 2, Yucalpetén, Progreso—, en donde se registraron 22 especies de peces. Celestún 2 fue el sitio con mayor riqueza y diversidad (Gambusia yucatana, Poecilia velifera, Mugil cephalus y Anchoa mitchilli las más abundantes). Progreso registró la diversidad más baja y alta dominancia de G. yucatana (>90%). El sitio con mayor tiempo de restauración presentó organismos juveniles detritófagos y zoobentófagos. Los resultados demuestran la función del manglar como zona de crianza y alimentación para especies marinas que intervienen en la transferencia de energía y nutrientes con sistemas adyacentes, también demuestran gran dominancia de G. yucatana, una especie endémica y característica del ecosistema de manglar en Yucatán.AbstractMangroves are well recognized for the ecological services that they provide to many fish species. Previous studies on ecological restoration have overlooked these ecological functions, as they are generally focused on the restoration of vegetation cover. The objective of this study is to determine the function of mangroves as nursery and feeding grounds for fishes, by assessing the species composition and abundance in sites with different restoration time. Two samplings were performed in 4 sites where mangrove is recovering along the Yucatán coast —Celestún 1, Celestún 2, Yucalpetén, Progreso—. A total of 22 fish species were recorded, the higher richness and diversity were recorded in Celestún 2 (Gambusia yucatana, Poecilia velifera, Mugil cephalus and Anchoa mitchilli were the most abundant). In Progreso, the diversity was lower due to the dominance of G. yucatana (>90%). The site with the longest restoration time presented juveniles of detritophagous and zoobentophagous species, which show the nursery and feeding functions of the area. These marine species are involved in the transfer of energy and nutrients to adjacent systems, also a great dominance of G. yucatana was found, which is an endemic and characteristic fish species from the mangrove ecosystem in Yucatán

Methane and sulfate dynamics in sediments from mangrove-dominated tropical coastal lagoons, Yucatan, Mexico

Porewater profiles in sediment cores from mangrove-dominated coastal lagoons (Celestún and Chelem) on the Yucatán Peninsula, Mexico, reveal the widespread coexistence of dissolved methane and sulfate. This observation is interesting since dissolved methane in porewaters is typically oxidized anaerobically by sulfate. To explain the observations we used a numerical transport-reaction model that was constrained by the field observations. The model suggests that methane in the upper sediments is produced in the sulfate reduction zone at rates ranging between 0.012 and 31 mmolm-2 d-1, concurrent with sulfate reduction rates between 1.1 and 24 mmol SO2- 4 m-2 d-1. These processes are supported by high organic matter content in the sediment and the use of non-competitive substrates by methanogenic microorganisms. Indeed sediment slurry incubation experiments show that non-competitive substrates such as trimethylamine (TMA) and methanol can be utilized for microbial methanogenesis at the study sites. The model also indicates that a significant fraction of methane is transported to the sulfate reduction zone from deeper zones within the sedimentary column by rising bubbles and gas dissolution. The shallow depths of methane production and the fast rising methane gas bubbles reduce the likelihood for oxidation, thereby allowing a large fraction of the methane formed in the sediments to escape to the overlying water column