Estimation of prokaryotic growth rates is critical to understand the ecological role and contribution of different microbes to marine biogeochemical cycles. However, there is a general lack of ...knowledge on what factors control the growth rates of different prokaryotic groups and how these vary between sites and along seasons at a given site. We carried out several manipulation experiments during the four astronomical seasons in the coastal NW Mediterranean in order to evaluate the impact of grazing, viral mortality, resource competition and light on the growth and loss rates of prokaryotes. Gross and net growth rates of different bacterioplankton groups targeted by group-specific CARD-FISH probes and infrared microscopy (for aerobic anoxygenic phototrophs, AAP), were calculated from changes in cell abundances. Maximal group-specific growth rates were achieved when both predation pressure and nutrient limitation were experimentally minimized, while only a minimal effect of viral pressure on growth rates was observed; nevertheless, the response to predation removal was more remarkable in winter, when the bacterial community was not subjected to nutrient limitation. Although all groups showed increases in their growth rates when resource competition as well as grazers and viral pressure were reduced, Alteromonadaceae consistently presented the highest rates in all seasons. The response to light availability was generally weaker than that to the other factors, but it was variable between seasons. In summer and spring, the growth rates of AAP were stimulated by light whereas the growth of the SAR11 clade (likely containing proteorhodopsin) was enhanced by light in all seasons. Overall, our results set thresholds on bacterioplankton group-specific growth and mortality rates and contribute to estimate the seasonally changing contribution of various bacterioplankton groups to the function of microbial communities. Our results also indicate that the least abundant groups display the highest growth rates, contributing to the recycling of organic matter to a much greater extent than what their abundances alone would predict.
Estuaries are among the most productive ecosystems in the world and are highly dynamic due to the interaction of freshwater and seawater, which results in strong spatial gradients in physico-chemical ...conditions. Bacterioplankton play a central role in these systems, driving the fluxes of carbon and energy, and being central for contaminant removal in human-impacted areas. Most studies on bacterioplankton dynamics have been carried out in temperate estuaries, and they show that salinity is a major factor driving bacterioplankton distribution. Tropical estuaries, although largely understudied, experience drastic variations in river discharge between the dry and the rainy seasons, influencing the spatial distribution of the salinity gradient and thus likely impacting bacterioplankton communities. Using Illumina sequencing of the 16S rRNA gene, here we studied bacterial communities from the Nicoya's Gulf (Costa Rica), a large tropical estuary characterized by high riverine discharge during the rainy season, to explore seasonal changes in the spatial distribution and connectivity of these communities along the Gulf. Our results show pronounced differences in bacterial diversity and community structure between seasons and zones within the estuary (the shallow upper Gulf, the middle zone and the lower zone, located in the marine end of the estuary). Bacterial communities from the different regions were more similar during the rainy season, suggesting a larger degree of microbial connectivity likely driven by the fast water circulation fueled by the riverine discharge. In the dry season, Enterobacteriales and Cyanobacteria dominated bacterial communities, whereas in the rainy season Alphaproteobacteria was the dominant group. These contrasting seasonal trends were consistent with the seasonal variations observed in bacterial assemblages during a year at a single station in the upper region of the Gulf. We conclude that the Gulf is highly dynamic in both the spatial and temporal scale and that bacterioplankton communities are strongly influenced by the riverine and tidal inputs during both seasons. This study sheds light on the sources of variability in the structure of bacterial communities in tropical estuarine systems, an understudied type of aquatic ecosystem, and sets the basis to design further comprehensive studies on their microbial diversity.
Luminescence in bacteria is catalyzed by luciferase. When these microorganisms are exposed to toxic substances, the bioluminescent enzyme system can be inhibited. The objective of this study was to ...analyze the potential that these microorganisms offer as native bioindicators of coastal marine pollution. The dynamics of luminescence intensity by visual classification and the effect of metal concentration on the growth and luminescence of 25 strains of luminescent bacteria, isolated during 2016 from seawater samples from the gulf of Nicoya, Costa Rica, was evaluated by the disk diffusion method. The sensitivity of each strain to different concentrations (0.1, 0.5 and 1 mg mL-1) of Cd, Cu, Cr, Pb and Zn was determined by its bioluminescent phenotype. In susceptible strains, a range of metal concentrations less than the growth inhibitory concentration affected the expression of luminescence. Strains with intense luminescence and defined zones of luminescence inhibition were considered to have greater potential as native bioindicators for monitoring environmental toxicity. More studies are required to determine the minimum concentrations that inhibit growth and luminescence with respect to the tested metals and other potentially toxic substances for the coastal marine ecosystems of Costa Rica.
Marine bivalves are a very important food source for human consumption, and species that has not been of traditional use as a fishery resource are gaining interest. Seasonal variation in proximate ...composition, condition index and energy or caloric content of the mussel Tagelus peruvianus were studied in the Gulf of Nicoya, Puntarenas, Costa Rica. From November 2007 to October 2008, a total of 35 to 40 specimens per month were collected. The proximate composition using the AOAC methods was determined. Results showed that the condition index during December, January and May decreased, indicative of two spawning periods and one gonadal resting phase. Soft tissues were respectively characterized by protein (61.9 +/- 4.3%), carbohydrates (15.7 +/- 2.4%), ash (14.0 +/- 1.9%) and lipids (8.5 +/- 1.7%). The average caloric content was 5.0 +/- 0.1 kcal/g. The results showed that the decrease in protein and fat percentage, and calories content, occurred during the spawning seasons. We suggest that T. peruvianus has an optimal nutritional value for human consumption because of the low-fat and moderate protein content.
La extracción del mejillón Tagelus peruvianus representa una actividad económica complementaria de los pescadores artesanales, es una de las especies de mayor pesca y consumo ya que son una fuente ...importante de proteína, minerales y vitaminas esenciales para la población humana. Por lo tanto, se estudió la variación estacional de su composición proximal, índice de condición y contenido energético. Mensualmente, entre noviembre de 2007 y octubre de 2008, se recolectaron de 35 a 40 especímenes. La composición proximal se determinó siguiendo la metodología recomendada por la AOAC. Los resultados mostraron que el índice de condición disminuyó en los meses de diciembre, enero y mayo, lo que indica que hay dos periodos de desove y una fase de reposo gonadal. El componente principal del mejillón es la proteína (61.9+ ó -4.3%), seguido de carbohidratos (15.7+ ó -2.4%), cenizas (14.0+ ó -1.9%) y lípidos (8.5+ ó -1.7%). El contenido calórico promedio fue de 5.0+ ó -0.1kcal/g. La disminución en los valores de proteínas, lípidos y calorías coinciden con los periodos de desove. Se puede concluir que T. peruvianus presenta valores nutricionales óptimos para el consumo humano, por su bajo contenido de grasa y su aceptable contenido proteico. Palabras clave: Tagelus peruvianus, mejillón, composición proximal, índice de condición, valor calórico, Golfo de Nicoya. Costa Rica. Marine bivalves are a very important food source for human consumption, and species that has not been of traditional use as a fishery resource are gaining interest. Seasonal variation in proximate composition, condition index and energy or caloric content of the mussel Tagelus peruvianus were studied in the Gulf of Nicoya, Puntarenas, Costa Rica. From November 2007 to October 2008, a total of 35 to 40 specimens per month were collected. The proximate composition using the AOAC methods was determined. Results showed that the condition index during December, January and May decreased, indicative of two spawning periods and one gonadal resting phase. Soft tissues were respectively characterized by protein (61.9+ or -4.3%), carbohydrates (15.7+ or -2.4%), ash (14.0+ or -1.9%) and lipids (8.5+ or -1.7%). The average caloric content was 5.0+ or -0.1kcal/g. The results showed that the decrease in protein and fat percentage, and calories content, occurred during the spawning seasons. We suggest that T.peruvianus has an optimal nutritional value for human consumption because of the low-fat and moderate protein content. Rev. Biol. Trop. 59 (4): 1517-1523. Epub 2011 December 01. Key words: Tagelus peruvianus, mussel, proximate composition, condition index, caloric content, Gulf of Nicoya, Costa Rica.
Costa Rica does not have references on the health quality of Crassostrea gigas growing areas, which can pose a potential public health risk. This study evaluated the temporal trends of Escherichia ...coli concentrations in the C. gigas oyster and in the seawater of Punta Cuchillo and Punta Morales growing areas as a basis for the classification and monitoring of bivalve mollusc production sites in the Gulf of Nicoya, Costa Rica. Monthly samples of seawater and C. gigas were collected from each site from July 2011 to June 2012, and their levels of E. coli were determined using the most probable number method. Temperature and salinity were recorded at a one meter depth. Precipitation data was provided by Instituto Meteorológico Nacional (the National Meteorological Institute). Results indicated that the evaluated areas are probably being affected by wastewater discharge. Punta Cuchillo and Punta Morales could be classified as class A or authorized areas for the production of bivalve molluscs. A significant seasonal variability of E. coli concentrations was determined in seawater and oysters from the Gulf of Nicoya, defined primarily by salinity. National legislation should be created to establish controls and implement a monitoring system ensuring the bacteriological quality of the areas used for the cultivation of bivalve molluscs in the country.
Costa Rica no cuenta con referencias sobre la calidad sanitaria de las zonas de cultivo de Crassostrea gigas y esto puede representar un riesgo para la salud pública. Se evaluó la tendencia temporal de las concentraciones de Escherichia coli en la ostra C. gigas y en el agua de mar de las zonas de cultivo de Punta Cuchillo y de Punta Morales como base para la clasificación y la vigilancia de los sitios de producción de moluscos bivalvos en el Golfo de Nicoya, Costa Rica. Muestras mensuales de agua de mar y de C. gigas de cada zona fueron recolectadas de julio de 2011 a junio de 2012 y se les determinó los niveles de E. coli por la técnica del número más probable. La temperatura y la salinidad fueron registradas a un metro de profundidad. Los datos de precipitación fueron suministrados por el Instituto Meteorológico Nacional. Los resultados indicaron que las áreas evaluadas podrían estar siendo afectadas por el vertido de aguas residuales. Punta Cuchillo y Punta Morales podrían clasificarse como zonas autorizadas o tipo A para la producción de moluscos bivalvos. Se determinó una variabilidad estacional significativa de las concentraciones de E. coli en agua de mar y en ostras del Golfo de Nicoya, definida principalmente por la salinidad. Se debe generar una normativa nacional que establezca controles e implemente un sistema de vigilancia que asegure la calidad bacteriológica de las áreas destinadas para el cultivo de moluscos bivalvos en el país.
Bivalve molluscs are sold without any sanitary control in Costa Rica, which represents a public health risk dueto the possible accumulation of pathogenic bacteria. Small scale bacterial depuration ...treatments were preliminarilyevaluated on Crassostrea gigas and Anadara spp. from the Gulf of Nicoya, Costa Rica, through the useof a recirculating system with UV irradiation. The levels of Escherichia coli in the water were determined usingthe MPN method. The MPN of E. coli and the presence of Salmonella spp., Vibrio parahaemolyticus and V. cholerae were determined in molluscs. Results confirm the effectiveness of the E. coli depuration system designin C. gigas and Anadara spp. The MPN of E. coli in the molluscs was reduced between 79% and 100% after 24h. None of the other types of bacteria were found in the samples analyzed. This is the first C. gigas depurationstudy in Costa Rica and the first report concerning UV depuration for bacterial indicators of fecal contaminationin Anadara spp. This research serves as a basis for the implementation and improvement of mollusc purification conditions in the country. It is recommended to monitor extraction and harvesting areas, as well as to implement the depuration of bivalve molluscs so that traditional producers can offer an innocuous product with added value.Los moluscos bivalvos son comercializados sin ningún control sanitario en Costa Rica; por tanto, representan un riesgo para la salud pública, debido a que pueden acumular bacterias patógenas. Se evaluaron preliminarmente tratamientos para la depuración bacteriana a pequeña escala de Crassostrea gigas y Anadara spp. en el Golfo de Nicoya, Costa Rica, utilizando un sistema recirculado e irradiado con luz UV. Los niveles de Escherichia coli en el agua se determinaron mediante el método del NMP. A los moluscos se les determinó el NMP de E. coli y la presencia de Salmonella spp., Vibrio parahaemolyticus y V. cholerae. Los resultados confirman la efectividad del diseño del sistema para la depuración de E. coli en C. gigas y Anadara spp. A las 24 h, el NMP de E. coli en los moluscos se redujo entre el 79% y el 100%. No se comprobó la presencia de las demás bacterias en las muestras analizadas. Este es el primer estudio sobre depuración de C. gigas en Costa Rica y el primer reporte de depuración con UV de indicadores bacterianos de contaminación fecal en Anadara spp. Este trabajo sirve de base para implementar y mejorar las condiciones de la depuración de moluscos en el país. Se recomienda monitorear las áreas de extracción y cultivo e implementar la depuración de los moluscos bivalvos para que los productores artesanales puedan ofrecer un producto inocuo y con valor agregado.
Bivalve molluscs are sold without any sanitary control in Costa Rica, which represents a public health risk dueto the possible accumulation of pathogenic bacteria. Small scale bacterial depuration ...treatments were preliminarilyevaluated on Crassostrea gigas and Anadara spp. from the Gulf of Nicoya, Costa Rica, through the useof a recirculating system with UV irradiation. The levels of Escherichia coli in the water were determined usingthe MPN method. The MPN of E. coli and the presence of Salmonella spp., Vibrio parahaemolyticus and V. cholerae were determined in molluscs. Results confirm the effectiveness of the E. coli depuration system designin C. gigas and Anadara spp. The MPN of E. coli in the molluscs was reduced between 79% and 100% after 24h. None of the other types of bacteria were found in the samples analyzed. This is the first C. gigas depurationstudy in Costa Rica and the first report concerning UV depuration for bacterial indicators of fecal contaminationin Anadara spp. This research serves as a basis for the implementation and improvement of mollusc purification conditions in the country. It is recommended to monitor extraction and harvesting areas, as well as to implement the depuration of bivalve molluscs so that traditional producers can offer an innocuous product with added value.Los moluscos bivalvos son comercializados sin ningún control sanitario en Costa Rica; por tanto, representan un riesgo para la salud pública, debido a que pueden acumular bacterias patógenas. Se evaluaron preliminarmente tratamientos para la depuración bacteriana a pequeña escala de Crassostrea gigas y Anadara spp. en el Golfo de Nicoya, Costa Rica, utilizando un sistema recirculado e irradiado con luz UV. Los niveles de Escherichia coli en el agua se determinaron mediante el método del NMP. A los moluscos se les determinó el NMP de E. coli y la presencia de Salmonella spp., Vibrio parahaemolyticus y V. cholerae. Los resultados confirman la efectividad del diseño del sistema para la depuración de E. coli en C. gigas y Anadara spp. A las 24 h, el NMP de E. coli en los moluscos se redujo entre el 79% y el 100%. No se comprobó la presencia de las demás bacterias en las muestras analizadas. Este es el primer estudio sobre depuración de C. gigas en Costa Rica y el primer reporte de depuración con UV de indicadores bacterianos de contaminación fecal en Anadara spp. Este trabajo sirve de base para implementar y mejorar las condiciones de la depuración de moluscos en el país. Se recomienda monitorear las áreas de extracción y cultivo e implementar la depuración de los moluscos bivalvos para que los productores artesanales puedan ofrecer un producto inocuo y con valor agregado.
Bivalve molluscs are sold without any sanitary control in Costa Rica, which represents a public health risk due to the possible accumulation of pathogenic bacteria. Small scale bacterial depuration ...treatments were preliminarily evaluated on Crassostrea gigas and Anadara spp. from the Gulf of Nicoya, Costa Rica, through the use of a recirculating system with UV irradiation. The levels of Escherichia coli in the water were determined using the MPN method. The MPN of E. coli and the presence of Salmonella spp., Vibrio parahaemolyticus and V. cholerae were determined in molluscs. Results confirm the effectiveness of the E. coli depuration system design in C. gigas and Anadara spp. The MPN of E. coli in the molluscs was reduced between 79% and 100% after 24 h. None of the other types of bacteria were found in the samples analyzed. This is the first C. gigas depuration study in Costa Rica and the first report concerning UV depuration for bacterial indicators of fecal contamination in Anadara spp. This research serves as a basis for the implementation and improvement of mollusc purification conditions in the country. It is recommended to monitor extraction and harvesting areas, as well as to implement the depuration of bivalve molluscs so that traditional producers can offer an innocuous product with added value.
Los moluscos bivalvos son comercializados sin ningún control sanitario en Costa Rica; por tanto, representan un riesgo para la salud pública, debido a que pueden acumular bacterias patógenas. Se evaluaron preliminarmente tratamientos para la depuración bacteriana a pequeña escala de Crassostrea gigas y Anadara spp. en el Golfo de Nicoya, Costa Rica, utilizando un sistema recirculado e irradiado con luz UV. Los niveles de Escherichia coli en el agua se determinaron mediante el método del NMP. A los moluscos se les determinó el NMP de E. coli y la presencia de Salmonella spp., Vibrio parahaemolyticus y V. cholerae. Los resultados confirman la efectividad del diseño del sistema para la depuración de E. coli en C. gigas y Anadara spp. A las 24 h, el NMP de E. coli en los moluscos se redujo entre el 79% y el 100%. No se comprobó la presencia de las demás bacterias en las muestras analizadas. Este es el primer estudio sobre depuración de C. gigas en Costa Rica y el primer reporte de depuración con UV de indicadores bacterianos de contaminación fecal en Anadara spp. Este trabajo sirve de base para implementar y mejorar las condiciones de la depuración de moluscos en el país. Se recomienda monitorear las áreas de extracción y cultivo e implementar la depuración de los moluscos bivalvos para que los productores artesanales puedan ofrecer un producto inocuo y con valor agregado.
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