Resumen.-Con el fin de caracterizar la composición, distribución y abundancia de la comunidad fitoplanctónica de la ensenada de Utría, se colectaron muestras procedentes de tres estaciones (dos costeras y una con influencia oceánica) y tres profundidades (superficie, profundidad Secchi y profundidad de compensación), tanto diurnas como nocturnas, durante los meses de julio, agosto y octubre de 1995 y febrero y julio de 1996. Se identificaron 218 especies de las cuales 137 fueron diatomeas, 73 dinoflagelados, 5 cianofíceas y 3 silicoflagelados. Dentro de esta comunidad se presentaron especies estuarinas, neríticas y oceánicas. Las principales diferencias ocurrieron entre muestreos, mientras que los cambios entre estaciones, profundidades y día-noche fueron menores. Estas variaciones probablemente fueron causadas por las entradas de aguas continentales y marinas, el régimen mareal y el lavado de playones, especialmente de las zonas de manglar. Palabras Claves: ecología, algas marinas, fitoplancton costero.Abstract.-With the purpose of characterising the composition, distribution and abundance of the phytoplankton community of the cove of Utría, samples from three stations (two coastal and one with oceanic influence) and three depths (surface, Secchi and compensation depths), as much as diurnal and nocturnal were collected, during the months of July, August and October of 1995 and February and July of 1996. 218 species were identified, 137 were diatoms, 73 dinoflagellates, 5 cyanophytes and 3 silicoflagellates. Within this community appeared estuarine, coastal and oceanic species. Main differences occurred between samplings, while stations, depths and day-night changes were less marked. Entrances of the continental and marine waters, tide regime and washing of beaches, especially from the mangrove zones, probably caused these differences.
For the first time in Colombia the relative abundance of Pseudomonas spp., Vibrio spp., Plesiomonas shigelloides, the Aeromonas hydrophila group, and the faecal and total coliforms were studied in three dams and a natural lagoon with a different trophic state. Coliforms were low in all the water bodies, but their number was greater in the dams with a greater anthropic activity. Vibrio spp. was not detected. The density of P. shigelloides was irregular. Pseudomonas spp. was always present and showed relatively high abundance. The bacteria of the A. hydrophila group were constant and their numbers increased with the trophic state, for which they could be indicators of the eutrophication phenomena. Significant correlation (P < 0.05) was established between total and faecal coliforms and pH, transparency, nitrites, nitrates, and orthophosphates. P. shigelloides was correlated with faecal coliforms and Aeromonas hydrophila with total coliforms and transparency.
Relations between bacterioplankton and phytoplankton abundance in three lentic ecosystems in the Colombian Andes. We analyzed relations among phytoplankton and total bacterioplankton fractions in three lentic ecosystems (Neusa and Prado dams, and Fúquene lagoon) with different physicochemical characteristics, in the Andes of Colombia. Samplings were made in three sites of each water body during three surveys. Neusa dam (meso to oligotrophic) had the lowest bacterial concentration; Prado dam (eutrophic) had a high bacterial and algal abundance, and the Fúquene lagoon (mesotrophic) had lower concentrations of phytoplankton but a high relative concentration of bacteria, probably because of its particular conditions: high organic matter and low nutrient levels in the water. There was a negative correlation of total bacterioplankton with the phytoplankton (Pearson=-0.4479, p=0.019, n=27) and a positive correlation between phytoplankton and heterotrophic bacteria (Pearson=0.3866, p=0.062, n=24) and between total bacterioplankton and DBO 5 (Pearson=0.4088, p=0.034, n=27). Apparently, total bacterioplankton and phytoplankton were not coupling, but cultivable bacteria and the phytoplankton had some degree of relationship. Rev. Biol. Trop. 55 (1): 135-146. Epub 2007 March. 31.
Acoplamiento entre las comunidades planctónicas de un lago amazónico de aguas claras (lago Boa, Colombia)Las comunidades planctónicas de un lago están relacionadas entre sí de diversas maneras. Para los lagos amazónicos colombianos poco es lo que se conoce sobre este acoplamiento. Se realizaron siete visitas al lago Boa (Caquetá Medio) desde mayo de 1999 a mayo de 2000, durante las cuales se tomaron muestras de bacterioplancton, fitoplancton, nanozooplancton (protozoos) y rotíferos y crustáceos (mesozooplancton) para conocer sus variaciones y sus relaciones numéricas a lo largo del ciclo hidrológico. Los promedios de abundancias de individuos por litro fluctuaron entre 4.1 • 10 9 a 1.4 • 10 10 bacterias, 5.5 • 10 3 a 6.4 • 10 6 microalgas, 2.2 • 10 4 a 1.1 • 10 5 protozoos nanoplanctónicos y 8.1 a 240 organismos mesozooplanctónicos (rotíferos y crustáceos). Todas las comunidades tuvieron mayores abundancias en el periodo de aguas bajas, cuando el lago se desconectó del río Metá. El fitoplancton fue muy diverso y poco abundante; los grupos dominantes fueron las clorofitas, dinofitas y cianobacterias. El mesozooplancton fue escaso y estuvo compuesto principalmente por rotíferos. Dentro de los protozoos nanoplanctónicos predominaron los ciliados. Se halló una asociación estadística significativa entre las abundancias totales del fitoplancton y del bacterioplancton (p = 0.0001), lo cual sugiere algún grado de interdependencia de las dos comunidades. Durante los meses de inundación la fuerza física del pulso hidrológico parece causar que las comunidades funcionen con mayor autonomía, ya que en esta época el lago Boa se comporta como un verdadero sistema lótico.
Evaluación de la eficiencia fotosintética del fitoplancton en un lago amazónico (Lago Boa) y en un lago andino (Lago Guatavita)Gabriel A. PINILLA 1 RESUMEN La relación entre la fluorescencia variable y la fluorescencia máxima (F v /F m ) de las comunidades de algas se ha utilizado comúnmente como una medida de la eficiencia fotosintética del fitoplancton. Dicha eficiencia puede estar afectada por la localización de los ambientes acuáticos en distintas provincias limnológicas. En este trabajo se quiso establecer la diferencia en la relación F v /F m entre el lago Boa (150 msnm, Amazonía colombiana) y el lago Guatavita (3000 msnm, cordillera oriental de los Andes colombianos). Los promedios de las eficiencias medidas fueron en general bajos (0,212 a 0,367 y 0,089 a 0,32 en los lagos Boa y Guatavita, respectivamente), lo que señala estrés fisiológico para las algas. La eficiencia fue mayor en aguas intermedias y presentó cambios fuertes entre épocas de muestreo y entre ecosistemas. En aguas superficiales se presentó fotoinhibición, la cual fue más fuerte en Guatavita. La eficiencia fotosintética fue menor en el lago andino debido posiblemente a diferencias climáticas, de altura sobre el nivel del mar y de estratificación. Durante los ensayos de laboratorio se observó que la eficiencia disminuyó con el tiempo, lo cual pudo deberse a una aclimatación de las algas a la oscuridad. Los datos de laboratorio confirmaron que el fitoplancton epilimnético del lago Guatavita estuvo fotoinhibido en la época de estratificación. PALABRAS CLAVE Eficiencia fotosintética, fitoplancton, Amazonas, AndesEvaluation of the phytoplanktonic photosynthetic efficiency in an Amazon Lake (Lake Boa) and in an Andean Lake (Lake Guatavita) ABSTRACT (0.212 to 0.367 and 0.089 to 0.32 in lakes Boa and Guatavita, respectively), which indicate physiological stress to algae. Efficiency was higher in middle waters and changed strongly between sample periods and ecosystems. Photoinhibition occurred in superficial waters was greater in Lake Guatavita. Photosynthetic efficiency was smaller in the Andean lake do possibly to climatic differences, elevation above sea level and stratification. During laboratory assays efficiency decreased along time, caused probably by the darkness adaptation of the algae. Laboratory data confirmed that epilimnetic phytoplankton of the Lake Guatavia was photoinhibited at the stratification period. Commonly relation between variable fluorescence and maximum fluorescence (F v /F m ) of the algae community has been utilized like a measure of the phytoplanktonic photosynthetic efficiency. Such efficiency can be affected by the water bodies' location in different limnological provinces. The goal of this work was to establish the differences in the F v /F m rate between Lake Boa (150 masl Colombian Amazon) and Lake Guatavita (3000 masl, East Range in the Colombian Andes). In general, averages of the photosynthetic efficiencies were low KEY WORDS Photosynthetic efficiency, phytoplankton, Amazon, Andean INTRODUCCIÓNLas primeras...
El departamento del Meta cuenta con un elevado potencial hidrológico que se traduce en oportunidades para los sectores agrícola, pecuario y ambiental. Por otra parte, se han incrementado considerablemente las actividades de la industria petrolera, lo cual ha traído nuevos retos y amenazas a la región. En consecuencia, los ríos del departamento se ven afectados por vertimientos de diferentes tipos, por captaciones y por modificaciones de los entornos de ribera y de los ambientes bentónicos. Sin embargo, es poco lo que se conoce acerca de estos sistemas y de las comunidades de microalgas y macroinvertebrados que los habitan, las cuales cumplen un papel fundamental en el funcionamiento ecológico de los ríos. Por esta razón se analizan las características más relevantes de dichas comunidades y se discuten las modificaciones que las actividades humanas provocan sobre la estabilidad ecológica de los ríos en un contexto regional. Adicionalmente, se presenta un listado de los taxones de microalgas perifíticas y macroinvertebrados bentónicos registrados para el departamento del Meta.
CLASSIFICATION: UnclassifiedThe last military and political results against the FARC's guerrillas have created different and controversial opinions about the future of this movement. For more than 40 years of internal struggle, this is the most optimistic period in history; not only because of the recent military defeats (Its main leaders have been killed in military actions, with more than 2000 members demobilized or in jail), but also because of the national and international rejection of the group as legitimate combatants and its reconfirmation as a "terrorist" group.Is this the end of the FARC, or simply a change of strategy? The experiences show that it is a very unpredictable group, with the capacity to recover the initiative easily. What is its future as a guerrilla organization? Could it become a group of delinquents to survive or continue as drug dealers? Which would be the next government move in order to maintain the initiative and to be successful? And finally, is the government prepared to face an eventual massive demobilization and to accept the political price? ARE WE APPROACHING THE REAL DEFEAT OF THE FARC IN COLOMBIA?"In Colombia every indicator that can be measured is proceeding in a positive direction, from the decline in murder and kidnapping rates, to the growth of the economy and freedom of movement. These factors can be quantified, but there is no way to tell when a magic line is crossed where one less murder makes all the difference in the way Colombians see their country" Gen. (ret.) Carlos Ospina, Colombian Army.To have a clear concept about this argument it is necessary to go back eight years before President Alvaro Uribe's election in 2002 to see how Colombia desperately needed deep reforms to avoid the advance of communism. At that time the FARC (Fuerzas Armadas Revolucionarias Comunistas) organization represented in the military and clandestine political arms was very optimistic about beginning its "strategic project". In the previous years, the FARC accumulated 15,400 armed rebels, distributed in seven "blocks" 1 around the country, and after three years (1999)(2000)(2001)(2002) in the "demilitarized zone" 2 , they were well prepared politically, military and logistically, to face the first great offensive phase against the government of Colombia.After 40 years of internal war, it is not a big challenge to identify the FARC's intentions. The application of the "all forms of struggle" 3 to reach its strategic goals are a clear demonstration of its lack of interest to finalize the conflict. More than one failed process demonstrated the real FARC's interests to waste the government's time. As a clear example we have the government of President Belisario Betancourt 4 that in the early 1980s started negotiations with the FARC. At that time, the FARC and the government agreed to a cease-fire in 1985, months later the FARC broke the negotiation unilaterally. In 1999 during the government of President Andres Pastrana 5 , the FARC decided to talk about peace in the middle of the war, deceivi...
Abstract. The catfish, Eremophilus mutisii, was cultured under different densities in artificial rainfall reservoirs at Caldas, Boyacá, Colombia. At capture, the average total length of the animals was 10 cm and the weight ranged between 9 and 10 g. These fish were in initial stages of sexual development. After a year in the reservoirs, they had increased in length and weight as follows (densities in parentheses): 5.22 cm and 27.23 g (0.5 individuals/m 2) ); 1.98 cm and 8.79 g (1 individual/m 2 ), and 2.45 cm and 0.82 g (2 individuals/m 2 ). They were at the early stages of sexual maturity, and their condition factor fluctuated between 0.61 and 0.96. They preferably ingested insect larvae that were found in benthic and littoral communities of the reservoirs. The benthos was dominated by ephippia of Daphnia, lumbriculids, and chironomid larvae. The biomass of benthic organisms ranged between 0.1126 and 1.3847 g/m 2 . In the littoral community aquatic insects were the most important component, especially the hemipterans. The biomass of the littoral fauna ranged between 0.14 and 4.05 g/m 2 . Rev. Biol. Trop. 54(2): 589-597. Epub 2006 Jun 01.Key words: Eremophilus mutisii, Trichomycteridae, growth observations, gut content, Colombia.The catfish Eremophilus mutisii is an endemic species and the only catfish present in the Cundiboya highlands of Colombia. Both the catfish and the highlands have suffered considerable habitat disturbance. This fish represent an important source of vitamins and animal protein to supplement the diet of the rural population. The deterioration of natural populations of E. mutisii has been evident; in Fúquene Lagoon, for example, Mayorga (1992) not only observed a decrease in size but also the attainment of sexual maturity at small sizes. This suggests that the reproduction of individuals takes place at early stages, perhaps as a survival mechanism for facing adverse conditions (Mayorga 1992). The impairment of the catfish habitat is related to a decrease in quality and quantity of continental waters due to pollution problems, loss of ground cover in the headwaters of rivers and streams, the improper use of water resources, etc. In addition to these problems, overfishing, the improper use of fishing methods and the absence of specific regulations can be added. This impairs the implementation of an adequate management of the species. Realizing the importance of E. mutisii, researchers have become interested in studying different aspects of its biology and ecology (Amaya 1975, Beltrán 1992, Mayorga 1992 and also the possibility of its cultivation (Del Castillo and Garzón 1985). The first attempt to culture E. mutisii in small land-based reservoirs was made in the microbasin of the stream La Playa in Caldas, Boyacá, in which a preliminary study was conducted over a
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