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.

The epifluorescence technique was used to quantify the total bacterial population in two dams (Neusa and Prado) and in a natural lagoon (Fúquene), which have different geographical locations and physicochemical characteristics. Bacterial abundance was similar in the three water‐bodies (8.4 × 108 cells L–1), but the density of plateable heterotrophs was always lower (1.4 × 106 CFU L–1) when obtained by the plate count method. Results obtained during validation of the epifluorescence technique show: (i) that there are no statistically significant differences between counts of samples fixed in the field and unfixed samples; (ii) that the median count of samples fixed and observed periodically over a period of 8 months was similar; (iii) that plate counts underestimate the population; and (iv) that epifluorescence counts were similar in the three water‐bodies studied, despite their different ecological conditions.

Marine bacterioplankton abundance, biomass, biovolume and shape were quantied in three stations within Gaira Bay at the Colombian Caribbean coast over three periods dened for this study as: “rainy” (July, August, 2003), “transition” (April, October 2004) and “dry” (February, March, 2004). Bacterioplankton samples were collected from 0.5 and 42 m depths, ltered onto 0.22 μm polycarbonate lters and quantied using epi!uorescence microscopy with Acridine Orange staining and image analysis. Average bacterial abundance ranged between 1.3 x 105-2.9 x 106 cells mL-1 during the rainy period, 8.8 x 104-2.2 x 106 cells mL-1 during the transition period and 6.7 x 104-3.9 x 105 cell mL-1 at the dry period, with a mean abundance of 4.4 x 105 cells mL-1. The differences in abundance were statistically signicant between sampling periods, stations and depths, the differences in biovolume were statistically signicant between sampling periods and stations, nally, the differences in biomass were statistically signicant between stations and water depths (ANOVA, p<0.05). Most of the cells had a coccoid shape and a small biovolume (0.01-0.08 μm3 cell-1). Over the sampling period, the mean bacterial biomass ranged between 0.88 and 32.1 μg C L-1, with the maximum observed during the rainy period. The results suggest that bacterial biomass increases during the rainy period, probably as a consequence of increased water discharge originating from the Gaira River and the Ciénaga Grande de Santa Marta lagoon. We hypothesize that the temporal dynamics of bacterial communities in Gaira Bay are being driven by the availability of organic nutrients (DOC).