Variations in planktonic bacterial biomass and production and phytoplankton blooms off A Coruña (NW Spain)

Abstract

SUMMARY: Bacterial abundance, biomass and heterotrophic activity, along with hydrographic and phytoplankton variables, were measured from February 1998 to September 1999 at two coastal stations off A Coruña (Galicia, NW Spain). Bacterial abundance varied from 0.1 to 1.8 x 10 6 cells ml -1 and water-column integrated bacterial production ranged from 34 to 1132 mg C m -2 d -1 . Two annual maxima of bacterial abundance and production were observed, in spring and summer, although relatively high abundance values remained until autumn. In autumn and winter production values were low with the exception of the results obtained in November 1998, when the highest values of bacterial production of the whole study were observed at both stations. Bacterial biomass constituted a significant, but low, fraction of particulate organic carbon (4-21 %) and was always lower than phytoplankton biomass (up to 40% of phytoplankton carbon). Also, bacterial production was generally < 30% of primary production, but in some situations (as in early spring or in autumn) bacterial production exceeded primary production, suggesting a delayed response of bacterial activity after a phytoplankton bloom.Key words: bacterial production, bacterial abundance, phytoplankton biomass, primary production, phytoplankton blooms, NW Spain. RESUMEN: VARIACIONES EN LA BIOMASA Y PRODUCCIÓN DE LAS BACTERIAS PLANCTÓNICAS, Y EN LAS PROLIFERACIONES DE FITOPLANCTON ENLA COSTA DE A CORUÑA (NO ESPAÑA). -Se midió la abundancia, biomasa y actividad heterotrófica bacteriana, junto con variables hidrográficas y fitoplanctónicas, entre febrero de 1998 y septiembre de 1999 en dos estaciones costeras de A Coruña (Galicia, NO España). La abundancia bacteriana varió entre 0.1 y 1.8 x 10 6 células ml -1 y la producción bacteriana integrada en la columna de agua tomó valores entre 34 y 1132 mg C m -2 d -1 . Se observaron dos máximos de abundancia y producción bacteriana en primavera y verano, aunque se mantuvieron valores relativamente altos de abundancia durante el otoño. En otoño e invierno los valores de producción fueron bajos con la excepción de los resultados obtenidos en noviembre de 1998, donde se observaron los mayores valores de producción de todo el estudio en ambas estaciones. La biomasa bacteriana constituyó una fracción significativa, aunque baja, del carbono orgánico particulado (4-21%) y fue siempre menor que la biomasa del fitoplancton (hasta un 40% del carbono fitoplanctónico). Del mismo modo, la producción bacteriana fue generalmente < 30% de la producción primaria, aunque en ciertas situaciones (como a principios de primavera o en otoño) la producción bacteriana excedió a la producción primaria, lo que sugiere un retraso en la respuesta de la actividad bacteriana a la proliferación del fitoplancton.Palabras clave: producción bacteriana, abundancia bacteriana, biomasa de fitoplancton, producción primaria, proliferaciones de fitoplancton, NO España.

Influence of allochthonous matter on microbial community structure and function in an upwelling system off the northwest Iberian Peninsula

“…The empirical leucine-to-carbon conversion factor averaged 2.19 kg C mol Leu -1 , which is higher that the mean value reported by Barbosa et al (2001) in the same region during the upwelling season. However, it is within the range of values reported by Morán et al (2002) for the same region during late summer, and is considerably lower than the empirical factor determined by Valencia et al (2003) in nearby shelf waters off A Coruña (northwestern Spain).…”

Empirical Leucine-to-Carbon Conversion Factors for Estimating Heterotrophic Bacterial Production: Seasonality and Predictability in a Temperate Coastal Ecosystem

“…All cellular variables were related to values for fluorescent beads. An empirical calibration between relative side scatter and cell diameter (7) was used to estimate bacterial biovolumes (BBv), which were very similar to previous values reported for these shelf waters obtained by microscope measurements (4,28). We used the allometric relationship of Norland (22) for converting BBv to cellular carbon content (CCC): CCC (pg cell Ϫ1 ) ϭ 0.12 ϫ BBv 0.72 .…”

Sample Dilution and Bacterial Community Composition Influence Empirical Leucine-to-Carbon Conversion Factors in Surface Waters of the World's Oceans

“…This problem may typically occur in coastal eutrophic waters, where the ambient leucine concentration may be higher than the commonly used concentrations of added radiotracer (20 to 40 nmol liter Ϫ1 ). In fact, leucine-to-carbon eCFs higher than the theoretical one have been repeatedly found at coastal sites (6,11,(32)(33)(34).…”