Diel variations in bacterioplankton, phytoplankton, and related parameters in the Southern California Bight.

• The principal objectives of this study were (i) to determine the extent of coupling betweenphytoplankton and microheterotrophs on the shelf off Southern California. (ii) to compare differentmeasures of primary and bacterial secondary production, and (iii) to assess whether sampling timesshould be as strictly controlled for microheterotroph as for autotroph studies. Two diel cycles (May andOctober) were studied by sampling an isotherm as the ship followed paired submerged drogues. Wefound significant die1 changes of chlorophyll, 14C bicarbonate incorporation, bacterial abundance andthymidine incorporation, frequency of dividing bacterial cells (FDC), abundance of non-pigmentedflagellates, particulate organic carbon and nitrogen and their ratios, and dissolved oxygen. Theseparameters all had higher values dunng daylight hours than at night, showing close coupling betweenthe phytoplankton (light-forced) and the microheterotrophs. The ratio of in vivo to extractedchlorophyll a fluorescence, however, displayed a maximum at midnight and minimum at midday,suggesting an endogenous rhythm. Primary production measured by the 14C method was similar to netproduction inferred from in situ oxygen changes. Short-lived peaks in FDC values suggested partlysynchronized bacterial division. 

Ämnesord

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

Nyckelord

Microbiology

Mikrobiologi

Mikrobiologi

Microbiology

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