Active bacteria (CTC+) in temperate lakes: temporal and cross-system variations

ISSN： 1464-3774

Source： Journal of Plankton Research, Vol.23, Iss.11, 2001-11, pp. : 1195-1206

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Abstract

The temporal variation in the abundance and proportion of highly respiration-active bacteria in the eutrophic lakes Esrum and Frederiksborg Slotssø was determined with the redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC). In addition, a comparative late summer study was undertaken across a gradient of nutrient enrichment in Danish lakes. The purpose was to investigate the importance of substrate (chlorophyll) and temperature for the control of CTC-active cells (CTC+). The abundance of CTC+ cells was much lower and more variable than the total number of cells counted after 4′,6-diamidino-2-phenylindole (DAPI) staining. The proportion of CTC+ cells in Lake Esrum and Frederiksborg Slotssø was normally <5%, and="" between="" 2.5="" and="" 20%="" in="" 14="" other="" lakes.="" the="" abundance="" as="" well="" as="" the="" proportion="" of="" ctc+="" cells="" increased="" with="" chlorophyll="" in="" lake="" esrum="" and="" frederiksborg="" slotssø,="" and="" chlorophyll="" explained="" 43%="" of="" the="" variability="" in="" ctc+="" abundance.="" in="" the="" comparative="" study,="" the="" abundance="" of="" ctc+="" cells="" increased="" along="" the="" chlorophyll="" gradient,="" which="" explained="" 49%="" of="" the="" variability.="" the="" results="" showed="" that="" the="" abundance="" and,="" to="" a="" lesser="" degree,="" the="" proportion="" of="" ctc+="" bacteria="" were="" controlled="" by="" substrate="" supply.="" one="" consequence="" of="" the="" low="" abundance="" of="" active="" bacteria="" is="" that="" in="" situ="" growth="" rates="" scaled="" to="" ctc+="" cells="" are="" 3-="" to="" 7-fold="" higher="" than="" those="" scaled="" to="" dapi="" counts.="" it="" is="" suggested="" that="" studies="" on="" factors="" controlling="" bacterioplankton="" activity="" at="" the="" single-cell="" level="" should="" be="" investigated="" scaled="" to="" active="" cells.="">