Naslov
Bacterial Activity along a Trophic Gradient

Autori
Karner, Marcus ; Fuks, Dragica ; Herndl, J. Gerhard

Izvornik
Microbial ecology (0095-3628) 24 (1992), 3; 243-257

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Heterotrophic bacteria ; secondary production ; extracellular enzymatic activity ; trophic gradient ; northern Adriatic Sea

Sažetak
Bacterial biomass, secondary production, end extracellular enzymatic activity [α -glucosidase and leucine-aminopeptidase, measured as cleavage of artificial fluorogenic substrates 4-methyl umbelliferyl (MVF) α -D-glucopyranoside and L-leucine 7-amido-4-methyl coumarin (MCA)] were measured along a trophic gradient in the Northern Adriatic Sea in four ecologically different situations. Bacterial parameters were compared with chlorophyll a and inorganic and organic nutrient concentrations. Bacterial secondary production and extracellular enzymatic activity markedly changed among different seasons and along the trophic gradient. Average bacterial secondary production increased from 0.61 to 2.09 μ g Cl-1 hour-1 preciding a bloom, to 2.09 μ g Cl-1 hour-1 during a bloom, decreasing again to 0.81 and 0.83 μ g Cl-1 hour-1 in the post-bloom and summer periods, respectively (values from .5 m depth). Leucine-aminopeptidase activity showed more consistent trends than α -glucosidase activity. Average values of leucine-aminopeptidase activity, measured by enzymatic reease of MCA, increased feom a pre-bloom value of 164.0 to 1, 712.0 (nM MCA) hour-1 released during a bloom, decreasing to 298.5 and 133.7 (nM MCA) hour-1 released for the post-bloomand summer situation, respectively (values from 0.5 m depth). Average growth rates decreased during the bloom, whereas average extracellular enzymatic activitylevels expressed on a cell basis increased by an average factor of 2. along the trophic gradient, a consistent increase in bacterial secondary production could be observed in all but the summer situation (values from 0.5 m depth). Leucine-aminopeptidase activity also showed positive trends along the gradient, while α -glucosidase activity did not exhibit a clear trend. Bacterial biomass trends were less obvious considering both seasonal changes and the trophic gradienr. Highly sidnificant interrelations were detected between bacterial proteolytic activity, secondary production, chlorophyll a content, and nitrite concentrations, especially in the surface horizon.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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