MEPS 179:231-240 (1999)  -  doi:10.3354/meps179231

Seasonal dynamics of bacterial biomass and production on eelgrass Zostera marina leaves

Erik Törnblom*, Morten Søndergaard

Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, DK-3400 Hillerød, Denmark
*Present address: Institute of Limnology, Uppsala University, Norbyv. 20, SE-752 36 Uppsala, Sweden. E-mail:

ABSTRACT: The seasonal dynamics and distribution of bacteria and bacterial activity on eelgrass leaves were followed at a shallow-water site in the Roskilde Fjord, Denmark. Eelgrass leaves were sites of highly active bacterial communities exhibiting distinct distribution patterns with increasing bacterial abundance and production with increasing leaf age and from base to tip of individual leaves. High bacterial production and very high specific growth rates (seasonal mean 0.30 h-1) suggest a strong coupling between attached bacterial communities and plant primary production. Incorporation rates of 14C-leucine and 3H-thymidine were significantly correlated but the ratio between bacterial production based on leucine and thymidine increased with increasing leaf age and from leaf base to leaf tip, indicating a higher protein synthesis compared to DNA synthesis with increasing biofilm age. Bacterial biomass production was very high compared to the standing stock of bacteria and it was concluded that close to 100% of the bacterial biomass produced on the leaves was lost on a daily basis. Moreover, bacterial specific growth rates corresponded to turnover times of 1 to a few hours on most occasions and did not differ between leaves of different ages or at different locations on the leaves. Such high growth rates can only occur in a very rich environment, where the standing stock of biomass is kept low and thus prevents resource competition.

KEY WORDS: Biofilm · Bacteria · Abundance · Production · Eelgrass · Zostera marina

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