Journal
AQUATIC SCIENCES
Volume 74, Issue 3, Pages 513-525Publisher
SPRINGER BASEL AG
DOI: 10.1007/s00027-011-0244-1
Keywords
Subarctic; DOC; Ponds; Bacterial biomass; Bacterial production; Bacterial community composition; Allochthonous carbon
Funding
- Societas pro Fauna et Flora Fennica
- Haavikko Foundation, Lapland Atmosphere-Biosphere Facility
- Finnish Academy of Science [119205, 140775]
- Academy of Finland (AKA) [119205] Funding Source: Academy of Finland (AKA)
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Bacterial communities in 16 oligotrophic ponds in Kilpisjarvi, subarctic Finland, were studied to test the hypothesis that dissolved organic carbon (DOC) quantity and quality differently influence bacterioplankton. The ponds were located below and above treeline at 600 m a.s.l., with 2-4 fold higher concentration of DOC below treeline. The concentration of DOC changed during the open-water season with highest values measured in mid-summer. Bacterial production, abundance, biomass were highest in mid-summer and correlated positively with the concentration of DOC. Quality indices of DOC showed that spring differed from the rest of the season. Highest specific UV-absorbance (SUVA) and humification index (HI), ratio a250/a265 and lowest fluorescence index (FI) were found during spring compared to summer and autumn, possibly indicating higher relative importance of allochthonous carbon during spring and a seasonal effect of photo-oxidation. According to Length Heterogeneity Polymerase Chain Reaction (LH-PCR) analyses, bacterial communities in spring were significantly different from those later in the season, possible due to the introduction of terrestrial bacteria associated with higher molecular weight material in spring DOC. Comparison between ponds situated above and below treeline revealed that bacteria were more abundant and productive at lower altitudes, which is probably connected to higher concentrations of DOC. The results also suggest that increased temperature and precipitation induced by global change and consequent higher allochthonous DOC runoff from the catchment could have a strong impact on biomass, productivity and community composition of micro-organisms in subarctic ponds and lakes.
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