Bacterioplankton production in freshwater Antarctic lakes
Laybourn-Parry, J and Henshaw, T and Jones, DJ and Quayle, W, Bacterioplankton production in freshwater Antarctic lakes, Freshwater Biology, 49, (6) pp. 735-745. ISSN 0046-5070 (2004) [Refereed Article]
1. Bacterioplankton production was measured in the water columns of two ultraoligotrophic,
freshwater Antarctic lakes (Crooked Lake and Lake Druzhby) during an annual
cycle. In both lakes bacterial production, measured by the incorporation of [3H] thymidine,
continued in winter and showed a cycle over the year. The range of production was between 0
and 479 ng C L)1 h)1 in Crooked Lake and 0354 ng L)1 h)1 in Lake Druzhby.
2. Abundance and mean cell volume both varied, producing marked changes in biomass
during the year, with highest biomass occurring in the winter and early spring. Biomass
showed similar seasonal trends in both lakes.
3. For most of the year inorganic forms of nitrogen and phosphorus were detectable in the
water columns of the lakes and were unlikely to have limited bacterial production.
Dissolved organic carbon (DOC) was below 3000 lg L)1. Dissolved amino acids and
carbohydrates contributed 525% of the DOC pool in Crooked Lake and 564% in Lake
Druzhby. Dissolved carbohydrates were consistently low, suggesting that this may have
been the preferred carbon substrate for bacterioplankton.
4. Aggregate associated bacteria had higher mean cell volume, abundances and production
than freely suspended bacteria in Lake Druzhby, while in Crooked Lake aggregate
associated bacteria consistently had higher mean cell volumes than free bacteria, but
abundance and production were on occasion higher in free bacteria compared with
aggregate associated communities.
5. The data indicated that production is limited by continuous low temperatures and the
limited availability of suitable DOC substrate. However, the bacterioplankton functions
year round, responding to factors other than temperature.