Virus and microbial loop dynamics over an annual cycle in three contrasting Antarctic lakes
Madan, NJ and Marshall, WA and Laybourn-Parry, J, Virus and microbial loop dynamics over an annual cycle in three contrasting Antarctic lakes, Freshwater Biology, 50, (8) pp. 1291-1300. ISSN 0046-5070 (2005) [Refereed Article]
1. Viral and microbial loop dynamics were investigated over an annual cycle in three
contrasting saline Antarctic lakes Highway Lake (salinity 4&), Pendant Lake (salinity
19&) and Ace Lake, a meromictic system (with a mixolimnion salinity of 18&) in order to
assess the importance of viruses in extreme, microbially dominated systems.
2. Virus like particles (VLP) showed no clear seasonal pattern, with high concentrations
occurring in both winter and summer (range 0.89 · 107 ± 0.038 to
12.017 · 107 ± 1.28 mL)1). VLP abundances reflected lake productivity based on chlorophyll
a concentrations. Bacterial abundances and biomass did not correlate with VLP
numbers except in Pendant Lake, the most productive of the three lakes studied.
3. Pendant Lake supported the highest bacterial biomass (range Highway: 18.44 ± 1.35 to
59.43 ± 2.80 ng C mL)1; Ace: 14.42 ± 2.69 to 68.39 ± 2.95 ng C mL)1; Pendant: 31.36 ± 3.94
to 115.95 ± 4.49 ng C mL)1) so that virus to bacteria ratios (VBR) (range 30.48 ± 7.96 to
96.67 ± 8.21) were higher in Ace Lake (range 30.58 ± 3.98 to 80.037 ± 1.60) and Highway
Lake (range 18.63 ± 3.12 to 126.74 ± 6.50).
4. Negative correlations occurred between VLP and cryptophytes (dominant phototrophic
nanoflagellates), suggesting that they were not hosts to lytic viruses. Among the other
protists only the heterotrophic nanoflagellates of Highway Lake (dominated by the marine
choanoflagellate Diaphanoeca grandis) showed a positive correlation with VLP.
5. The VLP was negatively correlated with photosynthetically active radiation (PAR) and
temperature, both of which increased with ice thinning and breakout, increasing viral
decay. In winter VLP probably persisted in cold, dark water.
6. High VLP concentrations and high VBR (values at the upper end of those reported for
marine and lacustrine systems) indicated that viruses, most of which were probably
bacteriophage, are a major element within the microbial communities in extreme, saline