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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4634

Emily C. Roberts, John C. Priscu, and Johanna Laybourn-Parry; Microplankton dynamics in a perennially ice-covered Antarctic lake - Lake Hoare. Freshwater Biology 49:853-869, 2004

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1. Temporal and spatial variation in planktonic abundance, biomass and composition were determined in Lake Hoare (McMurdo Dry Valleys, Antarctica) over two summer seasons (1996-97 and 1997-98). 2. Phototrophic nanoflagellates (PNAN) dominated biomass, with a mean monthly biomass ranging between 27.3 and 40.4 µgC/L. The deep chlorophyll maximum was mainly composed of cryptophytes (>87% of total PNAN biomass) and varied in depth between 6 and 12 m. 3. Maximum bacterial concentration was 11.8x10E5 cells/mL. Bacterial abundance showed relatively little temporal variation, with the exception of a drop in numbers that occurred in late November of both years studied. 4. Ciliates were the most successful heterotrophic protozoan group, with a mean monthly biomass (1.2-3.2 µgC/L) being typically at least double that of heterotrophic nanoflagellate (HNAN) biomass (0.1-0.7 µgC/L). 5. Microbial processes within this lake appear to be dominated by bottom up control. The relative importance of allochthonous inputs into the lake (from the ice-cover and stream flow) and autochthonous recycling (by microzooplankton regeneration) are considered. 6. Results from a horizontal transect indicate that the permanence of the main sample hole may have enhanced planktonic biomass over a relatively small spatial scale.