Flagellate nutritional versatility as a key to survival in two contrasting Antarctic saline lakes

• Published in: Freshwater Biology
• Main Authors: Laybourn-Parry, J, Marshall, WA, Marchant, HJ
• Format: Article in Journal/Newspaper
• Language: English
• Published: Blackwell Publishing Ltd 2005
• Subjects: Biological Sciences; Microbiology; Microbial Ecology; Antarctic; Vestfold Hills; Vestfold; Ace Lake; Highway Lake; Antarc*
• Online Access: http://interscience.wiley.com; https://doi.org/10.1111/j.1365-2427.2005.01369.x; http://ecite.utas.edu.au/49055

1. Seasonal patterns of grazing and photosynthesis were investigated in two salineAntarctic lakes (Highway and Ace) in the Vestfold Hills (68 degrees S). The phototrophicnanoflagellate (PNAN) community was dominated by Pyramimonas gelidicola and twomorphological forms of a cryptophyte species that occurred throughout the year. Bothspecies were mixotrophic on bacteria, and in Highway Lake they also exploited dissolvedorganic carbon as determined by the uptake of fluorescently labelled dextrans.2. Clearance rates ranged between 0.02 and 0.21 nL h)1 cell)1 in Ace Lake and 0.0041.05 nL h)1 cell)1 in Highway Lake. On occasion cryptophyte grazing equalled that of theheterotrophic nanoflagellates (HNAN).3. Photosynthetic rates showed similar trends in both lakes, but there were differences inchlorophyll a specific rates and photosynthetic efficiency, probably related to themeromictic characteristic of Ace Lake. Primary production was measurable in winter andpeaked in summer following the maxima of mixotroph grazing.4. The HNAN community of Highway Lake achieved clearance rates of 0.021.80 nL h)1 cell)1 and removing between 50 and 693 ng bacterial carbon L)1 day)1, withhighest impact in winter when HNAN were most abundant. The HNAN also ingestedfluorescently labelled dextrans showing a preference for 4 and 500 kDa molecules.The more diverse HNAN community of Ace Lake had lower clearance rates(0.040.37 nL h)1 cell)1) and exerted a lower grazing pressure on bacterioplankton. InHighway Lake, where the HNAN community was dominated by the choanoflagellateDiaphanoeca grandis, there was a significant correlation between mean cell volume andclearance rate.5. The major feature was that the microbial plankton functioned throughout the year byemploying nutritional versatility.